Development of an activated carbon filter to remove NO2 and HONO in indoor air

Abstract To obtain the optimum removal efficiency of NO 2 and HONO by coated activated carbon (ACs), the influencing factors, including the loading rate, metal and non-metal precursors, and mixture ratios, were investigated. The NO x removal efficiency (RE) for K, with the same loading (1.0 wt.%), was generally higher than for those loaded with Cu or Mn. The RE of NO 2 was also higher when KOH was used as the K precursor, compared to other K precursors (KI, KNO 3 , and KMnO 4 ). In addition, the REs by the ACs loaded with K were approximately 38–55% higher than those by uncoated ACs. Overall, the REs (above 95%) of HONO and NO x with 3% KOH were the highest of the coated AC filters that were tested. Additionally, the REs of NO x and HONO using a mixing ratio of 6 (2.5% PABA ( p -aminobenzoic acid) + 6% H 3 PO 4 ):4 (3% KOH) were the highest of all the coatings tested (both metal and non-metal). The results of this study show that AC loaded with various coatings has the potential to effectively reduce NO 2 and HONO levels in indoor air.