Characterisation and coagulation performance of an inorganic coagulant—poly-magnesium-silicate-chloride in treatment of simulated dyeing wastewater

• A composite coagulant poly-magnesium-silicate-chloride (PMSC) was prepared.
• The characterisation of PMSC shows a layer shape structure.
• PMSC presents more efficient coagulation–flocculation performance in the dyeing wastewater treatment than PSA.

A type of coagulant, poly-magnesium-silicate-chloride (PMSC) with different Mg/Si molar ratios was prepared by co-polymerization. The structure and morphology of PMSC were investigated by using FTIR and SEM. In addition, parameters affecting coagulation–flocculation behavior such as coagulant dosage, initial pH in simulated dyeing wastewater and settling time were also studied. The results show that the optimum Mg/Si molar ratio is 1.5. PMSC is a complex compound with mainly magnesium–silica polymeric species rather than a simple mixture of raw materials. In the coagulation–flocculation process, PMSC exhibits a better coagulation performance compared with poly-silicic acid (PSA). With an optimal pH of 12 and a settling time of 20 min, the best flocculation of PMSC is at a dosage of 40 mg/L and the color removal rate can reach 82.8%. Therefore, PMSC is promising in dyeing wastewater treatment.

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