Tsang Daniel C W, Lo Irene M C, Chan K L
Department of Civil Engineering, The Hong Kong University of Science and Technology, Hong Kong, China.
Environ Sci Technol. 2007 May 15;41(10):3660-6. doi: 10.1021/es061756m.
EDTA-flushing of artificially contaminated soils enhanced Cu extraction but also induced mineral dissolution simultaneously. The mobilization and transport of these metal-EDTA complexes was investigated with column experiments. A quantitative transport model was proposed for simulating the experimental breakthrough curves of Cu, Fe, Al, and Ca. The rate-limited EDTA-promoted extraction and dissolution could be described by respective second-order kinetic terms, which were necessary for explaining the time-dependent depletion of extractable metals (sorbed and indigenous) in soils with continuous EDTA-flushing. Simultaneous simulation of extraction of sorbed Cu and dissolution of soil Fe, Al, and Ca is more conceptually accurate than individual modeling of each metal because the latter approach tends to overestimate the concentration of free EDTA during transport and thus underestimate the rate coefficients of EDTA-promoted dissolution. The fitted rate coefficients of Cu were about an order of magnitude larger than those of Fe and Al; these values probably reflect Cu extraction from weakly sorbed fractions and Fe and Al dissolution from amorphous oxides. The apparent retardation of Fe, Al, and Ca transport had to be taken into account by empirical determination, which was attributed to the metal lability in soils and thermodynamics of surface complexation.
用乙二胺四乙酸（EDTA）冲洗人工污染土壤可增强铜的提取，但同时也会引发矿物溶解。通过柱实验研究了这些金属 - EDTA络合物的迁移和运输。提出了一个定量传输模型来模拟铜、铁、铝和钙的实验突破曲线。速率受限的EDTA促进的提取和溶解可以用各自的二级动力学项来描述，这对于解释在连续EDTA冲洗下土壤中可提取金属（吸附态和原生态）随时间的消耗是必要的。与对每种金属进行单独建模相比，同时模拟吸附态铜的提取以及土壤中铁、铝和钙的溶解在概念上更准确，因为后一种方法往往会高估运输过程中游离EDTA的浓度，从而低估EDTA促进溶解的速率系数。铜的拟合速率系数比铁和铝的大约大一个数量级；这些值可能反映了从弱吸附组分中提取铜以及从无定形氧化物中溶解铁和铝。铁、铝和钙运输的明显滞后必须通过经验测定来考虑，这归因于土壤中的金属活性和表面络合的热力学。
