Biosorption of Cd2+ using the fruiting bodies of two macrofungi

Discharge of heavy metals containing effluents into the water bodies contaminates the aqueous environment. This is one of the most serious environmental issues of the century. The conventional methods used for metal removal become less effective and more expensive when the volumes of wastewater are high, and the metal concentrations are low. Biosorption technology has gained important credibility during recent years because of its eco-friendly nature, excellent performance, and cost-effectiveness. Fruiting bodies of macrofungi are considered ideal for the biosorption of heavy metals, because it has been demonstrated that many fungal species exhibit high biosorptive potentials. Macrofungi grow prolifically and are found in many parts of the world. They are macro in size, tough in texture and have other physical characteristics conducive for their development as biosorbents without the need for immobilization or deployment of sophisticated reactor configuration as in the case of microorganisms. The aim of the present work was to evaluate the biosorption capacity of two different macrofungi, Trametes robiniophila and Fomes fomentarius in respect of heavy metals, viz. cadmium from aqueous solutions. The biosorption characteristics of Cd 2+ from aqueous solution using the fruiting bodies of two macrofungi belonging to Polyporaceae (T. robiniophila and F. fomentarius) was investigated as a function of initial pH, biosorbent dosage, contact time, and initial Cd 2+ concentration. The optimum initial pH of the aqueous solution was found to be 6.0 for the removal of low concentrations Cd 2+ (10 mg/ L). The percent removal of Cd 2+ was found to increase with the increase in biosorbent dosage and contact time, and the biosorption of Cd 2+ by two macrofungi all achieved equilibrium with biosorbent dosage of 2 g/ L. The contact time achieved the biosorption equilibrium was 30 min for T. robiniophila and 60 min for F. fomentarius. Langmuir and Freundlich models are the most widely used models in the case of the adsorption of metal ions with biosorbents. Langmuir and Freundlich models were applied to describe the biosorption isotherm of Cd 2+ by T. robiniophila and F. fomentarius. Langmuir model fitted the equilibrium data all better than the Freundlich isotherm for two macrofungi. The maximum biosorption capacities of T. robiniophila and F. fomentarius were found to be 17.40 and 8.91 mg/ g, respectively, at optimum conditions of pH 6.0, contact time of 60 min and biosorbent dosage of 2 g/ L. The prediction of biosorption rate gives important information for designing batch biosorption systems. Information on the kinetics of pollutant uptake is required for selecting optimum operating conditions for full-scale batch process. In order to clarify the biosorption kinetics of Cd 2+ onto T. robiniophila and F. fomentarius fruiting bodies, two kinetic models, pseudo-first-order and pseudo- second-order models were applied to the experimental data. The results showed that the biosorption processes of Cd 2+ by two macrofungi followed well pseudo-second-order kinetics. Chemical ion-exchange may be the main mechanism for the biosorption of Cd 2+ by two macrofungi. Based on all results, it can also be concluded that T. robiniophila and F. fomentarius can be used as alternative biosorbent to treatment wastewater containing Cd 2+ since they are low-cost biomass and have a considerable high biosorption capacity.