Indoor levels of volatile organic compounds at Florentine museum environments in Italy

Indoor Air Quality monitoring in cultural institutions is of particular concern to protect these places and the cultural heritage content. An indoor monitoring campaign was performed in three museums in Florence (Italy) to determine the occurrence and levels of volatile organic compounds (VOCs). VOCs of interest included BTEX (benzene, toluene, ethylbenzene, xylenes), terpenes, aldehydes, organic acids, and cyclic volatile methyl siloxanes (cVMS). The most abundant VOCs in all samples analyzed were BTEX, which were strictly related to the traffic source, followed by siloxanes and terpenes. Among BTEX, toluene was always the most abundant followed by xylenes, ethylbenzene, and benzene. cVMS in exhibition rooms with the presence of visitors showed higher values compared to samples collected when the museums were closed. Terpenes showed not only the influence of vegetation-biogenic sources surrounding a museum but could also be related to the wood used for the construction of showcases and furniture and the use of cleaning products. Data obtained also showed the presence of organic acids and aldehydes whose source can be traced back to exhibits themselves and wood-based furniture. Assessing the levels of organic acids in museums is important because, over time, it can cause deterioration of the artifacts.     

Modelling and kinetic aspects of a BTEX contaminated air-treating biofilter

In this study, the overall performance of a biofilter was evaluated in terms of its elimination capacity by using 3-D mesh techniques. The overall results indicate that the agreement between experimental data and model predictions is excellent for benzene, toluene, ethylbenzene and o-xylene (BTEX). In this study, the maximum removal rate (r _max) values for BTEX were 0.0117, 0.0126, 0.0081 and 0.0146 g m^–3 h^–1, and the half-saturation constant (K_S ) values were calculated to be 0.269, 0.297, 0.156 and 0.394 g m^–3, respectively. For this system, the coefficients of determination (r ²) of BTEX compounds were greater than 0.97. The BTEX concentration profiles along the depth were also determined using a convection–diffusion reactor (CDR) model. The sums of squares of the errors (SSEs) of BTEX were 0.0078, 0.0059, 0.0129 and 0.0269, respectively, with r ² values greater than 0.99 for all four compounds at low concentrations.     

Design and performance of biofilters for the removal of alkylbenzene vapors

Three identical biofilters, run under the same conditions but inoculated with different mixed cultures, were fed a mixture of toluene, ethylbenzene, and o-xylene (TEX) gases. Inert porous perlite was used as support material, in contrast to the more conventional biofiltration systems where natural supports are used. Biodegradation started in all three biofilters a few hours after inoculation, without previous adaptation of the inocula to the toxic mixture. Despite acidification of the systems to pH values below 4·5, the elimination capacities reached were fully satisfactory. The best performing biofilter, in which bacteria were dominant, showed an elimination capacity of 70 g TEX m⁻³ h⁻¹ with a near complete removal of the mixture up to an influent concentration of 1200 mg TEX m⁻³ at a gas residence time of 57 s. Most of the ingoing carbon was recovered as carbon dioxide in the outgoing gas. In the other biofilters fungi dominated and performance was slightly worse. With single substrates, the elimination capacity was higher for toluene and ethylbenzene than for the TEX mixture, whereas o-xylene removal was slowest in all cases. Also when feeding the mixture to the biofilters, o-xylene was removed most slowly.     

原位厌氧修复化工园区地下水有机污染物的研究进展

综述了化工园区的发展带来的地下水污染现状、地下水主要有机污染物和地下水原位生物修复的研究进展,重点探讨了厌氧修复技术相关的有机污染物厌氧降解,并对地下水厌氧修复技术研究前景进行了简要分析。     

顶空毛细管柱气相色谱法测定水中苯系物的研究

采用顶空气相色谱-氢火焰离子化检测器法(HS-GC-FID)测定水中八种苯系物(包括苯、甲苯、乙苯、对二甲苯、间二甲苯、邻二甲苯、异丙苯、苯乙烯),对其分析条件进行了优化,详细讨论了分析过程中各因素对测定结果的影响,如:色谱柱极性、气液体积比、水浴温度和平衡时间等。结果发现:DB-FFAP极性石英毛细管柱可以实现了水中苯系物各组分的完全分离。在气液体积比为1∶2时、水浴温度为50℃平衡40 min后进行测定,获得了最佳实验效果,同时加入适量的氯化钠可以提高灵敏度。该方法条件下,苯系物各组分线性方程的相关系数均大于0.999,方法检出限在0.85～4.44μg.L-1,加标回收率在98.7～103.6%之间,相对标准偏差小于6.8%(n=6)。该方法准确快捷、线性范围广,适用于饮用水和地表水中低浓度挥发性苯系物的测定。     

程序升温升压GC法快速分析汽油中的BTEX

采用程序升温和程序升柱头压的技术建立了一种快速分析汽油中BTEX的气相色谱方法,对汽油中芳烃的分离条件进行了选择,比较了用不同内标的定量分析结果,并测定了几种汽油中的BTEX。该方法可用于直馏汽油、催化裂化汽油、重整汽油、裂解汽油中BTEX和其它芳烃的测定,适合于汽油质量的快速监测分析。     

Fate of hazardous aromatic substances in membrane bioreactors

In this work, the removal of hazardous aromatic compounds was investigated in two types of membrane bioreactors (MBRs), based on cross-flow and semi dead-end filtration systems. BTEX and PAH were efficiently eliminated from wastewater during treatment via a membrane bioreactor (90-99.9%) but non-biotic processes, i.e. volatilisation and sorption, contributed significantly. The semi dead-end MBR showed slightly better removal efficiencies than the cross-flow MBR. However, non-biotic processes were more significant in the first process and, finally, degradation rates were higher in the cross-flow MBR. Higher degradation rates were explained by a higher bio-availability of pollutants. Differences in shear stress imposed in cross-flow and semi dead-end filtration systems radically modify the sludge morphology. High shear stress (cross-flow filtration) generates dispersed bacteria and larger quantities of dissolved and colloidal matter. Sorption of hydrophobic compounds (PAHs) on suspended solid was less marked in disaggregated sludge. The results suggest new strategies for improving micro-pollutant degradation in MBRs.     

苯系物(BTEX)检测气敏材料研究进展

金属氧化物半导体传感器因具有体积小、成本低廉、使用方便等优点,越来越受到研究者的关注并被用于有毒有害气体的监测。传感材料是气敏传感器的核心,本文综述了近年来氧化物半导体BTEX气敏传感材料的研究进展,对传感材料的微结构、负载/掺杂改性、气敏性能、气敏机理及存在的问题进行了分析,并探讨了其下一步发展趋势。     

The adsorption of PAHs, BTEX, and heavy metals on surfactant-modified desulfurization sorbents in a dry scrubber

The injection of dry Ca-based sorbents for removing acid gases had been investigated previously. However, the utilization of Ca-based sorbents for adsorbing other air pollutants was rarely examined. The objective of this study was to investigate the reduction of organic compounds polycyclic aromatic hydrocarbons (PAHs) and benzene, toluene, ethylbenzene, and xylene (BTEX) and heavy metals by using the desulfurization sorbents in a dry scrubber integrated with a fabric filter. Four surfactants, calcium lignosulfonate, sodium lignosulfonate, alkyl naphthalene sodium sulfonate and β-naphthalene sodium sulfonate condensates, were used as additives to modify the surface characteristics of desulfurization sorbent calcium hydroxide (Ca(OH)₂). Modifying the desulfurization sorbents with surfactants showed different effects on removal of PAHs, BTEX, and heavy metals, and exploited the potential of Ca-based sorbents for adsorbing air pollutants other than SO₂.     

Effectiveness of UV-based advanced oxidation processes for the remediation of hydrocarbon pollution in the groundwater: a laboratory investigation

The effectiveness of advanced oxidation processes in a batch and a flow reactor was investigated for the remediation of hydrocarbon pollution in the groundwater underlying a petrochemical industrial site. The main organic contaminants present in the groundwater were MTBE, benzene, alkyl-benzenes and alkyl-naphthalenes. Experimental results with a batch reactor showed that for all the organic contaminants the removal efficiency order is UV/TiO2 approximately UV/H2O2>UV (medium-pressure) in a synthetic aqueous solution, compared to UV/H2O2>UV (medium-pressure)>UV/TiO2 for the real polluted groundwater. The much lower performance of UV/TiO2 with respect to UV/H2O2 was inferred to the matrix of the groundwater, i.e. the salt content, as well as the organic and particulate matter. In fact, it is likely that the salts and dissolved organic matter quench the superoxide anion O2(-) and hydroxyl radicals just formed at the surface of the TiO2 catalyst. MTBE was the hardest compound to remove with each of the investigated treatments. UV and UV/TiO2 treatments were not able to reach a residual concentration of 10 microg/L (set by Italian legislation) even after 180 min. As for the UV/H2O2 process, only the MTBE degradation rate resulted affected by the initial H2O2 concentration, while for other compounds a complete removal was obtained within 20 min even with the lowest H2O2 concentration used (0.13 g/L). Only after 120 min of treatment, with an initial H2O2 concentration of 0.13 g/L, did the residual MTBE concentration fall below the above reported maximum admissible concentration. Instead, by using an initial concentration of 2g/L a residual concentration lower than 5 microg/L was obtained after just 30 min of reaction. The UV/H2O2 process was also investigated with a flow reactor. Results showed that it was more efficient than the batch reactor for removing MTBE, in terms of reaction time and initial H2O2 concentration required. This is consistent with the higher power of the UV lamp and with the different geometry of the flow reactor, which has a much shorter optical path than the batch reactor. By-product characterisation was also performed showing that t-butyl-formate and low molecular weight organic acids are formed as intermediate and final by-products, respectively. Finally, a preliminary evaluation of the operational cost of the UV/H2O2 process showed a value of 1.7 euro/m3 under the optimised condition.