Preparation of PSSS‐grafted polysulfone microfiltration membrane and its rejection and removal properties towards heavy metal ions

Abstract

3‐Hydroxy‐N,N‐diethylaniline (HDEA) as a tertiary aromatic amine was introduced onto the surface of chloromethylated polysulfone (CMPSF) microfiltration membrane through modification reaction, resulting in the modified membrane PSF‐DEA. A redox surface‐initiating system (DEA/APS) was constituted by the bonded tertiary aromatic amine group DEA and ammonium persulfate (APS) in aqueous solution, and so, the free radicals formed on the membrane initiated sodium p‐styrenesulfonate (SSS) as an anionic monomer to produce graft polymerization, getting the grafting‐type composite microfiltration membrane, PSF‐g‐PSSS membrane. Subsequently, the adsorption property of PSF‐g‐PSSS membrane for three heavy metal ions, Pb2+, Zn2+, and Hg2+ ions, was fully examined, and the rejection performance of PSF‐g‐PSSS membrane towards the three heavy metal ions was emphatically evaluated via permeation experiments. The experimental results show that by the initiating of the surface‐initiating system of DEA/APS, the graft polymerization can smoothly be carried out under mild conditions. PSF‐g‐PSSS membrane as a functional microfiltration membrane has strong adsorption ability for heavy metal ions by right of strong electrostatic interaction (or ion exchange action) between the anionic sulfonate ions on the membrane and heavy metal ions. The order of adsorption capacity is Pb2+ > Zn2+ > Hg2+, and the adsorption capacity of Pb2+ ion gets up to 2.18 μmol/cm2. As the volume of permeation solutions, in which the concentrations of the three metal ions are 0.2 mmol/L, are in a range of 50 to 70 mL, the rejection rate of PSF‐g‐PSSS membrane for the three heavy metal ions can reach a level of 95%, displaying a fine rejection and removing performance towards heavy metal ions.