Pyrite Cinder as an Effective Fenton-like Catalyst for the Degradation of Reactive Azo Dye: Effects of Process Parameters and Complete Effluent Characterization

This research investigates the potential use of pyrite cinder (PC) as an efficient Fenton-like catalyst for the removal of the reactive azo dye Reactive Red 120 (RR120) from aqueous solutions. The characterization of its PC structure and composition confirmed its great potential to act as catalytic iron source in a heterogeneous Fenton system. Dye removal optimization was performed in terms of PC dosage (0.4-8 g/L), H2O2 concentration (2-25 mM), pH value (2-4.6), initial dye concentration (50-200 mg/L), and mixing time. The highest decolorization efficiency (92%) was achieved after a reaction time of 480 min under following conditions: RR120 = 50 mg/L, PC = 4 g/L, H2O2 = 10 mM, and pH = 3. After decolorization, an extensive analysis of the generated effluent was performed regarding metal leaching, mineralization, toxicity, and degradation product formation. The metal leaching indicated the necessity for a pH increase in order to remove the settled metal hydroxides. The mineralization efficiency was satisfactory, reaching 85% and 62% of the COD and TOC removal, respectively. The respirometry measurements and bioluminescence tests indicated the detoxification of the treated solution. The absorption spectra and GC/MS analysis confirmed the changes in the molecular structure in the form of the destruction of the azo bond, with a simpler aromatic and aliphatic intermediates formation. This study provides an effective method for removing azo dye in polluted water by employing waste tailings as alternative Fenton-like catalysts, while also using waste tailings as the secondary resource.

Automated summary

This research explores the potential use of pyrite cinder as a Fenton-like catalyst for removing Reactive Red 120 from water. The PC demonstrated excellent catalytic properties in a heterogeneous Fenton system. Optimal conditions for decolorization were found to be a reaction time of 480 min, RR120 concentration of 50 mg/L, PC dosage of 4 g/L, H2O2 concentration of 10 mM, and pH of 3. The efficiency of metal leaching and detoxification of the effluent was assessed, as well as the formation of degradation products. The study provides an effective method for removing azo dye from polluted water using waste tailings as catalysts.