[Characterization and thermodynamic properties of Cu(II) imprinted chitosan crosslinked membrane]

A new type of Cu(II)-imprinted chitosan crosslinked membrane (IM Cu(II)-E-CTS) was prepared via molecular imprinting technology, chemical pre-crosslinking and crosslinking methods for treatment of wastewater containing low concentration of copper ion. IM Cu(II)-E-CTS was characterized by porosity, swelling ratio, amino group content, surface morphology, functional group and crystallinity. The thermodynamic properties of Cu (II) adsorption on the as-synthesized membrane at the low concentration (20-70 mg x L(-1)) were studied. It is found that porosity, swelling ratio and amino group contents of IM Cu(II)-E-CTS are 76.9%, 109% and 4.26 mmol x g(-1), respectively. Compared to the pristine chitosan membrane (CTS), 44.0% lower swelling ratio, 528% higher of porosity, 16.5% lower of amino group content are found with IM(Cu) (II)-E-CTS. Compared to crosslinked chitosan membranes (E-CTS), 24.6% higher amino group content is found with IM(Cu) (II)-E-CTS. Compared to CTS and E-CTS, the membrane morphology of IM Cu(II) E-CTS has undergone significant changes, and the internal structure became loose. Compared with CTS, molecular chain of IM Cu(II)-E-CTS is irregular and its crystallinity ability is lowered. IM Cu(II)-E-CTS adsorbs more Cu(II) than that of the other two metal cations [Ni(II) and Zn(II)]. The adsorption of copper ion on IM Cu(II)-E-CTS for 20-70 mg x L(-1) of initial Cu(II) concentration follows the Freundlich adsorption isotherm (R2 > 0.99). The adsorption is a spontaneous, exothermic, and entropy-decreased process.