Enhanced degradation of an azo dye by catalytic ozonation over Ni-containing layered double hydroxide nanocatalyst

Abstract

• For the first time catalytic activity of Ni-based LDH was studied in ozonation. • Catalytic degradation of methyl orange showed a COD removal of 72%. • Ozone-Ni ions interaction on catalyst surface generated active complexes. • Active complexes are the key for achieving such high catalytic performance. The catalytic activity of Ni-based layered double hydroxides (Ni-LDHs) nanomaterials was studied for the first time in ozonation of simulated dyeing wastewater for dye degradation (methyl orange (MO)). For the purpose of comparison, degradation of MO by non-catalyzed ozonation was also considered. The degradation experiments were performed in a laboratory scale cylindrical batch reactor. The effect of catalyst was studied using UV–Vis, chemical oxygen demand (COD) and ion chromatography (IC) analyses. The influence of various operating factors such as reaction temperature, dye concentration, catalyst dosage and hydroxyl radical scavengers (bicarbonate-carbonate) on the MO dye degradation rate were investigated. The catalytic ozonation exhibits total discoloration with faster reaction rate and clearly enhances the COD removal. In optimized conditions, after 60 min reaction, COD removal has reached 72% in the catalytic ozonation process, while it reached only 30% in non-catalytic ozonation. Additionally, the characterization results of Ni-LDH catalyst before and after ozonation experiments were discussed. A possible mechanism of degradation was suggested.