International Journal of Engineering & Technology Research Volume-2, Issue-3, May-June, 2014, pp. 95-99, © IASTER 2014 www.iaster.com, ISSN Online: 2347-4904, Print: 2347-8292
Comparative Studies on Removal of Heavy Metals from Wastewater by Low Cost Adsorbents
Sunil J. Kulkarni1, Ajaygiri K. Goswami2 1Chemical Engineering Department, Datta Meghe College of Engineering, Navi Mumbai, India. 2Chemical Engineering Department, University Institute of Chemical Technology, Jalgaon, India.
ABSTRACT
Removal of heavy metal from wastewater by adsorption demands low operating cost. Use of low cost adsorbent is one way of reducing the treatment cost. In the present research adsorbent prepared from waste materials like groundnut shells and bagasse are used for adsorbent preparation. The removal of heavy metals like chromium and iron by these adsorbents has been studied. Also The effect of parameters like contact time, pH and adsorbent dose on the metal removal is studied.The maximum percentage removal was 91 percent for iron and 92.4 percent for chromium. The adsorption process was dependent on the parameters like contact time, pH and adsorbent dose.With adsorbent dose, the percent removal increases upto certain point and thereafter remains constant.The adsorption was more in acidic conditions.The percentage removal increases with time upto certain point and then remains constant because of saturation.
Keywords: Adsorbent, concentration, heavy metal, adsorbate
1. INTRODUCTION
The heavy metal removal from effluent is very important envrionmental problem. Heavy metals can be toxic to living things at certain levels. Heavy metals can enter the environment by various sources like some mining industries, burning of fossil fuels, like coal, burning garbage or tobacco, and even forest fires, release heavy metals into the environment. Heavy metals can be absorbed by plants, wildlife and people through the food they eat. They can also be absorbed through water and breathing. Some heavy metals can become more concentrated when animals (predators) use other animals for food (prey) as part of the food chain. Chromium and iron are two such heavy metals. Chromium(III) occurs naturally in the environment, while chromium(VI) and chromium(0) are generally produced by industrial processes. In the form of the mineral chromites, it is used by the refractory industry to make bricks for metallurgical furnaces. Chromium is important ingredient in the compounds used in the chemical industries such as chrome plating, the manufacture of pigments, leather tanning, wood treatment, and water treatment. Exposure may occur from natural or industrial sources of chromium. Chromium III is much less toxic than chromium (VI). The respiratory tract is also the major target organ for chromium(III) toxicity, similar to chromium (VI). Chromium (III) is an essential element in humans. Human studies have clearly established that inhaled chromium(VI) is a human carcinogen, resulting in an increased risk of lung cancer. Animal studies have shown chromium (VI) to cause lung tumors via inhalation exposure. Chemical precipitation, Reverse osmosis, Ion exchange, Electro dialysis, Photo catalysis and Adsorption are few methods for chromium removal. The sources of iron in wastewater are the steel industries, mining,food, ulp and paper, organic and nuclear industries. The maximum acceptable concentration of Iron (II) in drinking water recommended by World Health Organization (WHO) is 0.2 mg/l. The most important techniques for its removal are chemical precipitation including coagulation–flocculation, flotation, filtration methods like ultrafiltration,nanofiltration and reverse osmosis, electrochemical
95 International Journal of Engineering & Technology Research (O) 2347-4904 ISSN Volume-2, Issue-3, May-June, 2014, www.iaster.com (P) 2347-8292
treatment techniques like electrodialysis, membrane electrolysis and chemical methods like electrochemical precipitation, electroextraction, sorption treatment techniques like ion exchange,adsorption. Removal of Cr(VI) and Hg(II)from aqueous solutions using fly ash and impregnated fly ash has been reported to be very efficient treatment method(Banerjee et al,2004)[1].Also sorption on saw dust for chromiumremoval has been carried out with success.(Dixit,1989)[2]. Research by use of various biosorbents for chromium removal has been reoported.(Gupta et.al, 2001, Huang et.al, 1979)[3,4]. Liquid−Liquid Extraction of Chromium(VI) with Tricapryl methyl ammonium Chloride Using Isoamyl alcohol as the Diluent was also carried (Kalidhasan et al,2010)[5].Cellulose-Clay Composite Biosorbent was tried for removal of chromium from industrial wastewater (Kumar et al.,2012) [6] Reverse osmosis membrane for chromium removal from aqueous solution was reported (Red et al.,2009) [7] .Biosorption by using husk of cicerarientinum has been used as efficient treatment technology for iron removal (Ahalya et.al.,2009)[8].
2. AIM AND OBJECTIVE
The current investigation aims at studying low cost adsorbents prepared from bagasse and groundnut shell for chromium and iron removal. It also involves comparative studies on removal of these metals by the two adsorbent. The parameters like adsorbent dose, time and pH were optimized.
3. METHODOLOGY
The adsorbent was prepared by initially sun drying the waste materials and then crushing. It was impregnated with strong hydrochloric acid and heated in a oven at about 400 degree C.It was then washed with hot water, dried and then used as adsorbent.Batch studies were carried out in a 500 ml conical flask. 100 ml of synthetic effluent was taken in flask.Then required amount of adsorbent was added to it. The sample was filtered after proper contact time and analyzed. The equilibrium concentrations were determined by spectrophotometric(SL-159) methods.
4. RESULT AND DISCUSSION
4.1 Effect of contact time:
Fig 1 shows effect of contact time or agitation time for iron and chromium removal. The values of equilibrium time for iron and chromium were 60 and 50 minutes. The percentage removal for chromium was slightly more, about 88 percent than that for iron , about 84 percent.
Fig.1: Effect of Contact Time for Bagasse Adsorbent Fig.2: Effect of Contact Time for Groundnut Shell for Iron and Chromium Removal Adsorbent for Iron and Chromium Removal
96 International Journal of Engineering & Technology Research (O) 2347-4904 ISSN Volume-2, Issue-3, May-June, 2014, www.iaster.com (P) 2347-8292
Fig3: Effect of Contact Time for Iron Using Bagasse Fig 4: Effect of Contact Time for Chromium Using and Groundnut Shell Adsorbent Bagasse and Groundnut Shell Adsorbent
From fig.2 it can be seen that , by using groundnut shell adsorbent, equilibrium is reached within 50 minutes with percentage removal of 84 percent for iron. In case of chromium, the equilibrium percentage removal of 86 percent was achieved in 70 minutes. If we consider removal of iron by these two adsorbent, grounut shell adsorbent needs less contact time of 50 minutes as compared to bagasse adsorbent, which needs 60 minutes for equilibrium.. It is depicted in fig.3. From fig. 4 it is evident that chromium needs more contact time i.e. 70 minute compared to 50 mnutes for iron.
4.2.Effect of Adsorbent Dose
For chromium, 2 grams/100 ml of adsorbent was optimum and for iron the optimum dose was 2.5 grams/100 ml using bagasse adsorbent as shown in fig.5. For grounutrshell adsorbent, adsorbent dose required was 2.5 grams for both iron and chromium removal as shown in fig.6. For removal of iron both the adsorbent were needed in same amount of 2.5 grams/100 ml, as shown in fig.7.From fig. 8 it is evident that For chromium removal 2-3 grams of bagasse adsorbent was optimum, and the optimum value for groundnut adsorbent was 2.5 grams.
Fig 5: Effect of Adsorbent Dose for Bagasse Fig 6: Effect of Adsorbent Dose for Groundnut Shell Adsorbent for Iron and Chromium Removal Adsorbent for Iron and Chromium Removal
97 International Journal of Engineering & Technology Research (O) 2347-4904 ISSN Volume-2, Issue-3, May-June, 2014, www.iaster.com (P) 2347-8292
Fig 7: Effect of Adsorbent Dose for Iron Using Fig 8: Effect of Adsorbent Dose for Chromium Using Bagasse and Groundnut Shell Adsorbent Bagasse and Groundnut Shell Adsorbent
4.3 Effect of pH
From fig.9, pH value of 5 was optimum for iron for bagasse adsorbent. For chromium, the optimum pH was 3. These pH values , had corresponding percentage removal of 81 and 87 percent respectively.For grounut shell adsorbent, the optimum pH values were 4 and 3 with removal percentage of 88 and 92 for iron and chromium as shown in fig.10. The removal of iron for two different adsorbents is plotted in fig 11 and removal of chromium by these two adsorbents is plotted in fig.12. For bagasse and groudnut shell, pH of 3 is the optimum pH for chromium removal. For iron, the optimum values of pH values for these two adsorbents were 5.5 and 4 respectively with removal percentage of 81 and 88 percent respectively.
Fig.9: Effect of Ph for Bagasse Adsorbent for Iron Fig.10: Effect of Ph for Groundnut Shell Adsorbent and Chromium Removal for Iron and Chromium Removal
Fig 11: Effect of Ph for Iron Using Bagasse and Fig 12: Effect of Ph for Chromium Using Bagasse Groundnut Shell Adsorbent and Groundnut Shell Adsorbent
98 International Journal of Engineering & Technology Research (O) 2347-4904 ISSN Volume-2, Issue-3, May-June, 2014, www.iaster.com (P) 2347-8292
5. CONCLUSION
The study carried out to study the adsorption of iron and chromium shows that the waste materials like bagasse and groundnut shells can be used effectively for heavy metal removal. The percentage removal of 90-92 percent has been obtained by using the adsorbent prepared from these materials. The optimum time, adsorbent dose for iron and chromium varies with the adsorbents used. Optimum contact time values were 50 and 70 minutes for iron by using bagasse adsorbent and groundnut adsorbent respectively. For chromium these values were 50 and 70 minutes respectively. Optimum adsorbent dose for iron by bagasse adsorbent and groundnut adsorbent was equal and was 2.5 grams each. For chromium, these values were 1.5 grams and 2.5 grams respectively. The optimum pH values for iron were 5 and 4 respectively for bagasse and groundnut adsorbent. The optimum pH for chromium was 3 for both the adsorbents.It can be concluded that the adsorption by using low cost adsorbents is very economical and efficient method for iron and chromium removal.
REFERENCES
[1] Banerjee S S, Joshi M V and Jayaram R V. 2004, Removal of Cr (VI) and Hg(II) from Aqueous Solutions using Fly Ash and Impregnated Fly Ash, Sep. Sci. Technol.,39,2004,pp.1611–1629. [2] Dikshit V. P., Removal of Chromium (VI) by Adsorption using saw-dust, Nat.Acad. Sci. Lett. 12(12),1989,pp 419-421. [3] Gupta V. K., Shrivastava A. K. and Neeraj Jain, Biosorption of Chromium(VI) From Aqueous Solutions by Green Algae Spirogyra Species, WaterResearch.35(17),2001,pp.4079-408. [4] Huang C.P., and Bowers A.R., The development of an activated carbon process for the treatment of chromium (VI) containing plating wastewater,2nd Conference on Advanced Pollution Control for the Metal Finishing Industries, Cincinnati, Ohio,1979,pp:114-122 [5] Kalidhasan, S., Sricharan, S.,Ganesh, m., Rejesh, N., Liquid Extraction of Chromium wih Tricaprylmethylammonium Chloride Using Isoamyl Alcohol as the Diluent and Its Application to Industrial Effluents, Journal of Chemical Engineering Data,55,2010, pp.5627-5633. [6] Kumar, A., Kalidhasan, S., Vidyarajesh, Rejesh, N., Application of Cellulose Clay Biosorbent towards the Effective Adsorption and Removal of Chromium from Industrial Wastewater, Ind. Engg. Chem. Res,52,2012,pp. 58-69. [7] Red, S., Mirbagheri, S., Mohammadi, T., Using Reverse Osmosis Membrane for Chromium Removal from Aqueous Solution, World Academy of Science, Engineering and Technology, 57,2009. pp.347-350 [8] Ahalya N, Kanamadi RD and Ramachandra TV 2006, Biosorption of Iron (III) using the husk of Cicerarientinum, Indian Journal of Chemical Technology,13,2006,pp.122-127.
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