Arsenite oxidation by a poorly crystalline manganese-oxide. 2. Results from X-ray absorption spectroscopy and X-ray diffraction.
نویسندگان
چکیده
Arsenite (As(III)) oxidation by manganese oxides (Mn-oxides) serves to detoxify and, under many conditions, immobilize arsenic (As) by forming arsenate (As(V)). As(III) oxidation by Mn(IV)-oxides can be quite complex, involving many simultaneous forward reactions and subsequent back reactions. During As(III) oxidation by Mn-oxides, a reduction in oxidation rate is often observed, which is attributed to Mn-oxide surface passivation. X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) data show that Mn(II) sorption on a poorly crystalline hexagonal birnessite (δ-MnO₂) is important in passivation early during reaction with As(III). Also, it appears that Mn(III) in the δ-MnO₂ structure is formed by conproportionation of sorbed Mn(II) and Mn(IV) in the mineral structure. The content of Mn(III) within the δ-MnO₂ structure appears to increase as the reaction proceeds. Binding of As(V) to δ-MnO₂ also changes as Mn(III) becomes more prominent in the δ-MnO ₂ structure. The data presented indicate that As(III) oxidation and As(V) sorption by poorly crystalline δ-MnO₂ is greatly affected by Mn oxidation state in the δ-MnO₂ structure.
منابع مشابه
Arsenite oxidation by a poorly-crystalline manganese oxide. 3. Arsenic and manganese desorption.
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 oxides (Mn oxides) have the ability to decrease overall As mobility both by oxidizing toxic arsenite (As(III)) to less toxic arsenate (As(V)), and by sorbing As. However, the effect of competing ions on the mobility of As sorbed on Mn-oxide ...
متن کاملSynthesis and characterization of SnO2 nanoparticles by Co-Precipitation method
Tin oxide (SnO2)nanoparticles were synthesized by co-precipitation method and the synthesized nanoparticles were annealed at different temperatures for characterization. The powders were investigated with X-ray diffraction, scanning electron microscopy and optical spectroscopy. The structural characterization was carried out by X-ray diffraction which confirms the crystalline nature ...
متن کاملFabrication and Optical Characterization of Zinc Oxide Nanoparticles Prepared via a Simple Sol-gel Method
In this research zinc oxide (ZnO) nano-crystalline powders were prepared by sol-gel method using zinc acetate. The ZnO nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet-visible (UV-Vis), Fourier transform infra-red (FT-IR) and energy dispersive X-ray (EDX) spectroscopy. The structure of nanoparticles was studied using XRD pattern. The c...
متن کاملX-ray absorption spectroscopy of lithium insertion and de-insertion in copper birnessite nanoparticle electrodes.
The combination of ex situ X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) measurements on 2D layered copper birnessite cathode materials for lithium ion battery applications provides detailed insight into both bulk-crystalline and localized atomic structural changes resulting from electrochemically driven lithium insertion and de-insertion. Copper birnessite electrodes that had...
متن کاملZSM-5 Zeolite As Host Material for Semiconductor Nanoparticles
This work describes the optical and structure properties of nickel sulfide and cobalt sulfide nanoparticles in ZSM-5 zeolite. The samples were obtained by sulfidation of the Ni2+ and Co2+ ion-exchange ZSM-5 zeolites in a Na2S solution at room temperature. The optical properties of the samples were studied by UV-visible spectroscopy. Their crystalline structure and morphology were studied by X-r...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- Environmental science & technology
دوره 44 22 شماره
صفحات -
تاریخ انتشار 2010