Calcium hypochlorite‑potassium ferrate synergy: A novel strategy for stabilizing Fe(VI) while enhancing coagulation for emerging contaminants removal in source water

In this study, calcium hypochlorite (Ca(ClO) 2 ) combined with potassium ferrate (Fe(VI)) (Ca(ClO) 2 /Fe(VI)) oxidation system was developed to enhance the stability of Fe(VI) and removal efficacy of emerging contaminants. For the removal of micropollutants with various moieties, carbamazepine (CBZ) and phenol removals (50 % and 35 %) in the initial stage were enhanced by Ca(ClO) 2 /Fe(VI) oxidation system, which were primarily attributed to the Ca(ClO) 2 enhanced micropollutant removal by stabilizing Fe(VI) through H 2 O 2 scavenging in the Ca(ClO) 2 /Fe(VI) system, increasing Fe(VI) exposure to boost direct degradation efficiency for Fe(VI)-reactive contaminants (CBZ or phenol), but showed limited efficacy for ClO − reactive pollutants (SMX), because the reaction of Ca(ClO) 2 with SMX was more favorable than that of Fe(VI) with SMX. The microplastics (MPs) removal achieved by the Ca(ClO) 2 /Fe(VI) oxidation system (86 %) was also higher than the sum values (65.69 %) achieved by each individual reactant, indicating the synergy of Ca(ClO) 2 and Fe(VI) could enhance coagulation and improve the removal efficiency of microplastics. Moreover, the UV 254 , electron-donating capacity (EDC), and turbidity removals by Ca(ClO) 2 /Fe(VI) oxidation system from simulated source water (36 %, 53 % and 32 %) and real source water (48 %, 86 % and 53 %) were higher than those by Fe(VI) alone (26 %, 43 % and 21 %). This study provided novel insights into optimizing Fe(VI)-based systems applied for pre-oxidation process in drinking water treatment.