氟离子、磷酸根和铬酸根在可变电荷土壤表面吸附过程中羟基释放动力学  

Kinetics of Hydroxyl Release from Three Variable Charge Soils due to Specific Adsorption of F^-, Phosphate and Chromate

作　　者：姜军[1,2] 徐仁扣[1] 王永[1,2] 赵安珍[1] 

机构地区：[1]土壤与农业可持续发展国家重点实验室(中国科学院南京土壤研究所),南京210008 [2]中国科学院研究生院,北京100049

出　　处：《土壤》2008年第6期949-953,共5页Soils

基　　金：中国科学院知识创新工程重要方向项目(KZCX2-YW-409)资助

摘　　要：用恒pH自动电位滴定装置研究了氟离子(F-)、磷酸根(H2PO4-)和铬酸根(CrO42-)在3种可变电荷土壤表面吸附过程中羟基(-OH)释放的动力学。研究结果表明,3种阴离子在可变电荷土壤表面吸附时-OH释放量的大小顺序为:F->>H2PO4->CrO42-,这与土壤对3种阴离子吸附量的大小顺序一致。pH对不同阴离子体系中-OH释放的影响不同,在F-体系中,pH5.0时-OH释放量最高,其次为pH6.0时,pH4.0时-OH释放量最小;CrO42-体系中-OH释放量随pH的增加而减小;pH对H2PO4-体系中-OH释放的影响较小。Elovich方程(Y=a+kln(t))能够很好拟合2～60min之间的动力学数据,说明-OH释放的速率随时间增加而减小。比较速率常数k的大小可以发现,虽然F-体系中3种可变电荷土壤在前2min释放的-OH量有很大差异,但在2～60min内,-OH释放速率差别不大。在H2PO4-和CrO42-体系中,-OH释放速率的大小顺序是:昆明砖红壤>徐闻砖红壤>江西红壤,与土壤铁、铝氧化物含量一致。The kinetics of hydroxyl released from three variable charge soils due to specific adsorption of F^-, phosphate and chromate were investigated with automatic potentiometric titration meter. The results indicated that the amount of hydroxyl released by three anions followed the order： F^-〉〉 H2PO4〉 CrO4^2-, which was consistent with the data of adsorption of these anions by the soils, pH showed different effects on hydroxyl release from the soils in different anions＇ systems. In F^- system, the highest amount of hydroxyl release was observed at pH 5.0, followed by pH 6.0 and the lowest amount of hydroxyl was released at pH 4.0. In chromate system, the amount of hydroxyl released decreased with the increase of system pH, while the effect ofpH on hydroxyl release in phosphate system was small. The Elovich equation fits the kinetics data from 2 to 60 minute well and the rate of hydroxyl release decreased with the increase of reaction time. Although a big difference of hydroxyl release due to F^- adsoprtion was observed within the first 2 minutes, small difference was found in F^- system for the rate of hydroxyl release from three different soils from 2 to 60 minute. While in phosphate and chromate systems, the rate of hydroxyl release from the three soils followed the order： Latosol from Kunming 〉 latosol from Xuwen 〉 red soil from Jiangxi, which was consistent with the content of iron and aluminum oxides in these soils.

关 键 词：可变电荷土壤 氟离子 磷酸根 铬酸根 专性吸附 羟基释放 

分 类 号：S153[农业科学—土壤学]