Villalobos Mario, Leckie James O.
Department of Civil and Environmental Engineering, Stanford University, Stanford, California, 94305
J Colloid Interface Sci. 2001 Mar 1;235(1):15-32. doi: 10.1006/jcis.2000.7341.
Experimental data for carbonate adsorption onto synthetic goethite, spanning 3 orders of magnitude in carbonate concentrations, were simulated using the triple-layer surface complexation model (TLM). A single set of TLM parameters successfully described the adsorption behavior versus pH over the concentration range obtained from closed and open CO(2) conditions. An optimization analysis was performed for all possible interfacial charge configurations using FITEQL3.2. The results yielded an optimum charge allocation of 0 and -1 in the 0- and beta-planes, respectively, which suggests a monodentate complex most probably in an inner-sphere configuration (SOCOO(-beta)). Fourier transform infrared (FTIR) spectroscopic measurements on open systems at atmospheric P(CO(2)) confirmed this result by showing a clear peak split (155 cm(-1)) of the nu(3) C-O asymmetric stretching frequency of surface-bound carbonate, consistent with that reported for monodentate Co(III)-carbonato inner-sphere solution complexes. An additional Na(+)-ternary complex (SOCOONa) was invoked in the TLM construct to improve simulations of the enhanced carbonate adsorption occurring at high ionic strength and high pH. The model was successful in predicting carbonate adsorption behavior under diffferent conditions than it was calibrated for. Projections for equilibration at higher P(CO(2))'s (1-10%) than those used in this work show the potential for carbonate sorption densities of up to 2.5-3 µmol/m(2). Copyright 2001 Academic Press.
使用三层表面络合模型（TLM）模拟了碳酸根在合成针铁矿上的吸附实验数据，碳酸根浓度范围跨越3个数量级。在封闭和开放CO₂条件下获得的浓度范围内，同一组TLM参数成功地描述了吸附行为与pH值的关系。使用FITEQL3.2对所有可能的界面电荷构型进行了优化分析。结果表明，在0平面和β平面上的最佳电荷分配分别为0和 -1，这表明最有可能是内球构型的单齿络合物（SOCOO⁻β）。在大气P(CO₂)条件下对开放系统进行的傅里叶变换红外（FTIR）光谱测量证实了这一结果，表面结合碳酸根的ν₃ C - O不对称伸缩频率出现明显的峰分裂（155 cm⁻¹），这与报道的单齿Co(III)-碳酸根内球溶液络合物一致。在TLM结构中引入了额外的Na⁺三元络合物（SOCOONa），以改善对高离子强度和高pH条件下增强的碳酸根吸附的模拟。该模型成功地预测了与校准条件不同的其他条件下的碳酸根吸附行为。与本研究中使用的相比，在更高P(CO₂)（1 - 10%）下达到平衡的预测表明，碳酸根吸附密度有可能高达2.5 - 3 µmol/m²。版权所有2001年学术出版社。
