Department of Creative Science and Engineering, Faculty of Science and Engineering, Waseda University, Tokyo 169-8555, Japan.
Environ Sci Technol. 2010 Jan 15;44(2):638-43. doi: 10.1021/es902284c.
Dilute arsenate (As(V)) coprecipitation by ferrihydrite was investigated to determine if treatment of acid mine drainage containing dilute As(V) using coprecipitation is feasible. The sorption density obtained at pH 5 and 7 was nearly identical when As(V) was coprecipitated with ferrihydrite, while it was higher at pH 5 when As(V) was adsorbed on the ferrihydrite. The high sorption density of As(V) to ferrihydrite in coprecipitation with 1-h reaction time suggested that coprecipitation occurs via both adsorption and precipitation. Furthermore, the relationship between residual As(V) and sorption density revealed a BET-type isotherm, with a transition point from a low residual As(V) concentration to a high residual As(V) concentration being observed for all initial As(V) concentrations between 0.15 and 0.44 mmol/dm(3) when the initial molar ratio was 0.56 at pH 5 and 7. X-ray diffraction and the zeta potential revealed that the transition point from surface complexation to precipitation was obtained when the initial As/Fe ratio was 0.4 or 0.5. When dilute As(V) was coprecipitated with ferrihydrite at pH 5 and 7, it was primarily adsorbed as a surface complex when the initial molar ratio was As/Fe < 0.4, while a ferric arsenate and surface complex was formed when this ratio was >or= 0.4.
采用铁氢氧化物共沉淀法处理含低浓度砷（V）的酸性矿山废水，考察砷（V）在铁氢氧化物上的共沉淀行为，以确定利用共沉淀法处理含低浓度砷（V）的酸性矿山废水是否可行。在 pH 值为 5 和 7 时，砷（V）与铁氢氧化物共沉淀的吸附密度几乎相同，而当砷（V）吸附在铁氢氧化物上时，在 pH 值为 5 时的吸附密度更高。在 1 h 反应时间内，砷（V）在铁氢氧化物上的高共沉淀吸附密度表明共沉淀是通过吸附和沉淀两种机制同时发生的。此外，残余砷（V）浓度与吸附密度之间的关系揭示了 BET 型等温线，当 pH 值为 5 和 7 时，初始摩尔比为 0.56，初始砷（V）浓度在 0.15-0.44 mmol/dm3 之间时，所有初始砷（V）浓度都观察到残余砷（V）浓度从低浓度到高浓度的转折点。X 射线衍射和zeta 电位表明，当初始 As/Fe 比为 0.4 或 0.5 时，从表面络合到沉淀的转变点就会出现。当在 pH 值为 5 和 7 时，低浓度砷（V）与铁氢氧化物共沉淀时，当初始摩尔比 As/Fe < 0.4 时，主要以表面络合物的形式被吸附，而当该比值为≥0.4 时，则形成铁砷酸盐和表面络合物。
