Adsorption Investigation Of PVDF Chelating Membrane Modified By The Diethylenetriaminepentaacetic Acid Towards Copper Ions In Copper-Plating Wastewater

A 3-aminopropyltrimethoxysilane-diethylenetriaminepentaacetic acid/polyvinylidene fluoride(APTMS-DTPA/PVDF) chelating membrane was employed to remove Cu(II) from aqueous solution. The surface and sectional morphologies of the chelating membrane, the elements distribution and functional groups before and after Cu(II) adsorption were characterized by SEM, EDS, XPS, FTIR techniques. Adsorption investigation of this chelating membrane modified by the diethylenetriaminepentaacetic acid towards Cu(II) was carried out using density functional theory(DFT) on the basis of experimental results. It reveals the influences of coexisting cations and organic complexing agent on the chelating membrane towards Cu(II) adsorption on the molecular level, which will provide an insight for the removal of Cu(II) from Cu(II)-EDTA solution.Herein, the influences of Co(II), Ni(II), tartrate and ethylenediaminetetraacetic acid(EDTA) on the sorption of Cu(II) by the chelating membrane was investigated via a series of tests. Isotherms and kinetics of the membrane sorption process towards Cu(II) in the presence of the two other cations and the two complexing reagents were elucidated. It shows that EDTA exhibits a much more negative influence on Cu(II) uptake than Ni(II), Co(II) and tartrate. The interference of the four coexistent substance follows the order of EDTA > Ni(II) > Co(II) > TA. Adsorption isotherms and adsorption kinetics are fitted to the Langmuir and the Lagergren second-order models, respectively. The thermodynamic parameters demonstrate the spontaneous and exothermic nature of the adsorption. Results of DFT computations indicate that Cu(II) shows a higher electrophilicity than Co(II) and Ni(II); Ni(II) exhibits a much more negative influence on Cu(II) uptake than Co(II) and EDTA exhibits a much more negative influence than tartrate.To improve the adsorption properties of APTMS-DTPA/PVDF chelating membrane towards Cu(II) in the Cu(II)-EDTA solution effectively, detailed studies regarding the addition of Ca(II), Fe(II), Fe(III) were carried out. The batch adsorption experiments with respect to the kinetics and isotherms were performed with the presence of the three cations. In addition, the breakthrough curves were determined in the continuous adsorption tests. The results show the addtions of metallic cations can stimulate the adsorption of Cu(II) effectively, and the stimulative roles of them are in the order of Fe(III) > Fe(II) > Ca(II). Lagergren second-order model and Langmuir model are suitable for describing the adsorption kinetics and adsorption isotherms of the chelating membrane towards Cu(II) for the four systems Cu(II)-EDTA, Cu(II)-Ca(II)-EDTA, Cu(II)-Fe(II)-EDTA and Cu(II)-Fe(III)-EDTA. Also, the coexistence of the three cations increases the breakthrough time, exhaustion time, and show the positive effects on the Cu(II) uptake of the chelating membrane. Compared with Ca(II) and Fe(II), the addition of Fe(III) enhances the Cu(II) uptake of the membrane by 68% and 29%, respectively.