Enhanced phycocyanin and DON removal by the synergism of HO and micro-sized ZVI: Optimization, performance, and mechanisms.

Micro-sized zero-valent iron (mZVI) has proven effective for phycocyanin (PC) removal, but efficiency needs to be enhanced. Here, hydrogen peroxide (HO) was used to enhance PC removal by mZVI and the corresponding mechanisms are discussed. The results showed that HO could effectively enhance PC removal by mZVI and the PC removal efficiency increased from 37.8% to 80.6% with 1.5 g/L mZVI in 60 min reaction time. The trends of dissolved organic nitrogen (DON) removal were consistent with PC removal. Low pH value, high mZVI dosage, and a suitable amount of HO were conducive to PC removal. The SEM-mapping indicated that PC removal was not primarily by adsorption. Similarly, no obvious change was observed in PC molecular structure based on fluorescence spectroscopy and SDS-PAGE analyses. However, the PC removal mechanism could be inferred from the variation of iron concentration in the process. The coagulation of dissolved iron ions dissolved from mZVI was the main removal pathway. The OH oxidation only accounted for 20% of PC removal. PC removal led to the reduction of disinfection by-products with similar efficiency. The combination of mZVI and HO is a promising strategy for the simultaneous removal of PC and DON in drinking water treatments.