Kinetic and thermodynamic studies on biosorption of Cu(II) by chemically modified orange peel

Cu(II) biosorption by orange peel that was chemically modified with sodium hydroxide and calcium chloride was investigated. The effects of temperature, contact time, initial concentration of metal ions and pH on the biosorption of Cu(II) ions were assessed. Thermodynamic parameters including change of free energy), (ΔGθ), enthalpy (ΔHθ) and entropy (ΔSθ) during the biosorption were determined. The results show that the biosorption process of Cu(II) ions by chemically treated orange peel is feasible, spontaneous and exothermic under studied conditions. Equilibrium is well described by Langmuir equation with the maximum biosorption capacity(qm) for Cu(II) as 72.73 mg/g and kinetics is found to fit pseudo-second order type biosorption kinetics. As the temperature increases from 16 °C to 60 °C, copper biosorption decreases. The loaded biosorbent is regenerated using HCl solution for repeatedly use for five times with little loss of biosorption capacity.