A study of the mechanisms of divalent copper binding to a modified cellulose adsorbent

A modified cellulose material was prepared by grafting glycidyl methacrylate to cellulose (Cell-g-GMA) with subsequent functionalization with imidazole (Cell-g- GMA-imidazole). This latter compound was used in the adsorption of copper from aqueous solution. The mechanism of Cu(II) binding onto the cell-g-GMA-imidazole was investigated at the molecular level using scanning electron microscopy (SEM), Fourier transform infrared (FTIR), x-ray photoelectron spectroscopy (XPS), energy dispersive x-ray analysis (EDX) and X-ray diffraction (XRD). FTIR and Raman spectroscopy provided an insight into the extent to which perturbation of the imidazole ring occurred following adsorption of the metal while XPS spectra indicated the binding of Cu(II) ions to nitrogen atoms by the appearance of additional binding energy peaks for nitrogen on the cellulose- g-GMA-imidazole sample post adsorption. The EDX technique provided clear evidence of the physical presence of both the copper and sulfate on the cellulose-g-GMA-imidazole material post adsorption. XRD analysis further confirmed the presence of a copper species in the adsorbent material as copper sulfate hydroxide (Cu₃(OH)₄SO ₄ - antlerite). The XRD studies further suggest that the overall extent of Cu(II) adsorption is not alone a combination of true metal chelation as suggested by FTIR, Raman and XPS, but also a function of surface precipitation of the polynuclear copper species.