Nature of surface interactions among Fe3O4 particles and arsenic species during static and continuous adsorption processes

This study explored the mechanistic approaches to understand the adsorptive removal of arsenic species from aqueous medium in static and continuous adsorption processes. Fe₃O₄, an adsorbent is this study, is synthesized by reverse coprecipitation method using iron oxide waste of steel industry as a starting material. The surface properties of Fe₃O₄ were confirmed by several characterization techniques including XRD, XPS, SEM, TEM, FTIR, EDS, Raman, and zeta potential. The arsenic removal rate was found to be dependent on the synthesis pathway ofFe3O4 especially, the pH during reverse coprecipitation. Beside synthesis conditions, the adsorbent size, adsorbent quantity, an initial concentration of arsenic species, contact time, and the solution pH also influenced the arsenic removal rate. Over 90% arsenate and arsenite concentrations were effectively removed from the solution in initial 10 min of contact between Fe₃O₄ and arsenic solution. The adsorption sites of Fe₃O₄ were successfully reclaimed by regeneration of used particles with 0.1N NaOH solution. To assess the practicability of the Fe₃O₄ particles in continuous adsorption process, particles were used in column and plug flow reactors and the adsorption profile is examined under different operational conditions (operational scheme, influent flow direction, contact time, initial arsenic concentration, etc.). The operational performances of reactors confirmed that the synthesized particles have the potential to be successfully applied for arsenic removal from water.