Low-concentration formaldehyde removal from air using a cycled storage–discharge (CSD) plasma catalytic process

Cycled storage–discharge (CSD) plasma catalytic process was applied to low-concentration formaldehyde removal from air for the first time. HZSM-5, Ag/HZSM-5 (Ag/HZ), Cu/HZSM-5 (Cu/HZ) and AgCu/HZSM-5 (AgCu/HZ) catalysts were used for the process and their performance for formaldehyde storage and plasma catalytic oxidation of stored formaldehyde towards carbon dioxide was investigated in details. AgCu/HZ exhibited the highest formaldehyde adsorption capacity among these catalysts due to the synergistic effect of Ag and Cu, and it was very selective for oxidizing stored formaldehyde into CO2 by either oxygen or air plasmas at the discharge stage. The CSD process for low-concentration formaldehyde removal had extremely low energy cost, excellent humidity tolerance and almost no secondary pollution. At the discharge stage, in addition to pure oxygen, air can also be used as the discharge gas for complete oxidation of formaldehyde, and the nitrogen oxides produced can be negligible because the discharge period was much shorter than the storage period. The stability of the AgCu/HZ catalysts during the CSD process was also investigated.

► AgCu/HZ catalysts possess very large breakthrough capacity for HCHO storage across a whole range of humidity.
► AgCu/HZ catalysts exhibited synergistic effect of Ag and Cu towards complete oxidation of stored HCHO.
► Extremely low energy cost, excellent humidity tolerance and almost no secondary pollutants were achieved.