Remarkable lignin degradation in paper wastewaters over Fe2O3/γ-Al2O3 catalysts using the catalytic wet peroxide oxidation method

Abstract

Heterogeneous catalytic wet peroxide oxidation (CWPO) has been found to be one of the most effective approaches for the degradation of toxic and paper factory wastewater. Fe₂O₃/γ-Al₂O₃ catalysts were prepared by an impregnation method and characterized by X-ray diffraction (XRD), temperature-programmed desorption (TPD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The catalytic activity of Fe₂O₃/γ-Al₂O₃ for the CWPO of lignin was assessed. The effects of initial solution pH, catalyst dosage, initial concentration of hydrogen peroxide, reaction temperature and initial concentration of lignin on the reactivity of the system were investigated. Higher lignin degradation can be achieved under not only under acidic but also neutral and slightly alkaline conditions. Under initial conditions of pH = 9, T = 348 K, 6 g L⁻¹ catalyst, 6.396 mM hydrogen peroxide and 100 mg L⁻¹ lignin, 87% lignin degradation and 86% total organic content (TOC) removal were achieved in 60 min. The negligible amount of leaching Fe ions found in solution was measured by inductively coupling plasma-atomic emission spectra (ICP-AES).