Equilibrium, thermodynamic and kinetic studies on biosorption of Pb(II) and Cd(II) from aqueous solution by macrofungus (Lactarius scrobiculatus) biomass

The equilibrium, thermodynamics and kinetics of the biosorption of Pb(II) and Cd(II) onto (Lactarius scrobiculatus) macrofungus from aqueous solution were investigated at different experimental conditions. Optimum experimental parameters were determined to be pH 5.5, contact time 60 min, biomass concentration 4 g/L of solution, and temperature 20 °C. The maximum biosorption capacity of L. scrobiculatus was found to be 56.2 mg/g for Pb(II) and to be 53.1 mg/g for Cd(II). The mean free energy values evaluated by using the Dubinin-Radushkevich (D-R) model indicated that the biosorption of the metal ions onto L. scrobiculatus biomass was taken place by chemical ion-exchange. The kinetic studies indicated that the biosorption process of the metal ions followed well pseudo-second order model. The calculated thermodynamic parameters (ΔG°, ΔH° and ΔS°) showed that the biosorption of Pb(II) and Cd(II) ions onto L. scrobiculatus biomass was feasible, spontaneous and exothermic in nature. The recovery of the metal ions from L. scrobiculatus biomass was found as higher than 95% using 1 M HCl and 1 M HNO₃. Furthermore, the reusability of the biosorbent was determined after six consecutive sorption-desorption cycles.