Characterstics and adsorption capacities of biosorbents for removal of Cr (VI) from aqueous solution: A Review

Low-cost biosorbents can be made from the by-products of agricultural, household and various industrial processes. It has been proved by several researches that these biosorbents provide a better solution for the removal of contaminants from wastewater. The object of the study is to find a sustainable low cost biosorbent for the removal of Cr (VI) from wastewater. In current review both adsorbent’s characteristics and adsorption capacities of nine biosorbents for the removal of Cr (VI) from aqueous solution were studied. Batch experiments of various adsorbents revealed the optimum conditions required for better removal of this heavy metal. The results showed that maximum adsorption occurs at highly acidic pH. Contact time, initial conc. of adsorbent & adsorbate also affect the heavy metal removal efficiency of biosorbent material. Under optimum conditions, the removal efficiency of adsorbent prepared from mango kernel was found upto 100% out of nine adsorbents studied. The Langmuir and Freundlich adsorption isotherm gave the better explanation for the surface properties of adsorbents. Maximum Cr (VI) uptake per unit mass (Qmax.) values obtained from Langmuir adsorption isotherm for different biosorbents ranged from 6.17mg/g to 151.51mg/g. The adsorption kinetics was explained through pseudo-first order and pseudo-second order kinetic model. The results of study suggest that these biosorbents could be a better solution for the removal of Cr (VI) from the wastewater.