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

Yuparat Limmongkon^a, Jeff Johns^b, Lertchai Charerntanyarak^c,*

 
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 TiO₂ 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% TiO₂ 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.

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* Corresponding author, E-mail: lertchai@kku.ac.th

Received 6 Nov 2012, Accepted 14 Mar 2013