Adsorption of oxy-anions of selenium and aresenic at oxide/water interfaces
AuthorNayak, Deba Chandan
Mining and Metallurgical Engineering
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The removal of oxyanions of selenium and arsenic from dilute aqueous industrial effluents is a challenging problem. In aqueous environment selenium and arsenic occur in different oxidation states depending upon the solution composition, pH, and oxidation/reduction potential of the system. Removal of the selenium and arsenic species from solution to meet the stringent regulatory compliance using conventional precipitation, adsorption, and ion exchange process are rather difficult. In this investigation an attempt was made for removing selenium and arsenic species from solution using commercial grade alumina, activated y-alumina (Al20 3), lanthanum oxide (La2O3) and activated y-alumina doped with lanthanum oxide. The adsorption of anions of selenium and arsenic was studied as a function of concentration, pH, time and redox potential. The oxidation-reduction potential also greatly affects the surface chemical interactions of all species of selenium and arsenic on hydrous alumina and lanthanum oxide. The combination of the above two oxides was found to be effective for removal of selenium and arsenic for a wide range of pH. It is observed that La(t) oxide which is the combination of activated y alumina and lanthanum oxide works well for the removal of selenium from aqueous solution. As far as the arsenic is concerned, LD(t) oxide which is the combination of commercial grade activated alumina (DD-6) and lanthanum oxide is selective. The removal efficiency was found to be nearly 100 % for both selenium and arsenic from aqueous solutions in low concentrations and in low pH.
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