The Efficiency Appraisal for Removal of Malachite Green by Potato ...

April 2014, Volume 5, No.2 International Journal of Chemical and Environmental Engineering

The Efficiency Appraisal for Removal of Malachite Green by Potato peel and Neem Bark: Isotherm and Kinetic Studies c

Neetu Sharma a, *; D.P. Tiwari b; S. K. Singh a B.M. Institute of Engineering and Technology, Sonepat-131001, Haryana b Department of Chemical Engineering, DCRUST, Murthal, Sonepat-131039, Haryana c Department of Civil Engineering, DTU, Delhi- 110042 *Corresponding author E-mail:[email protected]

Abstract: Adsorption is a well known process to get rid of harmful contaminants from aquatic ecosystem. From last few decades the agricultural adsorbents being low cost and ample availability are remained quite encouraging before the scientists. Many of these adsorbents are reported to have remarkable performance for adsorption of dyes. In the present study, two chemically modified agricultural adsorbents potato peel and neem bark are used to adsorb malachite green. The nature of adsorption of PP and NB is well defined by all the three isotherms, Langmuir, Freudlich and Temkin studied but PP favored the Freudlich isotherm while NB is well supported by Temkin model due to high correlation coefficient values of 0.99 and 0.95 obtained respectively. Both the acid treated adsorbents APP and ANB favored chemisorptions process which is finely suggested by the good correlation value of 0.97 estimated by both the adsorbents from the Freudlich model. The Pseudo-second order kinetic model fitted well with the observed data of all the four adsorbents. The results obtained reveal that neem bark performs efficiently in acid treated nature while Potato peel is efficient in HCHO treated form. The maximum removal efficiency among the four adsorbents studied in 100 ml of 100 ppm dye solution with 0.250 gm dose was measured maximum in ANB followed by NB, PP and APP with the percentage removal of 94.4%, 92.7%, 92.2% and 82.7% respectively. Keywords: HCHO treated Potato peel (PP); HCHO treated Neem bark (NB); H2SO4 treated potato peel (APP); H2SO4 treated neem bark (ANB); Malachite green (MG); Adsorption Efficiency.

1. Introduction Despite of hazardous and persistent behavior, synthetic dyes are widely accepted and used indiscriminately in various industries like paper, plastic, leather, cosmetics, food and textile industries. These dyes are used in powder and granule form which are easily soluble in water. The presence of minute quantity of color in water bodies poses great threat to aquatic ecosystem by varying the path of sunlight which further effects on photosynthetic activity under water and thus lowers down the dissolve oxygen. Synthetic dyes are hazardous in nature due to presence of harmful organic and inorganic recalcitrant substances which exhibit toxic and carcinogenic effects towards microbial population, human beings and animals [1]. Numerous low cost adsorbents are developed by the researchers in past for removing synthetic dyes like clay [2-6], flyash [7-9], industrial sludge [10], zeolites [11] etc but sorption of dyes by agricultural waste is gaining wide concern for adsorption technology due to their extensive presence and eco-friendly nature for removal of toxic

substance [12-13]. Various agricultural adsorbents are tried by the researchers with remarkable performance in recent past such as tamarind fruit shell [14], Jack fruit peel, a nano-porous adsorbent [15], grapefruit peel [16], rice husk [17], yellow passion fruit peel [18], saw dust [19], Bagasse [20]. The adsorption of Malachite Green by potato peel and neem bark is previously studied by Guechi and Hamdaoui 2011 and Srivastva and Rupainwar 2011 respectively [37, 31]. Here the key ambition of the present research is to evaluate the potential of agricultural adsorbents in chemically treated form. Here both the adsorbents are treated separately with formaldehyde and concentrated sulphuric acid solution. The formaldehyde treatment is considered to restrict the integration of adsorbents own color with the dye tint whereas the acid treatment of the adsorbents is done due to significant performance recorded by acid treated adsorbents in past (19, 20). The significant approach of the study is to evaluate a non conventional low cost adsorbent for removal of synthetic dye.

2. Objectives In the present study, the removal efficiency of the potato peel and neem bark in chemically modified form is

The Efficiency Appraisal for Removal of Malachite Green by Potato peel and Neem Bark: Isotherm and Kinetic Studies

observed on Malachite Green. The efficiency of four adsorbents PP, APP, NB and ANB for removing malachite green is evaluated by varying dose, pH and concentration. Besides the efficiency, adsorption isotherms and kinetic models are also examined to find out the nature and rate of adsorption.

triarylmethane dye which is widely used basic dye among its category for coloring purpose in textile industries [21]. It is traditionally used as a dyestuff for coloring silk, leather and paper materials. It is also used as fungicide and these fungicidal effects are well known from mid 1930’s [22]. This dye accumulates easily from the aquatic ecosystem. The negative effects of this dye are summarized by E. Sudova [23].

3. Materials and Method

3.3 Analytical Method: In situ experiments are conducted in batches by preparing 1000 ppm of stock solution of MG. For determining the concentration of dye, Lambert Beer’s method is used by using double beam Chemito uv-visible spectrophotometer having the wavelength range of 190-1100 nm and bandwidth of 1.6/1.0 nm. The λmax measured for MG is 612 nm. Standard concentrations of MG dye (1-10 ppm) are prepared to obtain a standard curve having R2 equals to 0.99. Graph factor is calculated from the linear equation to get accurate results with minimum error. A comparative sorption study is performed at room temperature with different initial concentration, dose, and pH to obtain equilibrium isotherm and rate of reaction followed by all the four adsorbents. The experiments are performed in batches by shaking 100 ml of 100 ppm (except study of concentration effect) dye solution at room temperature with 0.250 gm (except study of dose effect) of each adsorbent taken in 200 ml of flask at the speed of 125 rpm.

3.1 Sorbents selection and preparation: 3.1.1 Potato Peel (PP): Potato peel is easily available low cost adsorbent and the concern is also attributed by the food industries to overcome the problem of waste management in industry. The raw potato peels are obtained from the university canteen. The peels are first washed with water and air dried in oven at 65°C for 24 hrs. After drying they are grinded and further treated to eliminate their own color. For this, the grinded PP are dipped in 6% HCHO overnight and washed further with distil water until the decanted water

became colourless and pH reached at neutral. The peels are then dried in oven at 70°C and further sieved to obtain the particle of 80-150µm mesh size.

3.1.2 Neem Bark (NB): Neem (Azadiracta indica) bark is obtained easily as the neem tree is a native species of Indian subcontinent. NB is collected in the vicinity of BMIET. The pieces are first washed with water and air dried in oven at 65°C or 24 hrs. The dried bark pieces are grinded and further treated to restrict the own colour of the parent material. For this the grinded mixture of neem bark is dipped in a solution of 37% HCHO & 0.2 N H2SO4 overnight followed by soaking in NaHCO3 overnight to remove acid [19]. After that the mixture is washed further with distil water until the decanted water became colourless and pH reached at neutral. It is then further dried in oven at 70°C and sieved to obtain the particle of 80-150µm mesh size.

Figure1. Structure of Malachite Green

3.1.3 Acid treatment of PP and NB:

Sorption of dye on the adsorbents is calculated by the mass balance equation given below where q denotes the amount of dye adsorbed on the adsorbent (mg/gm); V denotes the volume of the solution (l), m denotes the amount of adsorbent taken in gm; Ci and Cf denotes dye concentration in mg/l before and after adsorption respectively.

Both the adsorbents are treated with H2SO4 in 1:1 ratio of Weight/Volume and left overnight followed by washing with distil water many times until the pH reached at neutral. The black coloured powders of both the adsorbents are obtained after drying the adsorbents in oven at 105 ċ and sieving through the mesh size of 80150µm. All the four types of adsorbents the HCHO treated potato peel (PP) and neem bark (NB) and the acid treated potato peel (APP) and neem bark (ANB) are filled in air tight container for further use.

q=

×V

(1)

Whereas percentage removal of dye is calculated by the given formula:

3.2 Sorbet:

% removal =

The dye, Malachite Green (MG), CI=42,000, Chemical formula=C50H52N4O8, and MW=927.03 is used. The structure of dye is given below in fig.1. MG is a

×100

3.4 Experimental validation

84

(2)


Three different isotherm models Langmuir, Freudlich and Temkin are employed to analyze the isotherm data. This is most vital step for selecting suitable model which can be used to design the unit for adsorption [24]. The linear form of Langmuir model supports the monolayer sorption hypothesis which occurs on the outer surface having infinite number of active sites. The empirical equation of Freudlich isotherm model is based on the sorption of dye over heterogeneous surface. Temkin isotherm model usually applied to observe the chemisorptions behavior of sorbent and sorbet. The linear form of Langmuir, empirical equation of Freudlich and temkin isotherm models are respectively explained by the following expressions: =

+

Log =LogKF+ log =BlnA+Bln

respectively. The maximum removal was achieved by ANB while minimum removal was observed in APP. It might be due to presence of more active sites on the surface of ANB. Uptake of dye increases with increase in adsorbent dose is due to availability of more surface area on the adsorbents [25; 19]. The amount of dye adsorbed per unit mass of the adsorbents (q) decreased in all cases after increasing dose may be due to overlapping of adsorption sites as a result of overcrowding of adsorbent particles [26].

4.2 Effect of pH Adsorption of dye on all the four adsorbents showed significant change in removal efficiency with change in pH as shown in fig. 3 PP and APP showed maximum removal in alkaline condition at pH 12 while NB and ANB showed significant removal in acidic pH at 2. PP and APP showed varied increase in percent removal from 82.2% to 92.2% and 80.5% to 82.7% respectively on changing pH from 2 to 14 while NB and ANB showed overall decrease in percent removal from 92.7% to 83.8% and 94.4% to 76.6% respectively by varying the same pH. Increase in negative charged ions on PP and APP favored the adsorption of cationic dye in alkaline condition due to pectin present on surface of adsorbent [18]. Maximum removal of MG on NB and ANB in acidic medium might be due to the cellulosic compounds (carboxylic and phenolic groups) present on the adsorbent surface [27]. The pH values of the batch study are not adjusted since the addition of strong acid and base could alter the surface properties of sorbents as well as ionic character and aggregation state of dye [27].

(3) (4) (5)

Here in Langmuir’s equation Ce is the equilibrium concentration (mg/l); qe is the amount of dye adsorbed (mg/g); Q0 is the maximum dye per gram of adsorbent (mg/g) and b is Langmuir constant related to energy of adsorption (l/mg). In Freudlich’s equation KF is the constant related to sorption capacity. 1/n is an empirical parameter related to the sorption intensity of the adsorbent. A is Temkin’s constant representing sorbet – sorbent interactions and B is another constant related to the heat of adsorption. The experimental data is also considered to observe the appropriate kinetic model followed by adsorption process studied. The integrated form of Lagergen first order kinetic model and the linear form of pseudo-second order kinetic model are used to reveal the chemical kinetics of various adsorbents. The respective model equations are given below Log (qe-qt) = Log qe (k1/2.303) t

(6)

t/qt =1/K2qe2+(1/qe) t

(7)

4.3Effect of concentration Effect of dye concentration is studied by keeping adsorbent dose constant at 0.250 gm in 100 ml of different concentrations of dye varying from 50, 100, 150, 200 and 250. The % removal of dye in case of PP and NB decreases from 93.3% to 87.5% and 94.4% to 90% with increase in initial concentrations as shown in fig. 4. This suggested that both raw adsorbents PP and NB perform better at low concentrations. Significant increase is observed with change in concentrations in case of APP and ANB from 82.2% to 86% and 91.1% to 95.7% as depicted by the fig. 4. This favored the findings of other investigators [19; 28; 29]. The decrease in removal can be attributed to saturation of sorption sites on the adsorbents and increase in dye/sorbent ratio as the concentration of dye increased [30-32]. The acid treated adsorbents have higher sorption efficiency than the formaldehyde treated adsorbents at higher concentrations [19].

The initial sorption rate h (mg/g.min) is also determined with the help of second order kinetic model by the given equation: h=k2qe2

(8)

4. Results & Discussion 4.1 Effect of dose The effect of dose is examined by varying the amount of adsorbent’s dose from 0.1 gm to 0.250 gm in 100 ml of 100 ppm dye solution. It is clear from fig. 2 that with increase in doses the % removal of all the four adsorbents PP, NB, APP and ANB increases from 85% to 92.2%, 87.7% to 92.7%, 77.7% to 82.7% and 86.1% to 94.4%

85

% Removal


4.4 Isotherm Analysis

95 94 93 92 91 90 89 88 87 86 85 84 83 82 81 80 79 78 77

The initial concentrations for determining the suitability of adsorption isotherm model by all the four adsorbents are chosen from 50, 100, 150, 200 and 250. From table 1 it is clear that PP and NB exhibited good behavior with all three types of isotherm model but Freudlich isotherm fitted well with PP while NB favors Temkin model due to good correlation coefficient of 0.99 and 0.95 respectively. The impartial behavior of the two adsorbents with all the three models confirms that both the formaldehyde treated adsorbents favoured the initial monolayer adsorption followed by chemisorptions. As the natural agricultural adsorbents have rough surface, the adsorption sites are energetically non-equivalent [33] which facilitates the heterogeneous adsorption behavior which involved chemisorptions process. Also the value of n is greater than one for both the adsorbents stated that the nature of adsorption is favorable. The Temkin isotherm model followed by NB considers the acquisition of more energetic adsorption sites at first [34]. The acid treated adsorbents, APP and ANB supported both Freudlich and Temkin equilibrium models but the correlation values estimated was greater with Freudlich model as given in table 1. The value of n is near to or greater than one for both APP and ANB similar to PP and APP. The maximum amount of dye adsorbed per gram of the adsorbent (Q0) measured for acid treated adsorbents APP and ANB are 111 mg/gm and 500 mg/gm respectively. The maximum sorption capacity measured by both type of treated potato peel (PP and APP) for removal of malachite green is found to be 125 mg/gm and 111 mg/gm, which is higher than the value of 32.39 mg/gm estimated by Guechi and Hamdaoui 2011 on raw potato peel [37]. The Q0 determined for all the four adsorbents are higher than the value of 9.7 mg/gm and 63.8 mg/gm obtained by Hema and Arivoli and Y.C. Sharma et al respectively for Malachite green removal on activated carbon of dried leaves of Pandanus and rice husk respectively [35-36].

PP NB APP ANB

0.05

0.10

0.15

0.20

0.25

Dose(mg/gm)

Figure 2 Effect of dose on removal of MG dye

94 92

PP NB APP ANB

90

% Removal

88 86 84 82 80 78 76 74 2

4

6

8

10

12

pH

% Removal

Figure 3 Effect of pH on removal of MG dye

97 96 95 94 93 92 91 90 89 88 87 86 85 84 83 82

PP NB APP ANB

50

100

150

200

250

Concentration(ppm)

Figure 4 Effect of initial concentration on removal of MG

Table1. Comparative data of three adsorption isotherms of different adsorbents studied Isotherm models→ Adsorbents ↓ PP NB APP ANB

Langmuir Isotherm Model

Freudlich Isotherm Model

Temkin Isotherm Model

KL(b)

Q0

R2

KF

N

R2

B

A

R2

0.06 0.1 0.05 0.017

125 166 111 500

0.89 0.88 0.86 0.40

12.07 18.23 3.5 9.4

1.78 1.5 0.98 1.14

0.99 0.88 0.97 0.97

24.19 0.023 23.07 40.07

0.80 2.67x10-36 0.65 0.62

0.91 0.95 0.87 0.91

Table 2 - Comparison of rate constants for pseudo-first and second order of different adsorbents studied Adsorbents PP NB APP ANB

Pseudo first Order qe(cal) K1 1.12 9.2x10-3 1.64 2.30x10-3 3.89 1.0x10-3 1.68 3.0x10-3

R2 0.252 0.028 0.417 0.77

qe(cal) 35.71 34.4 35.7 37.0

86

Pseudo second order K2 R2 H 0.060 0.99 76.4 8.28 0.99 9.7 0.010 0.99 12.7s 0.365 0.99 499.6

qe(exp) 35.5 34.4 35.7 37.0


4.5 Chemical kinetics The kinetic plots of all the four adsorbents are examined at the initial concentration of 100 ppm. From table 2 it is concluded that the second order kinetic model fitted well with the observed data of all the four adsorbents due to better correlation coefficient values obtained. Moreover the calculated sorption capacities determined from pseudo second order model are more consistent with the experimental values obtained. Similar results have been reported by Srivastva and Rupainwar for removal of malachite green on neem bark and mango bark [31]. The initial adsorption rate (h) calculated was higher in

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5. Conclusion The removal efficiency of the potato peel and neem bark in HCHO and H2SO4 treated form is observed on malachite green. The percentage removal of all the four adsorbents increases with increasing dose [25; 19]. The change in pH affects significantly on the % removal. PP and APP are effective in alkaline condition while NB and ANB prove the efficiency in acidic environment. The excellent performance of both HCHO treated adsorbents measured at low concentrations while the same was estimated for H2SO4 treated adsorbents at higher concentrations [19]. PP and NB are quite agreed with all the three models studied but PP favors Freudlich isotherm while NB matched with Temkin model due to good correlation coefficient. The impartial behavior of PP and NB with all the three models reflected adequate sorption occurred on them. APP and ANB showed chemisorptions nature which is acknowledged by the good correlation coefficient values obtained from Freudlich isotherm. The second order kinetic model fitted well with the observed data of all the four adsorbents due to better correlation coefficient values obtained and the calculated values of qe for all the adsorbents were found to be agreed well with the experimental values of qe obtained in case of second order kinetics. Both PP and ANB showed high initial sorption rate. They attracted the dye molecule swiftly and this help in binding the molecule to the adsorbent surface efficiently. All the four adsorbents showed significant dye removal but neem bark reflected its efficiency in acid treated nature whereas potato peel proved to be significant in formaldehyde treated nature. The considerable efficiency for removal of Malachite green is shown by ANB among all the four adsorbents studied.

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ACKNOWLEDGMENT

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The corresponding author extends sincere thanks to SSN College, D.U for performing the experimental work. The support of the staff of D.T.U., Delhi and DCRUST, Murthal was greatly admirable throughout the work.

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