真空紫外光降解五氯酚钠以及过硫酸盐对反应的促进作用

研究了真空紫外光(VUV,185 am)对于水溶液中五氯酚钠的降解,反应2 h后,初始浓度为10 mg/L的五氯酚钠的去除率达到99%以上,有机氯的脱除率达到70%以上,有效地实现了五氯酚钠的脱毒.溶液初始pH值对五氯酚钠的真空紫外光解有很大影响,pH=10.9时的降解速率常数是pH=3.1时的3倍.表观一级反应速率常数随初始浓度的增加而线性下降.在反应溶液中加入过硫酸盐,可有效提高五氯酚钠的真空紫外光降解速率和矿化速率,过硫酸盐和五氯酚钠摩尔比为24时,降解速率提高3倍,反应4 h后TOC去除率达到95%.     

Experimental studies on ozonation of ethylenethiourea

The experimental study on ozonation of ethylenethiourea(ETU) is conducted.The reaction of gas-phase ETU with 0.63 × 10-6 mol/L ozone is carried out in a 200-L reaction chamber.The secondary organic aerosol(SOA) resulted from the ozonation of gas-phase ETU is observed with a scanning mobility particle size(SMPS).The rapid exponential growth of SOA reveals that the atmospheric lifetime of ETU vapor towards ozone reaction is less than four days.The ozonation of dry ETU particles,ETU-contained water droplets an...     

A VUV photoionization mass spectrometric study on the OH-initiated photooxidation of isoprene with synchrotron radiation

The gas-phase organic compounds resulting from OH-initiated photooxidation of isoprene have been investigated on-line by VUV photoionization mass spectrometry based on synchrotron radiation for the first time. The photoionization efficiency curves of the corresponding gaseous products as well as the chosen standards have been deduced by gating the interested peaks in the photoionization mass spectra while scanning the photon energy simultaneously, which permits the identification of the pivotal gaseous products of the photooxidation of isoprene, such as formaldehyde (10.84 eV), formic acid (11.38 eV), acetone (9.68 eV), glyoxal (9.84 eV), acetic acid (10.75 eV), methacrolein (9.91 eV), and methyl vinyl ketone (9.66 eV). Proposed reaction mechanisms leading to the formation of these key products were discussed, which were completely consistent with the previous works of different groups. The capability of synchrotron radiation photoionization mass spectrometry to directly identify the chemical composition of the gaseous products in a simulation chamber has been demonstrated, and its potential application in related studies of atmospheric oxidation of ambient volatile organic compounds is anticipated.     

Degradation and reduction of acute toxicity of environmentally persistent perfluorooctanoic acid (PFOA) using VUV photolysis and TiO2 photocatalysis in acidic and basic aqueous solutions

Degradation and toxicity reduction of perfluorooctanoic acid (PFOA) were investigated using TiO₂ adsorption, vacuum ultraviolet (VUV) photolysis, and VUV/TiO₂ photocatalysis in acidic and basic aqueous solutions. Chemical analyses of PFOA and its selected by-products and an acute toxicity assessment using the luminescent bacteria Vibrio fischeri (Microtox®) were conducted during and after the various treatment methods. PFOA was found to be best treated by VUV/TiO₂ at pH 4 with HClO₄, as illustrated by the almost complete degradation of PFOA within 360?min and rapid removal of acute microbial toxicity within 60?min. This difference in the efficiency may be attributed to the strong oxidation effectiveness of the radical species generated in acidic media and the electron scavenger effect of the addition of HClO₄ in VUV/TiO₂ photocatalysis. In addition, the proposed method could effectively decompose other perfluorocarboxylic acid (PFCA) species (C₃–C₇ perfluoroalkyl groups) if the initial intermediates formed were longer-chain species that degraded stepwise into shorter-chain compounds by VUV photolysis and VUV/TiO₂ photocatalysis in acidic and basic aqueous solutions.     

真空紫外光-TiO2催化降解气态偏二甲肼

以钛箔为载体,采用溶胶-凝胶法及浸渍-烘焙-煅烧法制备了负载型TiO₂薄膜,并进行了SEM,EDS,XRD表征。探讨了TiO₂薄膜对气态偏二甲肼的光催化降解效果,并对比研究了不同紫外光源、不同初始浓度对气态偏二甲肼降解效果的影响。实验结果表明：TiO₂均匀负载在钛箔上且为多孔状的薄膜;偏二甲肼质量浓度为877 mg/m³时,反应17 min后偏二甲肼的降解率为99.99%,500 mg/m³时反应60 min后偏二甲肼的矿化率达到41.58%。     

Phototransformation of ibuprofen and ketoprofen in aqueous solutions

The UV (254 nm) and UV/VUV (254/185 nm) photolysis of two anti-inflammatory drugs, ibuprofen and ketoprofen, have been studied in aqueous solutions as a possible process for the removal of non-biodegradable compounds.We have examined the effects of dissolved oxygen and initial target concentration. Upon irradiation at 254 nm, the decomposition rate of ketoprofen is almost forty times higher as it of ibuprofen whilst VUV irradiation only increased the ibuprofen decomposition rate. The presence of dissolved oxygen accelerated the photodegradation of ibuprofen, whereas no effect was observed on the degradation of ketoprofen. The maximum quantum yield for the phototransformation was 0.2. The rate of mineralization in both cases was ∼60%, even after 1 h of treatment and this suggests the formation of stable by-products which were identified using GC-MS and HPLC-MS, respectively.     

真空紫外灯动态降解空气中低浓度甲醛的研究

以集中空调中处理室内可挥发性有机物（VOCs）为应用背景，搭建了试验台。实验研究了真空紫外灯（主波长254nm，185nm）降解甲醛的影响因素以及产生O3的情况。研究表明，在产生的O3浓度低于室内空气质量标准（0．16mg／m^3）的情况下，真空紫外灯也能够高效地降解空气中低浓度甲醛（〈1mg／m^3）；甲醛降解率与反应器空气流速及甲醛初始浓度成反比；降解速率与甲醛初始浓度成正比，与反应器空气的流速成反比；绝对湿度对真空紫外灯降解甲醛有一定的影响；反应器空间大小对甲醛降解影响比较显著。应用于集中空调系统净化室内空气中VOCs，取得了很好的效果。     

Removal of gaseous volatile organic compounds via vacuum ultraviolet photodegradation: Review and prospect

Volatile organic compounds (VOCs) have attracted much attention for decades as they are the precursors of photochemical smog and are harmful to the environment and human health. Vacuum ultraviolet (VUV) photodegradation is a simple and effective method to decompose VOCs (ranging from tens to hundreds of ppmV) without additional oxidants or catalysts in the air at atmospheric pressure. In this paper, we review the research progress of VOCs removal via VUV photodegradation. The fundamentals are outlined and the key operation factors for VOCs degradation, such as humidity, oxygen content, VOCs initial concentration, light intensity, and flow rate, are discussed. VUV photodegradation of VOCs mixture is elucidated. The application of VUV photodegradation in combination with ozone-assisted catalytic oxidation (OZCO) and photocatalytic oxidation (PCO) systems, and as the pre-treatment technique for biological purification are illustrated. Based on the summary, we propose the challenges of VUV photodegradation and perspectives for its future development.     

VUV/Fe3+体系对水中全氟辛酸(PFOA)脱氟影响因素研究

采用VUV/Fe3+光催化体系对全氟辛酸(PFOA)进行脱氟处理,考察了PFOA初始浓度、Fe3+浓度、体系pH值对体系脱氟的影响,并运用响应面正交法(RSM)优化分析了最佳反应条件.结果表明,VUV/Fe3+体系对PFOA具有明显的脱氟作用.PFOA浓度与Fe3+浓度比为1.8∶1～1.2∶1和pH为3～4时,有利于体系的脱氟.基于Box-Behnken响应曲面法,各影响因子显著性排序为pH>Fe3+投加量>PFOA初始浓度,pH值和Fe3+投加量交互作用显著.模型回归性良好,最佳运行条件组合为:pH=3.41,Fe3+投加量为30μmol·L-1和PFOA初始浓度为38.6μmol·L-1(16mg·L-1)条件下,反应4h的脱氟率达到54.13%,与预测值相比偏差为0.36%.在VUV体系引入Fe3+提高了PFOA及中间产物对紫外光利用的效率.     

Protonated acetone ion chemical ionization time-of-flight mass spectrometry for real-time measurement of atmospheric ammonia

Ammonia (NH₃) is ubiquitous in the atmosphere, it can affect the formation of secondary aerosols and particulate matter, and cause soil eutrophication through sedimentation. Currently, the use of radioactive primary reagent ion source and the humidity interference on the sensitivity and stability are the two major issues faced by chemical ionization mass spectrometer (CIMS) in the analysis of atmospheric ammonia. In this work, a vacuum ultraviolet (VUV) Kr lamp was used to replace the radioactive source, and acetone was ionized under atmospheric pressure to obtain protonated acetone reagent ions to ionize ammonia. The ionization source is designed as a separated three-zone structure, and even 90 vol.% high-humidity samples can still be directly analyzed with a sensitivity of sub-ppbv. A signal normalization processing method was designed, and with this new method, the quantitative relative standard deviation (RSD) of the instrument was decreased from 17.5% to 9.1%, and the coefficient of determination was increased from 0.8340 to 0.9856. The humidity correction parameters of the instrument were calculated from different humidity, and the ammonia concentrations obtained under different humidity were converted to its concentration under zero humidity condition with these correction parameters. The analytical time for a single sample is only 60 sec, and the limit of detection (LOD) was 8.59 pptv (signal-to-noise ratio S/N = 3). The ambient measurement made in Qingdao, China, in January 2021 with this newly designed CIMS, showed that the concentration of ammonia ranged from 1 to 130 ppbv.