Assessment of copper(II) biosorption from aqueous solution by agricultural and industrial residues

In this study, newspaper scraps (NS) and maize spatha (MS) treated in turn by HNO₃ and MeOH were evaluated for the biosorption of Cu²⁺ ions, on the basis of batch experiments. The effects of several parameters were investigated, including contact time, solution pH, shaking speed, biosorbent dosage and ionic strength. Under optimal conditions, the maximum sorption capacities (Q_max) were (60.386 ± 0.006) and (44.90 ± 0.02) μmol Cu²⁺ per g of sorbent, respectively, for NS and MS chemically treated with HNO₃. The optimal parameters were pH: 5, contact time: 40 min and shaking speed: 100 rpm for NS, while for MS the same parameters were pH 5, 20 min and 150 rpm, respectively. It was found that Cu²⁺ biosorption is disfavored by an increase in ionic strength and by the presence of some interfering cations. The experimental data obtained with NS best matched the Langmuir’s sorption model (R² = 0.994) while the Temkin model best described biosorption on MS (R² = 0.987). The biosorption of Cu²⁺ on both materials followed pseudo-second order kinetics, and the desorption of Cu²⁺ ions was effective in 0.01 M HCl solution.