Manganese Amended Activated Alumina for Adsorption/Oxidation of Arsenic

In a laboratory study, manganese amended activated alumina (MAA), prepared by calcining $(400°\mathrm{C})$ manganese acetate-impregnated activated alumina, showed promise as a more effective medium than activated alumina (AA) for use in small municipal drinking water systems or point-of-use treatment, for removing arsenic [As(III) and As(V)] from groundwater. Batch adsorption/oxidation kinetic tests indicated that in fixed-bed operation, with a bed flowthrough time of $10–20\min$ , MAA would be a more effective medium than AA in removing arsenic [As(V), As(III), and As(III) and As(V) (present together)] from groundwater. In three cycles of downflow column test [bed depth $200\mathrm{mm}$ ; bed flowthrough time $20\min$ ; influent arsenic $1.0–0.6\mathrm{mg}∕\mathrm{L}$ As(III) and $0.4\mathrm{mg}∕\mathrm{L}$ As(V)], breakthrough bed volumes at the World Health Organization guideline value of $0.01\mathrm{mg}∕\mathrm{L}$ for arsenic in drinking water were 580, 550, and 485, and 825, 770, and 695, respectively, for AA and MAA. During regeneration (backwashing with a sodium hydroxide solution), 84–88% (for AA) and 86–89% (for MAA) of the removed arsenic was recovered. Manganese concentration in the MAA column effluent was low (below $0.02\mathrm{mg}∕\mathrm{L}$ ). A detailed study addressing the effects of some important factors (water pH, concentration and type of competing ions, and fouling by organics) on the process is needed.