Evaluation of indoor disinfection efficiency by photocatalysis and photolysis on air filters

FLORES, MARINA; CLAUDIO PASSALIA; BRANDI, RODOLFO J.

Buenos Aires

Congreso; WCCE11 - 11th World Congress of Chemical Engineering; 2023

Asociación Argentina de Ingenieros Químicos AAIQ

Introduction: Air pollution is a major public, environmental and health issue contributing to 7 million premature deathsworldwide annually. The removal of biological pollutants is therefore a challenging task for which photocatalysis hasattracted attention for acting as an efficient air treatment technology because of the oxidizing power of UVA-irradiatedsemiconductors. The present study aims at evaluating the efficiency of coated and bare air filters as well as the impactof important factors such as UVA at different intensities and humidity in reducing microorganisms. Also a kinetic modelwas proposed. Materials: Filtration materials were three hydrophobic woven air filters. Two filters corresponded to HighEfficient Particulate Air Filters, H11 and H13 class and the third is made of inert borosilicate glass. Aeroxide® P25Titanium dioxide was the catalyst used in all experimental trials. It exhibits a specific surface area range of 35-65 m2g-1(BET) with a primary particle size of 21 nm (TEM). The commercial catalyst is composed mainly of crystalline TiO2 withan anatase/rutile ratio 5.5 and around 10.0 wt% amorphous phase [1]. Rectangular samples (2,5 x 4 cm) were used forthe determination of catalysis loading and photocatalytic and photolysis activity tests. The catalyst was immobilized ontothe filters by a series of dip coating cycles. Each cycle consisted in immersing the substrate in the TiO2 suspension (50gL-1). E. coli (ATCC® 8739) was used as a model organism. The photocatalytic reactor employed in this work comprisesa UV-radiation emitting system, an irradiation compartment, and a support to hold filters. The upper side is providedwith five actinic UV-A lamps (Sylvania F15W T12, 15 Watts) with λmax = 365 nm. Before starting the irradiation, aliquotsof 100 μL of the microorganism’s suspension were spread resembling Flügge drops to cover the surface on filters. Then,they were introduced into the irradiation compartment, in which they were exposed to a given irradiation level for differenttimes. Once the irradiation time programmed for each sample had elapsed, the corresponding filters were removed fromthe irradiation compartment, agar EMB liquid was poured off on them and incubated for 24 hr at 37 °C. Results andconclusion: From the experimental results it was possible to determine the existence of UV-A photolysis formicroorganisms in the bared filters, it can be justified by a series event phenomenon in which the damage to the bacterialcell is cumulative rather than immediately lethal. In bared filters bacterial inactivation was in range of 0.9 -1.4 log for thedifferent filters. In coated filters, 2.5-3 log reduction was achieved confirming the viability of bacterial photocatalyticinactivation as a disinfection technology. The results predicted with the kinetic model proposal agreed quite satisfactorilywith the experimental results.