Effect of binders on airborne microorganism inactivation using TiO2 photocatalytic fluorescent lamps

5% Degussa P25 TiO2 was spray-coated onto black-light and white-light fluorescent lamps, using five different binders, namely DURAMAX B-1000, DURAMAX D-3005, silane-69, and two polyethylene glycols with molecular weight 1000 (PEG-1000) and 700 (PEG-700). The coated lamps were tested with Staphylococcus epidermidis, Escherichia coli, spores of Bacillus subtilis and spores of Aspergillus niger. It was found that 0.5% B-1000 and 1% PEG-1000 gave the highest inactivation rates: 93–96% from coated black-light lamps and 85–88% from coated white-light lamps for bacteria. In the case of spores, 70–72% and 55–57% inactivation rates were recorded from coated black-light and coated white-light lamps, respectively. The effects of UVA irradiance and face velocity were also examined. Significant improvement was observed from coated white-light lamps when the UVA irradiance increased. High face velocity adversely affected microorganism inactivation.