Coagulation performance and floc characteristics of Fe-Ti-V ternary inorganic coagulant for organic wastewater treatment

A novel Fe-Ti-V ternary inorganic coagulant (VTMS) was prepared from vanadium titanomagnetite (VTM) by two-step sulfuric acid leaching method, which is simple, efficient, and economical. VTMS was used to treat four typical organic wastewaters: synthetic domestic sewage, oily wastewater, surface water, and algae-laden water. The results indicated that it was superior to conventional coagulants. VTMS achieved a turbidity removal rate of nearly 100 % for all four wastewaters. In addition, it performed better in organic matter removal than polyaluminum chloride (PAC) with a larger floc size and higher growth rate. These results were attributed to the hydrolysis of Fe, Ti, and V, which formed a chain structure that improved the adsorption, bridging, and sweeping performances of VTMS. Based on the observations of coagulation performance, floc properties, and zeta potential, the predominant coagulation mechanisms appeared to be charge neutralization in synthetic domestic sewage and bridging flocculation in oily wastewater, surface water, and algae-laden water. Sweep coagulation also played a role in the coagulation processes for all four wastewaters. This study provided efficient technical guidance for large-scale production and application of Ti-based coagulants.