Tannic acid enhanced the removal of Phaeocystis globosa from seawater by Fe (II) activated persulfate

The frequent outbreaks of Phaeocystis globosa ( P. globosa ) blooms in coastal areas have seriously threatened nuclear power safety. In this study, tannic acid (TA) was used to accelerate the removal of P. globosa from seawater by Fe (Ⅱ) activated persulfate (PS). In comparison with the Fe (Ⅱ)-PS system, the higher removal efficiency of P. globosa was obtained in the TA-Fe (Ⅱ)-PS system (91.2% vs 67.5%). The removal efficiency of fluorescence value, chlorophyll a, turbidity and total organic carbon (TOC) reached up to 90.1%, 91.2%, 61.8% and 51.6% with the addition of 10 mg L −1 of TA, 100 mg L −1 of Fe (Ⅱ) and 240 mg L −1 of PS in 420 min. The flocs images confirmed that TA played a dual role in regulating Fe (Ⅱ) concentration and activating PS, which facilitated the pre-oxidation of algae cells. Finally, the inactivated P. globosa settled to the bottom with the iron mineral flocs. In addition, positive environmental impacts were also validated due to the decrease in total organic carbon (TOC), total nitrogen (TN), total phosphorus (TP) and chemical oxygen demand (COD). The findings demonstrated that TA-Fe (Ⅱ)-PS system is a promising candidate for the removal of P. globosa from seawater.