Development of iron-containing sorption materials for water purification from arsenic compounds

The paper is devoted to the development of a method for obtaining and using iron-containing sorption materials for the effective removal of arsenic compounds of different oxidation states from an aqueous medium. It is known that arsenic compounds have a harmful effect on biota due to high toxicity. The paper theoretically and experimentally substantiates the choice of iron-containing materials as the main sorbent material for arsenic compounds removal from the aqueous medium. A series of iron-containing adsorbents, including powder, activated carbon-based granular and suspension sorbents, was synthesized by different methods (heterogeneous and homogeneous precipitation). Experimental studies have confirmed that the adsorption of arsenate ions on iron-containing sorption materials corresponds to the pseudo-second order of the reaction (R2=0.999), which is inherent in adsorption processes. It was determined that oxyhydroxide sorption materials obtained by the homogeneous precipitation demonstrate higher sorption activity (up to 70 mg/g for As(III) and over 70 mg/g for As(V)). It was found that activated carbon-based iron-containing sorption materials showed approximately 2 times lower efficiency than powder iron(III) oxide, iron(III) oxyhydroxide and amorphous iron(III) hydroxide. It was shown that the use of microfiltration membranes is promising for the removal of spent suspension iron-containing sorption materials. Experimental studies have confirmed that the use of the combination “fine-particle iron(III) oxyhydroxide/membrane” allows removing arsenic compounds from contaminated water to the sanitary requirements level (less than 10 μg As/l) and separating effectively the spent fine-particle sorbent from water