Photocatalytic Disinfection of Indoor Air

1997 ◽  
Vol 119 (1) ◽  
pp. 92-96 ◽  
Author(s):  
D. Y. Goswami ◽  
D. M. Trivedi ◽  
S. S. Block
Keyword(s):  
Titanium Dioxide ◽  
Relative Humidity ◽  
Indoor Air ◽  
Retention Time ◽  
Photocatalytic Oxidation ◽  
Antibacterial Effect ◽  
Air Velocity ◽  
Complete Inactivation ◽  
Series Of Experiments ◽  
Uv Photons

The present study demonstrated the antibacterial effect of photocatalytic oxidation in indoor air using titanium dioxide as the catalyst. Through a series of experiments, it was determined that titanium dioxide did enhance the inactivation rate of the microorganisms under certain conditions. In these experiments the air velocity, relative humidity, and UV (350 nm) intensity were varied. It was found that higher velocities retarded the destruction rate due to the low retention time in the reactor. TiO2 also did not accelerate the reaction at low humidities (30 percent). At a relative humidity of 50 percent, there was complete inactivation of the organisms, but at higher humidities (85 percent), 10 percent of the organisms were still viable. The experiments showed that at higher UV intensities, most of the inactivation was done by the UV photons. However, the photons were not able to completely inactivate the microorganisms. In the photocatalysis experiments there was complete inactivation of the bacteria.

scholarly journals Performance of Calcium Chloride and Silica Gel as Solid Desiccant Dehumidifiers for Indoor Air Quality

2021 ◽  
Vol 88 (3) ◽  
pp. 57-70
Author(s):  
Nur Kamila Ramli ◽  
Yusri Yusup ◽  
Christabel Lam Pei Lin ◽  
Baharin Azahari ◽  
Mardiana Idayu Ahmad
Keyword(s):  
Air Quality ◽  
Relative Humidity ◽  
Indoor Air Quality ◽  
Calcium Chloride ◽  
Silica Gel ◽  
Indoor Air ◽  
Airborne Bacteria ◽  
Air Velocity ◽  
Ability Test ◽  
Test Room

Desiccant materials are recently discovered as a viable alternative in dehumidification technology due to their naturally hygroscopic qualities and minimal energy requirement. This paper discusses the performance of four brand samples of selected desiccants used for dehumidification. In this study, dehumidification ability and indoor air quality (IAQ) tests were carried out. The dehumidification ability test was conducted in a controlled environmental chamber at a temperature of 25°C, relative humidity of 70%, and air velocity of 2 m/s for 45-minute session. Meanwhile, the IAQ test was carried out in a naturally ventilated test room, and six IAQ parameters (relative humidity, air velocity, air temperature, particulate matter (PM10), airborne bacteria and carbon dioxide (CO2) were studied. The IAQ test was performed for five different conditions: control, application of brand samples A, B, C and D in the test room. From this study, it was found, brand A (0.6823 g/kg) and brand B (0.6849 g/kg) had a relatively good dehumidification ability during the 45-minute dehumidification ability test compared to brand C (0.3108 g/kg) and brand D (0.3982 g/kg). The IAQ test revealed that brand A had the biggest variation in indoor-outdoor relative humidity of 13.12%, while brand D had the smallest difference of 11.83%. Brand B had the highest average PM10 concentration of 0.037 μg/m3. The airborne bacterial count for all conditions had no statistical significance, indicating the application of desiccants were not effective in reducing airborne bacteria. From this study, it can be concluded that calcium chloride (brand A and B) samples performed better than silica gel (brand C and D) samples in terms of dehumidification ability and IAQ profile.

scholarly journals The Use of Photocatalysis and Titanium Dioxide on Diesel Exhaust Fumes for NOx Reduction

2018 ◽  
Vol 10 (11) ◽  
pp. 4031
Author(s):  
Beatrice A. Atzl ◽  
Maximilian Pupp ◽  
Marco Rupprich
Keyword(s):  
Titanium Dioxide ◽  
Diesel Engine ◽  
Relative Humidity ◽  
Nitrogen Oxides ◽  
Diesel Exhaust ◽  
Photocatalytic Oxidation ◽  
Catalytic Reduction ◽  
Nox Reduction ◽  
Conversion Rates ◽  
Exhaust Fumes

Nitrogen oxides are emitted in large quantities by vehicles, and solutions to the problem are sought after. Efforts towards abatement include Selective Catalytic Reduction, catalytic converters, and redesigning engines to make them more efficient. This article focuses on the photocatalytic oxidation, which involves the use of titanium dioxide and ultraviolet radiation to oxidise nitrogen oxides to nitrates. To test this, the interior of a serpentine reactor was coated with titanium dioxide and irradiated with various intensities of ultraviolet light, and the photocatalytic abatement was monitored for the exhaust fumes from a standalone 4-stroke test diesel engine. The conversion rates were calculated using the entering concentration and the concentration after a certain time increment. The rates varied between 13.7% and 37.3% and depended strongly on the relative humidity, as a higher relative humidity directly correlated with a better conversion. The irradiance was also varied, and a decline in the conversion rate occurred when the irradiance was increased.

Decontamination of Ventilation Systems Using Photocatalytic Air Cleaning Technology

2003 ◽  
Vol 125 (3) ◽  
pp. 359-365 ◽  
Author(s):  
D. Yogi Goswami
Keyword(s):  
Fiber Optics ◽  
Indoor Air ◽  
Photocatalytic Oxidation ◽  
Indoor Air Pollution ◽  
Theoretical Background ◽  
Air Contamination ◽  
Air Cleaning ◽  
Volatile Organic Chemicals ◽  
Uv Photons ◽  
Cleaning Technology

Indoor air pollution is caused by particulate matter and chemical and microbial contamination. Conventional technologies, including filteration, do not adequately provide complete answers to these problems. Photocatalytic oxidation combined with filteration provides one of the most viable solutions to the problem of indoor air contamination by microorganisms and volatile organic chemicals (VOCs). It can also provide a defense against bioterrorism. This paper describes the theoretical background of the technology and results of its effectiveness against VOCs, bacteria, spores, and dust mite allergens. Although the technology uses UV photons from blacklight, it can be designed to use sunlight with the help of fiber optics.

scholarly journals Synergistic Effect of Nanophotocatalysis and Nonthermal Plasma on the Removal of Indoor HCHO

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Yuanwei Lu ◽  
Dinghui Wang ◽  
Yuting Wu ◽  
Chongfang Ma ◽  
Xingjuan Zhang ◽  
...  
Keyword(s):  
Synergistic Effect ◽  
Indoor Air ◽  
Photocatalytic Oxidation ◽  
Reaction Rate ◽  
Nonthermal Plasma ◽  
Pollutant Removal ◽  
Pollutant Concentration ◽  
Air Purification ◽  
Plate Electrode ◽  
Air Treatment

Photocatalysis is an effective method of air purification at the condition of a higher pollutant concentration. However, its wide application in indoor air cleaning is limited due to the low level of indoor air contaminants. Immobilizing the nanosized TiO2particles on the surface of activated carbon filter (TiO2/AC film) could increase the photocatalytic reaction rate as a local high pollutant concentration can be formed on the surface of TiO2by the adsorption of AC. However, the pollutant removal still decreased quickly with the increase in flow velocity, which results in a decrease in air treatment capacity. In order to improve the air treatment capacity by the photocatalytic oxidation (PCO) method, this paper used formaldehyde (HCHO) as a contaminant to study the effect of combination of PCO with nonthermal plasma technology (NTP) on the removal of HCHO. The experimental results show that HCHO removal is more effective with line-to-plate electrode discharge reactor; the HCHO removal and the reaction rate can be enhanced and the amount of air that needs to be cleaned can be improved. Meanwhile, the results show that there is the synergistic effect on the indoor air purification by the combination of PCO with NTP.

scholarly journals Indoor Air Quality (IAQ): Accuracy of Natural Ventilation for Temperature, Air Flow Rate and Relative Humidity (RH) in School Building Classrooms

2018 ◽  
Vol 7 (3.9) ◽  
pp. 42
Author(s):  
Norsafiah Norazman ◽  
Adi Irfan Che Ani ◽  
Nor Haslina Ja’afar ◽  
Muhamad Azry Khoiry
Keyword(s):  
Air Quality ◽  
Relative Humidity ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Natural Ventilation ◽  
Air Flow ◽  
Weather Conditions ◽  
Potential Health ◽  
The Hours ◽  
Hot Weather

Indoor Air Quality (IAQ) is an essential matter in achieving students’ satisfaction for the learning process. Building’s orientation is a factor that may encourage sufficient natural ventilation for the classroom occupants. Inadequate ventilation is an issue for most existing classrooms. The purpose of this paper is to analyze the accuracy of natural ventilation in classrooms. Therefore, experimental on 20 classrooms has been conducted by using Multipurpose Meter at secondary school buildings in Malaysia. The findings indicated that the accuracy of natural ventilation testing was below the permissible limits throughout the hours monitored, thus this may cause potential health hazards to the students. Temperature and air flow rates were lower than 23 °C and 0.15 m/s respectively, it fulfilled the basic requirements as a standard learning environment. However, measurements taken showed the overall relative humidity (RH) in the classrooms can be categorized as acceptable with 40% to 70% range. On the basis of these findings, it is evident that naturally ventilated classrooms are important especially due to energy efficiency, whereas mechanical ventilation should only be installed as an alternative under extremely hot weather conditions.   

Thermal Lethality of Salmonella in Chicken Leg Quarters Processed via an Air/Steam Impingement Oven

2004 ◽  
Vol 67 (3) ◽  
pp. 493-498 ◽  
Author(s):  
R. Y. MURPHY ◽  
K. H. DRISCOLL ◽  
L. K. DUNCAN ◽  
T. OSAILI ◽  
J. A. MARCY
Keyword(s):  
Relative Humidity ◽  
Surface Area ◽  
Air Temperature ◽  
Cooking Time ◽  
Air Velocity ◽  
Poultry Products ◽  
Product Surface ◽  
Cooking Times

Chicken leg quarters were injected with 0.1 ml of the cocktail culture per cm2 of the product surface area to contain about 7 log(CFU/g) of Salmonella. The inoculated leg quarters were processed in an air/steam impingement oven at an air temperature of 232°C, an air velocity of 1.4 m/s, and a relative humidity of 43%. The endpoint product temperatures were correlated with the cooking times. A model was developed for pathogen thermal lethality up to 7 log(CFU/g) reductions of Salmonella in correlation to the product mass (140 to 540 g) and cooking time (5 to 35 min). The results from this study are useful for validating thermal lethality of pathogens in poultry products that are cooked via impingement ovens.

Photocatalytic Oxidation of Shenfu Bituminous Coal and Xilinhaote Lignite with H2O2 over TiO2

2011 ◽  
Vol 233-235 ◽  
pp. 1684-1689 ◽  
Author(s):  
Heng Shen Xie ◽  
Zhi Min Zong ◽  
Qing Wei ◽  
Pei Zhi Zhao ◽  
Jian Jun Zhao ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Titanium Dioxide ◽  
Catalytic Oxidation ◽  
Photocatalytic Oxidation ◽  
Bituminous Coal ◽  
Straight Chain ◽  
Photo Catalytic Oxidation ◽  
Alkyl Side Chains ◽  
Lignite Coal ◽  
Oxidation Effect

Shenfu bituminous coal (SFBC) and Xilinhaote lignite (XL) were subject to photo-catalytic oxidation with hydrogen peroxide over titanium dioxide. The reaction mixtures were extracted with acetone exhaustively. The extracts were analyzed with FTIR and GC/MS. The results show that coals be oxidized selectively and degraded partially. Compared with the bituminite coal, the oxidation effect of the lignite coal with active hydrogens is more obvious. The alkyl side chains of the macromolecules, particularly, chains of methyl, methylene and aromatic, are the most vulnerable in relation to other compounds in coals. Moreover, the increasing of straight-chain alkanes and the decreasing of condensed nucleus in SFBC and XL through oxidation suggest that the oxidation is an effective method of coal utilization with no difficultly, also be friendly towards the environment after treated as well as in the process of the treatment.

scholarly journals Indoor Particulate Matter (PM2.5) and Comfort Parameters in a University Building

2020 ◽  
Vol 8 (2) ◽  
pp. 61-67
Author(s):  
Nurul Bahiyah Abd Wahid ◽  
Intan Idura Mohamad Isa ◽  
Ahmad Khairuddin Hassan ◽  
Muhammad Izzat Iman Razali ◽  
Ahmad Haziq Hasrizal ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Relative Humidity ◽  
Indoor Air ◽  
National Policy ◽  
Lecture Hall ◽  
Airborne Microorganisms ◽  
Code Of Practice ◽  
The Mean ◽  
Indoor Particulate Matter ◽  
Comfort Parameters

This study aims to determine the particulate matter (PM2.5) mass concentrations and the comfort parameters (total bacterial counts (TBC), total fungal counts (TFC), relative humidity and temperature) in a university building. The samplings were carried out in three different indoor areas, including lecture hall, laboratory and lecturer office. PM2.5 samples were collected over a period of 8 h sampling using a low volume sampler (LVS). The anemometer Model Kestrel 0855YEL was used to measure relative humidity and temperature parameters. The sampling of airborne microorganisms was conducted by using microbial sampler at 350 L air sampled volume. The results showed that the highest average of PM2.5 was at lecture hall (88.54 ± 26.21 µgm-3) followed by lecturer office (69.79 ± 19.06 µgm-3) and laboratory (47.92 ± 24.88 µgm-3). The mean of TBC and TFC readings recorded as follow; 32.71 ± 5.91 cfu m-3 and 76.71 ± 21.5 cfu m-3 for laboratory, 112.1 ± 29.06 cfu m-3 and 124.67 ± 23.35 cfu m-3 for lecturer office, 121.74 ± 19.33 cfu m-3 and 115.33 ± 8.08 cfu m-3 for lecture hall. The average of all comfort parameter was within the prescribed standard by Industry Code of Practice on Indoor Air Quality 2010 for all sampling sites. Therefore, all occupants of the building can work in a conducive and comfortable environment. This study is in line with the objectives of National Policy on the Environment (DASN), which focusing on achieving a clean, safe, healthy and productive environment for present and future generations.

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