Construction of a modified Fenton system for degradation of reactive red X-3B: Performance, degradation pathway and degradation mechanism

Azo dyes have relatively persistent chromophores that can persist in the environment. The traditional Fenton method has the problems of narrow pH value and low utilization rate of hydroxyl radicals. Therefore, this study constructed a modified Fenton system that does not require adjustment of wastewater pH and improves the utilization rate of ·OH for efficient degradation of azo dye reactive red X-3B, while saving the engineering application cost of the Fenton method. In order to obtain a more efficient degradation efficiency, the response surface was used to optimize the reaction conditions, and it was concluded that the TOC removal efficiency reached 43.36 % when the H 2 O 2 dose was 0.44 mL, the Fe (II) dropping speed was 5.63 drops/min, and the pH value was 5.3. The degradation intermediates were mainly esters by GC–MS analysis. The quenching experiments showed that ·OH was the key species in the degradation of reactive red X-3B. In this study, a modified Fenton system was established to provide reliable support for efficient degradation and low-cost treatment of dye wastewater. • The Fenton reaction's elimination efficiency for reactive red X-3B can be increased by adding Fe (II) dropwise; • Detecting the intermediate products of reactive red X-3B and inferring its degradation pathway; • Estimate the cost of acid adjustment for Fenton reaction; • The improved Fenton method has a good prospect in engineering applications.