Enhanced phosphate adsorption performance by innovative anion imprinted polymers with dual interaction

Abstract

It is therefore difficult to develop anionic imprinted polymers due to its intrinsic properties of anionic templates, which have much smaller charge size ratio, species diversity, and irregular geometry than cationic templates. Moreover, its synthesis is not suitable for traditional apolar media. Hence, well-defined recognition cavities formed by coordination are almost impossible for anion imprinted polymers. Synthesized anion imprinted polymers (IIP) by electrostatic attraction of positive and negative charges to enhance the stability of anion and functional monomer in the pre-polymerization process were proposed. Speciation of phosphate and surface potential at different pH on IIP have effect on phosphate capture were investigated. The resultant IIP has a high 78.88 mg g−1 at 35 °C while non-anion imprinted polymers (NIP) has only 33.35 mg g−1 adsorption capacity. In coexist experiments, all the selectivity coefficients (α) of IIP are greater than 1.8, and selectivity would rise with anion concentration increased. All these shows IIP possessed outstanding selectivity and specificity to phosphate. Adsorption energy E, and ΔH0 of IIP are 14.26 kJ mol−1 and 36.32 kJ mol−1, respectively. It indicated that phosphate adsorbed to IIP is ion exchange reaction. It is further verified by FTIR and XPS that recognition sites of anion imprinted polymers are N+ of AMD and P–O− in H2PO4−. They moved to imprinted cavities and form N+–O−, NH hydrogen bonded, which also contribute to adsorption.