Preparation of magnetically-separated porous CoFe2O4 and its performance in activating PMS for methylene blue degradation

Abstract

Three kinds of porous transition metal oxide materials, Fe2O3, Co3O4 and CoFe2O4, were successfully prepared by oxalate-routed pyrolysis method. The crystal structure, morphology, specific surface area, magnetic property and surface chemical state of those materials were characterized by XRD, SEM, BET, VSM and XPS, respectively. The catalytic performance towards PMS activation for degradation of simulated printing and dyeing wastewater were evaluated, taking a typical cationic dye methylene blue(MB) as the degradation model. The results show that all the three materials present hierarchical micro/nano porous fibrous structure, and a much higher PMS activation performance of CoFe2O4 is observed comparing with Fe2O3 and Co3O4 due to its highest specific surface area as well as the concerted catalytic effect between iron and cobalt elements. Through a series of single-factor experiments, the optimal process conditions for MB(10 mg·L-1, 500 mL) degradation in CoFe2O4/PMS system are determined as follows: PMS dosage of 3 mL(0.1 mol·L-1), catalyst dosage of 0.07 g and reaction time of 50 min. Under this reaction condition, MB removal rate of 89.77% can be achieved. Meanwhile, effect of common anions on CoFe2O4/PMS advanced oxidation system is also investigated. It is found that the presence of Cl-, PO43- and C2O42- all exhibit inhibition for MB degradation in different degrees. Besides, quenching experiments and electron paramagnetic resonance (EPR) identification results both confirm that 1O2 is the primary active specie in CoFe2O4/PMS advanced oxidation system. Furthermore, the recycling experiments indicate that CoFe2O4 presents a long-term stability. More importantly, CoFe2O4 can be easily separated from liquids after the reaction with an external magnet owing to its good magnetic property. The results demonstrate that CoFe2O4 is a promising catalyst candidate in activating PMS to degrade dyeing wastewater.

Keywords

• oxalate-routed pyrolysis method
• cofe2o4
• peroxymonosulfate
• magnetic separation recovery
• methylene blue