| Summary: | In this work, the degradation performance of Fe<sup>2+</sup>/PAA/H<sub>2</sub>O<sub>2</sub> on three typical pollutants (reactive black 5, ANL, and PVA) in textile wastewater was investigated in comparison with Fe<sup>2+</sup>/H<sub>2</sub>O<sub>2</sub>. Therein, Fe<sup>2+</sup>/PAA/H<sub>2</sub>O<sub>2</sub> had a high removal on RB5 (99%) mainly owing to the contribution of peroxyl radicals and/or Fe(IV). Fe<sup>2+</sup>/H<sub>2</sub>O<sub>2</sub> showed a relatively high removal on PVA (28%) mainly resulting from ·OH. Fe<sup>2+</sup>/PAA/H<sub>2</sub>O<sub>2</sub> and Fe<sup>2+</sup>/H<sub>2</sub>O<sub>2</sub> showed comparative removals on ANL. Additionally, Fe<sup>2+</sup>/PAA/H<sub>2</sub>O<sub>2</sub> was more sensitive to pH than Fe<sup>2+</sup>/H<sub>2</sub>O<sub>2</sub>. The coexisting anions (20–2000 mg/L) showed inhibition on their removals and followed an order of HCO<sub>3</sub><sup>−</sup> > SO<sub>4</sub><sup>2−</sup> > Cl<sup>−</sup>. Humic acid (5 and 10 mg C/L) posed notable inhibition on their removals following an order of reactive black 5 (RB5) > ANL > PVA. In practical wastewater effluent, PVA removal was dramatically inhibited by 88%. Bioluminescent bacteria test results suggested that the toxicity of Fe<sup>2+</sup>/PAA/H<sub>2</sub>O<sub>2</sub> treated systems was lower than that of Fe<sup>2+</sup>/H<sub>2</sub>O<sub>2</sub>. RB5 degradation had three possible pathways with the proposed mechanisms of hydroxylation, dehydrogenation, and demethylation. The results may favor the performance evaluation of Fe<sup>2+</sup>/PAA/H<sub>2</sub>O<sub>2</sub> in the advanced treatment of textile wastewater.
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