Comparison of polysilicic acid (PSiA) and magnesium sulfate modified polysilicic acid (PMSiS) for effective removal of Congo red from simulated wastewater

Polymagnesium silicate sulfate (PMSiS) was prepared by using magnesium sulfate modified polysilicic acid (PSiA). The PMSiS's functional group and morphology were analyzed by FTIR and SEM, respectively. The coagulation performance of PMSiS and PSiA was studied and compared in terms of the Congo red (CR) dye removal efficiency. After modification, PMSiS was a complexation polymeric species with the compact rod-like structure. Compared with PSiA, PMSiS was more efficient and stable. In the process of treating simulated wastewater containing CR dye, the dye removal efficiency of PMSiS could achieve above 80% at the lower coagulant dosage of 0.4 g/L, while the dye removal efficiency of PSiA could only reach about 70% at the higher coagulant dosage of 1.2 g/L. Moreover, PMSiS had wider applicable range of dosage and temperature than PSiA at optimal conditions of pH 12 and once addition of feeding mode. Therefore, PMSiS will be a promising coagulant in the process of treating practical wastewater containing dyes.