Impellitteri Christopher A, Scheckel Kirk G, Ryan James A
U.S. EPA, ORD, LRPCD, RCB, 5995 Center Hill Avenue, Cincinnati, Ohio 45224, USA.
Environ Sci Technol. 2003 Jul 1;37(13):2936-40. doi: 10.1021/es026423d.
The sorption reactions of arsenate (As(V)) and arsenite (As(III)) on RuO2 x xH2O were examined using macroscopic and spectroscopic techniques. Constant solid:solution isotherms were constructed from batch sorption experiments and sorption kinetics assessed at pH 7. X-ray absorption near edge spectroscopy (XANES) was employed to elucidate the solid-state speciation of sorbed As. At all pH values studied (pH 4-8), RuO2 x xH2O showed a high affinity for As regardless of the initial As species present. Sorption was higher at all pH values when the initial As species was As(III). Oxidation of As(III) (250 mg/L solution) to As(V) was virtually complete (98-100%) within 5 s. XANES results showed the presence of only As(V) on the RuO2 x xH2O regardless of the initial As oxidation state. There was no change in the As oxidation state on the solid phase for 4 weeks in both oxic and anoxic environments. It is speculated that changes in the RuO2 x xH2O structure, due to oxidation reactions, caused the higher total As sorption capacity when As(III) was the initial species. The As sorption capacity of RuO2 x xH2O is greater than that of other metal oxides reviewed in this study. The ability of RuO2 x xH2O to rapidly oxidize As(III) is much greater than other oxides, such as MnO2.
采用宏观和光谱技术研究了砷酸盐（As(V)）和亚砷酸盐（As(III)）在RuO₂·xH₂O上的吸附反应。通过批量吸附实验构建了恒定固液等温线，并在pH 7下评估了吸附动力学。利用X射线吸收近边光谱（XANES）来阐明吸附态As的固态形态。在所研究的所有pH值（pH 4 - 8）下，无论初始存在的As形态如何，RuO₂·xH₂O对As都表现出高亲和力。当初始As形态为As(III)时，在所有pH值下的吸附量都更高。As(III)（250 mg/L溶液）在5秒内几乎完全氧化为As(V)（98 - 100%）。XANES结果表明，无论初始As氧化态如何，RuO₂·xH₂O上仅存在As(V)。在有氧和无氧环境中，固相上的As氧化态在4周内都没有变化。据推测，由于氧化反应导致RuO₂·xH₂O结构发生变化，使得当初始形态为As(III)时总As吸附容量更高。RuO₂·xH₂O的As吸附容量大于本研究中所综述的其他金属氧化物。RuO₂·xH₂O快速氧化As(III)的能力远大于其他氧化物，如MnO₂。
