Preparation of a TiO2-coated photocatalytic air filter for use with an electrostatic air filter pack for xylene removal

Abstract

This study evaluated surface morphology, mechanical stability, and the effectiveness for xylene removal of coated fibre glass filters and coated high-efficiency particulate air (HEPA) filters for use with an electrostatic air filter pack (ESF pack). Different surface pretreatment methods, two TiO 2 coating suspensions with different amounts of TiO2 and additive substances, varied baking temperatures, and various combinations between an ESF pack and a coated air filter were investigated. This investigation found that washing the substrates with 0.08 M sodium dodecyl sulphate and 0.01 M sodium fluoride before coating with 5% TiO2 suspension and then baking at 50 °C for 30 min after coating could yield the highest loadings of 285 g/m2 for the fibre glass filters and 182 g/m2 for the HEPA filters. Examination of these filters revealed that the TiO2 particles were agglomerated and stuck to the fibres as well, resulting in less loading loss. The highest removal efficiency of xylene (in 400-800 ppb) ranged from 41-49% when using a combination of one HEPA filter coated with 5% TiO 2 suspension together with four layers of ESF filters at an air flow rate of 10 m3/min and 45-5% RH. The suitable preparation of photocatalytic air filters is of great importance for their practical use, ensuring the stability of the coating and resulting in a product that is safe for human health and friendly to the environment.