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研究了可变电荷粘粒矿物和矿物学性质不同的代表性土壤对磷酸根的等温解吸特性。结果表明磷酸根的解吸等温线一般都滞后于吸附等温线。滞后的程度以铁、铝氧化物最大;含较多铁和铝氧化物的酸性土壤其次;高岭石、蒙脱石和中性、石灰性土壤较小。磷酸根的解吸率一般都随着吸附饱和度的增加而增加,但在各吸附饱和度下,解吸率都明显低于吸附磷的同位素(磷)交换率。在恒定pH和离子强度下,解吸主要涉及结合能较低的吸附态磷。可变电荷表面紧结合态吸附磷在同样条件下是极难解吸的,从而引起磷酸根吸附和解吸不可逆转。此外,吸附态磷还可能通过次生化学反应而转化成不溶性磷酸盐化合物,对这种形态磷就不能通过简单的水液平衡而发生可逆性的解吸作用,而必须加以某种化学处理(例如适当酸化或用有机物质)。
The isothermal desorption characteristics of phosphate on the representative soils with variable charge-bearing clay minerals and mineralogical properties were investigated. The results showed that the desorption isotherms of phosphate generally lag the adsorption isotherms. The degree of hysteresis was the largest in iron and aluminum oxides, followed by acidic soil with more iron and aluminum oxides, followed by kaolinite, montmorillonite and neutral and calcareous soils. The desorption rate of phosphate generally increases with the increase of adsorption saturation, but at each adsorption saturation, the desorption rate is significantly lower than the adsorption rate of phosphorus (phosphorus) exchange rate. At constant pH and ionic strength, desorption primarily involves lower bound phosphorus. Tightly charged surface adsorption of phosphorus in the same conditions is extremely difficult to desorb, causing phosphate adsorption and desorption is irreversible. In addition, adsorbed phosphorus may also be converted to insoluble phosphate compounds by secondary chemical reactions, and reversible desorption of phosphorus in this form by simple aqueous-liquid equilibrium may require some chemical treatment Appropriate acidification or organic material).