Removal of low-concentration formaldehyde in air by DC corona discharge plasma

The effects of discharge polarity, discharge electrode configuration, gas composition and downstream catalyst on the removal of low-concentration HCHO in air were systematically investigated in a link tooth wheel-cylinder plasma reactor energized by a DC power. Experimental results show that the positive DC corona discharge is much more effective in removing HCHO as compared to the negative one. The discharge electrode configuration significantly influences the energy input to the plasma reactor. For a given specific energy density (SED), longer reaction zone favors the HCHO conversion; however, the HCHO conversion is almost constant in spite of the different discharge electrode configurations within a fixed reaction zone. The conversion of HCHO increases with the increase of gas humidity, and decreases with increasing coexisting toluene in the gas stream. On the other hand, introduction of MnOx/Al2O3 catalyst downstream the plasma reactor significantly enhances the HCHO conversion and reduces the O3 emission.

► Removal of low-concentration formaldehyde (HCHO) in air by DC corona discharge plasma and plasma-catalysis was investigated.
► The positive DC corona discharge is much more effective in removing HCHO than the negative one.
► The discharge electrode configuration has limited effects on the HCHO conversion for a given discharge energy density.
► Increasing humidity has positive effects while coexisting toluene in the gas stream has adverse effects on the HCHO removal.
► The presence of downstream MnOx/Al2O3 catalyst significantly enhances the conversion of HCHO and reduces the emission of O3.