Abstract
Ferrous and ferric salts were tested for the persulfate activation (PS/Fe2+ and PS/Fe3+) and the oxidation of Acid Red 18 (AR18). A complete removal was attained after 90 min in both PS/Fe2+ and PS/Fe3+ processes with the persulfate concentration of 6 mM. High concentrations of PS, Fe2+, and Fe3+ promoted the AR18 degradation in both processes and the optimized pH were 3 and 3.3 for PS/Fe2+ and PS/Fe3+ processes, respectively. The mechanism of PS activation by Fe3+ was also investigated. It was found that hydroxyl radical (HO•) and sulfate radical (SO4−•) were formed and acted as dominating radicals in both processes. It is also deduced that Fe recycle offers Fe2+ for PS activation in PS/Fe3+ process to produce HO• and SO4−•. The less radical side reactions lead to a higher contribution of HO• and SO4−• on AR18 degradation in PS/Fe3+ process.
Highlights
Synthetic complex organic dyes are important coloring materials in textile industry
Acid Red 18 (AR18) was successfully degraded by PS/Fe2+ and PS/Fe3+ processes, and the degradation ratio increased with the increasing concentrations of PS, Fe2+, and Fe3+ with an
AR18 was successfully degraded by PS/Fe2+ and PS/Fe3+ processes, and the degradation ratio increased with the increasing concentrations of PS, Fe2+, and Fe3+ with an optimized pH of 3 and 3.3 for PS/Fe2+ and PS/Fe3+, respectively
Summary
Synthetic complex organic dyes are important coloring materials in textile industry. There are more than 0.7 million tons of dyes produced annually [1]. Are effective methods for refractory organic wastewater treatment due to the strong and nonselective oxidizability of HO [6,7]. Activated PS oxidation methods are newly emerging AOPs for organics degradation as a result of their strong oxidizability and low material cost [12,13,14]. Since iron catalytic process is easy to operate and has a high oxidation efficiency, Fe2+ is the most widely used transition metal ion for initializing radical chain reaction in PS activation process [14,20,21,22]. PS, combined with ferrous salt (PS/Fe2+ ) and ferric salt (PS/Fe3+ ), was used for the degradation of azo dye Acid Red 18 (AR18), and the oxidation abilities of PS/Fe2+ and PS/Fe3+ were explored and compared. The reactive species and oxidation efficiency of PS/Fe2+ and PS/Fe3+ processes were compared with AR18 as model contaminants in contrast experiments
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