Surface-catalysed reactions on pollutant-removing building products for indoor use

Investigation on the Organic Acid Content inside the Storage of a Woodblock Print Collection and Evaluation on the FFU System as a Mitigation Strategy

This paper describes an investigation on the storage environment of an Edo period woodblock print collection in terms of volatile organic acid content, using active air sampling and precision gas detector tubes that can measure organic acid emissions in the low microgram range, and evaluates an organic acid mitigation method based on the fan filter unit (FFU) system. Ion-exchange chromatography method was also employed for estimation of acetic and formic acid ratio. Findings revealed an organic acid-concentrated microclimate inside the storage box, nevertheless, the off-gassing rates of the woodblock prints were low, with the exception of a print positioned in the middle of the stack. The acetic acid/formic acid ratio was similar between the storage room environment and inside the storage box, but comparatively higher levels of formic acid were identified in the mulberry paper folder housing the prints. Finally, the FFU system was able to reduce organic acid concentrations inside the storage box for a 5-month observation period, but it did not eliminate the tendency of the storage materials to create organic acid-concentrated microclimates.

Indoor formaldehyde removal by three species of Chlorophytum comosum under dynamic fumigation system: part 2-plant recovery

Spider plants (Chlorophytum comosum) are known to be among the most common easy mountable indoor plants capable of purifying indoor air by absorbing carbon monoxide, formaldehyde, xylene, and many other hazardous gases. In addition, these plants are non-toxic and safe for pets and children. This project is focused on the investigation of the spider plants' capability of the formaldehyde purification under laboratory-controlled parameters of the indoor air environment. Two scenarios including employment of fresh plants as well as recovered ones damaged by 7-day exposure of formaldehyde were considered. A special attention was made to the investigation of physiological indexes of the plant leaves after damage, and whether the spider plant could be reused after its recovery. The physiological characteristics of the recovery period of potted Chlorophytum comosum immediately after 7 days of fumigation with formaldehyde were studied. Eight physiological indexes of leaves including chlorophyll, free protein, relative conductivity, MDA (malondialdehyde, lipid peroxidation), SOD (superoxide dismutase), POD (peroxidase), T-AOC (total antioxidant capacity), and stomata were selected to monitor plants' recovery processes. The results of 30-day experimental runs showed that three species of spider plants were mostly recovered within 15 days. Repeated 7-day fumigation of plants, conducted to study their ability to effectively clean the air after regeneration, confirmed such ability; the efficiency at the first day was similar to the performance of the fresh plant. However, from the second day, the efficiency was dropped by 35-50% and remained at these levels for the rest of the exercise.

Simultaneous photodegradation of VOC mixture by TiO2 powders

Volatile and semi volatile organic compounds' concentration have dramatically increased in indoor environments in recent years. UV light promotes titanium dioxide, which oxidises various molecules; however, most of the studies report the degradation of a single VOC. Here, we investigate the photo-oxidation of 17 molecules in mixture to have a realistic test of TiO₂ efficacy. We compare P25, a nanometric catalyst, and 1077, a micrometric sample, that poses less health concerns. A proton-transfer-reaction mass spectrometer measured online the concentration of all the pollutants simultaneously. Aldehydes compete for the adsorption on both the catalyst's active sites and thus they degrade 70% and 55% with P25 and 1077 respectively. Considering the single pollutant oxidation, instead, aldehydes fully oxidize. Even though benzene is recalcitrant to degradation, P25 and 1077 reduced toluene's concentration to 97% and 96% in 55 min, respectively. Acetonitrile is refractory to photocatalysis.

Portable photocatalytic air cleaners: efficiencies and by-product generation

Portable photocatalytic air cleaners were investigated in 24 and 48 m(3) emission test chambers with regard to efficiency and by-product generation. For this purpose, formaldehyde, decane, 1,2-dichlorobenzene, toluene, α-pinene and heptanal were doped at sub-ppm concentration levels into the chambers individually and in mixtures. By way of specified test protocols, efficiencies could be distinguished but were strongly dependant on the choice of test compounds, especially on whether single or multi compound dosing was used, and on long-term effects. Initial clean air delivery rates (CADRs) up to 137 m(3)/h were measured. Typical by-products were found in significant concentrations. The main ones were formaldehyde up to 50 ppb (62 μg/m(3)) and acetone up to 80 ppb (190 μg/m(3)). Other aldehydes were also found, but at smaller levels. The detection of chloroacetone, a strong irritating compound, at concentrations up to 15 ppb (57 μg/m(3)) strengthens the importance of such investigations especially in cases were chloro-organic compounds are involved.

Materials for selective photo-oxygenation vs. photocatalysis: preparation, properties and applications in environmental and health fields

Photosensitizing materials made of organic dyes embedded in various supports are compared to usual supported TiO₂-based photocatalysts.

Surface chemistry of a pine-oil cleaner and other terpene mixtures with ozone on vinyl flooring tiles

Indoor environments are dynamic reactors where consumer products (such as cleaning agents, deodorants, and air fresheners) emit volatile organic compounds (VOCs) that can subsequently interact with indoor oxidants such as ozone (O(3)), hydroxyl radicals, and nitrate radicals. Typically, consumer products consist of mixtures of VOCs and semi-VOCs which can react in the gas-phase or on surfaces with these oxidants to generate a variety of oxygenated products. In this study, the reaction of a pine-oil cleaner (POC) with O(3) (100ppb) on a urethane-coated vinyl flooring tile was investigated at 5% and 50% relative humidity. These results were compared to previous α-terpineol+O(3) reactions on glass and vinyl surfaces. Additionally, other terpene and terpene alcohol mixtures were formulated to understand the emission profiles as seen in the POC data. Results showed that the α-terpineol+O(3) reaction products were the prominent species that were also observed in the POC/O(3) surface experiments. Furthermore, α-terpineol+O(3) reactions generate the largest fraction of oxygenated products even in equal mixtures of other terpene alcohols. This finding suggests that the judicial choice of terpene alcohols for inclusion in product formulations may be useful in reducing oxidation product emissions.

Feasibility of a tandem photocatalytic oxidation-adsorption system for removal of monoaromatic compounds at concentrations in the sub-ppm-range

Unlike previous photocatalytic oxidation (PCO) studies incorporated with adsorption, this study investigates the feasibility of applying a tandem PCO-adsorption hybrid technique regarding low-level monoaromatic compound removal. The PCO efficiencies decreased as the hydraulic diameter (HD) increased. A PCO reactor of a medium HD size was selected for further experiments. Under conditions relevant to the use of the PCO system, the CO level measured during the PCO process was minimal in comparison to indoor CO levels. Trace level formations of formaldehyde and acetaldehyde were observed during the photocatalytic process, but these compounds were undetectable at the activated carbon unit outlet. The degradation efficiencies, obtained from the PCO unit, exhibited a dependence on both the inlet concentration (IC) and relative humidity (RH), whereas those from the PCO-adsorption hybrid system did not. Under specific conditions, the PCO unit presented a high degradation efficiency of close to, or exceeding 90%, in regards to ethyl benzene, o-xylene, and m,p-xylene. However, the benzene air concentrations, after being treated by the PCO unit, substantially exceeded the USEPA inhalation reference concentration guideline of 30microgm(-3) (corresponding to 0.01ppm). In contrast, the PCO-adsorption hybrid system presented a high removal efficiency of close to 100% regarding all compounds, regardless of the IC or RH range. Consequently, it is suggested that the PCO-adsorption hybrid system has a synergistic advantage of photocatalysis and adsorption in regards to the BTEX elimination process.