Magnetic polymer-supported adsorbent with two functional adsorption sites for phosphate removal

In this paper, a new magnetic polymer-supported phosphate adsorbent MPVC-EDA-Ce was prepared by loading cerium (hydr)oxides onto ethylenediamine-functionalized polyvinyl chloride for the first time. MPVC-EDA-Ce showed excellent adsorption performances towards phosphate and easy recovery. The adsorption isotherm and kinetics of MPVC-EDA-Ce followed Langmuir monolayer model and the pseudo-second-order model, respectively. The pH results demonstrated that the MPVC-EDA-Ce could effectively remove phosphate in a wide range of pH with insignificant cerium leaching. Furthermore, analyses on adsorption mechanism and effect of competing anions demonstrated the formation of strong inner-sphere complexation between cerium (hydr)oxides and phosphate, which was a selective adsorption process, while positively charged quaternary ammonium groups adsorbed phosphate via relatively weak electrostatic attraction which was a non-selective adsorption process. The study provided a good reference to design novel phosphate adsorbents with two even more functional adsorption sites and a deep insight to investigate the adsorption mechanism towards phosphate.