Cosmetic wastewater treatment by the ZVI/H₂O₂ process

The ZVI/H₂O₂ process was applied for cosmetic wastewater treatment. Two commercial zero-valent iron (ZVI) types with different granulations were chosen: Hepure Ferrox PRB and Hepure Ferrox Target. In addition, the pH and stirring method influence on ZVI/H₂O₂ process efficiency was studied. During the ZVI and ZVI/H₂O₂ processes, linear Fe ions concentration increase was observed. The addition of H₂O₂ significantly accelerated the iron dissolution process. The highest COD removal was obtained using finer ZVI (Hepure Ferrox Target) for doses of reagents ZVI/H₂O₂ 1500/1600 mg/L, in a H₂O₂/COD weight ratio 2:1, at pH 3.0 with stirring on a magnetic stirrer. After 120 min of the process, 84.0% COD removal (from 796 to 127 mg/L) was achieved. It was found that the efficiency of the process depends, as in the case of the Fenton process, on the ratio of the reagents (ZVI/H₂O₂) and their dose in relation to the COD (H₂O₂/COD) but does not depend on the dose of the iron itself. Statistical analysis confirms that COD removal efficiency depends primarily on H₂O₂/COD ratio and ZVI granulation, but ZVI dose influence is not statistically significant. The head space, solid-phase microextraction, gas chromatography, mass spectrometry results confirm high efficiency of the ZVI/H₂O₂ process.