Efficiency Enhancement of Dark Heterogeneous Fered-Fenton Process for Acid Blue 25 Removal Using Graphene Oxide–Coated Zero-Valent Iron Nanoparticles with Energy and Iron Consumption Reduction

Abstract

The Fered-Fenton process, a promising advanced oxidation technology, effectively degrades recalcitrant pollutants such as dyes. This study tackles limitations in the traditional homogeneous dark Fenton method by integrating it with electrochemical enhancements to form a homogeneous dark Fered-Fenton system. The use of nano-zero-valent iron (nZVI) as a catalyst improves pollutant adsorption and reactivity due to its higher surface area compared to ferrous ions. Additionally, graphene oxide–coated electrodes accelerate pollutant removal, aiming to reduce iron and energy consumption—key limitations in conventional Fenton processes. Under optimal conditions (pH 4, dye concentration 200 mg/L, [nZVI] to [H2O2] ratio 0.5, H2O2 concentration 340 mg/L, current 600 mA, temperature 23°C, and 90-min reaction time), the system achieved 95% dye removal, with corresponding chemical oxygen demand (COD) and total organic carbon (TOC) reductions of 78% and 56%, respectively. The results demonstrated that increasing the [nZVI] to [H2O2] ratio, H2O2 concentration, temperature, pH, and current up to specific optimal levels enhances removal efficiency, beyond which the efficiency declines. Kinetic studies indicated a first–second-order reaction model. Future research should explore scaling up the process and utilizing real wastewater to validate the system’s practical applications.