School of Environment, Beijing Normal University , Beijing 100875, China.
State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences , Beijing 100012, China.
Environ Sci Technol. 2017 Sep 5;51(17):10100-10108. doi: 10.1021/acs.est.7b02635. Epub 2017 Aug 25.
Treatment of arsenic by zerovalent iron (ZVI) has been studied extensively. However, the effect of arsenic on the formation of ferric hydroxide precipitates in the ZVI treatment has not been investigated. We discovered that the specific surface area (ca. 187 m/g) and arsenic content (ca. 67 mg/g) of the suspended solids (As-containing solids) generated in the ZVI treatment of arsenic solutions were much higher than the specific surface area (ca. 37 m/g) and adsorption capacity (ca.12 mg/g) of the suspended solids (As-free solids) generated in the arsenic-free solutions. Arsenic in the As-containing solids was much more stable than the adsorbed arsenic in As-free solids. XRD, SEM, TEM, and selected area electron diffraction (SAED) analyses showed that the As-containing solids consisted of amorphous nanoparticles, while the As-free solids were composed of micron particles with weak crystallinity. Extended X-ray absorption fine structure (EXAFS) analysis determined that As(V) was adsorbed on the As-containing suspended solids and magnetic solid surfaces through bidentate binuclear complexation; and As(V) formed a mononuclear complex on the As-free suspended solids. The formation of the surface As(V) complexes retarded the bonding of free FeO octahedra to the oxygen sites on FeO octahedral clusters and prevented the growth of the clusters and their development into 3-dimensional crystalline phases.
零价铁（ZVI）处理砷的研究已经很广泛了。然而，砷对 ZVI 处理中形成的氢氧化铁沉淀物的影响尚未得到研究。我们发现，在砷溶液的 ZVI 处理中生成的悬浮固体（含砷固体）的比表面积（约 187 m²/g）和砷含量（约 67 mg/g）比在无砷溶液中生成的悬浮固体（无砷固体）的比表面积（约 37 m²/g）和吸附容量（约 12 mg/g）要高得多。含砷固体中的砷比无砷固体中吸附的砷稳定得多。XRD、SEM、TEM 和选区电子衍射（SAED）分析表明，含砷固体由无定形纳米颗粒组成，而无砷固体则由弱结晶的微米颗粒组成。扩展 X 射线吸收精细结构（EXAFS）分析确定，As(V) 通过双齿双核络合吸附在含砷悬浮固体和磁性固体表面上；而 As(V)则在无砷悬浮固体上形成单核络合物。表面 As(V)配合物的形成阻碍了游离 FeO 八面体与 FeO 八面体簇上氧位的键合，阻止了簇的生长及其向三维结晶相的发展。
