Preparation and characterization of polymeric phosphatealuminum sulphate for source water treatment

Abstract

Aluminum sulphate (AS) as a common coagulant has been widely used in water treatment. Pre-hydrolysed AS (PAS) has higher molecular weight, presenting stronger water treatment performance; however, its poor stability has greatly limited its application. Therefore, there is still a need to obtain a stable PAS. In this study, a method for stabilizing PAS product was proposed and a new coagulant, phosphate-aluminum sulphate (PPAS), was prepared. The parameters affecting PPAS performance, such as n(P)/n(Al) and n(OH)/n(Al) molar ratios, and organic stabilizer dose containing a mixture of tartaric acid and sodium potassium tartrate, were examined. The coagulation-flocculation performance of PPAS was assessed by measuring source water treatment efficiency. The results showed that the PPAS at n(P)/n(Al) molar ratio of 0.15, n(OH)/n(Al) molar ratio of 0.2 and the stabilizer dose of 7.5% presented good performance and stability. PPAS was significantly distinct from AS in the morphology and species distribution, which indicated that the distribution of the Alb and Alc in PPAS largely affected the coagulation-flocculation performance, especially the Alb. The coagulation-flocculation examined at an appropriate pH was effective for source water turbidity, ultraviolet adsorption at 254 nm and total dissolved organic nitrogen removal in the investigated range.