Comparative analysis of Cu(II) and Ni(II) removal using <i>Agaricus bisporus</i> mushroom and spent mushroom compost as biosorbents

The use of agricultural waste products as biosorbents for the removal of heavy metals is inclining nowadays, as they are highly efficient and economically reliable. In the present study, <i>Agaricus bisporus</i> mushroom (ABM) and its spent mushroom compost (SMC) samples are used as biosorbents to find and compare their efficiency for the removal of Cu(II) and Ni(II) ions from aqueous solutions. The optimal conditions for maximum biosorption were obtained at pH 5, 0.5 g biosorbent dosage per 10 mL, 6 h of contact time, and initial concentration of 17 and 30 µg/mL for Cu (II) and Ni(II). Pseudo second order kinetic model, with (<i>R</i>² > 0.999) for both the metals and Freundlich isotherm model with (<i>R</i>² > 0.959) for Cu(II) and (<i>R</i>² > 0.985) for Ni(II) best described the biosorption data. Thermodynamic analysis revealed the spontaneous and endothermic nature of the biosorption process. The SEM, EDX, and FTIR analysis were conducted to determine the metal uptake and presence of functional groups responsible for biosorption of metals. FESEM analyses has confirmed the surface morphology; the presence of Cu(II) and Ni(II) peaks after adsorption were confirmed by EDX; and the FTIR study confirmed the presence of hydroxyl, carboxyl, amine, phosphate, and amide functional groups in the biomass. The results demonstrated that SMC exhibited greater biosorption efficiency [93.88% for Cu(II) and 88.5% for Ni(II)] than ABM [91.43% for Cu(II) and 86.63% for Ni(II)], in order Cu(II) > Ni(II), making both viable options for the removal of heavy metals from aqueous medium. Furthermore, both the biosorbents have shown remarkable regeneration and recyclability up to eight adsorption-desorption cycles with appreciable adsorption for both the metals.