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砷在土壤环境中的迁移转化受到土壤中存在的金属氧化物胶体的影响。砷在土壤和土壤溶液之间的吸附-解吸行为受到土壤溶液中存在的低分子量溶解性有机酸的制约。柠檬酸根是土壤常见的有机酸根之一,目前的研究认为:对于特定矿物质有限的吸附位而言,柠檬酸根作为一种与As(V)竞争吸附位的阴离子,可导致As(V)在针铁矿上的吸附量严重下降。结合环境中As(V)和柠檬酸根与土壤矿物质可能遭遇的状况,通过改变As(V)和柠檬酸根加入顺序建立了三种实验体系:第一种是先进行As(V)与针铁矿的吸附反应,平衡后再加入柠檬酸根[(As(V)-针铁矿)-柠檬酸根];第二种情况与此类似,所不同的是先加入柠檬酸根再加入As(V)[(柠檬酸根-针铁矿)-As(V)];第三种情况是柠檬酸根和As(V)同时加入[(柠檬酸根-As(V))-针铁矿]。为进一步考察柠檬酸根对砷吸附行为的抑制作用机理,选择乙酸根和草酸根作为对照进行As(V)吸附实验。结果显示:在酸性条件下,柠檬酸根对As(V)在针铁矿上吸附行为的影响是柠檬酸根溶解作用和竞争吸附位两种机理协同作用的结果,受到这两种机理的制约。
Migration and transformation of arsenic in soil environment is affected by the presence of metal oxide colloids in the soil. The adsorption-desorption behavior of arsenic between soil and soil solution is restricted by the presence of low-molecular-weight dissolved organic acids in the soil solution. Citric acid is one of the most common organic acid radicals found in soils. Current research suggests that citrate, an anion that competes with As (V) as a competitive adsorption site, for a limited number of mineral-specific adsorption sites, can cause As (V) Adsorption on goethite declined significantly. According to the situation that As (V), citrate and soil minerals might encounter in the environment, three kinds of experimental systems were established by changing the sequence of As (V) and citrate addition: the first is to carry out As (V) The adsorption reaction of the ore is balanced by the addition of citrate [(As (V) - goethite) - citrate]. The second case is similar except that citrate is added first followed by As (V) [ (Citrate-goethite) -As (V)]; the third case is the simultaneous addition of citrate and As (V) to [(citrate-As (V)) -goite]. In order to further investigate the inhibitory mechanism of citrate on arsenic adsorption, acetate (As) and oxalate were selected as controls for As (V) adsorption experiments. The results showed that under acidic conditions, the effect of citrate on As (V) adsorption on goethite was the result of synergistic effect of citrate dissolution and competitive adsorption sites, which were both controlled by these two mechanisms.