Catalytic ozonation of ammonia nitrogen with powdered activated coke: Influence of operational parameters and surface chemistries

Catalytic ozonation of ammonia nitrogen (NH4+-N) in wastewater has received widespread attention in recent years because of its high efficiency and mild reaction conditions. Activated carbon catalysts have good adsorption and catalytic properties, but less studies currently. Activated coke has very similar properties to activated carbon, and it is easy to prepare and inexpensive. This paper explored the effects of NH4+-N by catalytic ozonation with powdered activated coke (PAC). Specifically, operating parameters, ammonia nitrogen degradation products, and reaction mechanisms were discussed. Under the conditions of pH of 11, ozone dosage of 12 mg/min, and PAC dosage of 10.0 g/L, ammonia nitrogen was degraded to nitrate nitrogen (NO3−-N) and nitrogen in PAC/O3 system, achieving 92.16 % ammonia nitrogen removal and 49.46 % nitrogen selectivity after 60 min. The basic groups and phenolic hydroxyls on the surface of PAC were the active sites, which promoted ozone decomposition to hydroxyl radicals (OH), superoxide radicals (O2−) and singlet oxygen (1O2). Ammonia nitrogen was synergistically removed by PAC adsorption, ozonation and catalytic ozonation. After six times of reuse, PAC still maintained good catalytic activity, and the ammonia nitrogen removal rate and nitrogen selectivity remained higher than that of the single O3 system.