Study on the ability of indoor plants to absorb and purify benzene pollution.

The ability of indoor plants to purify benzene pollution is the basic basis for the selection of plants for ecological remediation of indoor benzene pollution. In this study, the purification rate and the purification amount per unit leaf area of 13 test plants at three benzene concentrations were determined by indoor fumigation experiments, and the benzene absorption and purification abilityability of indoor plants were comprehensively evaluated. The results showed that (1) there was a significant correlation between benzene concentration and purification rate and purification amount per unit leaf area. (2) At the three concentrations, Spathiphyllum floribundum showed the highest purification rate and Sansevieria trifasciata var. laurentii showed the highest purification per unit leaf area. (3) The combined results showed that Sansevieria trifasciata var. laurentii, Spathiphyllum floribundum and Aloe arborescens were the strongest absorbers and purifiers, while Podocarpus nagi and Anthurium andraeanum 'Pink champin' had the weakest absorption and purification capacity. The results of this study provide a theoretical basis and reference for the selection of plants with strong capacities to adsorb and purify benzene pollution in indoor air.

A case-control study of airborne dissemination of bacteria during CT colonography.

OBJECTIVES: The COVID-19 pandemic has highlighted the importance of aerosol spread of infection. We have conducted a study to detect bacterial contamination of room surfaces and room air during CT colonography and confirm the efficacy of room disinfection procedures carried out between examinations. METHODS: Systematic sampling of the CT examination couch and horizontal surfaces 1 m and 3 m from the couch was performed before and after patient examinations. A 1 m3 sample of room air was obtained during patient examinations. Samples were processed using routine laboratory methods. A case-control study design was used (30 CT colonography and 30 routine body CT scans). RESULTS: Evidence of airborne dissemination of bacteria was detected in >30% of CT colonography examinations and <10% of control examinations (p = 0.01). No pathogenic bacteria were detected in surface samples taken before patient examinations. CONCLUSION: The room disinfection policy in use in our CT department is effective in eliminating pathogenic bacteria from surfaces in the patient environment. CT colonography causes contamination of room air with enteric bacteria in a significant proportion of cases. ADVANCES IN KNOWLEDGE: CT colonography may possibly be an aerosol-generating procedure. Larger-scale investigation is needed to fully evaluate this potential infection risk.

Juncus effusus fiber-based cellulose cigarette filter with 3D hierarchically porous structure for removal of PAHs from mainstream smoke.

Polycyclic aromatic hydrocarbons (PAHs) from cigarettes are one of the main pollutants affecting public health. Herein, a cellulose cigarette filter with three-dimensional (3D) hierarchically porous structure was fabricated using a natural cellulose Juncus effusus (JE) fiber, whose pore size was well controlled by biocompatible polyvinylpyrrolidone (PVP) using a simple dip-dry method. The adsorption capacity and mechanism of the PVP-JE filter tips (PJF) against PAHs were investigated in detail. Compared with conventional cellulose acetate filter tips (CAF), the cellulose PJF were superior at filtering and adsorbing of PAHs from mainstream smoke with the removal efficiency of 61.79 %, which was 22.57 % higher than that of CAF (39.22 %). The ternary structures including polymer filter membrane, 3D network, and interconnected channels were demonstrated as the main roles for highly effective removal of PAHs. The JE-based cellulose cigarette filter can be a promising candidature to broaden the application range of polysaccharide in pollutant elimination.

Removal of particulate matter from pork belly grilling gas using an orifice wet scrubber.

Grilling restaurants are a major contributor to airborne particulate matter (PM) in metropolitan areas. In this study, the removal of PM during the grilling of pork belly using an orifice scrubber, which is a form of gas-induced spray scrubber, was assessed. During grilling, the particle mass concentration was the highest for 1.0 < PM ≤ 2.5 µm (55.5% of total PM emissions), followed by 0.5 < PM ≤ 1.0 (27.1%), PM ≤ 0.5 (10.7%), and PM > 2.5 µm (7.0%). The PM removal efficiency of the orifice scrubber at a gas flow of 4.5 m3 min-1 was > 99.7% for PM ≥ 2.5 µm, 89.4% for 1.0 < PM ≤ 2.5 µm, 62.1% for 0.5 < PM ≤ 1.0, and 36.5% for PM ≤ 0.5 µm. Although further research is necessary to optimize its use, the orifice scrubber offers a user-friendly technology for the control of PM in small grilling restaurants because of its simple design, uncomplicated operation, and satisfactory PM removal performance.

Dynamic performance of a fungal biofilter packed with perlite for the abatement of hexane polluted gas streams using SIFT-MS and packing characterization with advanced X-ray spectroscopy.

The use of Fusarium solani fungi in an expanded perlite packed biofilter was investigated for the treatment of a hexane polluted waste gas stream using selected ion flow tube mass spectrometry (SIFT-MS). The latter analytical technique proved to be of utmost importance to evaluate the performance of the biofilter at high time resolution (seconds) under various transient conditions, analogous to industrial situations. The biofilter was operational for 277 days with inlet loads varying between 1 and 14 g m-3 h-1 and applying an empty bed residence time of 116 s. The results showed a positive behaviour of the biofilter against different types of disruptions such as: (i) changes in the relative humidity of the inlet gas, (ii) stopping the carbon supply for 1, 5 and 10 days, (iii) varying the inlet hexane concentration (step increases and intermittent pulses) and (iv) limiting the availability of nutrients. X-ray imaging (both conventional 2D µCT and X-ray fluorescence, XRF) was applied for the first time on biofilter media in order to get insight in the internal structure of expanded perlite and to visualise the biomass growth. The latter in combination with online porosity measurements using SIFT-MS provides fundamental information regarding the biofiltration process.

Numerical simulation of the simultaneous removal of particulate matter in a wet flue gas desulfurization system.

The particulate matter (PM) could be simultaneously removed during the wet flue gas desulfurization (WFGD) process. To analyze the underlying mechanism and removal efficiency, the PM removal process in a desulfurization system was numerically simulated based on the population balance model and general dynamics equation in this study. The equation was solved using the fixed-step Monte Carlo method to determine the PM removal characteristics under different working conditions (such as spray intensity, velocity of the flue gas, and layers of slurry spray). When the flue gas velocity decreased from 7 to 3 m/s, the removal efficiency increased from 90.93 to 93.52%, and when the mean geometric droplet size decreased from 3 to 1 mm, the removal efficiency increased from 67.18 to 99.14%. Besides, large diameter PM was more easily removed by the desulfurization system. Thus, the numerical simulation method was proven to be feasible by comparing these results with field measurements of a WFGD system in a coal-fired power plant.

A combined microextraction procedure for isolation of polycyclic aromatic hydrocarbons in ambient fine air particulate matter with determination by gas chromatography-tandem mass spectrometry.

A novel combined vortex-assisted dispersive liquid-liquid microextraction (VA-DLLME)-micro-solid-phase extraction (µ-SPE) procedure for polycyclic aromatic hydrocarbons (PAHs) in ambient fine particulate matter of aerodynamic diameter of  ≤ 2.5 µm (PM2.5), was developed. PM2.5 was collected on polytetrafluoroethylene (PTFE)-coated glass fiber filter, that was first processed by ultrasonicating in aqueous solution. Then, VA-DLLME, followed by µ-SPE, were applied to the solution using 1-octanol and graphene oxide as extractant and sorbent, respectively for extracting the PAHs. The PAHs were determined by gas chromatography-tandem mass spectrometry (GC-MS/MS). Parameters affecting the extraction efficiency including selection of the sorbent, duration of DLLME and µ-SPE, desorption solvent type, and ultrasonication-assisted desorption time were investigated. Under the optimum extraction conditions, the method exhibited linear ranges of 0.5-50 µg/L and 0.5-100 µg/L depending on the analytes. The limits of detection were in the range of 0.013 µg/L-0.135 µg/L. The developed method was applied to determine the PAHs in genuine PM2.5 samples collected on PTFE glass fiber filters. The concentration levels in the atmospheric PM2.5 were determined to be from below the limit of quantification to 0.135 ng/m3. The relative recoveries obtained from spiked concentrations at 1 µg/L and 5 µg/L were in the range 57-88% with relative standard deviations <14%.

Gas-phase removal of indoor volatile organic compounds and airborne microorganisms over mono- and bimetal-modified (Pt, Cu, Ag) titanium(IV) oxide nanocomposites.

The photocatalytic deactivation of volatile organic compounds and mold fungi using TiO2 modified with mono- and bimetallic (Pt, Cu, Ag) particles is reported in this study. The mono- and bimetal-modified (Pt, Cu, Ag) titanium(IV) oxide photocatalysts were prepared by chemical reduction method and characterized using XRD, XPS, DR/UV-Vis, BET, and TEM analysis. The effect of incident light, type and content of mono- and bimetallic nanoparticles deposited on titanium(IV) oxide was studied. Photocatalytic activity of as-prepared nanocomposites was examined in the gas phase using LEDs array. High photocatalytic activity of Ag/Pt-TiO2 and Cu/Pt-TiO2 in the reaction of toluene degradation resulted from improved efficiency of interfacial charge transfer process, which was consistent with the fluorescence quenching effect revealed by photoluminescence (PL) emission spectra. The photocatalytic deactivation of Penicillium chrysogenum, a pathogenic fungi present in the indoor environment, especially in a damp or water-damaged building using mono- and bimetal-modified (Pt, Cu, Ag) titanium(IV) oxide was evaluated for the first time. TiO2 modified with mono- and bimetallic NPs of Ag/Pt, Cu, and Ag deposited on TiO2 exhibited improved fungicidal activity under LEDs illumination than pure TiO2 .

Influences of fine-grained NaCl particles on performance and denitration efficiency of activated carbon during sintering flue gas purification process.

Alkali metal chlorides emitted from sintering flue gas are easily adsorbed on the surface of activated carbon (AC) in the purification process. In this paper, NaCl particles adsorbing onto AC were simulated by impregnation method, and the size and morphology of NaCl particles were similar to those of NaCl-PM10 emitted from sintering flue gas. With the adsorption of NaCl particles, 2-10-µm pores of AC were filled, and the specific surface area of AC decreased. But NaCl led to the increase of acidic functional groups on the surface of AC. When 0.75 wt% NaCl was adsorbed, it was beneficial for AC catalytic denitration (de-NOx), because the chemical reaction was strengthened by acidic functional groups, so it showed a certain promotion of de-NOx efficiency. As 1.5 wt% NaCl and 3 wt% NaCl were adsorbed, NaCl had an inhibitory effect on AC de-NOx, which was because the specific surface area of AC decreased, and the prevention of physical adsorption played a major role. As a result, the de-NOx efficiency of AC adsorbed with 3 wt% NaCl decreased from 40.59 to 23.02% at 150 °C. Therefore, the absorption of NaCl fine particles on AC should not exceed 0.75 wt%.

Vegetal fiber paper matrix impregnated with silica gel for benzene removal.

Removing benzene from indoor space plays an important role in indoor air purification. A novel filter with vegetal fiber paper (VFP) as matrix hosting silica gel is proposed in this paper for benzene removal. In order to investigate the feasibility and performance of this idea, firstly, three pieces of VFP samples impregnated with different amounts of silica gel are fabricated and their benzene adsorption quantities are tested. The results show that three times is recommended as the optimal number for impregnating. The VFP sample impregnated with silica gel after the third impregnating exhibits commendable coating stability and good benzene adsorption performance. Additionally, at low relative pressure (Pb /Ps  ≤ 0.05), the experimental data of benzene adsorption isotherms fit well with the Langmuir model with R2 greater than 0.97. Then, two actual filters made of VFP impregnated with silica gel after the third impregnating were fabricated. It is found that the pressure drop of the actual filter is only 1200 Pa/m when the air velocity is 2 m/s. Besides, the one-pass efficiency of the filter can reach to 19.44%. It is expected that the silica gel coated on the filter can be modified to improve the purification performance of the filter.

The Study of an Ultraviolet Radiation Technique for Removal of the Indoor Air Volatile Organic Compounds and Bioaerosol.

This study examined the use of high dosages of ultraviolet germicidal irradiation (UVGI) (253.7 nm) to deal with various concentrations of air pollutants, such as formaldehyde (HCHO), total volatile organic compounds (TVOC), under various conditions of humidity. A number of irradiation methods were applied for various durations in field studies to examine the efficiency of removing HCHO, TVOC, bacteria, and fungi. The removal efficiency of air pollutants (HCHO and bacteria) through long-term exposure to UVGI appears to increase with time. The effects on TVOC and fungi concentration were insignificant in the first week; however, improvements were observed in the second week. No differences were observed regarding the removal of HCHO and TVOC among the various irradiation methods in this study; however significant differences were observed in the removal of bacteria and fungi.

Performance assessment of gas-phase toluene removal in one- and two-liquid phase biotrickling filters using artificial neural networks.

The main aim of this work is to study gas-phase toluene removal in one- and two-liquid phase biotrickling filters (O/TLP-BTF) and model the BTF performance using artificial neural networks (ANNs). The TLP-BTF was operated for 60 d in the presence of silicone oil at empty bed residence times (EBRTs) of 120, 60, and 45 s, respectively, and toluene concentrations in the range of 0.9-3.1 g m-3. A t-test analysis indicated that increasing the silicone oil volume ratio from 5 to 10% v/v, did not significantly improve the TLP-BTF performance (p-value = 0.65 > 0.05). The results from ANN modeling showed that toluene removal was more negatively affected by the inlet concentration (casual index, CI = -5.63) due to the kinetic limitation. The CI values for inlet concentration (+4.01) and liquid trickling rate (-2.45) indicated that the diffusion-limited regime controlled the removal process in the OLP-BTF.

A sulfur-resistant CuS-modified active coke for mercury removal from municipal solid waste incineration flue gas.

Adsorption is a typical method for air pollutant removal from flue gas. A CuS-modified active coke (CuS/AC) sorbent was developed to improve the elemental mercury removal efficiency from municipal solid waste incineration (MSWI) flue gas. The influences of the loading amount of CuS, reaction temperature, and flue gas components including O2, SO2, H2O, and HCl on Hg0 removal efficiency were investigated, respectively. The results showed that the mercury adsorption capacity of CuS/AC(20%) sorbent was about 7.17 mg/g with 50% breakthrough threshold, which is much higher than that of virgin active coke. The analysis of XPS indicated that HgS was the main species of mercury on spent CuS/AC, which implied that adsorption and oxidation were both included in Hg0 removal. S22- played a vital role in the oxidation of physically adsorbed Hg0. Meanwhile, the common components of MSWI flue gas exhibited no significant inhibition effect on Hg0 removal by CuS/AC sorbent. CuS/AC sorbent is a promising sorbent for the mercury removal from MSWI flue gas.

Photocatalytic oxidation of toluene and isopropanol by LaFeO3/black-TiO2.

Large amount of volatile organic compounds (VOCs) are emitted from industrial, mobile, and domestic sources, causing adverse effects on human health and environment. Among VOCs, toluene and isopropanol (IPA) are commonly used as solvent, soldering flux, and spray paint and their emissions need to be reduced. Several VOCs abatement technologies are available to reduce VOC emission and photocatalytic oxidation of VOC is regarded as a viable technique due to its advantage of utilizing solar energy. TiO2 has been investigated for its oxidation capability toward VOCs because of its good photocatalytic activity. However the utilization is limited to UV due to its wider bandgap; furthermore, its fast recombination rate of electron-hole pair reduces the oxidation rate of VOCs. Black-TiO2 and perovskite-type photocatalyst such as LaFeO3 can be applied to enhance photocatalytic activity due to narrower bandgap and longer electron-hole pair lifetime. In this study, black-TiO2 and LaFeO3 are prepared and investigated for their photocatalytic oxidation rates toward toluene and IPA. Results show that toluene removals achieved with black-TiO2 and LaFeO3 are 89% and 98% while IPA removals are 90% and 94%, respectively. Both photocatalysts show better photocatalytic activity than TiO2 and good absorption capability toward visible light. Graphical abstract.

Integrated lipid production, CO2 fixation, and removal of SO2 and NO from simulated flue gas by oleaginous Chlorella pyrenoidosa.

CO2, SO2, and NO are the main components of flue gas and can cause serious environmental issues. Utilization of these compounds in oleaginous microalgae cultivation not only could reduce air pollution but could also produce feedstock for biodiesel production. However, the continuous input of SO2 and NO inhibits microalgal growth. In this study, the toxicity of simulated flue gas (15% CO2, 0.03% SO2, and 0.03% NO, balanced with N2) was reduced through automatic pH feedback control. Integrated lipid production and CO2 fixation with the removal of SO2 and NO was achieved. Using this technique, a lipid content of 38.0% DW was achieved in Chlorella pyrenoidosa XQ-20044. The lipid composition and fatty acid profile indicated that lipid production by C. pyrenoidosa XQ-20044 cultured with flue gas is suitable as a biodiesel feedstock; 81.2% of the total lipids were neutral lipids and 99.5% of the total fatty acids were C16 and C18. The ratio of saturated fatty acids to monounsaturated fatty acids in the microalgal lipid content was 74.5%. In addition, CO2, SO2, and NO from the simulated flue gas were fixed and converted to biomass and lipids with a removal efficiency of 95.9%, 100%, and 84.2%, respectively. Furthermore, the utilization efficiencies of CO2, SO2, and NO were equal to or very close to their removal efficiencies. These results provide a novel strategy for combining biodiesel production with biofixation of flue gas.

Characterization and adsorption capacity of potassium permanganate used to modify activated carbon filter media for indoor formaldehyde removal.

This study examined the effect of potassium permanganate (KMnO4)-modified activated carbon for formaldehyde removal under different face velocities and different initial formaldehyde concentrations in building environment. We chose the coconut shell activated carbon due to their high density and purity. Moreover, they have a clear environmental advantage over coal-based carbons, particularly in terms of acidification potential. The chemical properties were characterized by FTIR to show the functional groups, EDS to calculate each component of their energy bands to know how the ratio is. Also, the morphology of the surface was examined with scanning electron microscopy (SEM). The BET determines specific surface area, pore size, and pore volume. It was found that where the initial formaldehyde concentration and the face velocity are low, adsorption capacity is high. The adsorption isotherms of formaldehyde on modified activated carbon are well fitted by both Langmuir and Freundlich equations. The rate parameter for the pseudo-first-order model, pseudo-second-order model, and intraparticle diffusion model was compared. The correlation coefficient of pseudo-second-order kinetic model (0.999 > R2 > 0.9548) is higher than the coefficient of pseudo-first-order kinetic model (0.5785 < R2 < 0.8755) and intraparticle diffusion model (0.9752 < R2 < 0.9898). Thus, pseudo-second-order kinetic model is more apposite to discuss the adsorption kinetic in this test, and the overall rate of the modified activated carbon adsorption process appears to be influenced by more than one step that is both the intraparticle diffusion model and membrane diffusion.

Efficient removal of benzene in air at atmospheric pressure using a side-on type 172 nm Xe2 excimer lamp.

The photochemical removal of benzene was studied in air at atmospheric pressure using a side-on type 172 nm Xe2 excimer lamp with a wide irradiation area. After 1.5 min photoirradiation, C6H6 (1000 ppm) in air was completely converted to HCOOH, CO, and CO2 at a total flow rate of 1000 mL/min. The initial decomposition rate of C6H6 was determined to be 1.18 min-1. By using a flow system, C6H6 (200 ppm) was completely removed at a total flow rate of 250 mL/min. The conversion of C6H6 and the energy efficiency in the removal of C6H6 changed in the 31-100% and 0.48-1.2 g/kWh range, respectively, depending on the flow rate, the O2 concentration, and the chamber volume. On the basis of kinetic model simulation, dominant reaction pathways were discussed. Results show that the O(3P) + C6H6 reaction plays a significant role in the initial stage of the C6H6 decomposition. Important experimental parameters required for further improvement of the C6H6 removal apparatus using a 172 excimer lamp were discussed based on model calculations.

Insight into elemental mercury (Hg0) removal from flue gas using UV/H2O2 advanced oxidation processes.

Elemental mercury (Hg0) emitted from coal-fired power plants and municipal solid waste (MSW) incinerators has caused great harm to the environment and human beings. The strong oxidized •OH radicals produced by UV/H2O2 advanced oxidation processes were studied to investigate the performance of Hg0 removal from simulated flue gases. The results showed that when H2O2 concentration was 1.0 mol/L and the solution pH value was 4.1, the UV/H2O2 system had the highest Hg0 removal efficiency. The optimal reaction temperature was approximately 50 °C and Hg0 removal was inhibited when the temperature was higher or lower. The yield of •OH radicals during UV/H2O2 reaction was studied by electron paramagnetic resonance (EPR) analysis. UV radiation was the determining factor to remove Hg0 in UV/H2O2 system due to •OH generation during H2O2 decomposition. SO2 had little influence on Hg0 removal whereas NO had an inhibitory effect on Hg0 removal. The detailed findings for Hg0 removal reactions over UV/H2O2 make it an attractive method for mercury control from flue gases.

Usefulness of Aspergillus Galactomannan Antigen Testing and the Prediction of an Outbreak during Hospital Reconstruction.

Objective This study retrospectively evaluated fungal dissemination due to hospital reconstruction and explored effective methods of predicting an outbreak. Methods Patients suspected of having invasive aspergillosis were tested for Aspergillus galactomannan antigen before and after reconstruction, and the mean values of three months of testing for positive patients were determined. The characteristics of patients with aspergillosis during this period were also assessed. Results Forty-five patients were positive for Aspergillus antigen (>0.5 cut-off index) from January 2013 to December 2014. Mean Aspergillus antigen values significantly increased following reconstruction (p<0.05). Three patients developed pneumonia due to Aspergillus and were diagnosed with "probable" invasive aspergillosis according to the European Organization for Research and Treatment of Cancer and the National Institute of Allergy and Infectious Diseases Mycoses Study Group (EORTC/MSG) criteria. We also discovered that the anteroom to contain dust was not prefabricated and a negative pressure system to remove dust was not used. After construction of the unit, no new cases of aspergillosis were diagnosed. Conclusion Many Aspergillus spores may be transiently floating during hospital reconstruction. Therefore, monthly surveillance with frequent serum galactomannan antigen testing to predict outbreaks is necessary. Surveillance of all patients in the hematology ward is especially important. Reconsideration of prophylactic antifungals may also be necessary during hospital reconstruction.

Purification of Hg0 from flue gas by wet oxidation method and its mechanism: a review.

The vast majority of Hg2+ can be removed while elemental mercury (Hg0) can hardly be removed due to its characteristic of high volatility and insolubility in water. Till now, how to oxidize Hg0 to Hg2+ is the key for the purification of Hg0, especially when there are others pollutants, such as HCl, SO2, and NOx. In this review, the method and mechanism of Hg0 purification from flue gas by H2O2, KMnO4, NaClO2, and O3 are reviewed comprehensively. It is concluded that the oxidation of Hg0 mainly depends on the electronic supply efficiency from the solution. The Fenton reagent, composed of H2O2 and metal cations, is superior to O3 and the solution of KMnO4 and NaClO2. Moreover, HCl, SO2, and NOx in the flue gas can influence the oxidation and purification mechanism of Hg0. It is found that HCl in flue gas had obvious auxo-action on the oxidation of mercury, and SO2 and NOx have different effects on the oxidation of Hg0 with the change of compositions and concentration of pollutants in the flue gas. In general, SO2 and NOx can slightly promote the oxidation of Hg0 due to the synergistic effect.