Pb²⁺ selective and highly cross-linked zirconium phosphonate membrane by sol-gel in aqueous media for electrochemical applications

Zirconium diethylene triamine pentamethylene phosphonic acid (ZrD) was synthesized and showed high adsorption capacity for Pb²⁺. Cross-linked ZrD nanocomposite Pb²⁺ selective membrane was prepared by sol-gel using poly(vinyl alcohol) (PVA) as plasticizer in aqueous media. Developed ZrD nanocomposite membrane showed good thermal, mechanical and chemical stabilities, which are essential parameters for its durability. Furthermore, conductivity and counter-ion transport studies of these membranes suggested their potential application for separating Pb²⁺ by electrodialysis (ED). Electro-dialytic studies revealed very high Pb²⁺ flux across ZrD membranes in comparison with other bi-valent metal cations (Cu²⁺, Cd²⁺ and Ni²⁺). Relatively high retention of Pb²⁺ in the membrane phase was attributed to its controlled cross-linked structural morphologies, and completely intermingled and well connected network between the metal phosphonates and the polymeric backbone. Furthermore, high separation factor (2.0-3.0) for separating Pb²⁺/Cu²⁺, Pb²⁺/Cd²⁺, and Pb²⁺/Ni²⁺, suggested practical applications of developed membrane for electro-dialytic fractionation/removal of Pb²⁺ from industrial waste water.