Use of microorganisms and agro-industrial wastes in the biosorption of chromium (VI): a review

Due to non-biodegradable nature, chromium (VI) ions in wastewater build up over time, reaching concentrations that are damaging for both the environment and human health. Extensive research has been carried to develop different techniques for the elimination of Cr (VI) from industrial effluents. However, recent developments have shown that agro-industrial wastes have the potential as biosorbents due to their lignocellulose composition. While microorganisms have the capability of reducing metallic ions. Thus agro-industrial wastes and biomass as biosorbents for Cr (VI) elimination from wastewater, have several advantages such as cost-effectiveness, high adsorption capacities, and ease of recovery and availability. In this review, the application of diverse biosorbents for Cr (VI) remediation have been summarized; additionally, the important role of some fundamental parameters, such as pH, temperature, treatment and pre-treatment time, of the process has been considered. Finally, representative models have been proposed for the mechanisms of reduction of Cr (VI) to Cr (III). Based on these mechanisms we believe that a method supported on the interaction and synergy between microorganisms and agro-industrial waste materials could present a viable solution to increase the efficiency in the removal and reduction of Cr (VI) to Cr (III). Graphical abstract: [Figure not available: see fulltext.].