Homogenous Oxidizing Oligomerization Coupled with Coagulation for Water Purification

Natural manganese oxides could induce the intermolecular coupling reactions among small-molecule organics in aqueous environments, which is one of the fundamental processes contributing to natural humification. These processes could be simulated to design novel advanced oxidation technology for water purification. In this study, periodate (PI) was selected as the supplementary electron-acceptor for colloidal manganese oxides (Mn(IV)aq) to remove phenolic contaminants from water. By introducing polyferric sulfate (PFS) into the Mn(IV)aq/PI system and exploiting the flocculation potential of Mn(IV)aq, a post-coagulation process was triggered to eliminate soluble manganese after oxidation. Under acidic conditions, periodate exists in the H4IO6− form as an octahedral oxyacid capable of coordinating with Mn(IV)aq to form bidentate complexes or oligomers (Mn(IV)-PI*) as reactive oxidants. The Mn(IV)-PI* complex could induce cross-coupling process between phenolic contaminants, resulting in the formation of oligomerized products ranging from dimers to hexamers. These oligomerized products participate in the coagulation process and become stored within the nascent floc due to their catenulate nature and strong hydrophobicity. Through coordination between Mn(IV)aq and H4IO6−, residual periodate is firmly connected with manganese oxides in the floc after coagulation and could be simultaneously separated from the aqueous phase. This study achieves oxidizing oligomerization through a homogeneous process under mild conditions without additional energy input or heterogeneous catalyst preparation. Compared to traditional mineralization-driven oxidation techniques, the proposed novel cascade processes realize transformation, convergence, and separation of phenolic contaminants with high oxidant utilization efficiency for low-carbon purification.