Biosorption of Cu²⁺ and Ni²⁺ Ions from Synthetic Waters

In this study, biosorption of Cu²⁺ and Ni²⁺ ions to tobacco stalks was investigated under different operational conditions. The effects of the initial pH, ion concentrations, temperature, and duration of contact and adsorbent dosage were determined in the batch experiments. Chemical oxygen demand (COD) analyses were also performed to identify the possible negative effects of the sorbent throughout biosorption process. The sorption capacities of this sorbent were predicted by use of the equilibrium and kinetic models. Within the scope of kinetic study, it was observed that biosorption fitted to second-order pseudo kinetic rate expression. The highest R ² value in isotherm studies was obtained from Freundlich isotherm (R ² = 0.9940-0.9929) for the inlet concentration. FTIR, SEM, and EDX analyses were performed to investigate the surface characteristics and chemical structure of the biosorbent. Under optimum conditions, qe value for Cu²⁺ was determined as 7.18 mg/g and removal efficiency was 86.24%; qe value for Ni²⁺ was determined as 6.45 mg/g and removal efficient was 77.4%. Sorbent recovery process was also performed within the scope of this study with 0.1 M H₂SO₄, 0.1 M HCl, and distilled water. A significant decrease was observed in efficiency when the recovered sorbent was reused.