Department of Environmental Science, Hubei Key Lab of Biomass Resource Chemistry and Environmental Biotechnology, School of Resources and Environmental Science, Wuhan University, Wuhan 430079, People's Republic of China.
Environ Sci Pollut Res Int. 2013 Jan;20(1):31-8. doi: 10.1007/s11356-012-1079-6. Epub 2012 Jul 18.
Iron and arsenic have been found to coexist in a water environment and the fate of arsenite in the aquatic system is influenced by iron. Goethite is a form of iron hydroxide, which is commonly found in sediments. In previous studies, we have used iron complexes to degrade organic pollutants. Results have shown that some organic pollutants could be totally degraded by iron complexes and our work indicated that iron might cause conversion of arsenic when irradiated. This work attempts to investigate the conversion of arsenite [As(III)] using natural goethite, as the iron source, to quantify the effect of various factors on photooxidation. We also consider the possible mechanism for photooxidation of As(III) using a suspension of natural goethite. The As(III) concentration variation under illumination was compared with the one in the dark to quantify the contribution of light to As(III) oxidation to As(V) in goethite suspended solution. The experiments under N(2) and air atmosphere confirmed the participation of dissolved oxygen. The photooxidation efficiency of As(III) under different conditions was compared to determine the effect of different environmental factors such as pH value, goethite concentration, and humic acid concentration on the photooxidation reaction. In the solution containing 100 μg L(-1) arsenite and 0.1 g L(-1) suspended goethite at pH 3.0, nearly 80 % of As(III) was photooxidized after irradiation by a 250-W metal halogen lamp (λ ≥ 313 nm) after 6 h. The effects of initial pH and goethite concentration and humic acid concentration were all examined. The results show that the greatest efficiency of photooxidation of As(III) was at pH 3.0. The extent of photooxidation decreased with increasing goethite concentration and fell sharply in the presence of humic acid under the conditions in this work. Although about 80 % of As(III) was photooxidized after irradiation by a 250-W halogen lamp at pH 3.0 in the presence of goethite suspension, photooxidation was also affected by factors such as pH, concentration of goethite, and presence of humic acid. The scavenger experiments showed that the HO• radical and photogenerated hole are the predominant oxidants in this system responsible for 87.1 % oxidation of As(III), while HO (2)(•) /O(2)(•-) is responsible for 12.9 % oxidation of As(III).
铁和砷在水环境中共存，亚砷酸盐在水系统中的命运受铁的影响。针铁矿是一种氢氧化铁，通常存在于沉积物中。在以前的研究中，我们使用铁复合物来降解有机污染物。结果表明，一些有机污染物可以被铁复合物完全降解，我们的工作表明，铁在辐照时可能会导致砷的转化。这项工作试图使用天然针铁矿作为铁源来研究亚砷酸盐 [As(III)] 的转化，以量化各种因素对光氧化的影响。我们还考虑了使用天然针铁矿悬浮液进行 As(III) 光氧化的可能机制。光照下的 As(III)浓度变化与黑暗中的浓度变化进行了比较，以量化光对针铁矿悬浮液中亚砷酸盐氧化为砷酸盐的贡献。在氮气和空气气氛下的实验证实了溶解氧的参与。比较了不同条件下 As(III) 的光氧化效率，以确定不同环境因素（如 pH 值、针铁矿浓度和腐殖酸浓度）对光氧化反应的影响。在 pH 值为 3.0、含 100 μg L(-1) 亚砷酸盐和 0.1 g L(-1) 悬浮针铁矿的溶液中，在 6 小时后用 250-W 金属卤灯（λ≥313nm）辐照后，近 80%的 As(III)被光氧化。还检查了初始 pH 值、针铁矿浓度和腐殖酸浓度的影响。结果表明，在 pH 值为 3.0 时，As(III) 的光氧化效率最高。随着针铁矿浓度的增加，光氧化程度降低，在本工作条件下，腐殖酸存在时急剧下降。尽管在 pH 值为 3.0、存在针铁矿悬浮液的情况下，用 250-W 卤素灯辐照后，约有 80%的 As(III)被光氧化，但光氧化也受到 pH 值、针铁矿浓度和腐殖酸存在等因素的影响。猝灭实验表明，在该体系中，HO•自由基和光生空穴是主要的氧化剂，负责 87.1%的 As(III)氧化，而 HO (2)(•)/O(2)(•-)负责 12.9%的 As(III)氧化。
