Enhanced coagulation for slightly polluted seawater using ferric sulfate and modified diatomite

摘要

The modified diatomite was prepared by calcination and alkali washing, and the feasibility of using modified diatomite for enhanced coagulation treatment of slightly polluted seawater was investigated in this study. SEM and BET analysis showed that the raw diatomite contained impurities, which were removed after refined and purified treatment. The use of diatomite as a coagulant aid improved interparticle bridging thus incorporating the cells into flocs more efficiently, producing settleable flocs of greater density, size and strength. The enhanced coagulation with ferric sulfate and modified diatomite improved the removal efficiency of turbidity, ammonia nitrogen, total phosphorus and COD_(Mn) in seawater samples. At the optimal diatomite dosage of 60 mg/L and ferric sulfate dosage of 6 mg/L, the removal efficiency of turbidity, NH3-N, TP and COD_(Mn) reached 93.8%, 26.3%, 94.8% and 44.4% respectively. It has been proved that the enhanced coagulation through the ferric sulfate and modified diatomite, as coagulant aid and adsorbent, is more efficient and environmentally than using traditional metal coagulant only for treatment of slightly polluted seawater.