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 10^th to 100^th 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.