混合有机污染物在土壤中的竞争吸附研究

采用3种不同的溶质加入法研究溶质的吸附平衡,即方案①:先加入萘,然后再加入菲;方案②:萘和菲同时加入;方案③:先加入菲,然后再加入萘.研究结果表明同一溶质在有其它溶质竞争的情况下,表现出与单一纯溶质吸附时不同的吸附行为.随着竞争溶质浓度的增加,萘的吸附等温线的线性程度不断升高,吸附量降低.而菲则只是在实验方案③时,线性程度明显升高.随着竞争溶质初始浓度的增加,K_OC的值不断减小,当竞争浓度大约增加到0.5S_w后,K_OC基本不变化,达到了最小值.同时发现分子体积较大、厌水性较强的菲比分子体积较小、厌水性较弱的萘具有更强的竞争吸附能力.

Competitive Sorption of Mixed Organic Pollutants by Soils

Binary sorption equilibria were measured using three different loading methods: METHOD (1): Naphthalene loaded before phenanthrene; Method (2): Both Solutes loaded simultaneously; Method (3): Naphthalene loaded after phenanthrene. Each having 110 reactors and 10 levels of initial concentrations for both tested organic solutes. This is very different from previous studies which employed one single initial concentration of the primary solute and multiple concentration levels of the competitor and loaded both solutes simultaneously. Results indicate that the adsorption behavior of the same solute on the same sorbent with competing solute is distinctly different from its single adsorption behaviors. Naphthalene isotherm becomes more linear as phenanthrene concentration increases in the binary systems tested using all three loading methods. In contrast, phenanthrene isotherm remains nonlinear when it was loaded after or loaded simultaneously with naphthalene. It becomes more linear as a function of naphthalene concentration only when phenanthrene was loaded before naphthalene. The Koc values decrease as a function of competing solute concentration (c(e)), and approach to the lowest value when this c, is about 0.5 Sw. IAST provides better predictions for the sorption only when the competing solute is at lower c(e)(< 0.01 Sw). Large-size and more hydrophobic phenanthrene competes favorably with the small-size and relatively less hydrophobic naphthalene, and the heterogeneity of natural organic matter associated with the soil may have strong influence on the competitive phenomena between the tested solutes.