A novel Pb(Ⅱ)ion-imprinted composite membrane with microporous polypropylene membrane(MPPM)as support was prepared by a modified UV-induced graft copolymerization.In the graft strategy

benzophenone was immobilized on membrane by combining physical entrapment and UV-induced covalent immobilization methods.The adsorption and selectivity capabilities of the imprinted composite membranes towards Pb(Ⅱ)were investigated with equilibrium adsorption and competitive permeation experiments.The imprinted composite membranes exhibit good adsorption and permselectivity towards Pb(Ⅱ).The maximum adsorption capacity towards Pb(Ⅱ)is 2.86 and 2.75 times that towards Cu(Ⅱ)and Zn(Ⅱ)

respectively

and the permeation amount of Pb(Ⅱ)in 48 h is 3.8 and 3.1 times.Langmuir adsorption isotherm models fit the equilibrium experimental data well(R2≥0.991)

indicating that the sorption is of monolayer-mode.The kinetics of the adsorption towards heavy metal ions follow the Lagergren pseudo- second-order model(R2≥0.998

ΔQ<10%)

and the adsorption process is dominated by chemical interaction.The thermodynamic parameters of Gibbs free energy change(ΔG)

enthalpy changes(ΔH)

and entropy change(ΔS)are calculated.Negative values of ΔH suggest exothermic nature of the adsorption

and negative values of ΔG indicate spontaneous nature of process.|ΔH| > |TΔS| suggests that the adsorption of heavy metal ions on the imprinted composite membranes is driven by enthalpy.