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This study aims to explore the feasibility of using iron slag derived from an electric arc furnace (EAFS) as a catalyst to degrade Reactive Black 5 (RB5). Raw EAFS (R-EAFS) subjected to 0.1 M NaOH solution treatment and thermal treatment was denoted as activated EAFS (A-EAFS). A-EAFS was characterized and examined for its capability to degrade RB5 in a dark-batch reaction under different catalyst dosages (0.01–0.06 g), H 2 O 2 dosages (2–12 mM), initial pH values (2–7), initial concentrations (25–150 ppm), and reaction temperatures (303–323 K). The optimal conditions (94% within 60 min) for RB5 degradation were 0.2 g L −1 , 8 mM H 2 O 2 , and pH 3. The degradation rate of A-EAFS for RB5 exceeded 94%, which was higher than that of R-EAFS. Recycling of A-EAFS after 10 reuses suggested that this stability is ascribed to the regeneration of the major constituent's ferrous ion magnetite and maghemite to decompose H 2 O 2 into hydroxyl radical catalytically. Therefore, A-EAFS is an alternative heterogeneous catalyst in the abatement of organic dyes from polluted water through a heterogeneous Fenton-like reaction.

The pollution of water by effluents from dye industries is a widely established environmental and health problem that requires new insights and urgent attention. In this study, methylene blue (MB) and acid blue 29 (AB29) dyes were oxidatively degraded under the dark-Fenton process conditions using abundant electric arc furnace steel slag activated by sulfuric acid (S-EAF). The severity of the oxidative degradation conditions was screened under conditions at 50–150 mg/l dyes solution initial concentration, the H2O2 concentration range of 2–12 mM, and pH from 2 to 7. The results show that predominant crystalline ferrous ions on the S-EAF catalyst stimulated the decomposition of the H2O2, to enhance the generation of •OH radicals, which promoted oxidation of the dyes to realize 95% and 82% removal under 6 mM (AB29), and 8 mM (MB) H2O2 concentration at 30 °C. The pseudo-first-order kinetic sufficiently described the experimental data and application of the Langmuir-Hinshelwood model validated the dominant role of surface reaction, which was collaborated by the activation energy. The S-EAF catalyst sustained the oxidative degradation for seven cycles with minor leaching of irons (Fe).

This work presents the iron oxide recovery from electric arc furnace slag with different temperature and time using acid leaching method. The results showed that formation of iron oxide from electric arc furnace (IO-EAFS) was influenced by the temperature and time of heating. This is evidenced by constant acid concentration and liquid to solid ratio, 5 hours of heating time was exhibited the highest amount of iron ion in extracted solution. The maximum of iron extract in heating temperature was at 100 °C. Throughout the characterization using Scanning Electron Microscopy (SEM), the iron oxide illustrated the microstructures were agglomerates predominantly with irregular shapes and XRD results further colobrated the presence of hematite combined with other metal oxide exists in the IO-EAFS. From the TGA analysis, it was identified that the recovered iron oxide was totally decomposed at 525°C. This results indicate that electric arc furnace slag is potential material of iron oxide for the future appliction.

In this work, an activated electric arc furnace slag (A-EAFS) was investigated as an effective Fenton catalyst for the photodegradation of methylene blue (MB) and acid blue 29 (AB29). Fourier transform infrared spectroscopy and UV–visible absorption analyses indicated that A-EAFS offers additional Fe 3 O 4 because of the changes in the iron oxide phase and the favorable response to visible light. It has been found that the highest degradation efficiency can reach up to 94% for MB under optimal conditions of 1 g L −1 of A-EAFS, 20 mM H 2 O 2 , and pH 3. The optimal conditions for AB29 were 0.1 g L −1 A-EAFS, 4 mM H 2 O 2 , and pH 3 to reach 98% degradation efficiency. Visible light enhanced the degradation of both dyes. In addition, A-EAFS, could be easily separated magnetically, exhibited good chemical stability after seven successive photodegradation cycles.

Iron–immobilized montmorillonite KSF (Fe-MKSF) has been recognized as promising catalyst in degrading persistence organic contaminants. However, detailed mechanistic insight during the catalysis which involving the formation and identification of radical species were remained indeterminate due to complex reaction. Inspiring by this gap, iron-immobilized clay (Fe-MKSF) was synthesized and used as heterogeneous catalyst in the oxidative degradation of methyl orange (MO) solution. Identification of radical species were determined through the inclusion of different types of radical scavenging agent during the Fenton-like reaction at optimum condition. Interestingly, dominant radical species were found to be hydroperoxyl radicals (•OOH) which subsequently followed by hydroxyl radicals (•OH) during the catalysis. Based on the percentage of MO removal, it was suggested that approximately 88% of the •OOH radicals existed at the interface of catalyst while 39% presence in bulk solution. Meanwhile, the interface •OH radicals promoted 38% of MO removal, whilst 4% by the bulk •OH radicals. Hence, these findings have conveyed novel insight on detailed radicals' identification as well as its' interaction during the catalysis.