Synthesis of trioctyl polyvinyl chloride ammonium, membrane extraction properties, and electrodriven mass transfer behavior of Chromium (VI)

Abstract

Trioctyl polyvinyl chloride ammonium (PVCTQAS) with quaternary ammonium salt content (QAS) of 25 % was synthesized by a nucleophilic substitution reaction of between polyvinyl chloride (PVC) and trioctylamine (TOA) for the first time. The mass transfer behavior of HCrO4−, CdCl3−, CoCl42−, FeCl4−, and CuCl42− metal complex anions within the plasticized PVCTQAS membrane followed a first-order kinetic rate equation. Taking the Cr(Ⅵ)-PVCTQAS system as a representative, the influences of plasticizer content and membrane thickness on the mass transfer performance were investigated, and the electrodriven mass transfer behavior of Cr(VI) was studied. The results showed that the mass transfer of HCrO4− in PVCTQASD followed a jumping mechanism, with a QAS content threshold of 22 %. In the Cr(VI)-PVCTQAS electrodriven mass transfer system, the PVCTQASD exhibited uniform electrochemical properties, and the membrane thickness had little influence on the mass transfer rate. The response of HCrO4− mass transfer rate to voltage depended on the distribution density of QAS in the membrane. The mass transfer performance of PVCTQASD with QAS between 15 % and 20 % had a high dependence on the voltage, while the permeability coefficient of Cr(VI)-PVCTQAS system became stable when the voltage exceeded 10 V after surpassing the QAS content threshold. 50 μm QAS 25 % Cr(VI)-PVCTQAS system had a treatment efficiency of 710 mg·m−2·h−1 for HCrO4− at 10 V, while maintaining exceptional selectivity and stability.