Environmental Soil Chemistry Research Group, Delaware Environmental Institute, University of Delaware , Newark, Delaware 19716, United States.
Key Laboratory of Surficial Geochemistry, Ministry of Education, School of Earth Sciences and Engineering, Nanjing University , Nanjing 210046, People's Republic of China.
Environ Sci Technol. 2015 Nov 17;49(22):13360-8. doi: 10.1021/acs.est.5b04087. Epub 2015 Nov 2.
Arsenic (As) mobility in the environment is greatly affected by its oxidation state and the degree to which it is sorbed on metal oxide surfaces. Manganese (Mn) and iron (Fe) oxides are ubiquitous solids in terrestrial systems and have high sorptive capacities for many trace metals, including As. Although numerous studies have studied the effects of As adsorption and desorption onto Fe and Mn oxides individually, the fate of As within mixed systems representative of natural environments has not been resolved. In this research, As(III) was initially reacted with a poorly crystalline phyllomanganate (δ-MnO2) in the presence of Fe(II) prior to desorption. This initial reaction resulted in the sorption of both As(III) and As(V) on mixed Fe/Mn-oxides surfaces. A desorption study was carried out using two environmentally significant ions, phosphate (PO4(3-)) and calcium (Ca(2+)). Both a stirred-flow technique and X-ray absorption fine-structure spectroscopy (XAFS) analysis were used to investigate As desorption behavior. Results showed that when As(III)/Fe(II) = 1:1 in the initial reaction, only As(V) was desorbed, agreeing with a previous study showing that As(III) is not associated with the Fe/Mn-oxides. When As(III)/Fe(II) = 1:10 in the initial reaction, both As(III) and As(V) can be desorbed from the Fe/Mn-oxide surface, and more As(III) is desorbed than As(V). Neither of the desorbents used in this study completely removed As(III) or As(V) from the Fe/Mn-oxides surface. However, the As desorption fraction decreases with increasing Fe(II) concentration in the initial reactions.
砷（As）在环境中的迁移性受其氧化态和在金属氧化物表面的吸附程度的影响很大。锰（Mn）和铁（Fe）氧化物是陆地系统中普遍存在的固体，对许多痕量金属，包括砷（As）具有高的吸附能力。虽然许多研究已经研究了 As 吸附和解吸到 Fe 和 Mn 氧化物上的单独作用，但在代表自然环境的混合系统中 As 的归宿尚未得到解决。在这项研究中，As(III)首先在 Fe(II)存在下与非晶态叶状锰矿（δ-MnO2）反应，然后进行解吸。该初始反应导致 As(III)和 As(V)在混合 Fe/Mn-氧化物表面上的吸附。使用两种具有环境意义的离子（磷酸盐（PO4(3-))和钙（Ca(2+)）进行了解吸研究。采用搅拌流动技术和 X 射线吸收精细结构光谱（XAFS）分析来研究 As 解吸行为。结果表明，当初始反应中 As(III)/Fe(II) = 1:1 时，只有 As(V)被解吸，这与先前的研究一致，表明 As(III)与 Fe/Mn-氧化物无关。当初始反应中 As(III)/Fe(II) = 1:10 时，As(III)和 As(V)都可以从 Fe/Mn-氧化物表面解吸，并且从 Fe/Mn-氧化物表面解吸的 As(III)多于 As(V)。本研究中使用的两种解吸剂都不能将 As(III)或 As(V)从 Fe/Mn-氧化物表面完全去除。然而，随着初始反应中 Fe(II)浓度的增加，As 的解吸分数会降低。
