Search Results (14)

Indoor air pollution poses a significant public health risk, particularly in urban areas, where PM2.5 and airborne contaminants contribute to respiratory diseases. In Thailand, including Chonburi Province, PM2.5 levels frequently exceed safety thresholds, underscoring the urgent need for effective mitigation strategies. To address this challenge, we developed a hybrid air purification system incorporating a bioplastic-based photocatalytic film of polylactic acid (PLA) embedded with titanium dioxide (TiO₂) nanoparticles. For optimization, PLA films were functionalized with varying TiO₂ concentrations and characterized using SEM, FTIR, TGDTA, and UV–Vis. spectroscopy. A 5 wt% TiO₂ loading was identified as optimal and further enhanced with silver (Ag) nanoparticles to boost photocatalytic efficiency. The Ag/TiO₂/PLA biofilm was fabricated via a compound pellet formulation process followed by blown film extrusion. Various compositions, with and without Ag, were systematically evaluated for photocatalytic performance. The novel customized hybrid air purifier developed in this study is designed to enhance indoor air purification efficiency by integrating Ag/TiO₂/PLA biofilms into a controlled oxidation system. The air purification efficacy of the developed biofilm was evaluated through a controlled study on Staphylococcus aureus (S. aureus) removal under different treatment conditions: control, adsorption, photolysis, and photocatalytic oxidation. The impact of light intensity on photocatalytic efficiency was also examined. The photocatalytic oxidation of S. aureus was subjected to the first-order kinetic evaluation through mathematical modeling. Results demonstrated that the Ag/TiO₂/PLA biofilm significantly enhances indoor air purification, providing a sustainable, scalable, and energy-efficient solution for microbial decontamination and pollutant removal. This innovative approach outperforms conventional adsorption, adsorption and photocatalytic oxidation systems, offering a promising pathway for improved indoor air quality. Full article

Long-time exposure to volatile organic compounds (VOCs) in the atmosphere can have negative health effects on humans and other living organisms. In order to purify ambient air, these VOCs can be degraded using photocatalysis. In this research, commercially available TiO₂ nanoparticles were immobilized in a porous poly(vinylidene fluoride-co-hexa-fluoropropylene) (PVDF) polymer matrix, synthesized using the phase inversion method. The most used solvent for PVDF is N-methyl-2-pyrrolidone (NMP). However, this solvent is known to be harmful to humans and the environment, and there is a need to replace NMP with a more ecological ‘green’ solvent. Here, triethyl phosphate (TEP), methyl-5-(dimethylamino)-2-methyl-5-oxopentanoate (Rhodiasolv^® PolarClean) and propylene carbonate (PC) were used to dissolve PVDF for the phase inversion synthesis of porous photocatalytically active PVDF/TiO₂ hybrid layers onto aluminium slides. The photocatalytic degradation under UV (365 nm) of gaseous ethanol in an argon/oxygen (Ar/O₂) atmosphere shows that these solvents are suitable replacements for NMP, but optimization is required to improve the performance of the layers. Apart from changing the solvent for PVDF, the UV and photocatalysis stability of PVDF has been determined, as well as the repeatability of the photocatalytic reaction, to prove that PVDF is a suitable polymer for this application. Full article

The aim of the circular economy is to treat waste as a valuable raw material, reintegrating it into the industrial economy and extending the lifecycle of subsequent products. Efforts to reduce the production of hard-to-recycle waste are becoming increasingly important to manufacturers, not only of consumer goods but also of specialized items that are difficult to manufacture, such as medical supplies, which have now become a priority for the European Union. The purpose of the study is to manufacture a novel human-purified type I collagen membrane from bone remnants typically discarded during the processing of cortico-cancellous bones in tissue banks and to evaluate its mechanical properties and effectiveness in regenerating bone-critical mandibular defects in rabbits. To prepare the novel membrane, cortico-cancellous bone chip samples from a local tissue bank were processed to isolate collagen by demineralization under agitation in HCl, cast into a silicone mold, and air-dried at room temperature and UV irradiation. The average thickness of the four batches analyzed by SEM was 37.3 μm. The average value of Young’s modulus and tensile strength obtained from the specimens was 2.56 GPa and 65.43 Mpa, respectively. The membrane’s efficacy was tested by creating a critical bicortical and bilateral osteoperiosteal defect in rabbit mandibles. The right-side defects were covered with the collagen membrane, while the left-side defects were left untreated as a control. Nine weeks post-surgery, clinical, radiological, and histological analyses demonstrated new bone formation in the treated areas, whereas the control sites showed no bone regeneration. This innovative approach not only contributes to sustainability in healthcare by optimizing biological waste but also exemplifies efficient resource use in line with the circular economy, offering a cost-effective, biocompatible option that could benefit national health systems. Full article

The spread of airborne diseases such as COVID-19 underscores the need for effective indoor air quality control. This review focuses on ventilation strategies and portable air purifiers as key mitigation solutions. Ventilation systems, including natural and mechanical approaches, can reduce pathogen concentrations by improving airflow. However, combining ventilation with portable air purifiers, particularly those using HEPA filters, ESP filters, and UV-C radiation, can enhance Indoor air quality. While HEPA and ESP filters focus on trapping airborne particles, UV-C radiation can inactivate pathogens by disrupting their RNA. A review of UV air purifiers reveals a lack of studies on their efficacy and effectiveness in real-world settings. A thorough investigation into the performance of this mitigation solution is necessary, focusing on varying key factors, such as purifier placement, airflow dynamics, and UV dosage, to ensure optimal effectiveness. High-fidelity computational methods are essential in accurately assessing these factors, as informed by the physics of airborne transmission. Such advanced computations are necessary to determine the viability of portable UV air purifiers in mitigating airborne transmission in enclosed environments such as hospitals and public spaces. Integrating advanced air purification technologies with proper ventilation can improve safety in indoor environments and prevent future disease-related outbreaks. Full article

This study successfully prepared and tested sulfur- and nitrogen-co-doped TiO₂-coated α-Al₂O₃ (S,N-doped TiO₂/Al₂O₃) hollow fiber (HF) membranes for efficient photocatalytic degradation of gaseous ammonia (NH₃). Thiourea was used as a sulfur- and nitrogen-doping source to produce a S,N-doped TiO₂ photocatalyst powder. For comparative purposes, undoped TiO₂ powder was also synthesized. Through the application of a phase-inversion technique combined with high-temperature sintering, hollow fibers composed of α-Al₂O₃ were developed. Undoped TiO₂ and S,N-doped TiO₂ photocatalyst powders were coated on the α-Al₂O₃ HF surface to obtain undoped TiO₂/Al₂O₃ and S,N-doped TiO₂/Al₂O₃ HF membranes, respectively. All prepared samples were characterized using XRD, TEM, XPS, UV-Vis, SEM, BET, FT-IR, and EDS. S and N dopants were confirmed using XPS and UV-Vis spectra. The crystal phase of the undoped TiO₂ and S,N-doped TiO₂ photocatalysts was a pure anatase phase. A portable air purifier photocatalytic filter device was developed and tested for the first time to decrease the amount of indoor NH₃ pollution under the limits of the lachrymatory threshold. The device, which was made up of 36 S,N-doped TiO₂/Al₂O₃ HF membranes, took only 15–20 min to reduce the level of NH₃ in a test chamber from 50 ppm to around 5 ppm, confirming the remarkable performance regarding the photocatalytic degradation of gaseous NH₃. Full article

Aims: With the ongoing pandemic and increased interest in measures to improve indoor air quality, various indoor air purifiers have become very popular and are widely used. This review presents the advantages and disadvantages of various types of technologies used in air purifiers in terms of reducing microbial contamination. Methods: A literature search was performed using Web of Science, Scopus, and PubMed, as well as technical organizations dealing with indoor air-quality to identify research articles and documents within our defined scope of interest. Relevant sections: The available literature data focus mainly on the efficiency of devices based on tests conducted in laboratory conditions with test chambers, which does not reflect the real dimensions and conditions observed in residential areas. According to a wide range of articles on the topic, the actual effectiveness of air purifiers is significantly lower in real conditions than the values declared by the manufacturers in their marketing materials as well as technical specifications. Conclusions: According to current findings, using indoor air purifiers should not be the only measure to improve indoor air-quality; however, these can play a supporting role if their application is preceded by an appropriate technical and environmental analysis considering the real conditions of its use. Full article

The study focused on increasing the efficiency of germicidal UV radiation by using highly diffuse reflective materials such as PTFE in irradiated cavities of UV air purifiers. In a conventional cylindrically symmetric cavity with a linear amalgam mercury lamp as UV-radiation source on the axis UV-radiation, flux directed from the lamp to the walls dropped from the axis to the periphery. To increase the UV irradiation, the walls are often made mirror-reflective, but the radiation flux distribution remained radially symmetric with a maximum on the source emitting surface in this case as well. When most of the emitted light is returned to the source after one reflection, the conditions of its operation are disturbed. If the walls are made of highly diffuse reflective materials, the radiation flux density inside the cavity increases on average, and its distribution becomes uniform and highly symmetric. Thus, the effect of amplification of the radiation flux due to the highly diffuse reflectivity of the walls increases with radius and reaches a maximum at the wall. Experiments were performed to demonstrate increasing amplification of germicidal UV radiation flux with a diffuse reflection coefficient in cylindrical cavities with walls of PTFE and ePTFE. The irradiation of the cavity wall was observed to increase up to 20 times at the resonant mercury line of 253.7 nm and up to 40 times at some non-resonant lines of the visible range due to highly diffuse reflectivity of the cavity walls. The flux amplification effect was limited by the diffuse reflectivity value of the walls and absorption coefficient of the radiation emitting surface. A formula for calculating the radiation flux amplification factor in a diffusely reflecting cylindrically symmetric cavity was derived for the case of Lambertian source and reflector, including wall reflectivity and source surface absorption coefficients. The effects of heating and cooling of the mercury lamp amalgam directly affected the amplification, and symmetrization of germicidal irradiation was observed and is discussed in the paper. Numerical calculations were performed by the ray tracing method. The calculated model was verified by comparing the numerical results with those of both the approximate theoretical consideration and experiments. The promising use of diffusely reflecting cylindrical cavities for UV air purifiers is discussed. Designs of air inlet and outlet ports that allow effective locking of germicidal radiation inside the UV air purifiers were considered. The results of this work may be of interest for further developments in the UV disinfection technique. Full article

The indoor air quality in public transport systems is a major concern in South Korea. Within this context, we investigated the effect of air purification systems on the indoor air quality of intercity buses, one of the most popular transport options in South Korea. Air purifiers were custom designed and equipped with high-efficiency particulate air (HEPA) filters to remove particulate matter and ultraviolet light-emitting diodes (UV-LEDs) to remove airborne bacteria. To investigate the effectiveness of the air purification systems, we compared concentrations of particulate matter (PM_2.5 and PM₁₀), airborne bacteria, and carbon dioxide (CO₂) in six buses (three with air purification systems and three without) along three bus routes (BUS1, BUS2, BUS3) in Gyeonggi Province, South Korea, between 6 April and 4 May 2021. Compared to the buses without air purification, those with air purification systems showed 34–60% and 25–61% lower average concentrations of PM_2.5 and PM₁₀, respectively. In addition, buses with air purification systems had 24–78% lower average airborne bacteria concentrations compared to those without air purification systems (when measured after 30 min of initial purification). Full article

Globimetula braunii is a hemi-parasitic plant used in African ethnomedicine for the management of microbial infections, rheumatic pain and tumors amongst others. We report the isolation and characterization of eight compounds with their antioxidant and antimicrobial activities. The air-dried powdered leaf was macerated in EtOH/H₂0 (4:1). The extract was solvent-partitioned into n-hexane, EtOAc, n-BuOH and aqueous fractions. The fractions were screened for their antioxidant properties, using DPPH, FRAP, TAC and FIC assays. Antimicrobial analysis was performed using the micro-broth dilution method. The active EtOAc fraction was purified for its putative compounds on a repeated silica gel column chromatography monitored with TLC-bioautography. The isolated compounds were characterized using spectroscopic methods of UV, FT-IR, NMR and MS. Eight compounds (1–8) were isolated and characterized as 13,27-cycloursane (1), phyllanthone (2), globraunone (3), three phenolics: methyl 3,5-dihydroxy-4-methoxybenzoate (4), methyl 3-methyl-4-hydroxybenzoate (5) and guaiacol (6), as well as two phenol derivatives: 4-formaldehyde phenone (7) and 6-methoxy-2H-inden-5-ol (8). The study identified 4 and 6 as natural antioxidant compounds with potential as antimicrobial agents. Full article

Vehicle exhaust seriously pollutes urban air and harms human health. Photocatalytic technology can effectively degrade automobile exhaust. This work prepared g-C₃N₄/CeO₂ photocatalytic material by constructing heterojunctions. Four kinds of g-C₃N₄/CeO₂ composite photocatalytic materials with different mass ratios were prepared. An indoor exhaust gas purification test was carried out under natural light and ultraviolet light irradiations. The optimum mass ratio of g-C₃N₄ material and CeO₂ material was determined by evaluating the exhaust gas degradation effective. Moreover, the structure and morphology of the g-C₃N₄/CeO₂ composite were investigated with microscopic characterization experiments (including XRD, TG-DSC, FT-IR, UV-Vis, SEM and XPS). The results obtained were that the optimum mass ratio of g-C₃N₄ material to CeO₂ material was 0.75. The degradation efficiencies under ultraviolet irradiation in 60 min for HC, CO, CO₂, NO_X were 7.59%, 12.10%, 8.25% and 36.82%, respectively. Under visible light conditions, the degradation efficiency in 60 min for HC, CO, CO₂ and NO_X were 15.88%, 16.22%, 10.45% and 40.58%, respectively. This work is useful for purifying automobile exhaust in the future. Full article

A powder synthesis of PbMoO₄ (PMO) from ancient lead (Pb) and deeply purified commercial MoO₃ powders was performed using a wet chemistry technique to achieve the low radioactivity scintillator for neutrinoless double beta decay search in ¹⁰⁰Mo. The synthesized powders were used to grow single crystals of PbMoO₄ by the Czochralski technique in an Ar environment. The luminescence and scintillation properties were measured with excitations using UV, X- and γ-rays in the temperature range of 10–300 K. Annealing of the grown PMO crystal in an air atmosphere significantly enhanced the scintillation light yield compared to that measured before annealing. The scintillation light yield of grown PMO crystal at 10 K was found to be 127% to that of a reference PMO crystal under 662 keV γ-rays excitation from a ¹³⁷Cs source. The background measurement of the grown crystal performed at 50 K shows a lower internal activity from ²¹⁰Pb compared to that of reference PMO (grown from modern Pb) crystal. These preliminary performances show that the PMO crystal grown from ancient Pb and deeply purified MoO₃ powders has a great potential to be used as a cryogenic scintillator for the neutrinoless double beta decay search in ¹⁰⁰Mo. Full article

Photocatalysts have multiple applications in air purifiers, paints, and self-cleaning coatings for medical devices such as catheters, as well as in the elimination of xenobiotics. In this study, a coating of a UV-responsive photocatalyst, titanium dioxide (TiO₂), was applied to an orthodontic resin. The antibacterial activity on oral bacteria as well as hydrophilic properties and mechanical properties of the TiO₂-coated resin were investigated. ultraviolet A (UVA) (352 nm) light was used as the light source. Antibacterial activity was examined with or without irradiation. Measurements of early colonizers and cariogenic bacterial count, i.e., colony forming units (CFU), were performed after irradiation for different time durations. Hydrophilic properties were evaluated by water contact angle measurements. While, for the assessment of mechanical properties, flexural strength was measured by the three-point bending test. In the coat(+)light(+) samples the CFU were markedly decreased compared to the control samples. Water contact angle of the coat(+)light(+) samples was decreased after irradiation. The flexural strength of the specimen irradiated for long time showed a higher value than the required standard value, indicating that the effect of irradiation was weak. We suggest that coating with the ultraviolet responsive photocatalyst TiO₂ is useful for the development of orthodontic resin with antimicrobial properties. Full article

The purpose of this study is to improve microbial air quality by improving water quality, particularly concerning microbiological aspects, by applying an ultraviolet water purifier system to a direct evaporative cooling (DEC) system. A direct evaporative cooler is an air cooling technique that uses the evaporation of water. Most DECs recirculate water to reduce water use. Evaporative cooling pads and water are biologically contaminated by recirculating water. This contamination can develop into air contamination and cause respiratory illnesses in occupants. It is necessary to use sterilized water in a DEC to prevent respiratory diseases and maintain air quality. In this study, we examine whether improvements in water quality in a DEC affect air quality by dividing experiments into a control group (Control) and a treated group (UV-treated). In the control group, the degree of contamination was measured when a DEC operated for four weeks without ultraviolet water treatment. In UV-treated, the degree of contamination was measured when UV water treatment was applied to a DEC for four weeks. In both Control and UV-treated, microbes were sampled from the water, the evaporative cooling pad surface, and the DEC inlet and outlet air samples in order to compare the levels of contamination. The surface was measured once at four points, and the air was measured four times at two points. A comparison of the two experiments indicated that the degree of microbial contamination of water and air was significantly reduced in the UV-treated group when compared to that in the control group. When the pollution degree of the evaporative cooling pad was compared to the degree of air pollution, it was difficult to obtain a correlation between the two factors, although the results confirmed that the contamination of the evaporative cooling pad caused water pollution. Therefore, it is necessary to operate a water treatment system to maintain the clean air in DECs. Full article

Use of silicon dioxide (SiO₂) and titanium dioxide (TiO₂) have been widely investigated individually in coatings technology, but their combined properties promote compatibility for different innovative applications. For example, the photocatalytic properties of TiO₂ coatings, when exposed to UV light, have interesting environmental applications, such as air purification, self-cleaning and antibacterial properties. However, as reported in different pilot projects, serious durability problems, associated with the adhesion between the substrate and TiO₂, have been evidenced. Thus, the aim of this work is to synthesize SiO₂ together with TiO₂ to increase the durability of the photocatalytic coating without affecting its photocatalytic potential. Therefore, synthesis using sonochemistry, synthesis without sonochemistry, physical characterization, photocatalytic evaluation, and durability of the SiO₂, SiO₂@TiO₂ and TiO₂ coatings are presented. Results indicate that using SiO₂ improved the durability of the TiO₂ coating without affecting its photocatalytic properties. Thus, this novel SiO₂@TiO₂ coating shows potential for developing long-lasting, self-cleaning and air-purifying construction materials. Full article