Preparation of aluminum–ferric–magnesium polysilicate and its application on oily sludge

Abstract

Aluminum–ferric–magnesium polysilicate (PAFMS) was prepared by introducing aluminum, ferric and magnesium metal ions into polysilicon acid solution. In this study, PAFMS was applied in the treatment of oily wastewater from the treatment of oily sludge, and the coagulation performance was evaluated by the efficiency of the removal of turbidity and color. The structure and morphology of PAFMS were characterized by Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD) and Scanning Electronic Microscopy (SEM). The results indicated that the mole ratio 6:4:15 of Al:Fe:Mg is beneficial to the formation of Al–O–Si, Fe–O–Si and Mg–Si–O. Fe played the main inhibition role among the three metals. XRD analysis showed that the addition of Al, Fe and Mg into polysilicic acid did not produce a simple mixture, but resulted in the formation of new chemical structures. The intensity of peaks was influenced by the mole ratios of metals. SEM showed that PAFMS appeared to be a spatial structure consisting of many irregular protuberant parts. The removal efficiency of turbidity and color in oily water from the treatment of oily sludge was better when the mole ratio of (Al+Fe+Mg):Si was 0.5 and if the mole ratios of Al:Fe:Mg are kept at 6:4:15. Moreover, when the dosage of PAFMS was 1.4–1.8 % and the pH value in range of 8–9, the efficiency of turbidity and color removal were up to 97.3 and 96.8 %, respectively.