Insights on the Behavior of Arsenic Species on Activated Carbon during Catalytic Arsenic Oxidation

摘要

A novel and robust process which uses activated carbon and oxygen to catalyze arsenic oxidation in acidic solutions was investigated. It is important to oxidize arsenic prior to removing it from hydrometallurgical streams because arsenate species are more efficiently and effectively removed as precipitates compared to arsenite species. Previous studies show that hydrogen peroxide is formed on the activated carbon surface when aerated with oxygen in acidic solutions. This study investigates how hydrogen peroxide formed affects the oxidation of arsenic in solution and the speciation of arsenic on the carbon surface. Arsenic adsorption and desorption tests were conducted to gain further insights into the adsorption and desorption behaviour of arsenic species on activated carbon during catalytic arsenic oxidation.It was determined that arsenic exists in the pentavalent and trivalent state on the activated carbon surface before arsenate appears in the solution. Arsenate begins to appear in solution once the adsorption of total arsenic on the carbon surfaces plateaus as the carbon reaches its saturation point. Desorption experiments indicate that arsenite is more readily desorbed than arsenate as the speciation of arsenic in solutions containing arsenite and arsenate were 46.3-46.6% arsenate and the remainder arsenite.