Simultaneous Removal of Heavy Metals and Organics using Biosorbents: A Review

This   work is a compilation of the studies done over the past decade on the simultaneous removal of co-existing heavy metals (HMs) and organics using biosorbents. A summary of the origin and classification of biosorbents were compiled. The mechanisms of biosorption of HM and organics were also studied, with emphasis on the effects of the functional groups of the biosorbents.  Furthermore, the optimum operating conditions of the solution pH, kinetics and isotherms were also investigated.  An attempt was made to investigate the synergistic and antagonistic effects of the pollutants on each other. The biosorption process were mostly suited to the Langmuir and Freundlich isotherms, while the pseudo second order (PSO) kinetics provided the best fit for most of the adsorption studies. The study also revealed that while adsorption capacities are usually higher in single component adsorption (SCA) systems, adsorption   of HMs and organics in multi-component adsorption (MCA) systems can be more than that in their individual SCA systems. The study showed the non-utilization of the modified isotherms for the equilibria studies of multi-component adsorption system, this may lead to the inaccuracy of the results obtained.