Selective adsorption performance and mechanism of magnetic cationic resin for emerging contaminants

The presence of emerging contaminants in the source water has become a critical issue to ensure the security of drinking water. In our study, a comprehensive investigation was carried out on the levels of three emerging contaminants (pesticides, antibiotics, and perfluorinated compounds) present in the source water from four water plants. Zero-valent iron modified cation exchange resin (ZVI-CER) and micron-sized magnetic cation ex-change resin (m-MCER) were fabricated by in-situ and copolymerization methods and their removal performances for atrazine (ATZ), tetracycline (TC) and erythromycin (ETM) in water were also evaluated. The influencing parameters (pH, co-existing cations, and humic acid) of m-MCER resin were investigated in batch experiments. The removal rates of ATZ, TC, and ETM could be controlled within the ranges of 84.1-91.6 %, 65.4-91.1 %, and 82.2-99.5 % at different pH levels. Both ATZ and ETM exhibited higher resistance to different pH levels, coexisting ions (Na+, Ca2+) and humic acid during the removal process, suggesting prospective application potential for hardness removal. Whereas, TC was notably affected by the presence of NaCl, resulting in a decrease in the removal rate from 88.9 % to 61.1 %. Furthermore, the selectivity of the resin towards both emerging contaminants and coexisting cations was also examined and the sequence of selective exchange of ions in simulated water was Ca2+>Mg2+>ATZ/TC/ETM>K+>Na+. Finally, the selective adsorption mechanism of m-MCER resin for ATZ, TC, and ETM was established by analyzing various pathways, including ion exchange, hydrogen bonding and 7C-7C stacking interactions.