Synergistic persulfate activation as an efficient and cost-effective approach for removal of organic synthetic-dyes from aqueous solutions using magnetic Pd-Fe3O4-flyash composite particles as catalyst

Magnetic palladium (Pd)-magnetite (Fe3O4)-flyash composite particles have been recently utilized for the removal of industrial azo reactive dyes from the aqueous solutions. The mechanism of dye-removal involves advanced oxidation process (AOP) such as the activation of costlier and hazardous oxidizer such as hydrogen peroxide (H2O2). The process also requires further backing-up with the adsorption treatment of activated carbon (AC) to control the enhanced chemical oxygen demand (COD) level of treated aqueous solution which not only increases the number of steps involved in the dye-removal process but also results in the generation of large amount of sludge. There is an urgent need to replace H2O2 with an efficient, cost-effective, and non-hazardous oxidizer which can resolve the aforementioned issues in the present dye-removal application. In this investigation, we utilize the magnetic Pd-Fe3O4-flyash composite particles for the decoloration of aqueous solutions containing industrial azo reactive dye such as Corafix Red ME4B via synergistic activation of persulfate anions (S2O82) involving the catalytic and thermal contributions. In contrast to the activation of H2O2, the synergistic activation of S2O82 anions is noted to significantly reduce the COD level almost in a single step which reduces the dependency on the post adsorption treatment of AC. Moreover, the regeneration of AC in the present dye-removal application has also been demonstrated using the synergistic activation of S2O82 anions. The latter, hence, appears to be an efficient, cost-effective, and non-hazardous approach for the removal of organic synthetic-dyes from aqueous solutions by using the magnetic Pd-Fe3O4-flyash composite particles as catalyst. (C) 2016 Elsevier Ltd. All rights reserved.