Insights on enhanced antibiotic sulfamethoxazole removal by magnetic activated carbon-ballasted coagulation: Efficacy and floc properties

Removal of antibiotics from wastewater is extremely important for the reduction of antibiotic resistance-related risk and safe water reuse. Coagulation is a promising approach for this purpose, but its practical implementation requires further upgrades in coagulation performances and antibiotics targeting. Here, the magnetic activated carbon ballasted coagulation (MAC-BC) process was proposed to enhance the coagulation process and antibiotic sulfamethoxazole (SMX) removal. Response surface curves indicated that MAC played a dominant role in SMX removal rather than coagulant. The MAC ballasting promoted the removal of DOC and SMX in the coagulation process by 1.4 and 1.6 times, which was attributed to hydrogen bonding interaction, pi-pi electro-donor-accepter interaction, and surface complexation introduced by COOH/C-O, C--C, and Fe-O/Al-O in the MAC flocs, respectively. MAC could serve as nuclei and readily bound to the hydrolyzed Al species, resulting in the for-mation of larger Al-species-induced primary clusters. The ratio of OH/Al on the surface of MAC-BC flocs was higher than that of the flocs generated in the single coagulation process. The higher binding ability with MAC addition facilitated the aggregation of primary clusters and increased the floc size by 1.3 times, which further accelerated floc settling and separation. The multiple functions of MAC ballasting enhanced the coagulation process and promoted SMX removal. This study opens a new avenue to upgrade traditional coagulation and adsorption processes.