Cr(VI)-Mediated Homogeneous Fenton Oxidation for Decolorization of Methylene Blue Dye: Sludge Free and Pertinent to a Wide pH Range

Abstract

Fe­(II)-mediated Fenton process is commonly employed for oxidative degradation of recalcitrant pollutants in wastewater. However, the method suffers from limitations like narrow working pH range and iron sludge formation. The present work deals with the degradation of Methylene Blue (MB) dye using Fenton-like oxidation by replacing Fe­(II) with Cr­(VI), which eliminates the limitations of classical Fenton oxidation. The Fenton-like oxidation of MB is brought about by HO• radicals generated by the disproportionation of chromium-coordinated peroxo complexes. It was observed that the working pH range for the Cr­(VI)-mediated Fenton oxidation was 3–10, and no sludge formation takes place up to four cycles as the oxidation remains in the pure solution phase. The complete mineralization of dye was confirmed by observing the decay of MB peaks by a spectrophotometer and cyclic voltammetry. The reaction parameters like pH of the solution, temperature, degradation time, concentrations of H2O2, Cr­(VI), and MB were studied for optimal performance of the Cr­(VI) as the catalyst. Kinetic studies revealed that the Cr­(VI)-mediated Fenton reaction follows pseudo-first-order reaction kinetics and depends on the concentration of HO• radicals. The proposed Cr­(VI)-mediated Fenton oxidation in the present work is best suited for the degradation of organic dyes by adding H2O2 as a precursor in chromate-contaminated wastewaters.

A novel cotton bio-scouring using pectinase in combination with Fenton system

“…It was possible to speed up the Fe 2+ /H 2 O 2 reaction by increasing temperature, thereby increasing the •OH generation rate. In contrast, only about 15% removal rate was reached at 65℃, and the pectin removal rate on fabrics was very low under high-temperature conditions because of the invalid decomposition of hydrogen peroxide into H 2 O and O 2 at these conditions (Watwe et al 2021).…”

Electrochemical oxidation of methylene blue dye in wastewater using mechanically alloyed high entropy alloy modified carbon paste electrode using cyclic voltammetry

“…The MB can be easily oxidized to cationic reactive radical by applying a suitable voltage [38]. MB dye in its cationic form can act as a strong electron/proton acceptor on the surface of the HEA-MCPE [39]. Therefore, oxidation of MB on the electrode can increase the number of protons [22].…”

The Role of 3D Printing in the Development of a Catalytic System for the Heterogeneous Fenton Process

“…In recent years, advanced oxidation processes (AOPs) have been studied as a promising organic wastewater treatment method based on the in situ generation of hydroxyl radicals (HO), which have a strong oxidation capacity (standard potential = 2.80 V versus standard hydrogen electrode) [ 22 ]. The two reactions involved in the classical Fenton process are: Fe +2 + H 2 O 2 = Fe +3 + HO ● + OH − Fe +3 + H 2 O 2 = Fe +2 + HOO ● + H + HO ● + pollutant = CO 2 + H 2 O …”