Mechanistic investigation of an inorganic-organic hybrid coagulant with Fe3O4 magnetic loading-enhanced flocculation for water treatment

Organic-inorganic hybrid coagulants combine the advantages of organic and inorganic components. In this study, magnetic loading-enhanced coagulation was employed to further enhance the coagulation efficiency of covalently bound organic silicon-ferrum hybrid coagulant. The performance of magnetic flocculation was improved as compared to the conventional coagulation procedure and the turbidity and UV254 removal by magnetic flocculation reached 99.26% and 84.03%, respectively. The optimization resulted in the best dosing sequence is magnetic powder followed by coagulant. Surprisingly, after this method, total phosphorus was able to meet the environmental quality standards for surface water Class I standard value of China (≤0.02 mg L−1) very quickly after this method. In addition, the optimal magnetic seed size was 20–30 μm and the dosage was 300 mg L−1. Compared with the traditional coagulation method, the settling time of magnetic coagulation was reduced to 2 min, which is 1/15 of that of the traditional coagulation method. The magnetic coagulation efficiency did not diminish even with the magnetic seeds recycled 4 times, showing excellent recovery performance (all above 90%). This provides a new reference path for the combination of organic and inorganic covalent hybrid coagulants with magnetic separation technology. [Display omitted] •Treatment of polluted surface water by MLEC method using SFHC combined with Fe3O4.•MLEC improves coagulation performance compared to conventional coagulation.•MLEC reduces settling time to 2 min, 1/15 of conventional coagulation.•Magnetic seeds can be recycled 4 times with no reduction in coagulation efficiency.•Magnetic adsorption of magnetic seed particles promotes contaminant removal.