Kinetics, equilibrium and thermodynamics studies of ...

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Journal of Molecular Liquids 219 (2016) 482–492

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Journal of Molecular Liquids journal homepage: www.elsevier.com/locate/molliq

Kinetics, equilibrium and thermodynamics studies of Pb2 + adsorption onto new activated carbon prepared from Persian mesquite grain Ensieh Ghasemian Lemraski ⁎, Soheila Sharafinia Faculty of Science, Ilam University, P.O. Box 69315516, Ilam, Iran

a r t i c l e

i n f o

Article history: Received 17 September 2015 Received in revised form 5 March 2016 Accepted 10 March 2016 Available online xxxx Keywords: Activation X-ray photoelectron spectroscopy Micro pores High surface area Surface functional group

a b s t r a c t In the present study, adsorption of Pb2+ from aqueous solutions onto prepared activated carbon using Persian mesquite grain was studied. Several techniques and methodologies such as, proximate analysis, N2 adsorption–desorption isotherms, scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature programmed desorption (TPD), Thermo gravimetric analysis TGA/DTA, elemental analysis(CHNS), Boehm titration, and point of zero charge (pHpzc) have been used to determine physicochemical properties of raw material and activated carbon. Through the XRD, SEM, TGA/DTA, elemental and FT-IR analysis, it could be observed that significant changes in porosity occurred after the activation process. The N2 adsorption results demonstrated that the activated carbon is composed mainly of microspores (63.8%), presenting high BET surface area of 1243 (m2·g−1) and exhibit Type I isotherm. According to Boehm titration, surface of activated carbon includes a majority of acidic groups which is in agreement with the obtained pHpzc value of 3.73. The maximum adsorption capacity for Pb2+ is much higher than the other granular and powdered activated carbons. High efficiency in Pb2+ removal indicates that activated Persian mesquite grain could be successfully used as an excellent adsorbent in water purification. © 2016 Elsevier B.V. All rights reserved.

1. Introduction The activated carbons (or ACs) are porous materials containing a high surface area and an appreciable amount of active sites available for adsorption of certain pollutants. Commercial production of activated carbon in recent years has been performed by the physical or chemical activation of a wide variety of materials, including waste hemp (Cannabis sativa) fibers [1], Prosopis cineraria [2], phoenix leaves [3], cotton stalks [4], rice husk [5], fir wood [6], Guava seeds, tropical almond shells and Dinde stones [7], olive stones [8], flamboyant pods or Delonix regia [9], and macadamia nut shells [10]. The main objective of the present work is to provide activated carbon with high surface area, high adsorption capabilities and desorption ability using natural products. Different experimental and instrumental analyses have been used to further understanding the structure of activated carbon. In our country traditionally raw materials such as shell walnuts, pistachios, bast joy, acorn caps, core fruit, and cereal waste have been used to produce activated carbon. But cork structure of Persian Prosopis farcta leads to prepare activated carbon from it as a new natural resource. Mesquite or Persian P. farcta is a short perennial foliage bush whose length often reaches 40–100 cm. Proximate analysis, elemental analysis, FT-IR, XRD, Scanning electron microscopy (SEM), and TG/DTA have been done in order to ⁎ Corresponding author. E-mail addresses: [email protected], [email protected] (E.G. Lemraski).

http://dx.doi.org/10.1016/j.molliq.2016.03.031 0167-7322/© 2016 Elsevier B.V. All rights reserved.

understand the structural changes during the activation process. Textural parameters such as BET surface area, volume and pore size distribution were evaluated by N2 adsorption. Although the nature and concentration of surface functional group are characterized using several techniques including chemical titration methods (Boehm titration and pHpzc), X-ray photoelectron spectroscopy (XPS), and temperature-programmed adsorption (TPD). X-ray photoelectron spectroscopy (XPS) is a surface-sensitive quantitative spectroscopic technique that measures the elemental composition at the surface of material [11]. Temperature-programmed desorption (TPD) is the method of observing desorbed molecules from a surface when the surface temperature is increased [12,13]. This work also focused on the study of Pb2+ removal from aqueous solution. In developing countries such as Iran water pollution is caused by industrial and municipal wastewater, as well as by agriculture. Except a few cases, there are no factories, industries and sewage disposal system in the country, especially in metropolitan areas. Also N200,000 m3 of daily sludge (2000 tons/day dry solids) of total fecal, septic and waste excrements sledges, only about 80,000 m3 (800 tons) is being digested and/or stabilized daily by different treatment methods. On the other hand concentrations of six heavy metals including Cr, Mn, Ni, Pb, V and Zn were determined in top soil (from 47 grid cells), surface water (4 streams) and groundwater (8 wells and 4 qanats) from an agricultural area located in different part of the Iranian big city. Lead is an old environmental metal which is present everywhere and lead poisoning is an important health issue in many countries in

E.G. Lemraski, S. Sharafinia / Journal of Molecular Liquids 219 (2016) 482–492

the world including Iran. It is known as a silent environmental disease which can have lifelong adverse health effects. Occupational lead exposure is an important health issue in Iran and mine workers, employees of paint factories, workers of copying centers, drivers, and tile making factories are at higher risk of lead toxicity. Moreover lead processing industry has always been a major of concern which affects surface water, drinking waters, and ground waters, even water of Caspian Sea, Persian Gulf and rivers due to increasing the number of industries in vicinity of rivers that release their waste discharges into river or sea [14–17]. Based on WHO standard, concentration of lead in drinking water was limited to 0.01 mg·L−1, and based on drinking water standard in Iran, upper limit of the concentration of lead in drinking water announced to 0.05 mg·L−1. AC in the present work showed maximum monolayer adsorption capacity 273 (mg·g−1) for lead (ΙΙ), noticeable value to the other granular and powdered activated carbons reported in the literatures. Various operational parameters like initial concentration, pH, time and temperature was optimized in the lead removal process and finally the adsorption kinetic models, equilibrium isotherms and thermodynamic parameters were also performed and analyzed. 2. Experimental 2.1. Materials The raw material was first washed with double-distilled water and then oven-dried at 100 °C for 48 h. The dried Persian mesquite grain was crushed in a laboratory mill and sieved until it attained a small particle size. Due to low ash content and high amount of volatile matter, Persian mesquite grain is a good feedstock for activated carbon production. All chemicals used in this study, were of the highest purity available and purchased from Merck (Darmstadt, Germany). Stock solutions of Pb(NO3)2 (1000 mg·L− 1) were prepared and suitably diluted to the required initial concentration. 2.2. Instruments The absorption studies were carried out using Jusco (Japan) UV– Visible spectrophotometer model V-570. The shape and surface morphology of samples were investigated by scanning electron microscope (SEM, VEGA model, TESCAN Company, Czech) under an acceleration voltage of 20 kV. Fourier transform infrared (FTIR) spectra of some of the activated carbon were obtained using a spectrophotometer (Bruker-Germany VBRTEX70). The composition of C, H and N in the activated carbon used as raw material was determined using an elemental analyzer (PE-2400 II, Perkin-Elmer Corp., USA). The BET surface area measurements were obtained from nitrogen adsorption isotherms using a Micrometrics Surface Area Analyzer (Chem BET-3000, Quantachrom C., USA). X-ray diffraction analysis was performed on activated carbon in order to determine the degree of crystalline or amorphous nature of the AC. Analyses were performed by Philips PW1800 X-pert diffractometer using Cu-Kα (=0.15406 Å) radiation source operating under a voltage of 40 kV and a current of 30 mA. The diffraction angle (2θ) was varied from 2.5° to 10°. Experiments were performed on a Perkin Elmer TGA Piers' 1 analyzer. About 10 mg of sample was heated from room temperature to 800 °C at a heating rate of 20 °C/min. in an inert atmosphere of nitrogen. XPS analysis was performed at CEMUP (Centro de Materiais da Universidade do Porto) with a VG Scientific ESCALAB 200A spectrometer utilizing a non-mono- chromatized Mg Ka radiation (1253.6 EV). The vacuum in the analysis chamber has been always, 1310 Pa. The TPD profiles were obtained with a custom built setup, consisting of a U-shaped tubular micro-reactor, placed inside an electrical furnace. The mass flow rate of the helium carrier gas (69 mg·s− 1) and the

483

heating rate of the furnace (5 K·min−1) were controlled with appropriate units. The amounts of CO2 desorbed from the carbon samples (0.1 g) were monitored with a SPECTRAMASS Dataquad quadrupole mass spectrometer. A Boehm method was used for the calculation of the number of acidic and basic groups on the particles' surfaces. This method is based on acid–base titration with NaOH, Na2CO3, NaHCO3, and HCl. The following procedure was used: 0.5 g of the powder and 25 mL of 0.05 M NaOH, Na2CO3, NaHCO3, or HCl solution was agitated for 3 h. In the next step, 5 mL of each filtrate were pipetted and the excess of base or acid was titrated with 0.05 M HCl or NaOH, respectively [18]. 2.3. Preparation of activated carbon Dried raw materials were mixed with H3PO4 solution at the H3PO4/C mass ratios of 1–1 and the mixture was dried at 105 °C for a 12 h. The obtained material was pyrolysed in a stainless steel reactor at a rate of 7 (°C/min) to 600 °C for 2 h and maintained for 100 min under N2 flow protection. After cooling activated carbon was boiled with 200 mL of 10% HCl solution for 60 min, was separated by filtration and washed with water to eliminate the inorganic species and to remove any residual phosphoric acid. Finally activated carbon was then dried in oven at 100 °C for 24 h. During carbonization of the raw material, condensation of polynuclear aromatic compounds and breakage of side chain groups occurs, resulting in a carbon residue. When H3PO4 is mixed with raw material at high temperature, it appears to function both as an acid catalyst to promote bond cleavage reactions and the formation of cross-links via cyclization and condensation processes. During oxidation various hydrophilic surface structures, but more oxygen containing functional groups (carboxylic, lactone and phenol groups) is generated. Also the effect of carbon oxidation and reduction on adsorption of inorganic electrolyte has been showing the acidic groups introduced by oxidation undergo cation exchange with the metal ion, hence acidifies the solution. The acidified solution significantly increases the potential that favors the adsorption of anions. This explains the simultaneous increases in the adsorption of both anions and the cations. This explains the simultaneous increase in the adsorption of both anions and cation. 2.4. Batch adsorption The stock solution of lead was prepared in a flask with an adsorbent concentration of 0.5 g/150 mL; all of the adsorption experiments were carried out at 175 rpm in an orbital shaker. The lead concentration was measured within a time range of 5 to 70 min until equilibrium was reached. The experiments with the adsorption isotherms were conducted in a solution at pH 5.0 with initial lead concentrations ranging from 5–100 (mg·L−1). Investigation of the pH effect was performed within an initial concentration range of 81–100 (mg·L−1) for the lead. The pH of the solution ranged from 2.0 to 12.0. The percentage removal was calculated by using the following equation: %Pb



removal ¼

C0  Ct  100 C0

ð1Þ

where C0 (mg·L−1) and Ct (mg·L− 1) are the initial and final concentrations of lead respectively. The maximum adsorbed amount at equilibrium, (qe (mg·g−1)) was calculated according to Eq. (2): qe ¼ ðC0  Ce Þ

V W

ð2Þ

where Ce (mg·L−1) is equilibrium concentrations, V (L) is the volume of the solution and W (g) is the mass of adsorbent.

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2.5. Effect of interfering ions The effect of foreign ions on Pb(II) adsorption capacity by activated carbon using different ion has been determined. A sample of activated carbon, was added to a mixture of Pb(II) and selected foreign solution (K+, Cl−, Fe2+, Fe3+, Cr3+, Ni2+, Co2+, and Ca2+). 3. Results and discussion 3.1. Characterization of activated carbon Characterization of activated carbon (AC) is very important due to different application of AC. Generally the surface structure of activated carbon has been characterized by physical and chemical properties. Potential extent, carbon, inorganic (i.e. low ash), and volatile content can affect the use of activated carbon. Results of proximate and elemental analyses of the raw material are given in Table 1. The high fixed carbon content and low ash content of the raw sample shows that Persian mesquite grain is suitable for activated carbon production. Ash content reduces the absorptive power of activated carbons and the efficiency of reactivation [19–21]. Also CHNS results show the carbon content of raw materials in the range of 37%, which is lower than the carbon content of activated carbon produced from Persian mesquite grain. Results obtained in this study are close to the earlier studies on C, H, N, O elemental analysis, reporting their concentrations in different agricultural wastes of 43.8–58.30%, 2.6–7.0%, 0.4–6.8%, and 32.05–50.20%, respectively [22–25]. Thermo-gravimetric analysis of the Persian mesquite grain in Fig. 1 revealed that major thermal decomposition occurred around 250– 400 °C. Generally, biomass consists of hemicelluloses, cellulose, lignin and extractives, so initial weight loss in thermo-gravimetric (TGA) curves (58.33 °C) corresponds to moisture removal, followed by a second degradation event around 330 °C, where the evolution of light volatile compounds occurs from the degradation of cellulose and hemicelluloses. Degradation of lignin slowly takes place in a wide temperature range and lasts to higher temperatures. Thermal degradation of these individual components may be superimposed to simulate the overall degradation of the original. Above 600 °C, there was almost no weight loss. On the other hand, the activation temperature of 600 °C was suggested for raw materials from the TG study, since the curve shows a straight line, which means a stable state. Therefore, no remains could be found at the heating temperature of 600 °C. XRD patterns of the raw material and activated carbon in Fig. 2 reveal the amorphous structure of all two samples. The amorphous structure of raw material and activated carbon is explained by the rupture of multiple C\\C bonds (mainly those of the aromatic rings) on the surface during the preparation. So activated carbon, relatively known as amorphous carbon, shows a very disordered microcrystalline

Fig. 1. (- - - -) TG and (—) DTG curves of raw material used in the present study.

structure due to random translation and rotation of layer planes along the c-axis. The interlayer spacing in this structure is larger than the spacing in a graphite single crystal [26]. However, a slight significant difference was observed to be associated with the XRD profiles. Also activated carbon presents higher intensity of diffraction peaks. The differences in the XRD patterns are caused by the lowering of crystallites of the AC, during the activation process. Generally, the adsorption capacity is related to the specific surface area and pore volume of the adsorbents. The most widely used commercial activated carbons have a specific surface area between 600 and 1200 (m2·g−1). The pore volume and surface area affect the size and the amount of the adsorbed molecules respectively [27]. Porous structure parameters (The BET surface area, total pore volume, and average pore diameter) of prepared activated carbon are listed in Table 1. The results show that presented AC has a high surface area (1253 m2·g− 1) and porous structure, which is favorable for the adsorption. As can be seen from Table 1 and Fig. 3, both micropore (b2 nm) and mesopore (2–50 nm) structures are present in the AC. Different surface area values and distribution of pores for lignocelluloses' materials have been reported in the literature. The difference between surface area values is due to the differences in the type of starting materials and activation method. As an example the activated carbons obtained from pine sawdust using H3PO4 had a surface area ranging from 1559 to 1767 (m2·g−1) [28] while that obtained from eucalyptus bark [29] pecan shell [30] woody biomass birch [31] olive mill waste [32], flax [33] and chestnut wood [34] using H3PO4 had a surface area of 1239, 1130, 761, 336, 1290 and 783 (m2·g− 1), respectively. On the other hand, the activated carbons obtained from macadamia nut shell [35] and wood [36] using ZnCl2 had a surface

Table 1 Physicochemical analysis of studying activated carbon. Proximate and elemental analysis Elemental analysis

Proximate analysis

Raw material

Activated carbon

C N

37.65 0.57

H O

4.36 57.42

Moisture Volatile matter Fixed carbon Ash

2.60 36.27 56.33 4.80

Porous structure parameters Adsorbent

Vt (m3/g)

Vmicr (m3/g)

Vmeso (m3/g)

SBET (m2/g)

Smeso (m2/g)

Smicr (m2/g)

Average pore diameter (nm)

AC

0.651

0.410714

0.240286

1243

420

823

0.53

E.G. Lemraski, S. Sharafinia / Journal of Molecular Liquids 219 (2016) 482–492

485

Fig. 2. XRD spectra of the raw material and activated carbon.

area of 1718 and (14–1700 m2·g−1), respectively, while that obtained from olive kernels [37], bamboo-derived granular activated carbon [38], using KOH had a surface area of 3049, and 3000 (m2·g−1). The differences between the results of this study and other studies were due to the differences in the type of starting materials and activation methods. Fig. 3 shows the pore size distribution calculated by the means of the original density functional theory by N2 adsorption data. The maximum incremental surface area and pore volume were observed at a pore width of 1–1.5 nm (micropore range of pore width). From this result it was deduced that the obtained activated carbon is composed of mostly micropores. The representative microscopy images of the raw material and activated carbon are given in Figs. 4. The SEM image shows the homogeneous and relatively smooth surface of the activated carbon. Fig. 4b also indicates the AC surface appears to be more damaging with many cavities, indicating the development of pore structure after the activation process. Most of the pores were enlarged to the range of 10–20 μm. These big pores were favorable for the diffusion of big molecules into the activated carbon. It is known that phosphoric acid causes chemical changes in the precursor facilitating formation of activated carbon at lower temperatures. Phosphoric acid is the most widely used chemical agents for dehydration of lingocellulosic materials at lower temperatures. H3PO4 has two important functions—it accelerates the cleavage of bonds between biopolymers (principally cellulose and lignin), followed by formation of phosphate linkages between the fragments in the biopolymer pyrolytic [39]. FT-IR spectrum analysis was used to investigate variations in the functional groups of the adsorbent. FT-IR spectra for the activated carbon before and after Pb2 + adsorption are presented in Fig. 5. The

Fig. 3. Pore size distribution of AC.

Fig. 4. SEM images of (a) raw material and (b) activated carbon.

Fig. 5. FT-IR spectra of activated carbon before (Red line) and after (blue line) Pb adsorption.

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Table 2 Results of surface chemistry analysis using FT-IR, Boehm method, XPS and TPD methods. FT-IR results Functional group

Present work

Reference wave number

Ref.

Carboxylic acid C_O (stretching) O\ \H Quinones

1719 3471 1610

1720 3500 1550–1680

[40] [41] [42]

Phenolic groups C\ \OH (stretching) O\ \H (alcohol/phenol O\ \H stretch) Lactones (C\ \O stretching) Ketones (C_O stretching) Ethers (C\ \O stretching) O\ \H (stretching)

1040 3471 1719 1508 1389 3709

1000–1220 3500 1720 1570 1100–1400 3200–3600

[42] [41] [40] [43] [44] [43]

Boehm titration Basic content (mmol/g) AC

0.82

Ev

C (1 s)

O (1 s)

284.4 285.2 286 287.1 288.5 531.1 532.2 533.3 534.2 535.9

Fig. 7. TPD curve for the activated carbon.

Acidic content (mmol/g) Phenolic Carboxylic Lactonic

0.74 0.03 0.37

1.14

XPS analysis (%)

(CO2) TPD results (μmol g−1)

Functional group

Temperatures (°C)

Group decomposed

C_C C (aliphatic) C\ \OH; C\ \O\ \C C_O COOH; COOC C_O C\ \OH; C\ \O\ \C COOCO COOH Adsorbed H2O

100–400 200–400 400–600

Carboxylic Lactone Anhydride

31.2 25.3 14.9 8.9

FT-IR spectrum of activated carbon in Fig. 5 showed adsorption peaks around 3000–3700 cm−1, which is indicative of the existence of bonded hydroxyl groups. The peak around 1300 cm−1 is due to the C\\C. The peak observed at 1610 cm− 1 is due to C_N and the peak around 1508 cm−1 can be assigned to the pyridine-like groups. These results have been show various surface functional groups include aromatic C_C stretching, carboxylic acid, lactone, ether bridge, quinine; phenol, and alcohol compounds on activated carbon. These surface functional groups play a key role in the surface chemistry of activated carbon and especially in the adsorption of reagents. As can be observed, the activated carbon spectrum after adsorption of Pb2+ exhibited lower absorption bands than did the activated carbon spectrum after adsorption,

Fig. 6. C1s and O1s XPS spectra of activated carbon.

mainly at 2927, 1719, 1610, 1508 and 1040 cm−1, indicating that van der Waals and electrostatic interaction between Pb2 + and surface functional group special carboxylic group. FTIR spectroscopy studies also showed that the adsorption bands of AC at 3746, 3071, 1738, 1511, 1390 and 1048 cm−1 before adsorbing Pb(II) had respectively shifted 3740, 3065, 1719, 1508,1389 and 1040 cm−1 to after adsorbing Pb(II), which indicated that AC had adsorbed Pb(II). These suggested that AC could be used as a potential and appealing adsorbent for the removal of Pb (II) from aqueous solutions. Some FT-IR assignments of functional groups on carbon surface were listed in Table 2. In the present work total acidity and basicity, of adsorbent were characterized using pH at the zero charge point and Boehm titration. Value of pHpzc 3.73 showed predominance of acidic groups on AC surface, which have been reported as being the carboxylic, lactonic, and phenolic groups. Generally oxidations in the liquid phase increase, especially the concentration of carboxylic acids as oxygen-surface functional groups. The results obtained through the Boehm titration in Table 2 showed that AC approximately contain 0.8 mmol·g−1 of basic group and 0.94 mmol·g−1 of the acid group. The acid groups are due to lactonic (0.37 mmol·g−1), phenolic (0.74 mmol·g−1) and carboxylic group (0.03 mmol·g−1). To assess the chemistry of the surface layers, the AC under this study were analyzed by XPS and the O (1 s) and C (1 s) spectra were obtained (see Fig. 6). The O (1 s) and C (1 s) spectra were convoluted according to the experimental procedure and quantified functional groups are summarized in Table 2 [45–47]. TPD analyses were carried out to quantify the oxygen functional groups present in the AC (see Table 2). The CO2 profiles in Fig. 7

Fig. 8. Effect of solution pH on the removal of lead on AC.

E.G. Lemraski, S. Sharafinia / Journal of Molecular Liquids 219 (2016) 482–492

487

Fig. 11. Effect of initial concentration on the removal of lead on AC. Fig. 9. Effect of contact time on the removal of lead on AC.

shows a first maximum in the temperature 239.7 °C, which is very likely due to the decomposition of carboxylic groups and the second maximum appears in 653.051 °C, which originates from the more stable anhydrides or lactone groups [48]. Comparing the results obtained by Boehm titration, XPS and TPD, have been showing a good agreement for the kind of surface oxygen functional group of activated carbon. On the other hand, no apparent agreement was found between the quantitative results obtained by XPS, TPD and Boehm methods, due to the limitations of the Boehm titration method and the presence of porosity. However, this method cannot assess the other acidic and neutral groups and the presence of porosity could reduce the solvent-accessible surface [49].

explained based on the point of zero charge (PZC). It was clearly observed that the removal percentage decreased as the pH value of solution came close to alkaline conditions. The decrease in signal at pH b 6 may be due to competition of hydronium ion toward complexation with activated carbon surface functional groups, in an acidic solution the protonation of activated carbon occurs and there is a weak tendency for reaction between Pb2+ and AC, which leads to the decrease in the adsorption yield.

3.2.1. Effect of pH The initial pH has a distinct role in the chemistry of lead, the surface charge of adsorbent, electrostatic interaction, hydrogen bonding formation, electron donor-acceptor, and π-π dispersion interactions in solution [9]. The effect of initial pH was studied under acidity and alkaline conditions and results are shown in Fig. 8. The plots in Fig. 8 confirm that adsorption of Pb2 + are strongly influenced by pH, which is

3.2.2. Effect of contact time Equilibrium time is one of the most important parameters in the evaluation of adsorption efficiency. Rapid uptake and quick establishment of equilibrium time imply the efficiency of a particular adsorbent in wastewater treatment. The kinetic of lead adsorption onto activated carbon in Fig. 9 show the extent of adsorption is rapid during the initial stages, becoming slow during the later stages until saturation is achieved. It was found that N97% of Pb2+ removal occurred in the first 40 min at initial time or the equilibrium can be assumed to be achieved after 40 min. Equilibrium being basically due to the saturation of the active site and slow pore diffusion, at which time further adsorption cannot take place [50,51]. Rapid uptake and quick establishment of equilibrium time imply the efficiency of prepared activated carbon as a good adsorbent in terms of usage in wastewater treatment.

Fig. 10. Effect of adsorbent dose on the removal of lead on AC.

Fig. 12. Regeneration yield of lead at different time using (♦)HNO3; and (●)HCl.

3.2. Adsorption of lead onto activated carbon

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E.G. Lemraski, S. Sharafinia / Journal of Molecular Liquids 219 (2016) 482–492 Table 3 Isotherm constant and correlation coefficients calculated for Pb2+ adsorption. Isotherm

Parameters

Pb2+

Exp.

Langmuir

Qm (mg/g) Ka (L·mg−1) R2 1/n Kf (L·mg−1) R2 B1 KT (L·mg−1) R2

270.27 0.05918 0.9958 1.71 11.58 0.8355 189.65 0.27 0.904

273.30

Freundlich

Temkin

Fig. 13. Reusability of AC by adsorption–desorption process for 9 consecutive cycles in the presence of HCl.

3.2.3. Effect of adsorbent dose The adsorbent dose is an important parameter in adsorption studies because it determines the capacity of adsorbent for a given initial concentration. The effect of the adsorbent dose on the removal of the Pb2+ was studied by varying the adsorbent amount between 0.01 and 0.25 g for activated carbon at fixed times, pH values, temperatures, and initial concentrations, and results presented in Fig. 10. It was observed that the removal percentage increased rapidly at first with the increase in adsorbent dose till 0.1 g and after the critical dose the removal percentage almost reached a constant value. This can be attributed to increase the adsorbent surface area and availability of more adsorption sites with the increasing dosage of the adsorbent, while the adsorption density of lead decreased when the adsorbent dosage was increased [52].

3.2.4. Effect of initial lead concentration and adsorption isotherms It is worth to compare the effect of the initial lead concentration on the adsorption process onto activated carbon. The results in Fig.11 show the amount of adsorption increased for lead when the initial concentration was changed from 6 to 96 (mg·L−1). The single, smooth, and continuous curve of these compounds can be ascribed to the S2

type, according to the Giles classification scheme [53]. This type of curve is typical for microporous sorbents and was observed with monolayer sorption of microporous activated carbon. Activated carbon is an excellent adsorbent for most metal ions due to the special surface area and the various surface functional groups (containing oxygen, nitrogen, and other heteroatoms). Adsorption isotherms represent the amount of material bound at the surface (the sorbate) as a function of the material present in the gas phase and/or in the solution. In the present work, the Langmuir [54], Freundlich [55], and Temkin isotherms [56] were used to analyze the experimental equilibrium data. The Langmuir isotherm was developed by Irving Langmuir in 1916 to describe the pressure dependence to surface coverage and gas pressure at a fixed temperature. The linear form of this model is presented as follows: Ce 1 Ce ¼ þ qe K L Q m Q m

ð3Þ

where KL is the Langmuir adsorption constant (L·mg−1) and Qm is the theoretical maximum adsorption capacity (mg·g−1). These parameters were obtained from slope and intercept of a linear plot of (Ce/qe) vs. Ce. The correlation coefficient (R2) of 0.99 indicates that this isotherm is suitable for adsorption prediction. Theoretical maximum adsorption capacity in Table 3 is near the experimental adsorbed amounts and corresponds closely to the adsorption isotherm plateau, which indicates that the modeling of Langmuir for the adsorption system is acceptable. The values of adsorption capacity and correlation coefficient show the AC had a high adsorption capacity of 273 (mg·g−1) for Pb2 + as compared to some data obtained from the literature (see Table 4). Generally, the adsorption capacity of activated carbon depends on different factors: the surface chemistry (surface functional groups), the texture (surface area, pore size distribution) and its ash content. The prepared activated carbon exhibited the maximum adsorbed amount much higher than other reported granular, powdered and nano sized activated carbons. According to the authors, the complexing of lead with metals present in the adsorbents is primarily responsible

Table 4 Maximum adsorption capacity (Qm) of Pb2+ and the surface area of different adsorbents found in the literature.

Fig. 14. Reusability of AC by adsorption–desorption process for 9 consecutive cycles in the presence of HNO3.

Materials

Qm (mg/g)

Ref.

(AC) Persian mesquite grain (AC) Euphorbia rigida (AC) Tamarind wood Fe3O4 MNPs Dry P. chrysosporium Palm shell (AC) coconut shells Activated periwinkle shell carbon AC Eichhornia AC marine green alga

384 279.72 43.85 36 69.77 95.2 43.1 0.0558 16.61 22.93

Present study [57] [58] [59] [60] [61] [62] [63] [64] [65]



E.G. Lemraski, S. Sharafinia / Journal of Molecular Liquids 219 (2016) 482–492

Table 3 summarizes the Langmuir, Freundlich and Temkin isotherms parameters, and correlation coefficients (R2). According to these parameters, the Langmuir model fitted the experimental data best by linear analysis, while the Freundlich fitted worst. Thus the adsorption equilibrium of lead on AC can be more effectively described with Langmuir model than Freundlich and monolayer surface adsorption occurs on specific homogeneous sites.

Table 5 Adsorption kinetic parameters for Pb2+ adsorption onto activated carbon. Model

Parameter

Pb2+

First-order

qe (cal.) k1 × 10−3 (L·min−1) R2 qe (cal.) k2 × 10−3 (L·min−1) R2 b a R2 Kdif (L·min−1) C R2 qe (EXP.) Qm,Exp.

2.85 2.41 0.87 277.77 1.3616 0.9998 0.18 7.91 × 1017 0.9617 2.83 222.1 0.9942 278.33 273.30

Second-order

Elovich

Intraparticle

3.2.5. Adsorption kinetics Adsorption kinetics governs the solute uptake rate, measures the adsorption efficiency of the adsorbent, and determines its applicability for explaining the experimental data. Firstly, the adsorption rate of the sorbents was analyzed using Lagergren's first-order rate equation in linear form as follows [66]: logðqe  qt Þ ¼ logðqe Þ 

for their high Qm [65]. The K parameter is also evaluated from the Langmuir equation is equilibrium constant that visualizes the affinity of the solute toward the adsorbent surface. The Freundlich isotherm based on the well-known assumption for lead adsorption on heterogeneous surfaces can be expressed in the linear form as follows: logqe ¼ logK f þ

1 logCe n

ð4Þ

where n is the Freundlich constant related to adsorption intensity (which indicates how favorable the process is) and Kf is the Freundlich constant related to the relative adsorption capacity of the adsorbent when the adsorption process is physical (n N 1), chemical (n b 1), or linear (n = 1). The ratio 1/n provides information related to the surface heterogeneity. In the current study, the 1/n value was 1.71 for activated carbon, indicating that activated carbon has a low degree of heterogeneity. The values of Kf and 1/n were extrapolated from the intercept and slope of plot of ln qe versus ln Ce. In a similar manner, the Temkin and Pyzhev isotherm, in terms of a dimensionless binding energy (KT), may be presented as follows qe ¼ B1 ln K T þ B1 ln Ce :

489

ð5Þ

This isotherm takes into account the indirect adsorbate–adsorbate interactions on adsorption isotherms. In Eq. (5), KT is the binding energy of adsorbent and adsorbate, B1 (=RT/b) is the heat of adsorption, T is the absolute temperature in Kelvin, and R is the universal gas constant (8.314 J/K·mol). In exothermic and endothermic adsorption reactions, the value of B1 is higher and lower than unity, respectively. Values of B1 and KT were calculated from the plot of qe against ln Ce (see Table 3). Temkin model didn't show suitable R2 value (0.90), indicating that this model was fitted to experimental data. The reported value of B1 in Table 3 indicates that the adsorption reaction of lead onto activated carbon occurs exothermically in the concentration range studied. This fact suggests that there is an electrostatic interaction and the heterogeneity of pores on activated carbon surface plays a significant role in the adsorption of lead.

k1 2:303 t

ð6Þ

where qe and qt are adsorption capacity at equilibrium and at time t, respectively; and k1 is the rate constant of pseudo first-order adsorption (min− 1). Values of k1 and qe can be determined from the slope and intercept of the plot of log (qe − qt) versus t, respectively. The data in Table 5 show the pseudo first-order adsorption rates were not suitable to describe the experimental data, considering the range of values for R2 (0.94,0.99) and the fact that the greatest gap appeared between the experimental and theoretical qe values. The pseudo second-order model [52] with well-known Eq. (7) was tested to analyze and evaluate the efficiency of experimental data. t 1 1 ¼ þ qt k2 q2e qe ðt Þ

ð7Þ

where k2 is the equilibrium rate constant of pseudo second-order adsorption (g·mg−1·min−1). In the pseudo second-order model, the rate-limiting step is the surface adsorption that involves chemisorption, where the removal from the solution is due to physicochemical interactions between the two phases. The experimental kinetic data were adjusted according to the indicated model. The results of R2, k2, and qe in Table 5 showed that the pseudo second-order model provided the best correlation with experimental results. The calculated adsorption capacity is also near the experimental adsorbed amount which indicates that the pseudo second-order model for the adsorption system is acceptable. The Elovich equation was developed to describe adsorption capacity and is generally expressed as linear form: qt ¼

1 1 ln ðαβÞ þ ln ðt Þ β β

ð8Þ

where qt is the amount of adsorbed lead by adsorbent at a time t, α is the initial lead adsorption rate (mg·g−1·min−1) and β is desorption constant (g·mg−1) during any one experiment. The general explanations for this form of kinetic equation involve variations of chemisorption energy, in which the active sites are heterogeneous in the adsorbent. This supports that the heterogeneous sorption mechanism is likely responsible for uptake of the lead. The Elovich model basically

Table 6 Thermodynamic parameters for the adsorption of lead onto AC. Adsorbate

Parameter

AC

Kc ΔG° (kJ/mol) ΔH° (kJ/mol) ΔS° (kJ/mol)

Temperature (K) 293.15

298.15

303.15

308.15

313.15

381.7797 −14.4800 −0.82 −0.0458

464.7959 −15.2100

512.3100 −15.7100

500.5400 −15.9100

500.6200 16.1700

490

E.G. Lemraski, S. Sharafinia / Journal of Molecular Liquids 219 (2016) 482–492

In general, the kinetics of Pb2+ adsorption onto activated were best described by the pseudo second-order model based on the correlation coefficient values for all three equations.

Table 7 Effect of foreign ions on the metal capacity values of lead. mg·g−1 capacity of lead in presence of interfering species Pb2+ K+ Cr3+ Fe+2 Fe+3 Ni2+ Cl+ Ca2+ CO2+

150.1 149.6 151.8 109.6 139.6 139.6 139.0 131.8 140.7

3.3. Adsorption thermodynamics The adsorption thermodynamic parameter, i.e., Gibbs free energy change for adsorption, was calculated using the following equation: 

ΔG ¼ RT ln K c

supports chemisorption; the Elovich plots of qt versus ln(t) yield a linear relationship. The reported parameters in Table 5 show the lack of success for the Elovich model. The last applied alternative kinetic model in this study is intraparticle diffusion model [51]. The intraparticle diffusion model describes adsorption processes based on sorbate diffuses toward adsorbent (i.e., the process is diffusion controlled), as depicted by Eq. (9):

where R is the universal gas constant (8.314 J mol− 1 K− 1), T is the temperature (K), and Kc is the equilibrium constant. Values of Kc may be calculated from the relation ln qe/Ce versus qe at different temperatures and extrapolated to zero. The calculated thermodynamic parameters are listed in Table 6. The negative ΔG° values confirm the spontaneous nature and feasibility of the adsorption process. The standard entropy and enthalpy change for adsorption can be calculated from the slope and intercept of lnK° vs. 1/T by using the Van't Hoff equation. 

ln K ¼ qt ¼ K dif t 1=2 þ C:

ð9Þ

The calculated values of Kdif and C from the slope and intercept of qt versus t1/2 are reported in Table 5. Intraparticle diffusion is the sole ratelimiting step, when the plot of qt versus t1/2 passes through the origin and the value of C (in this case) is equal to zero. This phenomenon shows that the intraparticle diffusion model may be the controlling factor in determining the adsorption kinetics. The distance of R2 values (Table 5) from unity for adsorption of lead on AC indicates the nonapplicability of this model that rejects the rate-limiting step in the intraparticle diffusion process. As already mentioned, the adsorption mechanism for any lead removal by an adsorption process may be assumed to involve the following four steps: (i) bulk diffusion; (ii) film diffusion; (iii) pore diffusion or intraparticle diffusion; (iv) adsorption of lead on the adsorbent surface [50]. Previous studies showed that such plots may present a multi-linearity [67], indicating the occurrence of two or more steps. The first, sharper portion is the external surface adsorption or instantaneous adsorption stage. The second portion is the gradual adsorption stage, in which the intraparticle diffusion is rate-controlled. The third portion is the final equilibrium stage, during which the intraparticle diffusion starts to slow down due to extremely low solute concentrations in the solution.

ð10Þ

ΔS R



! 

ΔH RT



! :

ð11Þ

The negative value of ΔH° reflects exothermic adsorption of lead on to adsorbents, while the negative value of (ΔS°) indicate a decrease in the degree of freedom (or disorder) of the adsorbed species. 3.4. The effect of foreign ions Evaluation of the possible interference of foreign ions was performed on the basis of equimolar concentration of lead nitrate versus other interfering species. The determined metal capacity values of lead in the presence of these interfering anions and cations are listed in Table 7 along with those determined for lead capacity. The existence of K+ and Cr3 + was characterized by low or no interfering effect in the sorption processes of lead by activated carbon. Fe2+ was found to show the high interfering impact on the process of lead adsorption by activated carbon. Other ions were found to exhibit low interfering effect owing to the determined metal capacity values of lead. 3.5. Regeneration studies The reusability of prepared activated carbon was tested for consecutive 9 cycles using HNO3 and HCl solution (see Figs. 12–14). The regeneration yield is found to be really the same for HNO3 and HCl

Table 8 Physicochemical analysis of activated carbon in the present work and commercial activated. Property

Activated carbon type

Mean

SD

t

df

pHpzc

Persian mesquite grain Commercial activated carbon Persian mesquite grain Commercial activated carbon Persian mesquite grain Commercial activated carbon Persian mesquite grain Commercial activated carbon Persian mesquite grain Commercial activated carbon Persian mesquite grain Commercial activated carbon Persian mesquite grain Commercial activated carbon Persian mesquite grain Commercial activated carbon

3.73 7.00 2.60 16.67 4.80 17.10 36.27 37.32 0.03 0.12 0.37 0.27 0.74 0.61 0.83 0.82

0.03 0.01 0.05 0.02 0.02 0.10 0.01 2.02 0.05 0.02 0.03 0.02 0.02 0.03 0.01 0.02

151.35

2.27

Significant

261.27

14.07

Significant

120.61

12.30

Significant

0.52

1.05

No significant

1.67

0.09

Significant

2.77

0.10

Significant

3.61

0.13

Significant

0.45

0.01

Significant

Moisture % Ash % Volatile matter% Carboxylic Phenol Lactones Basic

E.G. Lemraski, S. Sharafinia / Journal of Molecular Liquids 219 (2016) 482–492

solution. In these cases, the regeneration yield is larger than 70% and complete desorption of the loaded lead in 1 h could be achieved. Though the %removal decreased per cycle, the pronounced decrease was observed only after the 5th cycle, suggesting the uninhibited efficiency of the adsorbents for a very long time and a very high concentration of the solute. On the other hands the higher regeneration yield is found for HCl solution. 3.6. t-Test analyses The surface properties of present activated carbon were compared with commercial activated carbon using statistical t-test analyses [68]. From Table 8, texp b DF (degree of freedom value) was found for the carboxylic and phenol content of the activated carbon. This shows that there is no significant difference between the mean values of the carboxylic and phenol content of the activated carbon samples derived from Persian Mesquite Grain and commercial activated carbon. There is a significant difference in the properties of moisture, ash content, iodine number, lactones content, pHpzc and basic sites content of the activated carbons. In spite of the significant differences that existed for most of the surface properties between the commercial and the Persian Mesquite Grain activated carbon, the activated carbons were very efficient and effective in the removal of Pb2+ from solution, indicating that though surface properties of adsorbents play significant role in sorption, such properties also depends on the method and conditions of activation, which may therefore not be the sole determining factor for adsorption as illustrated in this study. 4. Conclusion Persian mesquite grain has been effectively used as a new raw material for the preparation of activated carbon with high-surface area and adsorption capacity. The thermodynamic parameters indicated a spontaneous and exothermic adsorption. The kinetic model analyses revealed that the experimental data were well fitted to the pseudosecond-order model. Desorption of Pb2 + could be totally carried out using nitric acid and Hydrochloric acid. Fe2 + was found to show the high interfering impact on the process of lead adsorption by activated carbon. Due to the high adsorption capacity and regeneration capability the present activated carbon could be successfully used as an excellent adsorbent in water purification. Acknowledgements The authors are grateful for the financial support (Grant number: 32/ 1012) from the Research Councils of Ilam University. References [1] M.M. Vukcevic, A.M. Kalijadis, T.M. Vasiljevic, B.M. abic, Z.V. Lausevic, M.D. Lausevic, Production of activated carbon derived from waste hemp (Cannabis sativa) fibers and its performance in pesticide adsorption, Microporous Mesoporous Mater. 214 (2015) 156–165. [2] T. Aysu, M.M. Kucuk, Removal of crystal violet and methylene blue from aqueous solutions by activated carbon prepared from Ferula orientalis, Int. J. Environ. Sci. Technol. 12 (2015) 2273–2284. [3] Z. Wang, Efficient adsorption of dibutyl phthalate from aqueous solution by activated carbon developed from phoenix leaves, Int. J. Environ. Sci. Technol. 12 (2015) 1923–1932. [4] A.A. El-Hendawy, A.J. Alexander, R.J. Andrews, G. Forrest, Effects of activation schemes on porous, surface and thermal properties of activated carbons prepared from cotton stalks, J. Anal. Appl. Pyrolysis 82 (2008) 272–278. [5] P. Manoj Kumar Reddy, K. Krushnamurty, S.K. Mahammadunnisa, A. Dayamani, C.H. Subrahmanyam, Preparation of activated carbons from bio-waste: effect of surface functional groups on methylene blue adsorption, Int. J. Environ. Sci. Technol. 12 (2015) 1363–1372. [6] F.C. Wu, R.L. Tseng, R.S. Juang, Preparation of highly microporous carbons from fir wood by KOH activation for adsorption of dyes and phenols from water, Sep. Purif. Technol. 47 (2005) 10–19.

491

[7] L. Largitte, T. Brudey, T. Tant, P. Couespel Dumesnil, P. Lodewyckx, Comparison of the adsorption of lead by activated carbons from three lignocellulosic precursors, Microporous Mesoporous Mater. 219 (2016) 265–275. [8] R. Ubago-Perez, F. Carrasco-Marin, D. Fairen-Jimenez, C. Moreno-Castilla, Granular and monolithic activated carbons from KOH-activation of olive stones, Microporous Mesoporous Mater. 92 (2006) 64–70. [9] A.M.M. Vargas, C.A. Garcia, E.M. Reis, E. Lenzi, W.F. Costa, V.C. Almeida, NaOH activated carbon from flamboyant (Delonix regia) pods: optimization of preparation conditions using central composite rotatable design, Chem. Eng. J. 162 (2010) 43–50. [10] G.E.J. Poinern, G. Senanayake, N. Shah, X. Thi-Le, G.M. Parkinson, D. Fawcett, Adsorption of the aurocyanide, Au(CN)2–complex on granular activated carbons derived from macadamia nut shells — a preliminary study, Miner. Eng. 24 (2011) 1694–1702. [11] U. Zielke, K.J. Huttinger, W.P. Hoffman, Surface-oxidized carbon fibers: I. Surface structure and chemistry, Carbon 34 (1996) 983–998. [12] J.L. Falconer, J.A. Schwarz, Temperature-programmed desorption and reaction: applications to supported catalysts, Catal. Rev. Sci. Eng. 25 (1983) 141–227. [13] H.P. Boehm, Some aspects of the surface chemistry of carbon blacks and other carbons, Carbon 32 (1994) 759–769. [14] A. Behbahaninia, S.A. Mirbagheri, J. Nouri, Effects of sludge from wastewater treatment plants on heavy metals transport to soils and groundwater, J. Environ. Health Sci. Eng. 7 (2010) 401–406. [15] A. Jafarian-Dehkordi, M. Alehashem, Heavy metal contamination of vegetables in Isfahan, Iran, Res. Pharm. Sci. 8 (2013) 51–58. [16] P. Karrari, O. Mehrpour, M. Abdollahi, A systematic review on status of lead pollution and toxicity in Iran; guidance for preventive measures, Daru 20 (2012) 2. [17] M. Ahmedna, W.E. Marshall, A.A. Husseiny, R.M. Rao, I. Goktepe, The use of nutshell carbons in drinking water filters for removal of trace metals, Water Res. 38 (2004) 1062–1068. [18] M.V. Lopez-Ramon, F. Stoeckli, C. Moreno-Castilla, F. Maring-Carrasco, On the characterization of acidic and basic surface sites on carbons by various techniques, Carbon 37 (1999) 1215–1221. [19] S. Rengarag, B. Arabindoo, V. Murugesan, Activated carbon from rubber seed and palm seed coat, preparation and characterization, J. Sci. Ind. Res. 57 (1996) 129–132. [20] S. Rengarag, M. Seung-Hyeon, S. Sivabalan, B. Arabindoo, V. Murugesan, Agricultural solid waste for the removal of organics: adsorption of phenol from water and wastewater by palm seed coat activated carbon, Waste Manag. 22 (2002) 543–548. [21] T. Yang, A.C. Lua, Characteristics of activated carbons prepared from pistachio-nut shells by potassium hydroxide activation, Microporous Mesoporous Mater. 63 (2003) 113–124. [22] M.M. Rao, G.P.C. Rao, K. Seshaiah, N.V. Choudary, M.C. Wang, Activated carbon from Ceiba pentandra hulls, an agricultural waste, as an adsorbent in the removal of lead and zinc from aqueous solutions, Waste Manag. 28 (2007) 849–858. [23] A.J. Tsamba, W. Yang, W. Blasiak, Pyrolysis characteristics and global kinetic of coconut and cashew nut shells, Fuel Process. Technol. 87 (2006) 523–530. [24] S. Srikanth, K. Das, B. Ravikumar, D.S. Rao, K. Nandakumar, P. Vijayan, Nature of fire deposits in a bagasse and groundnut shell fire 20 mw thermal boiler, Biomass Bioenergy 75 (2004) 273–384. [25] S. Timura, I. Cem Kantarlib, S. Onenca, J. Yanika, Characterization and application of activated carbon produced from oak cups pulp, J. Anal. Appl. Pyrolysis 89 (2010) 129–136. [26] V. Gomez-Serrano, E.M. Cuerda–Correa, M.C. Fernandez-Gonzalez, Preparation of activated carbons from chestnut wood by phosphoric acid - chemical activation: study of microporosity and fractal dimension, Mater. Lett. 59 (2005) 846–853. [27] R.B. Lartley, F. Acquah, Developing national capability for manufacture of activated carbon from agricultural waste, Ghana Eng. (1999) 5. [28] Y. Munoz, R. Arriagada, G. Soto-Garrido, R. Garcia, Phosphoric and boric acid activation of pine sawdust, J. Chem. Technol. Biotechnol. 78 (2003) 1252–1258. [29] P. Patnukao, P. Pavasant, Activated carbon from Eucalyptus camaldulensis Dehn bark using phosphoric acid activation, Bioresour. Technol. 99 (2008) 8540–8543. [30] Y. Guo, D.A. Rockstraw, Physicochemical properties of carbons prepared from pecan shell by phosphoric acid activation, Bioresour. Technol. 98 (2007) 1513–1521. [31] A.C. Lua, T. Yang, Effect of activation temperature on the textural and chemical properties of potassium hydroxide activated carbon prepared from pistachio-nut shell, J. Colloid Interface Sci. 274 (2004) 594–601. [32] C. Moreno-Castilla, F. Carrasco-Marin, M.V. Lopez-Ramon, M.A. Alverez-Merino, Chemical and physical activation of olive-mill waste water to produce activated carbon, Carbon 39 (2001) 1415–1420. [33] P.T. Williams, A.R.J. Reed, High grade activated carbon matting derived from the chemical activation and pyrolysis of natural fiber textile waste, Anal. Appl. Pyrol. 71 (2004) 971–986. [34] T. Budinova, E. Ekinci, F. Yardim, A. Grimm, E. Björnbom, V. Minkova, M. Goranova, Characterization and application of activated carbon produced by H3PO4 and water vapor activation, Fuel Process. Technol. 87 (2006) 899–905. [35] A. Ahmadpour, D.D. Do, The preparation of activated carbon from macadamia nutshell by chemical activation, Carbon 37 (1997) 1723–1732. [36] C. Hu, J. Zhou, S. He, Z. Luo, K. Cen, Effect of chemical activation of an activated carbon using zinc chloride on elemental mercury adsorption, Fuel Process. Technol. 90 (2009) 812–817. [37] S. Rengaraj, Y. Kim, C.K. Joo, J. Yi, Removal of copper from aqueous solution by aminated and protonated meso porous alumina. Kinetics and equilibrium, J. Colloid Interface Sci. 273 (2004) 14–21. [38] S. Denga, Y. Niea, Z. Dua, Q. Huanga, P. Menga, B. Wanga, J. Huanga, G. Yua, Enhanced adsorption of perfluorooctane sulfonate and perfluorooctanoate by bamboo-derived granular activated carbon, J. Hazard. Mater. 282 (2015) 150–157.

492

E.G. Lemraski, S. Sharafinia / Journal of Molecular Liquids 219 (2016) 482–492

[39] W. Li, J. Peng, L. Zhang, H. Xia, N. Li, K. Yang, X. Zhu, Investigations on carbonization processes of plain tobacco stems and H3PO4-impregnated tobacco stems used for the preparation of activated carbons with H3PO4 activation, Ind. Crop. Prod. 28 (2008) 73–80. [40] J. Kazmierczak, S. Biniak, A. Swiatkowski, H. Radeke, The case of the basic groups, characterized by their HCl, J. Chem. Soc. Faraday Trans. 87 (1991) 3557–3561. [41] A.E. Vasu, Surface modification of activated carbon for enhancement of Nickel(II) adsorption, E. J. Chem. 5 (2008) 814–819. [42] P.E. Fanning, M.A. Vannice, A drifts study of the formation of surface groups on carbon by oxidation, Carbon 31 (1993) 721–730. [43] S. Biniak, G. Szymanski, J. Siedlewski, A. Swiatkowski, The characterization of activated carbons with oxygen and nitrogen surface groups, Carbon 35 (1997) 1799–1810. [44] J.B. Lambert, H.F. Shurvell, L. Verbit, R.G. Cooks, G.H. Stout, Organic Structural Analysis, Macmillan, New York, 1976. [45] J.L. Figueiredo, M.F.R. Pereira, The role of surface chemistry in catalysis with carbons, Catal. Today 150 (2010) 2–7. [46] A. Rey, M. Faraldos, A. Bahamonde, J.A. Casas, J.A. Zazo, J.J. Rodriguez, Role of the activated carbon surface on catalytic wet peroxide oxidation, Ind. Eng. Chem. Res. 7 (2008) 8166–8174. [47] C. Moreno-Castilla, Adsorption of organic molecules from aqueous solutions on carbon materials, Carbon 42 (2004) 83–94. [48] M. Saleh Shafeeyan, W. Mohd Ashri Wan Daud, A. Houshmand, A. Shamiri, A review on surface modification of activated carbon for carbon dioxide adsorption, J. Anal. Appl. Pyrolysis 89 (2010) 143–151. [49] A.M. Kalijadis, M.M. Vukcevic, Z.M. Jovanovic, Z.V. Lausevic, M.D. Lausevic, Characterizations of surface oxygen groups on different carbon materials by the Boehm method and temperature-programmed desorption, J. Serb. Chem. Soc. (2011) 757–768. [50] S. Chen, J. Zhang, C. Zhang, Q. Yue, Y. Li, C. Li, Equilibrium and kinetic studies of methyl orange and methyl violet adsorption on activated carbon derived from Phragmites australis, Desalination 252 (2010) 149–156. [51] J. Yang, M. Yu, W. Chen, Adsorption of hexavalent chromium from aqueous solution by activated carbon prepared from longan seed: kinetics, equilibrium and thermodynamics, J. Ind. Eng. Chem. 21 (2015) 414–422. [52] N. Kannan, M.M. Sundaram, Kinetics and mechanism of removal of methylene blue by adsorption on various carbons—a comparative study, Dyes Pigments 51 (2001) 25–40. [53] C.H. Giles, D.A. Smith, A general treatment and classification of the solute adsorption isotherm I. Theoretical, J. Colloid Interface Sci. 47 (1973) 755–765.

[54] I. Langmuir, The constitution and fundamental properties of solids and liquids. Part I, J. Am. Chem. Soc. 38 (1916) 2221–2295. [55] H.M.F. Freundlich, Over the adsorption in solution, J. Phys. Chem. 57 (1906) 385–470. [56] M.J. Temkin, V. Pyzhev, Recent Modifications to Langmuir isotherms, Acta Physiochim. RSS 12 (1940) 217–222. [57] O. Gercel, H.F. Gercel, Adsorption of lead(II) ions from aqueous solutions by activated carbon prepared from biomass plant material of Euphorbia rigida, Chem. Eng. J. 132 (2007) 289–297. [58] J. Acharyaa, J.N. Sahub, C.R. Mohantyc, B.C. Meikap, Removal of lead(II) from wastewater by activated carbon developed from Tamarind wood by zinc chloride activation, Chem. Eng. J. 179 (2009) 249–262. [59] K.P. Yadava, B.S. Tyagi, V.N. Singh, Effect of temperature on the removal of lead(II) by adsorption on China clay and wollastonite, J. Chem. Technol. Biotechnol. 51 (1991) 47–60. [60] Z.Y. Yao, J.H. Qi, L.H. Wang, Equilibrium, kinetic and thermodynamic studies on the biosorption of Cu(II) onto chestnut shell, J. Hazard. Mater. 174 (2010) 137–143. [61] G. Issabayeva, M.K. Aroua, N.M. Sulaiman, Removal of lead from aqueous solutions on palm shell activated carbon, Bioresour. Technol. 97 (2006) 2350–2355. [62] L. Largitte, J. Laminie, Modelling the lead concentration decay in the adsorption of lead onto a granular activated carbon, J. Environ. Chem. Eng. 3 (2015) 474–481. [63] M.A.O. Badmus, T.O.K. Audu, B.U. Anyata, Removal of lead ion from industrial wastewaters by activated carbon prepared from periwinkle shells (Typanotonus fuscatus), Turk. J. Eng. Environ. Sci. 31 (2007) 251–263. [64] P. Shekinah, K. Kadirvelu, P. Kanmani, P. Senthilkumar, V. Subburam, Adsorption of lead(II) from aqueous solution by activated carbon prepared from Eichhornia, J. Chem. Technol. Biotechnol. 77 (2002) 458–464. [65] R.P. Suresh Jeyakumar, V. Chandrasekaran, Adsorption of lead (II) ions by activated carbons prepared from marine green algae: equilibrium and kinetics studies, Int. J. Ind. Chem. 5 (2014) 1–10. [66] E. Tutem, R. Apak, C.F. Unal, Adsorptive removal of chlorophenols from water by bituminous shale, Water Res. 32 (1998) 2315–2324. [67] W.H. Cheung, Y.S. Szeto, G. McKay, Intraparticle diffusion processes during acid dye adsorption onto chitosan, Bioresour. Technol. 98 (2007) 2897–2904. [68] O.A. Ekpete, M.J.N.R. Horsfall, Preparation and characterization of activated carbon derived from fluted pumpkin stem waste (Telfairia occidentalis Hook F), Res. J. Chem. Sci. 1 (2011) 10–17.