A novel BiOI/TiO₂ nano-heterojunction was prepared using hydrothermal and sol-gel methods. The composite material was characterized by X-ray diffraction, ultraviolet-visible diffuse reflection spectroscopy, scanning electron microscopy, and transmission electron microscopy. The crystallinity and response to light of BiOI/TiO₂ were controlled by preparation conditions such as the optimal solvent condition and heat treatment temperature. The photocatalytic activity of the BiOI/TiO₂ catalyst was examined using benzene as a test molecule. The benzene degradation rate of the composite catalyst under visible light was enhanced compared to pure TiO₂, thus reaching 40% of the original benzene concentration, which increased further to >60% after surface acidification. The fluorescence spectra, light current, and electron paramagnetic resonance confirmed that the enhanced activity was attributed to carrier separation by the heterojunction. The acid sites and active chlorine of hydrochloric acidification offer a novel mechanism for photocatalytic reactions.

Pleated filter media are widely used in particulate filtration, but the particle deposition and pressure drop during particle loading remain insufficiently explored. This study visualizes the particle deposition patterns in pleated filter media, along with the evolution of pressure drop and the effective filtration area (EFA) using simulations. The results indicate that, as the volume of deposited particles increases, the pressure drop of the pleated filter media initially grows linearly, but this rate of increase accelerates as particle deposition continues. The particle deposition characteristics are related to the pleat ratio. A smaller pleat ratio results in a smaller initial EFA, leading to a high initial resistance growth rate. Conversely, a larger pleat ratio leads to faster aggregation of particles, resulting in a faster rise in the resistance growth rate. The dust-holding capacity is optimal at a pleat ratio of 6.67. When the inlet flow rate or the particle size increases, it is more favorable to reduce the pleat ratio. The reliability of the results is verified using experiments, and the error is within 20%. The findings provide theoretical and practical insights for optimizing the design of pleated filter media for better performance in particulate filtration.

Protection from nuclear biochemical aerosol and air pollution pays attention to aerosol mass concentration. The concentration of upstream aerosol of the commonly used filtration efficiency detection device for high-efficiency filter materials is low, making it insufficient for detecting the filtration efficiency of high-efficiency filter materials. This study designed and built a set of filtration efficiency detection devices for high-efficiency filter materials based on mass concentration. By adjusting the oil bath temperature, injection pressure, the degree of spiral-separator separation, as well as the number and size of nozzles, we investigated the effects of each condition on the concentration and particle size distribution of aerosol generation. As a result, the oil mist generator of the device can stably generate high-concentration aerosol with a mass concentration of up to 1587.9 mg/m³ and a number concentration of up to 10⁷–10⁸ P/cm³. The high-concentration aerosol generated can meet the E11–U15 filter material performance requirements.

Antibacterial filter materials have been effectively utilized for controlling biological contaminants and purifying indoor air, with the market for such materials experiencing continuous expansion. Currently, textile antibacterial testing standards are widely adopted to evaluate the antimicrobial efficacy of filter materials, yet no dedicated assessment protocols specifically tailored for filtration media have been established. This study aims to investigate the applicability of textile antibacterial testing methods to high-efficiency glass fiber filter materials (filtration efficiency > 99.9%), as well as to explore the factors that affect the rate of bacterial elution from high-efficiency glass fiber filter materials. By referencing the textile antibacterial testing standard (absorption method), significant discrepancies in bacterial recovery counts were observed between the high-efficiency glass fiber materials and the various textile control samples, with the former exhibiting a markedly lower recovery rate (approximately 10%). Pore structure and wettability analyses revealed the underlying causes of these differences. To ensure the accuracy of the antibacterial evaluation results, the effects of oscillation elution parameters (time and intensity) and material incubation conditions (duration, sealing and humidity) on bacterial recovery rates in glass fiber filter materials were systematically investigated to optimize the elution methodology. The results indicate that specimen type, size, elution method, incubation duration (4 h or 24 h), sealing conditions, and environmental humidity (10% or 30%, 60% and 95% RH) collectively influence bacterial recovery efficiency. The highest recovery efficiency (55%) was achieved when the filter materials were incubated in a sealed environment with humidity maintained at ≥60% RH. These findings emphasize the critical need to establish clear and specialized antibacterial performance testing standards for filter materials. The study provides essential guidance for developing material-specific evaluation protocols to ensure a reliable and standardized assessment of antimicrobial efficacy in high-efficiency filtration systems.

Ultra-high-efficiency filter media ensure high air cleanliness but need periodic replacement due to pressure drop increase. Adding a pre-filter can extend the filtration system’s service lifetime, yet the pre-filter and main-filter matching lacks systematic study. This research explored how different filter media combinations affected a two-stage ultra-high-efficiency filtration system’s performance. This study focused on five pre-filter grades (F7–F9, H10, H11) and two different types of main-filter media, fiberglass and composite. It was found that the F8 pre-filter media had the best effect on extending the service lifetime of BX and BX + PTFE. The service lifetimes were extended from 44 min and 70 min to 231 min and 326 min, respectively, reaching 5.25 times and 4.65 times the original lifetime. Moreover, the optimal pre-filter grade was less affected by the initial resistance of the main filter. Meanwhile, the BX + PTFE filtration system always showed a longer service lifetime and dust holding capacity compared to the BX filtration system. This study provides guidance for the design and combination of two-stage filters in the context of high-cleanliness applications as well as the improvement of multi-stage filter performance in building ventilation.