Removal of gaseous DiBP and DnBP by ionizer-assisted filtration with an external electrostatic field

Phthalic acid esters (PAEs) have been widely used in indoor applications and cause severe sicknesses. In this study, we developed an ionizer-assisted filtration method with an external electrostatic field to efficiently remove gaseous DiBP (Diisobutyl phthalate) and DnBP (Dibutyl phthalate). We used low-pressure drop polyurethane (PU) foams as substrate filters, and loaded fine activated carbon powder into PU foams as PU-C foams. The pressure drop of new filters ranged from 5.28 Pa to 14.3 Pa at the face velocity of 1 m/s. We investigated the influence of filter materials and electrostatic charging on the single-pass filtration efficiency of PAEs and net ozone production. The filtration efficiency of 30 ppi (pores per inch) filter increased from 15.4% (PU) to 29.3% (PU-C) for DiBP. Only pollutant pre-charging cannot enhance the filtration efficiency of PAEs. It may be because negative ions accumulate on the filter surface and cause electrostatic repulsive forces between the charged gaseous PAEs and filters, which lowers the electrostatic filtration efficiency. When charging the pollutants at -8.0 kV and the filter at +10.0 kV simultaneously, the filtration efficiency of 30 ppi PU-C filter increased from 29.3% to 45.5% for DiBP. However, the simultaneous charging on pollutants and filters did not improve the efficiency of 40 ppi PU-C filter. The reason may be that the specific resistance of 40 ppi PU-C filter was 6 times larger than that of 30 ppi PU-C filter, which leads to more negative ions accumulating on the filter surface. The tendency for the removal of DnBP is similar. The net ozone productions of all experiments were less than 0.38 mg/h. Overall, this study developed an ionizer-assisted filtration method with an external electrostatic field, which is based on inexpensive, low pressure drop coarse filters, and is efficient for the active control of gaseous PAEs.