Adsorption Investigation Of Polyethersulfone-Type Chelating Membrane Towards Lead Ions

In this research,with the combined technique of the chemical grafting and phase inversion pocesses,reagents containing polyethersulfone?PES?,chloroacetyl chloride,and diethylenetriamine,methyl alcohol,trimethylamine,paraformaldehyde and phosphorous acid were employed to prepare a PES-type chelating membrane.Then the fabricated membrane was used to remove Pb???from the wastewater.The optimal dosages of the above reagents were optimized by the orthogonality experiment.The PES-based chelating membrane was characterized by Field-Emission Scanning Electron Microscope?SEM??energy dispersive X-ray spectrometry?EDS??X-rayphotoelectronspectroscopy?XPS?andFouriertransforminfrared spectroscopy?FTIR?techniques.Dynamic adsorption experiments were performed in view of pH,temperature,contact time and initial Pb???concentration as the controlling parameters.Concentrations of the coexisting Cd???,Cu???,Ni???,citrate,nitrilotriacetic acid?NTA?and ethylenediaminetetraacetic acid?EDTA?were varied to assess their effects on the Pb???adsorption.The adsorption kinetics,adsorption isotherms,and breakthrough curves of the modified PES-type chelating membrane toward Pb???at the presence of above-mentioned coexisting substances were also elucidated.Furthermore,the adsorption-diffusion differential equation was also analyzed.Finally,the adsorption/desorption experiment was carried out.The FTIR results suggest the poly?amino phosphonic acid?polymer have been grafted to the chelating membrane successfully and the chelation dominates in the Pb???adsorption.The EDS and XPS results show that the PES-based separation membrane was exposed to concentration gradients along the thickness of the separation membrane,and this result is in accordance with that of the analysis of adsorption-diffusion equation.The PES-based separation membrane exhibits a considerable affinity toward Pb???,and the uptake of this metal ion is beyond to 0.88mmol g^-1.At the presence of coexisting substances,the decrease in Pb???uptake of the membrane was validated.The coexistent cations interfere the Pb???adsorption in the order of Cu???>Ni???>Cd???.The negative effect of the three organic acids is in the order of citrate<nitrilotriacetic acid?NTA?<ethylenediaminetetraacetic acid?EDTA?.The Langmuir,and the Lagergren second-order models are competent for the descriptions in adsorption isotherms and adsorption kinetics of the Pb???capture.The thermodynamic parameters?G⁰<0??H⁰<0??S⁰>0,demonstrate the spontaneous and exothermic nature of the Pb???uptake by the membrane.Moreover,the adsorption/desorption test manifests that this PES-type separation membrane possesses an excellent property of reuse.