DFT investigation of the effects of coexisting cations and complexing reagents on Ni(II) adsorption by a polyvinylidene fluoride-type chelating membrane bearing poly(Amino phosphonic acid) groups

Abstract

A polyvinylidene fluoride (PVDF)-type chelating membrane bearing poly(amino phosphonic acid) groups, denoted as ethylenediamine tetra(methylene phosphonic acid) (EDTMPA)-tetrabutyl orthotitanate (TBOT)/PVDF, was employed to remove Ni(II) from the aqueous solution. The effects of coexisting Ca(II), Pb(II), citrate, nitrilotriacetic acid (NTA) and ethylenediaminetetraacetic acid (EDTA) on the Ni(II) adsorption by this chelating membrane were revealed using density functional theory (DFT) calculations. Pb(II) showed a more detrimental effect than Ca(II) on the Ni(II) uptake; EDTA interfered with the capture of Ni(II) more remarkably than citrate and NTA. The results derived from DFT calculations were consistent with the experimental data. Ni(II) and Pb(II) showed more excellent affinity to the EDTMPA-TBOT/PVDF membrane than Ca(II). The stabilities between Ni(II) and the [EDTMPA-TBOT]7− chelating ligand of the membrane and those between Ni(II) and the three aforementioned complexing reagents followed the sequence: [Ni(II)-(EDTMPA-TBOT)]5− > Ni(II)-EDTA > Ni(II)-NTA > Ni(II)-citrate. The complexation between Ni(II) and the chelating membrane was prominent with the presence of citrate, NTA and EDTA.