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In batch experiments the influence of various factors on adsorption were studied, including initial As concentrations, initial pH values and competitive adsorption of As (III) and As (V). The effect of initial As concentrations was studied in the range of 0.01–20 mM As (III) or As (V) at pH 7.5. The influence of pH was evaluated by the adsorption of 5 mM As solution in the pH range of 2–12. The experiment of competitive adsorption of arsenite and arsenate was performed for various proportion of As (III) to As (V) in the range of initial concentrations 0.025–20 mM at pH 7.5. The bonding strength of As with bog iron ore surface was estimated on the basis of three-step desorption experiments, which were conducted for the samples previously treated with As (III) or As (V) at pH 7.5 and at constant 20 mM initial concentration of arsenic. Arsenic concentrations in filtered (filter with a 0.22 µm pore size) solutions after all the experiments were analyzed using AAS and UV-Vis spectrophotometry. The results showed that arsenic sorption depends on its oxidation state. All the bog iron ores bound more As (III) than As (V). The highest amount of As (III) was sorbed by ST sample

Arsenic is a toxic element, elevated concentration of which in the environment can result from both anthropogenic activity and natural geochemical processes. The contamination of water, especially groundwater, with As has been recognized as a major environmental problem (Choong et al. 2007). The mobility and toxicology of As is related to its valence state which can be (+ III) or (+ V), depending mainly on pH and redox conditions. Because even low As concentrations in drinking water …