改性高岭土对废水中磷的吸附性能及机理研究

Phosphorus Adsorption Capacities and Mechanisms of Different Modified Kaolin in Wastewater

采用盐酸和煅烧2种方法对苏州高岭土进行了改性,分析其对模拟含磷废水中磷的吸附效果,并初步探讨了其作用机制,继而进行了等温吸附和吸附动力学试验研究。结果显示,酸、热改性均不同程度地提高了高岭土对模拟废水中磷的吸附净化能力,尤以9%酸改性和500℃煅烧效果最为明显。在处理25 ml浓度为20 mg/L的模拟含磷废水中,高岭土投加量为2%(重量比)时,经9%酸改性高岭土对磷去除率达81.8%,较天然高岭土提高了44.6%。在处理50 ml浓度为20 mg/L的模拟含磷废水时,经500℃煅烧改性高岭土对磷的去除率高达99.5%,残留溶液中磷浓度仅为0.10 mg/L,达到我国相应排放标准。酸改性可通过改变高岭土的吸附活性点位来提高其对磷的吸附净化性能,而煅烧通过活化高岭石中的铝而提高其对磷的吸附净化性能。天然、9%酸改性及500℃煅烧高岭土磷吸附等温线均符合Freundilch和Langmuir方程,皆达极显著水平(P<0.01)。天然、9%酸改性及500℃煅烧高岭土对磷的动力学吸附特征一致,皆与准二级方程拟合最佳,达极显著水平(P<0.01)。500℃煅烧高岭土对磷的饱和吸附量最大,在净化含磷废水中具有良好的应用前景。

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 AI 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.