Preparation of polyaluminium silicate sulphate by gravity supercritical method and its coagulation in oily sewage

In this work, different synthetic methods of polymeric aluminum silicate sulfate (PASS) and their coagulability to oily sewage were comparatively studied. PASS was synthesized by two methods: gravity supercritical method and basic titration method, denoted as PASS-B and PASS-S, respectively. The results show that the PASS prepared by gravity supercritical method has better Alb and stability. By applying two coagulants to oily sewage, it was found that PASS-B exhibited better turbidity and oil removal. It was found that PASS-B still has good coagulation by testing its coagulation after placing the coagulant for 2 months. In acidic test water, PASS-B exhibited stronger deprotonation ability. Finally, the polymerization mechanism and coagulation mechanism of PASS-B were analyzed in combination with Al morphology distribution and coagulation experiments. Gravity supercritical method as a new polymerization method may replace the traditional preparation method of inorganic polymer coagulants in the future, especially in large-scale applications.