Persulfate-enhanced lanthanum iron oxide-mediated photocatalysis can effectively degrade an aqueous industrial dye and mineralize water and wastewater

A novel, home-made lanthanum iron oxide (LF; 0.125–1.00 g/L) was used to treat an industrial model pollutant (Reactive Black 5 dye-RB5; C_o = 20 mg/L) under UV-A irradiation (1.3 W/L). Aqueous, hydrolyzed RB5 solution that was prepared to mimic reactive dyehouse effluent could be success-fully degraded by LF-mediated photocatalytic treatment and the degradation rate was remarkably enhanced in the presence of persulfate (PS; 0.6–1.2 mM). LF-mediated heterogeneous photoca-talysis was only effective at pH ≤ 4. The dissolved organic carbon (DOC) content of the aqueous RB5 solution (DOC_o = 5.15 mg/L) could also be substantially removed by LF/UV-A (LF = 0.5 g/L; 52%–54% DOC removal after 150–180 min) and PS-enhanced LF/UV-A (LF = 0.5 g/L; 60%–66% DOC removal after 120 min). Reuse of the same LF photocatalyst for complete color and par-tial DOC removals was confirmed for the selected LF/UV-A/pH3 and LF/PS/UV-A/pH3 treatment conditions in four treatment cycles. LF/UV-A/pH3 and LF/PS/UV-A/pH3 were also applied to real water and wastewater samples; tap water (DOC_o = 1.98 mg/L) and two secondary treated sewage (DOC_o = 5.39 and 16.83 mg/L) samples. A decrease in DOC removals to 25% (tap water), 22% (second-ary treated, low-DOC sewage sample) and 5% (secondary treated, high-DOC sewage sample) was observed for the real water and wastewater samples.