Cu(II) Ion Adsorption onto Hydroxymethylated Lignin-Chitosan Crosslinked Membrane

A crosslinked chitosan membrane (I) and a hydroxymethylated lignin-chitosan crosslinked membrane (II) were prepared using glutaraldehyde as the crosslinking agent. Fourier transform infrared spectroscopy (FTIR) was used to identify the chemical structures of the crosslinked membranes and the presence of an absorption peak at 1515 cm-1 indicated the presence of lignin. Scanning electron microscope (SEM) images revealed that membrane (I) possessed a smooth surface, while membrane (II) exhibited a homogeneous embossed surface without any agglomeration. The Cu(II) ion adsorption properties of both membranes were analyzed. The results indicated that the static adsorption capacities of membranes (I) and (II) were 195 g Cu(II)/cm2 and 275 g Cu(II)/cm2, respectively, and their dynamic chelation capacities were 2.89 g Cu(II)/cm2 and 4.59 g Cu(II)/cm2, respectively. Membrane (I) was suitable only for use in aqueous solutions with pH values of 3.5 to 9.0, while membrane (II) maintained its shape even in concentrated hydrochloric acid or 1 M NaOH solution. The Cu(II) ion absorption properties and resistance to acid and alkali of membrane (II) were superior to those of membrane (I), indicating that hydroxymethylation of the lignin-chitosan crosslinked membrane is worthy of further investigation.