Photocatalytic Degradation of Organic Pollutants over MFe2O4 (M = Co, Ni, Cu, Zn) Nanoparticles at Neutral pH

Abstract

in this study, we report a surfactant-mediated synthesis of ferrites (Mfe 2 o 4 : M = co, ni, cu, Zn) using the co-precipitation-oxidation method. The band gap calculated from UV-Visible diffuse reflectance spectra were found in the range of 1.11-1.81 eV. These ferrite nanocatalysts were studied for the photocatalytic degradation of multiple organic dyes in a 32 W UV-C/H 2 o 2 system. All the four ferrites showed an excellent dye degradation rate in the range of 2.065-2.417 min −1 at neutral pH. in the optimized condition, NiF was found to degrade 89%, 92%, 93%, and 78% of methylene blue, methyl orange, bromo green, and methyl red, respectively within 1 min of UV-irradiation. A 40% TOC removal was recorded after 5 min of degradation reaction, which increased to 60% after 50 min. Mechanism elucidated by scavenger studies and fluorescence spectroscopy revealed that • oH and holes were the primary reactive radicals responsible for the degradation process. ferrite photocatalysts showed an insignificant performance loss in seven consecutive cycles. The photocatalyst was found efficient in the presence of a high concentration of salts. thus, it was concluded that these photocatalysts are highly suitable for the remediation of dye-contaminated wastewater. The ever-increasing population, coupled with rapid urbanization and industrialization, have deteriorated the quality of life. Excessive contamination of water bodies could be a severe threat to both human beings and other life forms. Organic dyes are considered as one of the major pollutants discharged into the environment by textile, printing, food, and leather industries 1. Though a large segment of these synthetic dyes is non-toxic or less toxic, their presence in water increases the oxygen demand, which in turn affects aquatic animals 2. Among the dyes consumed in industries, up to 70% belong to azo dye family (those with azo-functional group "-N = N-"). Azo dyes have genotoxic, mutagenic, and carcinogenic effects on living beings 3. Some of the azo dyes are known to be carcinogenic in the non-cleaved state, and for many of the azo dyes, their cleaved products such as benzidine are known to induce tumors 4. Conventional biological, chemical, and physical methods like adsorption 5,6 , chemical precipitation 7 , and microbial degradation 8 have been established for the remediation of dye-contaminated wastewater. The practical application of these processes suffers due to high operational cost, sludge production, or formation of secondary pollutants. For a complete or partial degradation of organic dyes (into non-toxic byproducts), degradation by adopting the photocatalytic process is one of the viable options. In recent years, advanced oxidation processes based on the generation of highly reactive hydroxyl radicals have gained momentum for the degradation of toxic organic pollutants 9. Though the Fenton process is easier to operate, it suffers badly due to a slow regeneration of Fe 2+ ions 10. Thus, the ultraviolet radiation or electrochemical method is generally cou...

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