Arsenic(III) Remediation from Contaminated Water by Oxidation and Fe/Al Co-Precipitation

Abstract

Battery grade γ-MnO 2 powder was investigated as an oxidant and an adsorbent in combination with Fe/Al coagulants for removal of arsenic from contaminated water. Simultaneous oxidation of As(III) and removal by coprecipitation/adsorption (one step process) was compared with pre-oxidation and subsequent removal by coprecipitation/adsorption (two step process). The rate of As(III) oxidation with MnO 2 is completed in two stages: rapid initially followed by a first order reaction. As(III) is oxidised to As(V) by the MnO 2 with a release of approximately 1:1 molar Mn(II) into the solution. No significant pH effect on oxidation of As(III) was observed in the pH range 4 -6. The rate showed a decreasing trend above pH 6. The removal of As(V) by adsorption on the MnO 2 decreased significantly with increasing pH from 4 to 8. The adsorption capacity of the γ-MnO 2 with particle size 90% passing 10 µm was determined to be 1.5 mg/g at pH 7. MnO 2 was found to be more effective as an oxidant for As(III) in the two step process than in the one step process.

Competitive Adsorption of Arsenic and Fluoride onto Economically Prepared Aluminum Oxide/Hydroxide Nanoparticles: Multicomponent Isotherms and Spent Adsorbent Management

“…Similar range of pH for the removal of fluoride is also reported in other published literatures. 24,25 The adsorption of pollutants depends on the speciation chemistry of these ions as well as the surface charge of the adsorbent at different solution pH. As(III) is predominately present in the form of H 3 AsO 3 in the pH range 3−8, at pH 9 some of H 3 AsO 3 is converted to H 2 AsO 3 − .…”

Research into arsenic (III) effective catalytic oxidation in an aqueous solution on a new active manganese dioxide in a flow column

“…The problem of industrial removal of arsenic (V) compounds from water is generally successfully resolved by, for example, converting these compounds into an insoluble phase using concentrated solutions of iron (III), followed by filtration. Since arsenic (III) compounds cannot be converted into an insoluble phase under industrial conditions or ion exchange technologies used, arsenic (III) compounds need to be converted into arsenic (V) compounds, i. e., arsenic (III) compounds must be oxidised [2][3][4][5][6][7].…”