几种粉煤灰对磷素吸附与解吸特性的研究

通过吸附解吸和培养试验, 研究了几种粉煤灰对磷素吸附与解吸特性.结果表明,粉煤灰的全磷含量和有效磷含量分别为0.545～4.540 g·kg^-1和19.55～163.0 mg·kg^-1,显著高于土壤,粉煤灰对磷吸附量随着加入溶液磷浓度的增加而增加,但其吸附率随着加入溶液磷浓度的增加而减少；粉煤灰的吸磷率比土壤高,但其解吸率低.这主要是由于粉煤灰比土壤存在更多的磷吸附位点且结合能大,不易解吸.Langmuir方程、Freundlich方程和Temkin方程都能很好地拟合粉煤灰对磷吸附,其中Langmuir方程的MBC、Freundlich方程的a和Temkin方程的k2都可以表征粉煤灰对磷吸附能力, MBC、a和k2值越大,则吸磷能力越强.不同来源的粉煤灰的MBC、a和k2值不同，其大小顺序为：湘潭电厂(5 167.7,4 056.2,831.5)>岳阳纸厂(1 650.7,2 803.4,711.9)>华能电厂(303.0,1 677.6,368.7)>株洲电厂(76.2,464.2, 211.0) > 洞庭氮肥厂(34.7,413.48,213.8).粉煤灰对磷吸附固定作用随粉煤灰含水量的增加有增大的趋势.粉煤灰对磷吸附主要是专性吸附和化学沉淀反应,所以在施用粉煤灰改良土壤或利用粉煤灰制造复混肥时,须考虑粉煤灰对磷的固定作用及粉煤灰含水量的影响.

Phosphate adsorption and desorption characteristics of several fly ashes

Through adsorption-desorption experiment and incubation test, this paper studied the phosphate adsorption and desorption characteristics of several fly ashes. The test fly ashes contained 0.545 - 4.540 g x kg(-1) of total P and 19.55 - 163.0 mg x kg(-1) of available P, which were significantly higher than those in soils. The P adsorption capacity of fly ashes increased with increasing added P, while their P adsorption rate was in adverse. Fly ashes had a higher P adsorption rate but a lower P desorption rate than soils, mainly because fly ashes had more P adsorption sites and stronger bound energy. In this study, Langmuir, Freundlich, and Temkin equations were fit to the measured data, and the MBC value in Langmuir equation, a value in Freundlich equation, and k2 value in Temkin equation could be used as a comprehensive index to characterize the potential phosphate adsorptivity of fly ashes. The larger these values were, the stronger the P adsorptivity was. The MBC, a and k2 value of 5 fly ashes collected from different locations was in order of Xiangtan power factory (5 167.7, 4 056.2 and 831.5) > Yueyang paper factory (1 650.7, 2803.4 and 711.9) >Huaneng power factory (303.0, 1677.6 and 368.7) > Zhuzhou power factory (34.7,413.48 and 213.8) > Dongting nitrogen fertilizer factory (34.7, 413.48 and 213.8). The P fixation by fly ashes generally increased with their increasing water content, and their phosphate adsorption was mainly specific adsorption and chemical precipitation, suggesting that the P fixation and the water content of fly ashes should be considered when fly ash was used as soil amendment or as compound fertilizer filling substance.