Comparative Study on Efficiency of Natural Adsorbents in Removal of Chromium

Transcription

1 Vol. 2, Issue. 1, 2015, ISSN Comparative Study on Efficiency of Natural Adsorbents in Removal of Chromium Rajkumar V. Raikar 1, Swati Patil 2 1 Professor, Department of Civil Engineering, KLE Dr. M. S. Sheshgiri College of Engineering and Technology, Belgaum , India. rvraikar@gmail.com 2 M. Tech. Scholar, Department of Civil Engineering, KLE Dr. M. S. Sheshgiri College of Engineering and Technology, Belgaum , India, swatipatil874@gmail.com Abstract: The occurrence of heavy metals in the environment, which are known to be toxic and non-biodegradable, has become a serious issue. As the conventional methods of removal of heavy metals are expensive, the use of alternative treatment methodologies has become the subject of importance. This paper presents the results of an experimental study undertaken to evaluate the potential of utilizing natural adsorbents to remove chromium from the aqueous solutions through adsorption process. The natural adsorbents used in the study are orange peel, tamarind shell (oxalic acid and HCl treated) and tridax procumbens. The synthetic wastewater is used in this study. The efficiency of the activated carbon of the biomaterials for Chromium VI [Cr (VI)] removal was evaluated by varying the contact time, quantity of adsorbent and concentration of Cr (VI) in synthetic solution. It is found that the maximum removal efficiency of.86% of Cr (VI) in achieved by using orange peel adsorbent, 98% removal efficiency with tamarind shell (oxalic acid treated), 97% removal efficiency from tamarind shell (HCl treated), and % removal efficiency with tridax procumbens. The optimum ph value obtained is in the range of for all the adsorbents with batch experiments being performed. Batch experimental data were used to fit Freundlich and Langmuir isotherms. It is observed that the Freundlich isotherm fit very well as compared to the Langmuir isotherm. Keywords: Chromium, Heavy metals, Isotherms, Natural Adsorbents. I. INTRODUCTION The presence of heavy metals in the environment causes adverse impacts on flora and fauna of the earth. Though many metallic elements are essential for nutritional and physiological requirements in living organisms, their overabundance can cause toxicity symptoms or even death. There are number of toxic heavy metals such as chromium, zinc, lead, thallium, copper, mercury, nickel whose increasing levels in the environment are of considerable concern. Heavy metal pollution is arising from effluent discharges from a variety of industries such as mining, ore processing, metal processing operations, and industrial activities that make use of metallic compounds such as pigments, bio-acidic agents, tanning, electroplating textile dyeing etc. As chromium (Cr) is used to make steel highly corrosion resistant and discoloration of stainless steel, hence it has received great interest. However, hexavalent chromium [Cr (VI)] can cause cancer or make people sick, even though they are not directly exposed. Hexavalent chromium can be destroyed by turning it into trivalent chromium by reacting Cr (VI) with reducing agents. On the other hand, many natural adsorbents are employed in the removal process of heavy metals from wastewaters. Dubey et al. [1] employed ground husk as an adsorption media for Cr (VI). Singanan et al. [2] used tridax as a biomaterial for the removal of hexavalent chromium from industrial waste water. Tamarind fruit shells were used by Srinivas Rao et al. [3] in the removal of chromium. Vinodhini and Das [4] used neem sawdust, mango sawdust, wheat shell, sugarcane bagasse and orange peel as sorbents to remove chromium (VI). Ekpete et al. [5] used orange peel to remove Cr (VI) and Zn (II). Tridax Available 1

2 Vol. 2, Issue. 1, 2015, ISSN procumbens was employed by Karthika et al. [6] as biosorbent of copper from aqueous solutions and Kanawade et al. [7] in removing lead from industrial waste. Ferda and Selen [8] studied the use of orange peel in the removal of Nickel (II) ions from aqueous solution. In the present study, the comparative study on Chromium VI removal efficiency of four natural adsorbents such as orange peel, tamarind shell (oxalic acid and HCl treated) and tridax procumbens was carried out. In addition, to find the optimum interaction of adsorbent with solutes, which help in the design of adsorbent columns, adsorption isotherms were fitted to the experimental data. II. METHODOLOGY This section presents the methodology used in the study. A. Activation of Adsorbents The natural adsorbents used in the study namely orange peel, tamarind shell and tridax procumbens were activated using the standard procedure of chemisorption. 1. Activation of Orange Peels Orange peels were first cut into pieces and dried completely. Then 10 gm of dried orange peel pieces were taken along with 2 litres of distilled water in a beaker. These orange peel pieces were agitated vigorously by a magnetic stirrer at ambient temperature for 4 hours. After 4 hours of agitation, these orange peel pieces were washed continuously with distilled water to remove the surface adhered particles and water soluble materials. After washing and filtration the orange peels were oven-dried at 60 o C o C for 24 hours. The dried orange peels were powdered to have particles of size mm. 2. Activation of Tamarindus Shells The tamarind shells were initially crushed. Then 10 gm of crushed tamarind shells were treated separately with ml HCl and ml oxalic acid for 24 hours. After 24 hrs, these beakers containing treated tamarind shell were kept on water bath (70 o C) for 30 minutes. Once the beakers containing the treated solutions were cooled they are neutralized with 50 ml of NaOH so that traces of acid are removed. The filtrates are separated and dried in the oven for 4 hours at 60 o C. These pre-treated tamarind shells with HCl and oxalic acid were used as the bio-adsorbents. 3. Activation of Tridax Procumbens The tridax procumbens flowers are the weeds, which are grown large in number. The tridax procumbens flowers were air dried to remove the moisture present. After ensuring that there is no moisture these flowers were powdered. This powered homogeneous powder was used after activation. The activated carbon of biomaterial was prepared by treating with concentrated sulphuric acid in weight ratio of 1: 1.8. The resulting black powder was kept in the oven at 160 o C 165 o C for 6 hours. Then this black powder is washed with distilled water until excess acid is dried in oven for 4 hrs at 105 o C 110 o C. The dried powder was ground and used for metal adsorption experiments. B. Sample Analysis The adsorbance was determined by UV- spectrophotometer. Ten ppm of chromium standard solution was taken in series of ml conical flasks and distilled water was added to make up to mark. Then 1 g of the adsorbent was added to each of the conical flasks and agitated for different time intervals of 30, 60, 90 and 1 min, respectively. After 30 min of agitation the solution was filtered with Whitman filter paper No. 42. From the filtered solution 10 ml of the sample was taken in 50 ml volumetric flask and to make it up to the mark, the distilled water was added. Ten ml of sample was pipetted out from the volumetric flask in to a conical flask and 2 ml of concentrated sulphuric acid and 2 ml of 0.5% Diphenyl Carbazide were added to each of the conical flasks. Then the adsorbance of chromium was measured at wavelength of 560 nm using the UV spectrophotometer. The same procedure was carried out with different time intervals of 60 min, 90 min and 1 min, and with different doses of adsorbent of 3 g and 5 g. Available 2

3 Vol. 2, Issue. 1, 2015, ISSN C. Chromium Analysis by UV Spectrophotometer The purpose of UV spectrophotometer analysis is to determine the adsorption of chromium ions and to plot the standard calibration curve. The calibration curve was drawn from the standard solutions of chromium and their adsorbance values. Fig. 1 shows a plot of the known concentration versus adsorbance. The constant obtained from the calibration curve is used to determine concentration of unknown solution Adsorbance Chromium concentration in ppm Figure 1: Calibration curve III. RESULTS AND DISCUSSIONS The results of percentage removal of chromium using orange peel, tamarind shell (with HCl and oxalic acid treated) and tridax procumbens with varying concentration with different time of agitation are presented in this section. Also the effect of ph and the fitting of the adsorption isotherms are discussed. A. Percentage Removal of Chromium according to Agitation Time and Concentration The percentage removal of chromium at different agitation time (30 min, 60 min, 90 min and 1 min) having different initial concentration of chromium in synthetic waste water (,, 30 ppm and ) using natural adsorbents: orange peel, tamarind shell (oxalic acid and HCl treated) and tridax procumbens with dosages of 1gm, 3 gm and 5 gm are discussed. 1. Percentage Removal of Chromium using Orange Peel The experimental results on removal of chromium using orange peel with 1 gm, 3 gm and 5 gm dosages is presented in Fig. 2(a-c). Figure 2(a) illustrates the chromium removal results with 1 gm dosage of orange peel. It can be observed that the percentage removal of chromium increases with an increase in agitation time up to 120 min and then reaches a steady value for each of initial chromium concentrations. Similar results were also observed by Sivaraj et al. [9] in chromium removal using orange peel adsorbent. Karthika et al. [6] also observed the similar variation of removal of copper from aqueous waste using tridax procumbens. From Fig. 2(a), it is observed that the percentage removal is minimum of 86.30% at 30 minutes with of initial chromium concentration while it is maximum of 98.5% at 1 minutes with of initial chromium concentration. Similarly, the percentage removal of chromium with 3 gm and 5 gm dosage of orange peel are presented in Figs. 2(b) Available 3

4 Vol. 2, Issue. 1, 2015, ISSN % Removal of Chromium (a) Dosage of adsorbent = 1 gm 30min 60min 90min 120min 150min 1min % Removal of Chromium (b) Dosage of adsorbent = 3 mg 30min 60min 90min 120min 150min 1min % Removal of Chromium (c) Dosage of adsorbent = 5 mg 30min 60min 90min 120min 150min 1min Figure 2: Percentage removal of chromium using orange peel and 2(c), respectively. From Fig. 2(b), it is clear that, the minimum percentage removal of chromium is 86.18% at 30 minutes with of initial chromium concentration and maximum of 94.35% at 1 minutes with of initial chromium concentration for 3 gm of orange peel dosage. On the other hand, with 5 gm of dosage, the percentage removal is minimum of 86.25% at 30 minutes with initial chromium concentration while it is maximum of.86% at 1 minutes with of initial chromium concentration [refer Fig. 2(c)]. From all this, it can be observed that 120 minutes of agitation time is most optimum to attain maximum removal efficiency of chromium using orange peel, that is 98.5% with 1 gm dosage, 94.35% with 3 gm dosage and.86% with 5 gm dosage, respectively. Further. 1 gm of adsorbent dosage is more efficient than the other two dosages used in the study. Available 4

5 Vol. 2, Issue. 1, 2015, ISSN % Removal of Chromium (a) Dosage of adsorbent = 1 mg 30min 60min 90min 120min 150min 1min (b) Dosage of sdsorbent = 3 mg 30min 60min 90min 120min 150min 1min (c) Dosage of adsorbent = 5 mg 30min 60min 90min 120min 150min 1min Figure 3: Percentage removal of chromium using tamarind shell (oxalic acid treated) 2. Percentage Removal of Chromium using Tamarind Shell (Oxalic acid treated) The percentage removal of chromium using tamarind shell with oxalic acid treated by 1 gm, 3 gm and 5 gm dosages obtained experimentally is presented in Figs. 3(a-c). The chromium removal results with 1 gm dosage of tamarind shell treated with oxalic acid are presented in Fig. 3(a), which indicate that the percentage removal of chromium increases with an increase in time up to 120 min and then Available 5

6 Vol. 2, Issue. 1, 2015, ISSN reaches a steady value for different initial chromium concentrations. Similar results were also observed by Srinivasa Rao et al. [3] for aqueous solution of chromium with tamarind shell adsorbent, Sivaraj et al. (2001) for chromium and orange peel adsorbent and Karthika et al. [6] for copper from aqueous waste with tridax procumbens. The percentage removal is minimum of 86.% at 30 minutes with 40 ppm initial chromium concentration and is maximum 97.50% at 1 minutes with initial chromium concentration. Figure 3(b) shows the removal efficiency of chromium with 3 gm of tamarind shell (oxalic acid treated). It can be seen that the percentage removal is minimum of 86.95% at 30 minutes with initial chromium concentration and is maximum 95.06% at 1 minutes at initial chromium concentration Figure 3(c) presents the results of 5 gm of oxalic acid treated tamarind shell, the percentage removal is being minimum 91.5% at 30 minutes with initial chromium concentration and is maximum of 97.99% at 1 minutes with initial chromium concentration. Hence, 5 gm dosage of oxalic acid treated tamarind shell is found to be more efficient. 3. Percentage Removal of Chromium using Tamarind Shell (HCl treated) The experimental results on use of adsorbent tamarind shell with HCl treated in removal of chromium with 1 gm, 3 gm and 5 gm dosages is presented in Figs. 4(a-c). Figure 4(a) illustrates the chromium removal with 1 gm of HCl treated tamarind shell adsorbent. From Fig. 4(a-c) it can be observed that the percentage removal of chromium increases with an increase in agitation time up to 120 min and then reaches a steady value for different initial chromium concentrations. Similar results were also reported by Sivaraj et al. [9]. Also, Karthika et al. [6] observed the similar variation of removal of copper from aqueous waste using tridax procumbens. From Fig. 4(a), the percentage removal is found to be minimum of 81.18% at 30 minutes with initial chromium concentration and is maximum 97.% at 1 minutes also with initial chromium concentration. The minimum removal of chromium is 83.05% at 30 minutes with initial chromium concentration and maximum is 93.16% at 1 minutes with initial concentration with 3 gm dosage of tamarind shell (HCl treated) as seen from Fig. 4(b). On the other hand with 5 gm of adsorbent dosage, the minimum percentage removal of chromium is 86.53% at 30 minutes with initial chromium concentration and is maximum of 93.99% at 1 minutes at and initial chromium concentration, respectively [see Fig. 4(c)]. The optimum dosage of HCl treated tamarind shell adsorbent is found to be 1 gm. 4. Percentage Removal of Chromium using Tridax Procumbens Figure 5 represents the experimental results on chromium removal using tridax procumbens with 1 gm, 3 gm and 5 gm dosages. From Fig. 5(a), which illustrates the results with 1 gm of procumbens, it can be observed that the percentage removal of chromium increases with an increase in agitation time up to 120 min and then reaches constant value for different initial chromium concentrations. The results obtained in present study are almost near to the results obtained by Singanan et al. [2] where in with dilute solutions the percentage removal is 65% of Cr (VI) and removal is % at 150 min. Similar results were also presented by Sivaraj et al. [9] for chromium and orange peel adsorbent. However, Karthika et al. [6] also observed similar variation of removal of copper from aqueous waste using tridax procumbens. The minimum percentage removal of chromium is 85.71% at 30 min with initial chromium concentration and is maximum % at 1 minutes with initial chromium concentration as seen from Fig. 5(a). From Fig. 5(b), drawn for 3 gm dosage of tridax procumbens, the minimum percentage removal of chromium is 83.23% at 30 minutes and maximum of 95.95% at 1 minutes both at initial chromium concentration. Similarly, for 5 gm dosage the percentage removal of chromium is minimum 75.31% at 30 minutes with initial chromium concentration and is maximum of 94.% at 1 minutes with initial chromium concentration as depicted from Fig. 5(c). In this case, the optimum dosage of tridax procumbens is found to be 1 gm with 1 min of agitation time. Available 6

7 Vol. 2, Issue. 1, 2015, ISSN (a) Dosage of adsorbent = 1 mg 30min 60min 90min 120min 150min 1min (b) Dosage of adsorbent = 3 mg 30min 60min 90min 120min 150min 1min (c) Dosage of adsorbent = 5 mg 30min 60min 90min 120min 150min 1min Figure 4: Percentage removal of chromium using tamarind shell (HCl treated) with dosage of (a) 1 gm, (b) 3 gm and (c) 5 gm Available 7

8 Vol. 2, Issue. 1, 2015, ISSN (a) Dosage of adsorbent = 1 mg 30min 60min 90min 120min 150min 1min (b) Dosage of adsorbent = 3 mg 30min 60min 90min 120min 150min 1min (c) Dosage of adsorbent = 5 mg 30min 60min 90min 120min 150min 1min Agitation Time in min Figure 5: Percentage removal of chromium using tridax procumbens with dosage of (a) 1 gm, (b) 3 gm and (c) 5gm B. Effect of ph on Percentage Removal of Chromium The ph is an important parameter for adsorption of metal ions from aqueous solution because it affects the solubility of the metal ions, concentration of counter ions on the functional groups of the adsorbent and the degree of ionization of the adsorbate during reaction. To examine the effect of ph on Cr (VI) removal efficiency, the ph was varied from 1 to 8 and the optimum ph was obtained. A fixed amount of adsorbent of 3 gm was added to 10 mg/l of heavy metal solution containing chromium. This ph range is selected following Karthika et al. [6] To avoid variation in ph value due to adsorbent Available 8

9 Vol. 2, Issue. 1, 2015, ISSN addition, the ph was adjusted with 0.1N HCl or 1N NaOH after the solution had been in contact with the adsorbent. From Fig. 6, it can be observed that the percentage removal of chromium is optimum in the ph range of 2 to 2.5 and the efficiency decreases as the ph increases. Therefore, the optimum ph was selected in the range of 2 to 2.5. Singanan et al. [2] also reported similar variation for chromium and tridax procumbens adsorbents. Further, Srinivasa et al. [3] indicated equivalent results for removal of chromium from aqueous solutions using tamarind shell (oxalic acid treated) and tamarind shell (HCl treated) adsorbent with maximum ph = 3. In addition, Vinodhini et al. [4] observed the similar variation of removal of chromium from aqueous solutions using Neem sawdust, Mango sawdust, Wheat shell, Sugarcane bagasse and Orange peel adsorbent and found optimum value of ph as Orange peel Tamarind shell oxalic acid treated Tamarind shell HCL treated Tridax ph Figure 6: Effect of ph on the percentage removal of chromium with different adsorbents C. Adsorption Isotherms Adsorption of the isotherm data is important in order to develop an equation which accurately represents the results of the adsorbent column and which could be used for column design purposes. Adsorption isotherm also describes how solutes interact with adsorbent and so is critical in optimizing the use of adsorbent. Therefore, the chromium uptake capacity of orange peel, tamarind shell (oxalic acid treated and HCl treated) and tridax procumbens was evaluated using the Langmuir and Freundlich equations. The comparative results on the fitted isotherms using Freundlich isotherm and Langmuir isotherm are presented in Table 1 with different adsorbent dosages of 1 gm, 3 gm and 5 gm. Table indicates that the Freundlich isotherm fits better as compared with Langmuir isotherm giving higher correlation coefficient value (R 2 0.9). In all the previous investigations, Freundlich isotherm was found to be more promising than Langmuir isotherm [10, 11]. Available 9

10 Adsorbent Raikar and Patil / International Journal of New Technologies in Science and Engineering Vol. 2, Issue. 1, 2015, ISSN Table 1 Fitted isotherm parameters Freundlich isotherm Langmuir isotherm n K R 2 Q m b R 2 Adsorbent dosage = 1 gm Orange peel Tamarind shell (OA treated) Tamarind shell (HCl treated) Tridax procumbens Adsorbent dosage = 3 gm Orange peel Tamarind shell (OA treated) Tamarind shell (HCl treated) Tridax procumbens Adsorbent dosage = 5 gm Orange peel Tamarind shell (OA treated) Tamarind shell (HCl treated) Tridax procumbens IV. CONCLUSIONS The chromium removal efficiency of natural adsorbents in synthetic wastewater was studied experimentally. The adsorbents used in the present study show a great potential in removal of chromium. On gm orange peel adsorbent gave highest percentage of 98.5 removal of chromium compared to 3 gm and 5 gm dosage. Tamarind shell with oxalic acid treated with 5 gm dosage resulted highest percentage removal (98%) of chromium compared to 1 gm and 3 gm adsorbent dosage. On the other hand, HCl treated tamarind shell of 1 gm dosage yielded 97.% removal of chromium. Similarly, 1 gm of tridax procumbens gave % removal of chromium compared to other two dosages. The percentage removal of chromium increases as the contact time increases. Out of all adsorbents, tamarind shell with oxalic acid treatment gives better removal efficiency. The percentage removal of chromium was efficient in the ph range of 2 to 2.5 and the efficiency decreases as the ph increases. Hence, the optimum ph was selected in the range of 2 to 2.5. Further, the Freundlich isotherm found to have the best fit when compared to the Langmuir isotherm. REFERENCES [1] S. Dubey, and Gopal Krishn, Adsorption of chromium (VI) on low cost adsorbents derived from agricultural waste material: a comparative study, Journal of hazardous materials. vol. 145, no. 3, pp , [2] M. Singanan, and Vinodhini, Studies on the removal of hexavalent chromium from industrial wastewater by using biomaterials, Electronic Journal of Environmental, Agricultural and Food Chemistry, vol. 6, pp , [3] P. Srinivasa Rao, J. Ajithapriya, V. N. Kachireddy, and A. Krishnaiah, Biosorption of hexavalent chromium using tamarind (Tamarindus indica) fruit shell, Electronic Journal of Biotechnology, vol. 10, no. 3. pp , [4] V. Vinodhini, and Nilanjana Das, Mechanism of Cr (VI) biosorption by neem saw dust, American-Eurasian Journal of Scientific Research, vol. 4, pp , Available 10

11 Vol. 2, Issue. 1, 2015, ISSN [5] O. A. Ekpete, F. Kpee, J. C.Amadi, and R. B. Rotimi, Adsorption of Chromium (VI) and Zinc (II) Ions on the Skin of Orange Peels (Citrus sinensis), Journal of Nepal Chemical Society, vol. 26, pp , [6] T. Karthika, A. Thirunavukkarasu, and S. Ramesh, Biosorption of copper from aqueous solutions using Tridax Procumbens, Pollution and environmental sciences recent research in science and technology, vol. 2, pp , [7] S. M. Kanawade, and R. W. Gaikwad, Lead ion removal from industrial effluent by using biomaterials as an adsorbent, International Journal of Chemical Engineering and Applications, vol. 2, no. 3. pp , [8] G. Ferda, and S. Selen, Adsorption study on orange peel: Removal of Ni (II) ions from aqueous solution, African Journal of Biotechnology, vol. 11(5), pp , [9] R. Sivaraj, C. Namasivayam, and K. Kadirvelu, Orange peel as an adsorbent in the removal of acid violet 17 (acid dye) from aqueous solutions, Waste management New York, vol. 21, pp , [10] M. Isa, S. R. M. Kutty, A. Malakahmad, and C. Y. Fei, Removal of chromium (VI) from aqueous solution using oil palm ash, ICCBT D-(30), pp , [11] S. Vikrant, and K. K. Pant, Removal of chromium from industrial waste by using eucalyptus bark, Bioresource Technology, vol. 97, pp , Available 11