Thermodynamic and kinetic investigations of a chelating membrane bearing polyaminecarboxylate groups towards Ni(II)

Melamine-diethylenetriaminepentaacetic acid/polyvinylidene fluoride (MA-DTPA/PVDF) chelating membrane bearing polyaminecarboxylate groups was used to remove Ni(II) from the solutions. The adsorption characteristic of the membrane towards Ni(II) was investigated in Ni(II)–Ca(II), Ni(II)–, and Ni(II)–Fe(III) binary systems. The organic complex systems including Ni(II)–lactic acid, Ni(II)–succinic acid, and Ni(II)–citric acid were also considered. The effects of the aforementioned coexistent cations and organic acids were determined based on the experimental data. Lagergren second-order equation and Langmuir model were competent for descriptions of the adsorption kinetics and the isotherms, respectively. The chemical chelation predominated the adsorption process. In the binary systems with the presence of coexistent cations, Ca(II) tended to form a more stable complex with MA-DTPA ligand of the membrane than and Fe(III), and Ca(II) could interfere with the formation of Ni(II)–MA-DTPA complex. The stabilities of Ni(II)–organic acid complexes followed the order of lactic acid < succinic acid < citric acid, but they cannot be comparable to that of Ni(II)–MA-DTPA complex. Therefore, the chelating membrane had a potential Ni(II) recovery from wastewater of the electroless nickel plating and electroplating industries.