Development of the TiO2-coated Silk Fibroin Filters for Treatment of Gaseous Formaldehyde in Indoor Air

Abstract

This research focuses on synthesis of TiO2-coated silk fibroin (SF) filters and their application for treatment of indoor air contaminant via photocatalytic oxidation process (PCO). Formaldehyde (HCHO), one of major indoor air contaminants, was selected in this study. This work can be divided into 4 phases including: phase 1 monitoring of HCHO concentrations in a gross anatomy laboratory (GAL) and general health survey, phase 2 synthesis of SF filters and study of morphological structure and physical properties, phase 3 treatment of HCHO in a small reactor using the synthesized SF filters and commercial filter, and phase 4 application of the TiO2-coated SF filters for PCO of HCHO in a large modeling room. For the first phase, the highest HCHO concentration observed was 15.66 ± 0.00 ppm. The result of general health survey showed that the most medical symptom occurred was irregular heartbeat. For the second phase, TiO2-coated SF filters were synthesized and analyzed for morphological structure by Scanning electron microscopy (SEM), UV–VIS spectrophotometer, Fourier transform infra-red spectroscopy (FT-IR), Thermogravimetric analysis (TGA), isotherm of adsorption and desorption of nitrogen gas on the SF filter, and physical properties by tensile strength method. The SEM images revealed that the TiO2 was relatively well scattered on SF surface. The band gap energy was 3.18 eV. The removal efficiency of HCHO in a small reactor with 40x45x50 cm3 was conducted for impact of initial HCHO concentration, catalyst (TiO2) dosage, and air flow rate. From the studies, the highest removal efficiency of approximately 68.23 ± 0.44 % was obtained at initial concentration of 5.0 ppm, catalysis dosage of 5.0 % (TiO2 wt /vol.sol.), and air flow rate of 5 L/min. Moreover, the results derived from the kinetic model revealed that the photocatalytic rate follows the first order reaction. The simplified L-H reaction rate constant was calculated to be 0.0061 min-1. For application of the TiO2-coated SF filters for treatment of HCHO in a large modeling room of 1.2x1.2x1.85 m3 at air flow rate of 84.40 ft3/min, it was found that the removal efficiency of HCHO was approximately 54.72 ± 1.75 %.