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 solu-tions. The biomass was characterized by Inductively Coupled Plasma-Mass (ICP-MS) spectrome-try 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) spec-troscopy, before and after adsorption. The influence of contact time (up to equilibrium), adsor-bent dose (1-50 g/L), initial metal ion concentration (5-300 mg/L) and pH (2-8) on copper sorp-tion 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 ad-sorption 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 effi-ciency. Kinetic data were satisfactorily fitted to the second-order kinetic model. Intraparticle dif-fusion 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 ef-ficient, renewable and economic adsorbent for metal removal and its use for that purpose consti-tutes an alternative for its management and valorization.

Automated summary

Untreated Pinus radiata sawdust was found to be a promising and efficient adsorbent for the removal of Cu+2 ions from aqueous solutions. The best conditions for adsorption efficacy (93.4% removal percentage and 0.82 mg/g adsorption capacity) were achieved by increasing the adsorbent dose to 5 g/L, adjusting the solution pH to 7, and decreasing the initial metal ion concentration to 5 mg/L. The adsorption process involved different stages and fitted well with the Langmuir isotherm and second-order kinetic model. Additionally, high desorption efficiencies up to 94.5% were achieved, and the possibility of sawdust regeneration was studied.