Removal of copper from aqueous solutions by biosorption onto pine sawdust

Untreated Pinus radiata sawdust was investigated for the removal of Cu+2 ions from aqueous solutions. The biomass was characterized by Inductively Coupled Plasma-Mass (ICP-MS) spectrometry and by Scanning Electron Microscopy with an Energy Dispersive X-ray spectroscopy (SEM-EDX), X-Ray crystalline powder Diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy, before and after adsorption. The influence of contact time (up to equilibrium), adsorbent dose (1–50 g/L), initial metal ion concentration (5–300 mg/L) and pH (2–8) on copper sorption efficiency was studied through batch experiments. The results demonstrated that adsorption equilibrium is reached in less than 2 h and the best conditions (Cu+2 removal percentage, 93.4% and adsorption capacity, 0.82 mg/g) were achieved by increasing the adsorbent dose up to 5 g/L and the solution pH up to 7, and decreasing the initial metal concentration to 5 mg/L. The adsorption was optimized by means of a Doehlert experimental design analyzing the influence of adsorbent dose (5–15 g/L) and copper initial concentration (5–45 mg/L) on adsorption efficiency. Kinetic data were satisfactorily fitted to the second-order kinetic model. Intraparticle diffusion model demonstrated that different stages are involved in the adsorption process. Langmuir isotherms fitted satisfactorily the copper bioadsorption equilibrium data. Desorption studies achieved high efficiencies up to 94.5% and the possibility of sawdust regeneration was studied with four adsorption-desorption cycles. Thus, this study evidenced that sawdust is a promising efficient, renewable and economic adsorbent for metal removal and its use for that purpose constitutes an alternative for its management and valorization