Abstract:This study, by modifing kaolin with different concentrations of hydrochloric acid and different temperatures of calcinations, studied the adsorption capacities and mechanisms of phosphorus (P) in synthetic wastewater by the modified kaolin as well as P adsorption isotherms and kinetics of modified kaolin. The results showed that P adsorption capacities of kaolin with hydrochloric acid and calcination in synthetic wastewater were improved differently. Particularly, the adsorption capacities of kaolin modified with 9% acid and 500℃ calcinations improved greatly. The removal capacity of 9% acid modification raised by 44.6% than the capacity of natural kaolin, enabling kaolin, applied at a rate of 2% (weight ratio), remove 81.8% of P from 25 ml initial synthetic wastewater (20 mg/L). P removal ratio by 500℃ calcinations was 99.5% in 50 ml initial synthetic wastewater (20 mg/L), P content in treated synthetic wastewater was 0.10 mg/L and lower than relative standard of China. The results revealed that acid modification changed adsorption sites of kaolin and calcinations activated Al in kaolinite, thus enhancing its P adsorption or removing capacity. The adsorption processes of natural kaolin, 9% acid modification and 500℃ calcinations were significantly (P<0.01) fitted with both Freundlich and Langmuir isotherm equations. The dynamics adsorption characteristics of natural kaolin, 9% acid modification and 500℃ calcinations were in good agreement, and the pseudo-second order kinetic equation gave better fitting results (P<0.01). The saturated adsorption amount of kaolin modified with 500℃ calcinations was the highest, suggesting that kaolin modified with calcinations has a good foreground in P removal in wastewater.