Preparation And Adsorption Properties Of Cu (Ⅱ) Imprinted Chitosan Crosslinked Membrane

Chitosan which is a natural polymer material with application value has become a hot research of new materials field, because it has good biocompatibility, biodegradability and well filmed.A new type of Cu(Ⅱ) imprinted chitosan crosslinked membrane (Cu (Ⅱ)-CTS crosslinked membrane) was prepared via molecular imprinting technology, chemical pre-crosslinking and crosslinking methods. The effect of preparation conditions on adsorption capacity was studied. Cu (Ⅱ)-CTS crosslinked membrane were characterized by porosity, swelling ratio, amino group content, surface morphology, functional group and crystallinity. The membrane was applied in the adsorption of low concentration(20-70mg/L) in waste water. The effect of pH, temperature, specific thickness, adsorption kinetics, adsorption thermodynamic, adsorption selectivity, regeneration were studied.Preparation and characterization experiments show that the preparation conditions ars that the best template molecule is CuSO4, the mole ratio of chitosan construction unit and Cu(Ⅱ) is 17, the mole ratio of formaldehyde and chitosan construction unit is 3, the mole ratio of epichlorohydrin and chitosan construction unit is 1.5, the best crosslinking temperature is 40℃, the best reaction temperature of hydrochloric acid is 80℃for 7h. The sequence of the preparation condition that effected the adsorption is:dosage of Cu(Ⅱ)> dosage of epichlorohydrin(ECH)> crosslinking temperature of ECH> dosage of formaldehyde.Adsorption experiments show that the optimum pH is 4, and the adsorption capacities reach adsorption equilibrium 19h. Adsorption reaction is exothermic, and lower temperatures is favor to the reaction. Reducing specific thickness can increase adsorption capacities. The adsorption of IMCu(Ⅱ)-E-CTS for 20～70 mg·L-1 of Cu(Ⅱ) concentration follows the Freundlich adsorption isotherm (R2>0.99). The adsorption is a spontaneous, exothermic, and entropy-decreased process. The adsorption process accords with second-order kinetic rate mode. The results on the experiment of selectivity adsorption indicate that IMCu(Ⅱ)-E-CTS has the ability of recognition to Cu(Ⅱ) (k(Cu/zn)=7.88,k(Cu/Ni)=7.33). It is also found that IMCu(Ⅱ)-E-CTS has good reusability and adsorption capacities for Cu(Ⅱ) after reused for 8 times. Porosity, swelling ratio and amino group content of IMCu(Ⅱ)-E-CTS are 76.9%,109% and 4.26 mmol/g, respectively. Compared to the pristine chitosan (CTS) membrane,44.0% lower swelling ratio, 528% higher of porosity,16.5% lower of amino group content are found with IMCu(Ⅱ)-E-CTS. Compared to crosslinked chitosan membranes(E-CTS),24.6% higher amino group content is found with IMCu(Ⅱ)-E-CTS. The SEM imege indicetes that the membrane morphology of IMCu(Ⅱ)-E-CTS has undergone significant changes, and the internal structure became loose. The infrared spectrum shows that every reaction step has happened. XRD shows that molecular chain of IMCu(Ⅱ)-E-CTS is irregular and its crystallization ability is lowered. The adsorption is realized through binding -NH2 and -OH in IMCu(Ⅱ)-E-CTS with ions. Cu(Ⅱ) can chelate the active group consisting in crystallization of chitosan.