Removal of Hexavalent Chromium Ion (Cr6+) From Industrial Effluents Using Low Cost Bio-Adsorbents: A Review

Corresponding Email- radhadas6@gmail.com Department of Chemical Engineering, Haldia Institute of Technology, Haldia 721657, India School of Applied Sciences and Humanities Effluents from various industries like electroplating, leather tanning, cement, petrochemicals, dye etc, contains significant amount of toxic hexavalent chromium, Cr(VI) with concentration of 10th to 100th ppm level. The toxic and carcinogenic effects of heavy metals present in industrial damages kidney function and lungs activity, also leads to respiratory problem in the aquatic life and human beings. Industrial effluents containing hazardous metals pollutes the soil and surface water . To avoid the health hazard from long term exposure of Cr(VI) , there is high demand of feasible cost effective, clean technologies which would save environment . Many technologies are used to eliminate the Cr(VI) from the industrial wastes are precipitation, coagulation, membrane separation and ion exchange. Adsorption is one of the low cost , environment friendly methods widely used for the elimination of toxic metals from industrial effluents mostly Cr(VI) . This review presents about the use of different types of waste materials as natural adsorbents for the removal of Cr(VI) from waste effluents. Results obtained from the experiments were fitted to the various isotherms and kinetic models. The effect of various factors on toxic heavy metals reduction have been studied thoroughly . The literature show that the effective removal of Cr(VI) from industrial effluent is strongly dependent on adsorbent amount , adsorbent type, time of contact , pH of the media, concentration of Cr(VI) ions and operating temperature. It was suggested by the researchers that the activated leaves and agricultural wastes may be applied as low coast alternative bio-sorbents as replacements of different chemicals for removal of metals from water . However, gaps have been recognized for the development of methodologies, regeneration od adsorbents, reuse of treated water and harmless disposal of the sorbents, optimization and industrialization of the appropriate agricultural adsorbents