More about Persulfate-Assisted Ferrilanthanide-Mediated Photocatalysis of Textile Industry Dye Reactive Black 5: Surface Properties and Structural Assessment

Abstract

Color and organic matter removal from dyehouse effluent remains a challenging issue for the environmentalist and textile dyer. Until now, various treatment processes have been proposed with limited success. In this study, the textile dye and model industrial pollutant Reactive Black 5 (RB5; 20 mg/L) could be rapidly degraded by persulfate (PS)-enhanced photocatalytic treatment using a novel, home-made lanthanum iron oxide (LF; 0.5 g/L). LF-mediated heterogeneous photocatalysis was effective when the solution pH was kept below 4. The photocatalytic degradation of RB5 solution was enhanced in the presence of 0.6 and 1.2 mM PS. The dissolved organic carbon (DOC) content of the aqueous, hydrolyzed RB5 solution (initial DOC = 5.15 mg/L) was effectively reduced by LF/UV-A (LF = 0.5 g/L; 52–54% DOC removal after 150–180 min) and LF/PS/UV-A (LF = 0.5 g/L; 60–66% DOC removal after 120 min) treatments. LF photocatalyst could be reused in four consecutive cycles for complete color and partial DOC removals without significant deterioration of the treatment performance with the LF/PS/UV-A/pH 3 process. Instrumental analyses of LF’s surface morphology/chemical composition and structural features via EDAX/SEM/Raman/FTIR/UV-vis/fluorescence spectroscopy indicated that LF remained practically intact throughout photocatalytic treatment, though slight changes/decreases in particle size/partial surface deformation and agglomeration coverage were observed, particularly during LF/PS/UV-A treatment. The presence of RB5 and its degradation products on the LF surface revealed that surface adsorption played a major role in LF-mediated photocatalysis. The Fe-content did not deviate appreciably from its original value after photocatalytic treatment.