Enhanced degradation of Rhodamine B by pre-magnetized Fe0/PS process: Parameters optimization, mechanism and interferences of ions

An efficient heterogeneous catalyst, pre-magnetized Fe0 (pre-Fe0) could significantly activate persulfate (PS) to remove Rhodamine B (RhB). The effect of pH, Fe0 and PS dose on the RhB removal in the pre-Fe0/PS and Fe0/PS processes were investigated, and optimized by response surface methodology (RSM) to analyze the rate constants of the RhB removal in the pre-Fe0/PS process and Fe0/PS process (f). High RhB removal was obtained at low pH and high dose of Fe0 and PS in both systems. Low Fe0 and high PS dose and large pH would result in big value of f, and the simulated maximum f of 44.3 was achieved at 2 mM Fe0, 16 mM PS and pH 9. The synergetic factor of pre-Fe0/PS (45.6) was larger than that of Fe0/PS (21.4). The pre-Fe0/PS process presented 2.1-37.5 folds enhancement than the Fe0/PS process for the degradation of RhB. The RhB removal in the pre-Fe0/PS process was 1.5-11.2 folds enhancement than that of the Fe0/PS process in the presence of different anions and cations. Scanning Electron Microscope (SEM) results and the larger intensity of DMPO-SO4− adduct signal in the Electron Paramagnetic Resonance (EPR) confirmed the primary role of sulfate radicals generated from the reaction of PS with Fe0 in the contaminant degradation. The pre-Fe0/PS process exhibited advantages over other processes to remove RhB in terms of contaminant removal, working pH range and chemical dose. Therefore, the pre-Fe0/PS process is a cost-effective approach for degrading RhB.