可变电荷土壤对水体中磷酸根的吸附去除作用

Role of Variable Charge Soils of Removing Phosphate From Water Body Through Adsorption.

采用一次平衡法和土柱淋溶法研究4种可变电荷土壤对磷的吸附容量,结果表明可变电荷土壤对磷有很强的吸附能力。4种土壤对磷吸附量的大小顺序为昆明砖红壤>柳州红壤≈徐闻砖红壤>鹰潭红壤,与土壤游离铁、铝氧化物的含量大小顺序一致,说明土壤铁、铝氧化物对磷酸根吸附有重要贡献。被土壤吸附的磷酸根在NO3-体系中的解吸量很小,一般不超过吸附量的10%,但在柠檬酸体系中磷酸根的解吸量显著增加,说明磷酸根主要通过非静电吸附机制被可变电荷土壤吸附。根据淋溶试验结果,昆明砖红壤、柳州红壤、徐闻砖红壤和江西红壤对磷的吸附量分别可达1792、1536、1408和1280mg·kg-1,说明富铁可变电荷土壤可以用作水体中磷的有效吸附剂。从土柱淋溶试验获得的吸附量大于一次平衡试验所得值,说明由于磷吸附慢反应的贡献,磷的吸附量随平衡时间的增加而增加。

An experiment was conducted to study P adsorption capacity of four kinds of variable charge soils in water,using the one-batch method and soil-column leaching method.Results show that the variable charge soils were very strong in P adsorption capacity,displaying an order of Oxisol（Kunming）〉Ultisol（Liuzhou） ≈ Oxisol（Xuwen）〉Ultisol（Yingtan）,which is the same as the ones for content of free Fe/Al oxides in the soils.This suggested that Fe/Al oxides in the soils were a major factor affecting adsorption of phosphate.Desorption of pre-adsorbed phosphate from the soils in 0.01 mol·L^-1 NaNO3 solution was found to be insignificant and normally less than 10% of the adsorbed phosphate.However,citric acid induced desorption of pre-adsorbed phosphate from the soils.The findings suggested that phosphate was adsorbed by the variable charge soils mainly through non-electrostatic adsorption mechanism.The results of the leaching experiment show that given that phosphorus concentration of the leachate is 0.4 mg·L^-1,the amounts of phosphate adsorbed by Oxisol（Kunming）,Ultisol（Liuzhou）,Oxisol（Xuwen） and Ultisol（Yingtan） reached as high as 1 792,1 536,1 408 and 1 280 mg·kg^-1,respectively.Therefore,the variable charge soils,especially the soils high in Fe/Al oxide content,may potentially be employed as P adsorbent to remove phosphate from water bodies.