Abstract: In order to determine the suitable technological conditions for phosphorus wastewater treatment by adopting composite flocculant PAFC which was prepared from fly ash and red mud by hydrochloric acid modification,tests are carried out to find out suitable pH value for phosphorus removal and PAFC dosage to treat simulated phosphorus wastewater with the concentration of 50.0 μg/mL,and the optimum hydraulic condition was investigated. The results showed that under conditions of pH value 8 and the dosage of PAFC 180 mg/L,rapid stirring for 60 s at 200 r/min,slow stirring for 15 min at 50 r/min,phosphorus removal rate reached 97.55%. The phosphorus removal mechanism analysis showed：① The PAFC has features of disorder and uneven structure,large surface area,high porosity,which are favor for adsorption of phosphorus. ② Based on the self-owned hydroxyl groups such as Fe—OH,Al—OH and H—OH,as well as hydroxy complex of aluminum hydroxide (iron) formed by hydrolysis of Al3+ and Fe3+,PAFC can adsorb phosphorus; In addition to reacting with the water dissolved orthophosphate to generate insoluble phosphate precipitation,Al3+ and Fe3+ among PAFC also can reduce or eliminate the zeta potential in colloid of wastewater by electrical neutralization,so as to eliminate electrostatic repulsion in colloid of water,and quickly keep the suspended matter stable and settle down to the bottom. PAFC shows good flocculation and phosphorus removal performance. The fly ash and red mud can be used to prepare the high-quality phosphorus removal flocculant PAFC. By this process,the industrial solid wastes can be recycled as resources,to gain the goal of treating wastes by one another.

Key words: Fly ash, Red mud, Simulated phosphorus wastewater, Compound flocculants PAFC