Removal of Hexavalent Chromium from Contaminated Waters By Mangifera indica Seed Powder (Biosorption)

Industrialization & urbanization of developing cities in unplanned manner has resulted in long term ecotoxicological impact on environment and human health. Certain metals such as chromium, mercury, lead, cadmium, etc., in wastewater are hazardous to the environment because of their toxicity and pollution impacts on our ecosystem. Among the different heavy metals, hexavalent chromium is a common and very toxic pollutant introduced into natural waters from a variety of industrial wastewaters. The Hexavalent Chromium discharged from various industries as solid or liquid waste has great potential to contaminate drinking water sources due to its more solubility and is one of the most important environmental problems due to its health impacts on human. Water quality regulatory authorities (WHO, BIS, ICMR) have recommended the maximum limit of 0.05 mg/L for drinking purposes. Adsorption is one of the effective techniques for hexavalent chromium removal from wastewater. In the present study, adsorbent has been prepared from Mangifera indica seed powder and studies are carried out for chromium (VI) removal. The parameters investigated in this study are contact time, adsorbent dosage, temperature, variable initial chromium (VI) concentration and pH using Diphenyl carbazide as color developing reagent and taking the absorbance at 540 nm spectrophotometrically. The adsorption process of chromium (VI) is tested with Linear, Langmuir and Freundlich isotherm models. Application of the Langmuir isotherm to the systems yielded maximum adsorption capacity of 23.25 mg/g at a solution pH of 7 having Cr (VI) concentration 50 mg/L and biosorbent dose 1g/L. The adsorption of chromium (VI) was found to be maximum 97.66% at low pH values of 2 having Cr (VI) concentration 50 mg/L and biosorbent dose 1g/L. The contact time of 60 min resulted to the 40.42% adsorption of metal in 50mg/L solution using adsorbent dose of 1g/L and can used for removal of chromium (VI) from the polluted water as a very low cost biosorbent. The scanning electron microscopy carried out shows the change in biosorbent surface significantly on edge of particles after hexavalent chromium adsorption.