Removal of VOCs and H₂CO from air by nanoparticulate silica adsorbents or TiO₂ photocatalysts

Constant concentrations of selected VOCs (toluene, ethylbenzene, cumene and dichlorobenzene) and formaldehyde (H₂CO) were successfully generated in separated sampling chambers. A commercially available sorbent (Tenax TA) and silica C₁₈ cartridges impregnated with trapping solution were used to determine experimental masses "references masses" of VOCs and H₂CO, respectively, using selected sampling conditions. Mesoporous silica samples (MCM-41, MWD-MCM-41 and SBA-15) were synthesised under harsh conditions by traditional sol-gel methods. Extraction efficiencies of these adsorbents were compared to Tenax TA, and showed similar performances (64 to 69 %) for VOCs extraction. However, SBA-15 had slightly higher dynamic capacity due to its bimodal pore structure which includes microporores. Novel silica green nanomaterials (GNs) were synthesised using a bioinspired route; under mild conditions of natural pH and ambient temperature, rapid synthesis (15 min) and in all aqueous solutions. However produced GN materials have significantly lower surface areas (58 - 355 m² g-¹) compared to MCM-41 (1014 m² g-¹), they had similar or better extraction efficiencies (60 - 80 %) of MCM-41 due to their unique porosity including micropores. In addition they had comparable capacities per unit surface area with MCM-41. A novel synthesis route "green" was applied to produce mesoporous silica (USG) with high surface area (up to 1100 m² g-¹), pore size of 2.6 nm and large pore volume (1.00 cm³ g-¹) which are similar to MCM-41 properties. The new produced USG demonstrated a similar performance (60 %) and adsorption capacity for VOCs extraction compared with MCM-41. Furthermore all silica adsorbents were successfully functionalised with organic amine groups in order to examine their performance for H₂CO extraction. Results demonstrated that H₂CO was removed from air permanently by chemisorption on functionalized adsorbents. Finally, porous TiO₂ thin films coated onto glass beads were used for VOCs degradation as the first time. The results indicated that the best performance of VOCs degradation (up to 80 %) was achieved by using smaller glass beads, at lower flow rate or an increase of coating number (thickness of films).Constant concentrations of selected VOCs (toluene, ethylbenzene, cumene and dichlorobenzene) and formaldehyde (H₂CO) were successfully generated in separated sampling chambers. A commercially available sorbent (Tenax TA) and silica C₁₈ cartridges impregnated with trapping solution were used to determine experimental masses "references masses" of VOCs and H₂CO, respectively, using selected sampling conditions. Mesoporous silica samples (MCM-41, MWD-MCM-41 and SBA-15) were synthesised under harsh conditions by traditional sol-gel methods. Extraction efficiencies of these adsorbents were compared to Tenax TA, and showed similar performances (64 to 69 %) for VOCs extraction. However, SBA-15 had slightly higher dynamic capacity due to its bimodal pore structure which includes microporores. Novel silica green nanomaterials (GNs) were synthesised using a bioinspired route; under mild conditions of natural pH and ambient temperature, rapid synthesis (15 min) and in all aqueous solutions. However produced GN materials have significantly lower surface areas (58 - 355 m² g-¹) compared to MCM-41 (1014 m² g-¹), they had similar or better extraction efficiencies (60 - 80 %) of MCM-41 due to their unique porosity including micropores. In addition they had comparable capacities per unit surface area with MCM-41. A novel synthesis route "green" was applied to produce mesoporous silica (USG) with high surface area (up to 1100 m² g-¹), pore size of 2.6 nm and large pore volume (1.00 cm³ g-¹) which are similar to MCM-41 properties. The new produced USG demonstrated a similar performance (60 %) and adsorption capacity for VOCs extraction compared with MCM-41. Furthermore all silica adsorbents were successfully functionalised with organic amine groups in order to examine their performance for H₂CO extraction. Results demonstrated that H₂CO was removed from air permanently by chemisorption on functionalized adsorbents. Finally, porous TiO₂ thin films coated onto glass beads were used for VOCs degradation as the first time. The results indicated that the best performance of VOCs degradation (up to 80 %) was achieved by using smaller glass beads, at lower flow rate or an increase of coating number (thickness of films)

Phytochemical Screening, Antioxidant Capacity Measurement, and Mineral Content Determination of Thymus vulgaris L. Extracts

The aim of this study was to evaluate the chemical composition and antioxidant activity of Thymus vulgaris L. extracts. T. vulgaris L. is a medicinal plant that has various bioactive compounds. Four different solvents (ethanol, water, ethyl acetate, and chloroform) were used to extract these compounds from the plant. The phytochemical screening of the extracts showed that the ethanolic extract had the highest diversity of compounds, including coumarins, flavonoids, alkaloids, tannins, phenols, carbohydrates, and proteins. The total phenolic and total antioxidant contents of the ethanolic extract were measured by the Folin–Ciocalteu and phosphomolybdenum methods, respectively. The ethanolic extract had a high phenolic content of 77.7 mg gallic acid equivalent/g dry weight, which indicates its potential antioxidant capacity. The mineral content of T. vulgaris L. was also assessed by flame photometry and atomic absorption spectrophotometry after dry digestion. The plant contained five macroelements (K, Na, Ca, Mg, P) and three microelements (Fe, Cu, Zn) in different concentrations. The highest concentration was found for potassium (15259 mg/kg), followed by calcium (5118 mg/kg) and sodium (4793 mg/kg). The lowest concentration was found for phosphorus (1400 mg/kg), which was still higher than the microelements. Among the microelements, zinc had the highest concentration (24.82 mg/kg), followed by iron (17.44 mg/kg) and copper (14.98 mg/kg). The results of this study provide useful information for the users, collectors and practitioners of medicinal plants from polluted areas, as they can evaluate the quality and safety of T. vulgaris L. for human consumption

Measurement of volatile organic compounds emitted in libraries and archives : an inferential indicator of paper decay?

A sampling campaign of indoor air was conducted to assess the typical concentration of indoor air pollutants in 8 National Libraries and Archives across the U.K. and Ireland. At each site, two locations were chosen that contained various objects in the collection (paper, parchment, microfilm, photographic material etc.) and one location was chosen to act as a sampling reference location (placed in a corridor or entrance hallway). Of the locations surveyed, no measurable levels of sulfur dioxide were detected and low formaldehyde vapour (< 18 μg m-3) was measured throughout. Acetic and formic acids were measured in all locations with, for the most part, higher acetic acid levels in areas with objects compared to reference locations. A large variety of volatile organic compounds (VOCs) was measured in all locations, in variable concentrations, however furfural was the only VOC to be identified consistently at higher concentration in locations with paper-based collections, compared to those locations without objects. To cross-reference the sampling data with VOCs emitted directly from books, further studies were conducted to assess emissions from paper using solid phase microextraction fibres (SPME) fibres and a newly developed method of analysis; collection of VOCs onto a polydimethylsiloxane (PDMS) elastomer strip. In this study acetic acid and furfural levels were consistently higher in concentration when measured in locations which contained paper-based items. It is therefore suggested that both acetic acid and furfural (possibly also trimethylbenzenes, ethyltoluene, decane and camphor) may be present in the indoor atmosphere as a result of cellulose degradation and together may act as an inferential non-invasive marker for the deterioration of paper. Direct VOC sampling was successfully achieved using SPME fibres and analytes found in the indoor air were also identified as emissive by-products from paper. Finally a new non-invasive, method of VOC collection using PDMS strips was shown to be an effective, economical and efficient way of examining VOC emissions directly from the pages of a book and confirmed that toluene, furfural, benzaldehyde, ethylhexanol, nonanal and decanal were the most concentrated VOCs emitted directly from paper measured in this study

Spectrophotometric Complex formation Study of Murexide with Nickel and Cobalt in Aqueous Solution

In the present study, the formation constant and the stoichiometry of murexide complexes with Co (II) and Ni (II) have been determined spectrophotometrically in aqueous solution at 25oC. Two experimental parameters governed the complex formation, pH and time, have been investigated. The formation and stoichiometry constants have been determined by two methods: Job's and mole ratio's methods. The absorption maxima for Co-murexide and Ni-murexide complexes were: 480, 460 nm, respectively. The two Spectrophotometric methods confirm the formation of 2:1 (M:L) complexes with stability arrange of: Co &gt; Ni. The formation constants (Kf) determined by the Job's method were as follows: 2.06x1014 and 1.21x1011 for Co-murexide and Ni-murexide, respectively. Also, using mole ratio's method, the formation constants were found to be:&nbsp; 9.18x1011 and 6.01x1011. Molar absorptivity values of the studied complexes have also been determined (by Job's and mole ratio's methods) and the average values were: 18235 and 13284 l/mol.cm for Co and Ni, respectively

Removal of formaldehyde from air using functionalized silica supports

This paper demonstrates the use of functionalized meso-silica materials (MCM-41 or SBA-15) as adsorbents for formaldehyde (H2CO) vapor from contaminated air. Additionally new green nanosilica (GNs) materials were prepared via a bioinspired synthesis route and were assessed for removal of H2CO from contaminated indoor air. These exciting new materials were prepared via rapid, 5 min, environmentally friendly synthesis routes avoiding any secondary pollution. They provided an excellent platform for functionalization and extraction of H2CO demonstrating similar performance to the conventional meso-silica materials. To the authors’ knowledge this is the first reported practical application of this material type. Prior to trapping, all materials were functionalized with amino-propyl groups which led to chemisorption of H2CO; removing it permanently from air. No retention of H2CO was achieved with nonfunctionalized material and it was observed that best extraction performance required a dynamic adsorption setup when compared to passive application. These results demonstrate the first application of GNs as potential adsorbents and functionalized meso-silica for use in remediation of air pollution in indoor air