Enhanced performance and mechanism of KMnO₄ pre-oxidation to coagulation on the removal of the DON and proteins

Proteins were the main category of the dissolved organic nitrogen (DON) in eutrophicate water sources and posed a threat to the water quality safety and common operation of water plants, while the KMnO₄ pre-oxidation and coagulation were the two important ways to control the organics. Intracellular organic matter (IOM) and phycocyanin were chosen as the target DON to study the performance of KMnO₄ pre-oxidation to the enhanced removal effects for coagulation process, and molecular weight distribution, hydrophobicity, two-dimensional electrophoresis and MnO₂ adsorption experiment were used to study the mechanism. The results showed that KMnO₄ pre-oxidation enhanced the IOM and phycocyanin removal performance of coagulation significantly, although poor removal was found for KMnO₄ oxidation alone. KMnO₄ pre-oxidation altered the molecular weight, hydrophobicity and proteins' categories insignificantly. However, the in-situ formed MnO₂ showed better adsorption ability for the IOM and phycocyanin. The main enhanced removal mechanism was the adsorption of MnO₂ formed from the reduction of KMnO₄ and little difference existed between the IOM and phycocyanin. In addition, the KMnO₄ pre-oxidation could enhance the turbidity removal of the coagulation due to a similar mechanism.