Application of Papaya Seeds as a Macro

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Sep 30, 2013 - of a large dye molecule, Procion Red, from aqueous solution was. 10 investigated. ... wastewater treatment is not attractive from the economic point of ... of Chemical Engineering, Federal University of Santa Maria,. 97105-900 ...
LSST #808213, VOL 48, ISS 18

Application of Papaya Seeds as a Macro-/Mesoporous Biosorbent for the Removal of Large Pollutant Molecule from Aqueous Solution: Equilibrium, Kinetic, and Mechanism Studies Edson Luiz Foletto, Caroline Trevisan Weber, Daniel Assumpc¸ a˜o Bertuol, and Marcio Antonio Mazutti QUERY SHEET This page lists questions we have about your paper. The numbers displayed at left can be found in the text of the paper for reference. In addition, please review your paper as a whole for correctness. "There are no Editor Queries for this paper"

TABLE OF CONTENTS LISTING The table of contents for the journal will list your paper exactly as it appears below: Application of Papaya Seeds as a Macro-=Mesoporous Biosorbent for the Removal of Large Pollutant Molecule from Aqueous Solution: Equilibrium, Kinetic, and Mechanism Studies Edson Luiz Foletto, Caroline Trevisan Weber, Daniel Assumpc¸ a˜o Bertuol, and Marcio Antonio Mazutti

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Separation Science and Technology, 48: 1–8, 2013 Copyright # Taylor & Francis Group, LLC ISSN: 0149-6395 print=1520-5754 online DOI: 10.1080/01496395.2013.808213

Application of Papaya Seeds as a Macro-/Mesoporous Biosorbent for the Removal of Large Pollutant Molecule from Aqueous Solution: Equilibrium, Kinetic, and Mechanism Studies 5

Edson Luiz Foletto, Caroline Trevisan Weber, Daniel Assumpc¸ a˜o Bertuol, and Marcio Antonio Mazutti Department of Chemical Engineering, Federal University of Santa Maria, Santa Maria, Brazil

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various kinds of low-cost materials have been used as alternative adsorbents to activated carbon, which are mainly vegetable waste such as rice husk (8), orange peel (9), seed shells of sesame (10), sugarcane bagasse pith (11), oil palm shell (12), and wheat husk (13). Unfortunately, these low-cost adsorbents usually present low adsorption capacities and, consequently, its applicability in an industrial wastewater treatment is not attractive from the economic point of view. Some recent studies are reporting that the use of papaya (Carica papaya L.) seeds for the removal of dyes from aqueous solutions has a high adsorption capacity. Hameed (14) reported the use of papaya seeds to adsorb methylene blue dye and obtained an adsorption capacity of about 555 mg g1, while Unuabonah et al. (15) using the same dye, reported values of 769 and 1250 mg g1 for the undeffated and deffated papaya seeds, respectively. Recently, papaya seeds have been used for the removal of tannery dye in aqueous solution, which showed adsorption capacity of 440 mg g1(16). Despite its high adsorption capacity, the use of papaya seeds in the adsorption of textile dye with large size molecule has not been reported. The use of papaya seeds as adsorbent to remove dyes from aqueous solutions is particularly attractive in Brazil. In the year of 2009 about 1.8 million of tons of papaya fruits were harvested that corresponds to about 30% of the world production (17). Also, India, Mexico, Nigeria, and Indonesia are big papaya fruits producers. The portion of seeds from papaya fruit is about 15 to 20% of its weight and its final disposition in the environment must be done carefully in order to avoid some serious pollution conditions. Consequently, the use of papaya seeds as dye adsorbent is very interesting from the environmental and economic point of view, since it is an agricultural residue that is available at low cost. In this sense, the aim of the present study was to evaluate the use of papaya seeds to remove textile dye that

The potential use of papaya seeds as biosorbent for the removal of a large dye molecule, Procion Red, from aqueous solution was investigated. Papaya seeds were characterized by nitrogen adsorption/desorption isotherms and scanning electron microscopy. The results revealed that the papaya seeds exhibit a macro-/mesoporous structure, which is desirable for applications in adsorption processes. The models of Langmuir, Freundlich, and Temkin were employed to fit the equilibrium data, where the Langmuir model showed the most suitable fitting. The maximum adsorption capacity for Procion red dye was found to be 73.26 mg g1. Pseudofirst-order, pseudo-second-order, Elovich, and intraparticle diffusion models were used to analyze the kinetic data obtained at different concentrations of dye. The adsorption process of Procion red dye followed the pseudo-second-order and intraparticle diffusion models. The results indicated that the adsorbent used in this work is adequate for the treatment of large dye molecules containing in aqueous solutions. This work highlights the potential application of papaya seeds in the field of adsorption. Keywords adsorption; dye; equilibrium; kinetics; papaya seed

INTRODUCTION Dyes are used as coloring agents in many industries such 30 as textile and tanneries. When improperly discharged into the environment, these dyes may affect aquatic life due to their toxicity and the reduction of light penetration (1). Some methods for dye removal from industrial wastewater include adsorption (2), coagulation (3), flotation (4), and 35 photocatalysis (5,6). Among these chemical and physical methods, the adsorption using activated carbon has been found to be promising compared with other techniques in terms of efficiency to remove a broad range of pollutant molecules (7). However, activated carbon is still considered 40 expensive, which limits their use. Besides, in recent years Received 5 August 2012; accepted 21 May 2013. Address correspondence to Edson Luiz Foletto, Department of Chemical Engineering, Federal University of Santa Maria, 97105-900, Santa Maria, Brazil. E-mail: [email protected]

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present large size molecule from aqueous solution. Kinetics and equilibrium studies using a linear procedure were 80 carried out to evaluate the mechanism and equilibrium isotherm of dye adsorption onto papaya seeds. MATERIALS AND METHODS Adsorbent, Characterization, and Adsorbate Papaya fruits were collected at a local farm. The seeds 85 were removed from the fruit and dried at 90 C in an oven for 24 h followed by crushing in a knife-mill. The resulting material was sieved, and a portion with particle diameter between 350 and 450 mm was used in the experiments. Analysis of the surface area (BET) of the solid was performed 90 using the N2 adsorption-desorption isotherm at 77 K by using Micrometrics ASAP 2020 equipment. The surface physical morphology of the papaya seed was observed by a scanning electron microscope (SEM, Shimadzu SSX550). Procion Red HE7B (CI Reactive Red 141; CAS num95 ber 61931-52-0; chemical formula is C52H34O26S8Cl12N14; molecular weight ¼ 1,952 g mol1), a dye extensively used in the textile industry, was used as the model compound. The chemical structure of the dye is given in Fig. 1.

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Adsorption Studies For the adsorption experiments, 50 mg of papaya seeds were added to 100 mL of aqueous solution of dye at

different initial concentrations (70 to 300 mg L1). The adsorption tests were carried out at various pH (2.5 to 9.0), which were adjusted using 0.1 M HCl or 0.1 M NaOH. The resulting solution was continuously stirred using a 105 thermostatic orbital shaker (Tecnal, Brazil) under stirring (100 rpm), at constant temperature (25 C). An aliquot of the aqueous solution was taken at various time intervals and filtered before analysis. The concentration of the dye in aqueous solution was determined through the use of a 110 UV-vis spectrophotometer (Spectro vision, model T6-UV). Absorbance values were recorded at the wavelength of maximum absorbance of dye (kma´x ¼ 545 nm). The amount of dye adsorbed per unit mass of adsorbent at equilibrium (qe; mg  g1) was determined from: 115 qe ¼ ½ðCo  Ce Þ  V =m

ð1Þ

where Co is the initial dye concentration in liquid phase (mg L1), Ce is the dye concentration at equilibrium (mg L 1 ), m is the mass of adsorbent (g), and V is the volume of dye solution (L). All the adsorption experiments were carried 120 out in duplicate and only the mean values were reported. The maximum deviation observed was about 4.5%. Equilibrium and Kinetic Models In this study, three equilibrium isotherm models were investigated: Langmuir (9), Freundlich (9), and Temkin 125 (18). The respective equations are given in Table 1, where qe, Ce and qmax are the equilibrium adsorption capacity (mg g1), equilibrium concentration (mg L1) and the maximum adsorption capacity (mg g1), respectively; kF, kL, and nF are the Freundlich adsorption constant 130 (mg g1), Langmuir equilibrium constant (L mg1), and Freundlich constant related to adsorption intensity, respectively; R, T, A, and B are the universal gas constant (8.314 J mol1 K1), absolute temperature (K), equilibrium binding constant (L mg1), and a constant related to the 135 heat of adsorption, respectively. Also, four kinetic models were tested: pseudo-first-order (8), pseudo-second-order (8), Elovich (9), and intraparticle diffusion (1) models. The respective kinetic equations are given in Table 2, where TABLE 1 Isotherm models Langmuir Freundlich

FIG. 1. Three-dimensional chemical structure of Procion Red dye, obtained by ChemBio 3D Ultra version 11.0 program. (Color figure available online)

Temkin

1 1 1 ¼ þ qe kL qmax Ce qmax 1 logðCe Þ nF   RT RT lnðAÞ þ qe ¼ lnðCe Þ B B

logðqe Þ ¼ logðkF Þ þ

PAPAYA SEED FOR THE REMOVAL OF LARGE POLLUTANT MOLECULE

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TABLE 2 Kinetic adsorption models Pseudo-first order Pseudo-second order

lnðqe  qt Þ ¼ lnðqe Þ  k1 t t 1 1 ¼ þ t qt k2 q2e qe h ¼ k2 q2e

Elovich Intraparticle diffusion

1 1 qt ¼ lnðabÞ þ lnðtÞ b b pffiffi qt ¼ kid t þ C

qe and qt are the adsorption capacity at equilibrium and at time t, respectively (mg g1); k1, k2, kid, h are the rate constant of pseudo-first-order adsorption (min1), rate constant of second-first-order adsorption (g mg1 min1), intraparticle diffusion rate constant (mg g1 min0.5) and 1 1 145 initial sorption rate (mg g min ) (at t ! 0), respectively; a, b, C are the initial adsorption rate (mg g1 min1), desorption constant (g mg1), and a parameter related to the thickness of the boundary layer, respectively. 140

RESULTS AND DISCUSSION Characteristics of the Adsorbent Figure 2 shows the nitrogen adsorption-desorption isotherms of the papaya seeds. According to the BrunauerBeming-Deming-Teller (BDDT) classification, the majority of physisorption isotherms can be grouped into six types 155 (19). Typically, papaya seeds sample is a combination of types II and IV, with a hysteresis loop, indicating the 150

FIG. 2. N2 adsorption=desorption isotherms and (inset) pore diameter distribution of the sample of papaya seeds.

FIG. 3.

SEM image of papaya seed.

predominant presence of mesopores (type IV) and some macropores (type II). The pore size distribution calculated from the adsorption blanch of the isotherm is presented in Fig. 2 (see inset). It can be seen that papaya seeds sample 160 ˚< has a wide pore size distribution from mesopore (20 A ˚ ) to macropore (pore diameter pore diameter < 500 A ˚ ). From the BET characterization of the sample a 500 > A specific surface of 0.23 m2 g1 was obtained and an average ˚. pore diameter of 332 A 165 The SEM image (Fig. 3) shows a papaya seed particle containing a heterogeneous, irregular, and rough surface. This surface characteristic may enhance the adsorption of large dye molecules onto papaya seed particles. Influence of Physicochemical Parameters on the 170 Adsorption Process One of the most important factors in adsorption studies is the effect of the acidity of the medium (20). Procion red dye removal by the papaya seeds at 25 C was found to be pH dependent as shown in Fig. 4. Equilibrium adsorption 175 was favored by acidic pH and maximum adsorption by

FIG. 4. Influence of initial pH on the adsorption of Procion Red dye by papaya seeds (Initial concentration of dye: 100 mg L1; T ¼ 25 C).

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sample was observed at pH 2.5. When the pH of the dye solution was increased from 2.5 to 5.5, the amount of the dye adsorbed decreased from 37.58 to 17.72 mg g1, respectively. A large decrease in adsorption capacity for this dye was observed under basic conditions. A decrease from 16.20 to 7.10 mg g1 was observed when the pH increased from 7.0 to 9.0, respectively. Similar adsorption behavior has been reported in the literature (21). The adsorption of dye onto adsorbent is influenced by the pH of the solution and also by the zero point charge (pHzpc) of the adsorbent. The pHzpc of papaya seeds has been found to occur at pH 6.25 (15). The surface of the papaya seeds is positively charged below pH 6.25, while it acquires a negative charge above this pH. Procion Red is an anionic dye that contains eight sulphonate groups (SO 3 ) (see Fig. 1). The adsorption of an anionic dye generally decreases, increasing the pH. This phenomenon is associated with the negative charge on the adsorbent surface and also with excess OH ions in the solution that compete for the adsorption sites (22). Therefore, at pH < 6.25 high electrostatic attraction occurs among the positively charged surface of the adsorbent and negatively charged dye. On the other hand, at pH > 6.25, an electrostatic repulsion occurs among the negatively charged surface on the adsorbent and the negatively charged dye. The influence of dye concentration and contact time on adsorption kinetics using papaya seed as adsorbent at pH 2.5 and 25 C is presented in Fig. 5. As can be seen, the amount of dye adsorbed per unit mass of papaya seed increases with increasing initial dye concentration and contact time. In addition, in the first minutes a fast adsorption of dye into the papaya seed was verified, indicating a fast adsorption process that is due to the availability of the positively charged surface of the adsorbent, which led to fast electrostatic adsorption of the anionic dye from the solution at pH 2.5. After this period, a slow adsorption rate of dye was verified that can be due to the electrostatic

repulsion between the adsorbed negatively charged sorbate species onto the surface of the adsorbent and the available 215 anionic sorbate species in solution as well as the slow pore diffusion of the solute ion into the bulk of the adsorbent (9). From Fig. 5, it was also observed that the contact time required to attain equilibrium was about 250 min for all the initial concentrations of dye used in this work. 220

FIG. 5. Influence of initial dye concentration and contact time on the adsorption of Procion Red by papaya seeds (T ¼ 25 C; pH ¼ 2.5).

FIG. 6. The plots of (a) Langmuir, (b) Freundlich, and (c) Temkin isotherm models for the Procion Red adsorption onto papaya seeds.

Adsorption Isotherms The analysis of the isotherm data indicates how the pollutant molecules are distributed among the aqueous solution and solid phase when the adsorption process reaches

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the equilibrium state, and also is an important step in finding a suitable model that can be used for design purposes. The data were fitted using the Langmuir, Freundlich, and Temkin isotherms, which are shown in Fig. 6. These equilibrium models provide important information concerning the adsorption mechanism, the surface properties, and affinity of the adsorbent. The Langmuir model is applicable to homogeneous adsorption systems when there is no interaction among the sorbate molecules, whereas the Freundlich model is an empirical equation used to describe heterogeneous systems and it is not restricted to the formation of the monolayer (20). The Temkin isotherm model assumes that the adsorption heat of all molecules in the layer decreases linearly with the coverage due to adsorbate-adsorbate interactions (9). The adsorption parameters obtained from the plots showed in Fig. 6 are listed in Table 3. The Langmuir isotherm (Fig. 6a) presented the best fitting of experimental data, since the correlation coefficient was higher than 0.98, whereas the other linear models (Figs. 6b and 6c) showed a lower correlation coefficient. These results strongly suggest that there was monolayer coverage of dye molecule on the activated carbon surface. The essential characteristics of the Langmuir isotherm can be expressed in terms of a dimensionless equilibrium parameter (RL) (12). The parameter is defined by: RL ¼ 1=(1 þ kLCo), where Co is the highest dye concentration in liquid phase (mg L1) and kL is the Langmuir adsorption constant (L mg1). The value of RL implies the adsorption to be unfavorable (RL > 1), linear (RL ¼ 1), favorable (0 < RL < 1), or irreversible (RL ¼ 0). The value of RL was found to be 0.17 and confirmed that the Langmuir isotherm was favorable for adsorption of Procion red dye onto the papaya seed under the conditions used in this study. The maximum capacity (qmax) obtained using the Langmuir isotherm for the adsorption of Procion red dye was 73.26 mg g1. This result is higher than the adsorption

TABLE 3 Isotherm parameters for Procion red adsorption onto papaya seeds. Conditions: pH ¼ 2.5, T ¼ 25 C; Adsorbent mass ¼ 50 mg Langmuir qmax (mg g1) 73.26 Freundlich KF (mg g1) 2.88 Temkin A (L mg1) 16.77

kL (L mg1) 0.016

R2 0.982

nF 0.346

R2 0.867

B 51.86

R2 0.906

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capacities of various low-cost adsorbents and activated carbons for different dyes reported in the literature. A qmax ¨ nal (23) for value of 63.53 mg g1 was observed by O adsorption of Crystal Violet on activated carbon prepared from waste apricot. Gupta et al. (24) reported that the qmax values for adsorption of Vertigo Blue and Orange DNA 13 from aqueous solution were 11.57 and 4.54 mg g1, respectively, on carbon slurry developed from a waste material. Bulut and Aydin (25) obtained a qmax value of 21.50 mg g1 for the adsorption of methylene blue on wheat shells. Cardoso et al. (26) found qmax values of 66 and 38.8 mg g1 for adsorption of the textile dyes Reactive Red 194 and Direct Blue 53, respectively, on cupuassu shell. These results mentioned above indicate that the papaya seed has a good ability to remove dye molecules from aqueous solution, which may be attributed to its macro-=mesoporous structure. These physical characteristics are of great importance for adsorption purposes because it allows for a greater accessibility of pollutant molecules to the adsorbent. As mentioned in the Introduction, Hameed (14) found a qmax of 555 mg  g1 for the methylene blue dye onto papaya seeds. However, the size of methylene blue molecule is lower (maximum length of ˚ ) (27) than the Procion red (maximum length of 14.2 A ˚ 23 A; see Fig. 1), which may explain the greater qmax for the methylene blue dye onto papaya seed. The adsorption capacity depends greatly on the porosity of the adsorbent material in relation to the size=volume of the adsorbate molecules. The ratios between the average pore diameter ˚ ) and the maximum lengths of of the adsorbent (332 A Procion red and methylene blue dye molecules are 15 and 24, respectively. This implies that each pore of the papaya seed particle could accommodate up to fifteen Procion red dye molecules, and twenty-four methylene blue molecules.

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Adsorption Kinetics and Mechanism Adsorption kinetic study is important because it provides valuable information concerning the mechanism of dye adsorption in liquid solution. The prediction of 300 adsorption kinetics is necessary for the design of industrial adsorption system. In this work, four kinetic models were fitted (Fig. 7) and the kinetic parameters are presented in Table 4. Only the pseudo-second-order kinetic model (Fig. 7b) presented satisfactory fitting of the experimental 305 data, as can be seen by its high correlation coefficient (R2). This indicates that the adsorption of Procion red dye on papaya seed follows a pseudo-second-order kinetic model. Similar phenomenon has also been observed in the adsorption of basic blue 3 on activated carbon derived 310 from hevea brasiliensis seed coat (28), adsorption of Bismark brown on activated carbon prepared from rubberwood sawdust (29), and the adsorption of reactive orange dye on activated carbon prepared from sugarcane bagasse

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FIG. 7. Kinetic models for the adsorption of Procion Red dye: (a) Pseudo-first order, (b) Pseudo-second order, (c) Elovich, and d) Intraparticle diffusion.

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pith (11). The pseudo-first-order kinetic (Fig. 7a) and Elovich (Fig. 7c) models presented no satisfactory fitting of the experimental data, as indicated by the low values of correlation coefficient obtained.

Adsorption kinetic data also were treated in this work using the intraparticle diffusion model. The model is represented in Fig. 7d. According to Fig. 7d, a plot of qt versus t0.5 should be a straight line when the adsorption

TABLE 4 Kinetic parameters for the dye adsorption onto papaya seeds. Experimental conditions: pH ¼ 2.5, T ¼ 25 C; Adsorbent mass ¼ 50 mg Co (mg L1) Kinetic models Pseudo-first order k1 (min1) R2 Pseudo-second order k2  103 (g mg1 min1) h (mg g1 min1) R2 Elovich a (mg g1 min1) b (g mg1) R2 Intraparticle diffusion kid (mg g1 min0.5) C

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0.0112 0.728

0.0085 0.727

0.0054 0.870

0.0060 0.907

0.0064 0.771

4.031 4.65 0.992

5.37 7.35 0.995

2.03 5.07 0.997

1.25 3.806 0.998

2.11 7.35 0.995

102.10 0.171 0.913

21.59 0.124 0.910

694.81 0.187 0.870

1.506 25.99

1.554 27.89

1.574 36.01

283.87 0.297 0.914 0.786 20.79

11.30  103 0.375 0.903 0.797 25.11

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mechanism follows the intraparticle diffusion process. Such types of plots may present multilinearity, implying that two or more steps occur (30). The sharp first-stage portion is the external surface adsorption stage. The second portion is the gradual adsorption stage, where the intraparticle diffusion is rate-limited. From Fig. 7d it was observed that there were two linear steps, indicating that the adsorption process of the Procion red dye on the papaya seed tends to be controlled by both surface adsorption and intraparticle diffusion. Vadivelan and Kumar (30) observed a similar behavior, with two linear portions for the adsorption of methylene blue on rice hulls. Two linear steps also were found for the adsorption of Basic violet 3 and Acid black 1 dyes on unburned carbon from coal combustion residue (31). Thus, several factors can affect the kinetics of dye adsorption onto the adsorbent. These factors include the chemical and physical structure of the dye molecule, the physical properties of the adsorbent, and the experimental solution conditions.

CONCLUSIONS The present study showed that the presence of mesopores together with macropores in the papaya seed make it a good 345 alternative as biosorbent to remove large molecule as Procion red from aqueous solution. The Langmuir isotherm was the most suitable to fit the equilibrium data, indicating a monolayer adsorption of Procion red dye onto papaya seed particles with a maximum capacity of 73.26 mg g1. 350 Four kinetic models were used to evaluate the adsorption mechanism and the best fit was using the pseudo-secondorder kinetic model. The adsorption process was found to be controlled by both surface and pore diffusion. REFERENCES 355

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1. Kismir, Y.; Aroguz, A.Z. (2011) Adsorption characteristics of the hazardous dye Brilliant Green on Saklıkent mud. Chem. Eng. J., 172 (1): 199. 2. Foletto, E.L.; Jahn, S.L.; Moreira, R.F.P.M. (2009) Synthesis of high surface area MgAl2O4 nanopowder as adsorbent for leather dye removal. Sep. Sci. Technol., 44: 2132. 3. Szyguła, A.; Guibal, E.; Palacı´n, M.A.; Ruiz, M.; Sastre, A.M. (2009) Removal of an anionic dye (Acid Blue 92) by coagulation–flocculation using chitosan. J. Environ. Manage., 90 (10): 2979. 4. Shakir, K.; Elkafrawy, A.F.; Ghoneimy, H.F.; Beheir, S.G.E.; Refaat, M. (2010) Removal of rhodamine B (a basic dye) and thoron (an acidic dye) from dilute aqueous solutions and wastewater simulants by ion flotation. Water Research, 44 (5): 1449. 5. Collazzo, G.; Jahn, S.; Foletto, E.L. (2012) Removal of Direct Black 38 dye by adsorption and photocatalytic degradation on TiO2 prepared at low temperature. Latin Am. Appl. Res., 42: 55. 6. Collazzo, G.C.; Foletto, E.L.; Jahn, S.L.; Villetti, M.A. (2012) Degradation of direct Black 38 dye under visible light and sunlight irradiation by N-doped anatase TiO2 as photocatalyst. J. Environ. Manage., 98 (15): 107. 7. Tan, I.A.W.; Hameed, B.H.; Ahmad, A.L. (2007) Equilibrium and kinetic studies on basic dye adsorption by oil palm fibre activated carbon. Chem. Eng. J., 127 (1–3): 111.

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8. Malik, P.K. (2004) Dye removal from wastewater using activated carbon developed from sawdust: adsorption equilibrium and kinetics. J. Hazard. Mater., 113 (1–3): 81. 9. Khaled, A.; Nemr, A.E.; Sikaily, A.E.; Abdelwahab, O. (2009) Removal of Direct N Blue-106 from artificial textile dye effluent using activated carbon from orange peel: Adsorption isotherm and kinetic studies. J. Hazard. Mater., 165 (1–3): 100. 10. Thinakaran, N.; Panneerselvam, P.; Baskaralingam, P.; Elango, D.; Sivanesan, S. (2008) Equilibrium and kinetic studies on the removal of Acid Red 114 from aqueous solutions using activated carbons prepared from seed shells original research. J. Hazard. Mater., 158 (1): 142. 11. Amin, N.K. (2008) Removal of reactive dye from aqueous solutions by adsorption onto activated carbons prepared from sugarcane bagasse pith. Desalination, 223 (1–3): 152. 12. Tan, I.A.W.; Ahmad, A.L.; Hameed, B.H. (2008) Adsorption of basic dye using activated carbon prepared from oil palm shell: batch and fixed bed studies. Desalination, 225 (1–3): 13. 13. Gupta, V.K.; Jain, R.; Varshney, S. (2007) Removal of Reactofix golden yellow 3 RFN from aqueous solution using wheat husk: An agricultural waste. J. Hazard. Mater., 142 (1–2): 443. 14. Hameed, B.H. (2009) Evaluation of papaya seeds as a novel non-conventional low-cost adsorbent for removal of methylene blue. J. Hazard. Mat., 162 (2–3): 939. 15. Unuabonah, E.I.; Adie, G.U.; Onah, L.O.; Adeyemi, O.G. (2009) Multistage optimization of the adsorption of methylene blue dye onto defatted Carica papaya seeds. Chem. Eng. J., 155 (3): 567. 16. Weber, C.T.; Foletto, E.L.; Meili, L. (2013) Removal of tannery dye from aqueous solution using papaya seed as an efficient natural biosorbent. Water Air Soil Poll., 224: 1. 17. FAOSTAT. Food and Agricultural Organization of the United Nations. Statistical database, 2011; FAO, Rome, Italy. 18. Foo, K.Y.; Hameed, B.H. (2010) Insights into the modeling of adsorption isotherm systems. Chem. Eng. J., 156 (1): 2. 19. Sing, K.S.W.; Everett, D.H.; Haul, R.; Moscou, L.; Pierotti, R.A.; Rouquerol, J.; Siemieniewska, T. (1985) Reporting physisorption data for gas=solid systems. Pure Appl. Chem., 57: 603. 20. Foletto, E.L.; Collazzo, G.C.; Mazutti, M.A.; Jahn, S.L. (2011) Adsorption of textile dye on zinc stannate oxide: Equilibrium, kinetic and thermodynamics studies. Sep. Sci. Technol., 46: 2510. 21. Al-Degs, Y.S.; El-Barghouthi, M.I.; El-Sheikh, A.H.; Walker, G.M. (2008) Effect of solution pH, ionic strength, and temperature on adsorption behavior of reactive dyes on activated carbon. Dyes Pigments, 77 (1): 16. 22. Vieira, S.S.; Magriotis, Z.M.; Santos, N.A.V.; Cardoso, M.G.; Saczk, A.A. (2012) Macauba palm (Acrocomia aculeata) cake from biodiesel processing: An efficient and low cost substrate for the adsorption of dyes. Chem. Eng. J., 183 (15): 152. ¨ nal, Y. (2006) Kinetics of adsorption of dyes from aqueous solution 23. O using activated carbon prepared from waste apricot. J. Hazard. Mater., 137 (3): 1719. 24. Gupta, V.K.; Ali, I.; Saini, V.K. (2007) Adsorption studies on the removal of Vertigo Blue 49 and Orange DNA13 from aqueous solutions using carbon slurry developed from a waste material. J. Coll. Interf. Sci., 315 (1): 87. 25. Bulut, Y.; Aydın, H. (2006) A kinetics and thermodynamics study of methylene blue adsorption on wheat shells. Desalination, 194 (1–3): 259. 26. Cardoso, N.F.; Lima, E.C.; Pinto, I.S.; Amavisca, C.V.; Royer, B.; Pinto, R.B., Alencar, W.S.; Pereira, S.F.P. (2011) Application of cupuassu shell as biosorbent for the removal of textile dyes from aqueous solution. J. Environ. Manage., 92 (4): 1237. 27. Royer, B.; Cardoso, N.F.; Lima, E.C.; Vaghetti, J.C.P.; Simon, N.M.; Calvete, T.; Veses, R.C. (2009) Applications of Brazilian pine-fruit shell in natural and carbonized forms as adsorbents to removal of

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methylene blue from aqueous solutions: Kinetic and equilibrium study. J. Hazard. Mater., 164 (2–3): 1213. 28. Hameed, B.H.; Daud, F.B.M. (2008) Adsorption studies of basic dye on activated carbon derived from agricultural waste: Hevea brasiliensis seed coat. Chem. Eng. J., 139 (1): 48. 29. Kumar, B.G.P.; Shivakamy, K.; Miranda, L.R.; Velan, M. (2006) Preparation of steam activated carbon from rubberwood sawdust

(Hevea brasiliensis) and its adsorption kinetics. J. Hazard. Mater., 136 (3): 922. 30. Vadivelan, V.; Kumar, K.V. (2005) Equilibrium, kinetics, mechanism, and process design for the sorption of methylene blue onto rice husk. J. Coll. Interf. Sci., 286 (1): 90. 31. Wang, S.; Li, H. (2007) Kinetic modelling and mechanism of dye adsorption on unburned carbon. Dyes Pigments, 72 (3): 308.

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