Kinetics of lead adsorption by iron oxides formed under the influence of citrate
Kinetics of lead adsorption by iron oxides formed under the influence of citrate
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DOI：
10.1016/s0016-7037(02)01036-0
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发表时间：
2003-03-01
影响因子：
5
通讯作者：
Huang, PM
中科院分区：
文献类型：
--
作者：
Liu, C;Huang, PM
有机酸的存在极大地影响了铁氧化物的形成和表面性能；然而，有机酸作用下形成的铁氧化物对Pb吸附动力学和机理的后续影响尚不清楚。采用宏观批处理方法，研究了在初始浓度为8.33 muM、pH为5.0、278、288、298和313 K条件下，柠檬酸盐与Fe（II）的摩尔比（MRs）分别为0、0.001、0.01和0.1时，柠檬酸盐与Fe（II）的摩尔比分别为0、0.001、0.01和0.1时，柠檬酸盐与Fe（II）的吸附动力学。结果表明：Pb吸附遵循多个一级动力学过程，吸附速率系数、活化能、在不同的柠檬酸/铁（II） mrs下形成的铁氧化物表面性质变化较大，在柠檬酸/铁（II） MR为0.1时形成的铁氧化物表面性质的变化以及对Pb吸附快、慢反应速率系数的影响尤为显著。除了在初始柠檬酸/铁（II） MR为0时形成的铁氧化物上的Pb吸附反应缓慢外，铅在铁氧化物上的吸附反应主要是扩散过程。1，其中限速过程显然是一个化学过程，可能涉及到共沉淀柠檬酸配体与氧化铁之间的键断裂。在不同的柠檬酸/铁（II） MRs下形成的铁氧化物对Pb的吸附速率系数不能只用活化能来解释。指前因子对铁氧化物吸附Pb的速率系数有重要影响。有机酸（如柠檬酸）在影响铁氧化物结晶和由此引起的表面性质改变中的作用，以及对陆地和水生环境中Pb动力学的影响，因此值得密切关注。版权所有爱思唯尔科学有限公司
The presence of organic acids greatly affects the formation of Fe oxides and surface properties; however, the subsequent effect on the kinetics and mechanisms of Pb adsorption by the Fe oxides formed under the influence of organic acids remains obscure. The kinetics of Pb adsorption on the Fe oxides formed in the presence of citrate ligands at initial citrate/Fe(II) molar ratios (MRs) of 0, 0.001, 0.01, and 0.1 was studied at the initial Pb concentration of 8.33 muM and pH 5.0 at 278, 288, 298, and 313 K using macroscopic batch method. The results indicate that the Pb adsorption followed multiple first-order kinetics and the rate coefficient, activation energy, and pre-exponential factor in the Arrhenius equation of the adsorption varied greatly with the surface properties of the Fe oxides formed at various citrate/Fe(II) MRS. The alteration of surface properties of Fe oxides formed at the citrate/Fe(II) MR of 0.1 and the effect on the rate coefficient of the fast and slow reactions of Pb adsorption were especially significant. The rate-limiting step of Pb adsorption reactions on the Fe oxides was predominantly a diffusion process, except for the slow reaction of Pb adsorption on the Fe oxides formed at the initial citrate/Fe(II) MR of 0. 1, where the rate-limiting process was evidently a chemical process, which may involve bond breaking between the coprecipitated citrate ligand and Fe oxide. The rate coefficients of Pb adsorption by the Fe oxides formed at various citrate/Fe(II) MRs cannot be explained by the activation energy alone. The pre-exponential factor plays an important role in influencing the rate coefficient of Pb adsorption by the Fe oxides. The role of organic acids such as citric acid in influencing the crystallization and the resultant alteration of surface properties of Fe oxides, and the impact on the dynamics of Pb in terrestrial and aquatic environments, thus merit close attention. Copyright (C) 2003 Elsevier Science Ltd.