Enhanced degradation of malachite green through heterogeneous processes using an iron oxide catalyst

Abstract This laboratory-scale study investigated the removal of Malachite Green (MG) dye using the goethite composite (α-FeOOH) (GOE). In the dark, an interaction between MG and GOE, attributed to physical adsorption, was observed, reaching 28 % after 4 h and confirmed by FTIR analysis. The addition of hydrogen peroxide (H 2 O 2 ) enhanced the thermal process in the MG-GOE system. By varying parameters such as pH, GOE concentration, and H 2 O 2 amount, the MG disappearance rate increased with higher GOE and H 2 O 2 concentrations. Alkaline pH favored dye removal. Under UV light (365 nm), GOE effectively degraded MG, especially at pH 9 (97 % degradation in 180 min). The scavenging of hydroxyl radicals (˙OH) by tert-butanol in the GOE-MG-UV 365nm system indicated ˙OH-dominated degradation. Fe(II) formation monitoring supported this result. Additionally, H 2 O 2 addition significantly enhanced photodegradation. Partial mineralization of dye molecules was observed via Total Organic Carbon (TOC) analysis. The kinetics of MG degradation followed pseudo-first order behavior. Overall, this promising process holds potential for recalcitrant environmental pollutant removal.