Ladeira Ana C Q, Ciminelli V S T Virgínia S T
Department of Metallurgical and Materials Engineering, Universidade Federal de Minas Gerais-UFMG, Rua Espírito Santo 35, Belo Horizonte-M.G. 30160-030, Brazil.
Water Res. 2004 Apr;38(8):2087-94. doi: 10.1016/j.watres.2004.02.002.
The present work investigates the adsorption and mobility (desorption) of As(III) and As(V) on an oxisol, and its main mineral constituents, as part of a broader project aimed at selecting a soil liner to be used in tailings dams at a sulfidic gold ore plant. Emphasis was given to a quantitative comparison of As mobility-here assessed by the amount of As leached from the loaded samples-under different experimental conditions. From among the soil constituents, goethite was the most efficient adsorbent with regard to arsenic adsorption, 12.4 mg x g(-1) for As(V) and 7.5 mg x g(-1) for As(III), respectively. Gibbsite also presented a relevant adsorption capacity (4.6 mg x g(-1) for As(V) and 3.3 mg x g(-1) for As(III)); adsorption on kaolinite was negligible (<0.23 mg x g(-1) for As(V) and As(III)). Desorption of the arsenic was shown to vary largely with the arsenic oxidation state, the adsorbents and the leaching solutions. While only 1-2% max. of As(V) was released from the loaded samples, leaching the A(III) reached 32%, the highest values corresponding to the solutions containing sulfate ions. Oxisol and goethite were superior to gibbsite with respect to As immobilization. Adsorption and mobility were also discussed with the help of electrophoretic mobility and isoelectric points (IEP) determined prior and following arsenic adsorption on goethite and gibbsite. The results indicated that As(V) is mainly adsorbed as an inner sphere complex. As(III) may be adsorbed as an inner or an outer neutral complex.
作为一个更广泛项目的一部分，本研究调查了三价砷（As(III)）和五价砷（As(V)）在一种氧化土及其主要矿物成分上的吸附和迁移（解吸）情况，该项目旨在为一家硫化金矿石厂的尾矿坝选择一种土壤衬层。重点是对不同实验条件下砷迁移率进行定量比较——这里通过从负载样品中浸出的砷量来评估。在土壤成分中，针铁矿是最有效的砷吸附剂，对As(V)的吸附量为12.4 mg x g(-1)，对As(III)的吸附量为7.5 mg x g(-1)。三水铝石也具有相当的吸附能力（对As(V)为4.6 mg x g(-1)，对As(III)为3.3 mg x g(-1)）；在高岭石上的吸附可忽略不计（对As(V)和As(III)均<0.23 mg x g(-1)）。结果表明，砷的解吸随砷的氧化态、吸附剂和浸出溶液的不同而有很大差异。负载样品中As(V)的最大释放量仅为1 - 2%，而As(III)的浸出率达到32%，最高值对应于含硫酸根离子的溶液。在固定砷方面，氧化土和针铁矿优于三水铝石。还借助于在砷吸附到针铁矿和三水铝石之前和之后测定的电泳迁移率和等电点（IEP）对吸附和迁移进行了讨论。结果表明，As(V)主要以内层配合物的形式被吸附。As(III)可能以内层或外层中性配合物的形式被吸附。
