Efficient purification of toluene gas by anoxic denitrification

As a part of volatile organic compounds (VOCs), toluene does harm to human health. This paper reported the purification of toluene waste gas by liquid-phase absorption and anoxic denitrification. In this work, two same biofilm reactors were set to treat toluene waste gas, one of which was added into nitrate as an electron acceptor. Then, the purification properties of toluene waste gas treated by anoxic denitrification and biological methods were compared. The results indicate that with the increase of toluene mass concentration, the toluene removal rate of the denitrifying reactor decreased slightly. When the inlet concentration increased from 50 mg m^-3 to 3440 mg m^-3, the removal efficiency of the denitrifying reactor remained over 94.1% while the removal efficiency of the traditional bioreactor decreased to 82.9%. The highest removal capacity of the denitrifying reactor was 127.2 g m^-3 h^-1, which was 11.8% higher than that of the traditional bioreactor. Toluene was degraded by denitrification inside the biofilm microenvironment hypoxia; the denitrification rate increased along with the increase of inlet concentration within certain limits and reached a maximum of 2.4 mg NO₃^--N L^-1 h^-1. Nitrate can act as an electron acceptor, and denitrification can promote aerobic degradation and intensify the concentration gradient inside the biofilm to strengthen the toluene transfer process.