Precise preparation of CoO @KSB catalysts by atomic layer deposition for peroxymonosulfate activation and landfill leachate treatment

The construction of desired active sites is critical for enhanced activity in heterogeneous peroxymonosulfate (PMS) systems. In view of the shortcomings of the current construction methods, such as low precision and harsh conditions, CoOx@KSB catalysts were precisely prepared at the atomic level using atomic layer deposition in this study. Using alkali-modified sludge biochar (KSB) as a feedstock, two different deposition processes were proposed to investigate the preparation pattern on the treatment efficiency of landfill leachate. Results showed that the small-cycle layer-by-layer deposition (B process) not only preserved the original N sites of the catalyst after 150 depositions, but also obtained satisfactory Co2+. Under the optimal experimental conditions, KSB-B150 degraded more than 90% of SMX within 120 min. After 8 h of continuous operation in the packed column reactor, the COD concentration of the effluent landfill leachate was still below 100 mg/L, and the biotoxicity of the effluent was reduced to 0.41 times of the original. The Co2+, OV and graphite N sites could generate SO4•− and •OH, which played dominant roles in SMX degradation. This study provides a new strategy for constructing active sites in heterogeneous PMS system. It is beneficial to promote the application of heterogeneous advanced oxidation technology in landfill leachate treatment.