Degradation of pentachlorophenol and 2,4-dichlorophenol by sequential visible-light driven photocatalysis and laccase catalysis

Chlorophenols (CPs) can be degraded by visible-light driven photocatalysis or laccase catalysis. However, previous and present studies have shown that neither of the two methods was efficient when being used individually. Low degradation rates were observed for the degradation of pentachlorophenol (PCP) by laccase-catalysis and that of 2,4-dichlorophenol (2,4-DCP) by photocatalysis. To remove CPs more completely, a sequential photolaccase catalytic system was designed to degrade PCP and 2,4-DCP mixture in water at the optimal pH value. The results showed that photocatalysis prior to laccase-catalysis (PPL) is a better approach than laccase-catalysis prior to photocatalysis (LPP), eliminating CPs more efficiently and generating lower toxic products. The identified intermediate products consisted of adipic acid, hexanediol, glycol, propylene glycol, hydroquinol, and phthalandione. Based on the products identified, the sequential degradation process was proposed, including the interlace reactions involving quinoid oxidation, reductive dechlorination, and no-enzyme polymerization. Upon reaction optimization, a piston flow reactor (PFR) was designed to treat the continuous feeding of simulated wastewater containing PCP and 2,4-DCP. After a 128 h period of treatment, 87.4-99.5% total concentration of CPs were removed (PPL removed 99.7% PCP and 99.2% 2,4-DCP; LPP removed 95.9% PCP and 78.9% 2,4-DCP).     

Activity of Desulfitobacterium sp. strain Viet1 demonstrates bioavailability of 2,4-dichlorophenol previously sequestered by the aquatic plant Lemna minor

Aquatic plants take up and sequester organic contaminants such as chlorophenols through incorporation in cell wall materials and storage in vacuoles. The ultimate fate of plant-sequestered chlorophenols, however, remains unclear. This research investigated 2,4-dichlorophenol (2,4-DCP) sequestration by the aquatic plant Lemna minor and evaluated contaminant release and bioavailability after plant death and cellular disruption. 14C-labeled 2,4-DCP was used to establish that contaminant removed from the aqueous phase was retained internal to L. minor. An assay with Desulfitobacterium sp. strain Viet1 was used to assess the readily bioavailable fraction of plant-sequestered 2,4-DCP and plant metabolites of 2,4-DCP. In plant-free systems, strain Viet1 dechlorinated 2,4-DCP to stoichiometric amounts of 4-chlorophenol (4-CP) as a stable and quantifiable end product. Anaerobic microcosms containing inactivated L. minor, which had accumulated 3.8 micromol of 2,4-DCP equivalents/g of plant material (fresh weight) during a preceding aerobic exposure, were inoculated with strain Viet1. After 118 d of incubation with strain Viet1, 43.5% (+/-1.4%) of the contaminant was recovered as 4-CP, indicating a large portion of plant-sequestered 2,4-DCP was bioavailable for dechlorination by strain Viet1. In contrast, 4-CP formation was not observed in autoclaved microcosms, and only 26.1% (+/-1.0%) of plant-sequestered 2,4-DCP was recovered in the aqueous phase. These findings demonstrate contaminant cycling between plants and microorganisms, and emphasize that understanding the mechanisms and pathways of contaminant sequestration by plants is critical for predicting long-term contaminant fate.     

Design of BDD-TiO2 hybrid electrode with P-N function for photoelectroatalytic degradation of organic contaminants

P-N hybrid electrode of boron-doped diamond (BDD) and TiO2 were designed and fabricated via selective deposition of TiO2 onto BDD electrode. This hybrid electrode exhibit high photoelectrocatalytic activities toward degradation of acid orange II (AOII) and 2, 4-dichloropheonl (2,4-DCP) due to the P-N effect and high electrocatalytic and photocatalytic activities of BDD electrode and TiO2 particles. The structures of TiO2 and BDD were confirmed by Raman spectra analysis. Atom force microscopy and scanning electron microscopy showed that the TiO2 deposits consist of adherent nanomicro-sized particles, scattered on the BDD substrate. AOII and 2,4-DCP in a solution can be efficiently degraded at the hybrid electrode in the photoelectrocatalysis (PEC) process. Effect of applied bias potentials and solution pH values on AOII and 2,4-DCP degradation were investigated. In the electro-oxidation process, some intermediates such as phenols were detected and they accumulated with the reaction evolution based on the analysis of UV-vis and GC-MS variation. By contrast, phenols intermediates will be degraded with the reaction evolution in the photoelectrocatalysis process. And, organic aromatic and aliphatic carboxylic acids were detected. Furthermore, different degradation mechanism of AOII and 2,4-DCP in the electro-oxidation, photocatalysis, and photoelectrocatalysis is proposed.     

Occurrence of 2,4-dichlorophenol and of 2,4-dichloro-6-nitrophenol in the Rhone River Delta (Southern France)

The compounds 2,4-dichlorophenol (2,4-DCP) and 2,4-dichloro-6-nitrophenol (6-nitro-2,4-DCP) have been detected at microg L(-1) levels (10(-9)-10(-8) M) during the summer season 2005 in the water of the Rh?ne river delta. Compound 2,4-DCP would mainly derive from the transformation of the herbicide dichlorprop, heavily used in flooded rice farming (1400 kg in the delta region in 2005), in addition to being an impurity of the commercial herbicide. Field data show a fast concentration decrease of 2,4-DCP in the period June 21st to July 5th, accompanied by a corresponding increase of 6-nitro-2,4-DCP. This could imply a possible nitration process of 2,4-DCP into 6-nitro-2,4-DCP, with quite elevated yield (33%). Nitration of 2,4-DCP can be induced by photoproduced *NO2, the reaction kinetics (calculated in the presence of Fe(III) + nitrite under irradiation as model system) being d[6-nitro-2,4-DCP]/dt = 650 [2,4-DCP] [*NO2]. Interestingly, the yield of the process (38%) is similar to that suggested by field data. An indirect assessment of [*NO2] in surface water in different sites of the Rh?ne delta indicated that 2,4-DCP could be transformed into 6-nitro-2,4-DCP in a couple of weeks or less in the shallow water (10 cm depth) of the rice fields, a time scale that is compatible with field data. Photonitration of 2,4-DCP is thus a possible process to account for the occurrence of 6-nitro-2,4-DCP in the Rh?ne delta.     

GC-MS法分析不同产地酿酒葡萄的香气成分

以昌黎和蓬莱的酿酒葡萄浆果为试验材料,采用水蒸汽蒸馏法提取赤霞珠、玫瑰香和蛇龙珠葡萄浆果中的香气成分,并用气相色谱-质谱对样品进行分析。结果表明,6个样品共检出85种香气成分,以醇类和酯类最为主。在检出的香气物质中,棕榈酸和2,4-二叔丁基苯酚是6个样品共有的,同时在蓬莱蛇龙珠中还检出具有强抗癌抑癌活性的镰叶芹醇。说明相同成分在同一品种中的含量相差不大,但微量香气成分有较大差别,为葡萄酒原产地保护提供了理论依据。     

漂白废水中氯酚光催化降解及其动力学研究

氯酚是纸浆漂白废水中常含有的有毒、难降解污染物,本文研究了4-氯酚和2,4-二氯酚在负载纳米TiO2膜的反应器中的降解.结果显示,在TiO2和UV同时存在的情况下才能有效地光催化降解废水中的氯酚,光照强度越大,PH值越高,氯酚的去除率也越高;TiO2光催化氧化氯酚水溶液的动力学可以用L-H动力学方程描述,加入少量H2O2,仍遵守一级动力学反应,而且能增大表观一级反应速率常数.     

活性炭吸附脱除废水中2,4-二氯苯酚的研究

2,4-二氯苯酚(2,4-DCP)毒性大、难降解,是化工、农药、染料、防腐剂等行业废水中常见的有机污染物。本文以活性炭为吸附剂处理含2,4-DCP的废水,考察了pH、活性炭添加量、吸附时间、2,4-DCP浓度以及活性炭使用次数对废水处理能力的影响。实验结果表明,pH、活性炭添加量、吸附时间、2,4-DCP浓度对2,4-DCP的去除率影响显著;在293K温度下,浓度为100mg/L的2,4-DCP废水,在pH为5、活性炭添加量为50mg、吸附处理100min后,2,4-DCP的去除率可达99.5%。实验表明,含2,4-DCP的废水处理后符合国家综合污水一级排放标准,为污水处理设计、工程建设等提供了有价值的实验数据。     

Catalytic activity of laccase hosted in reversed micelles

Nanostructured reversed micelles induce a high laccase activity in organic solvents, because enzymes can maintain their highly dimensional structure in water pools of reversed micelles [RMs]. Laccase attracts considerable attention as a novel industrial enzyme due to its high capability to catalyze the oxidation of aromatic compounds. The catalytic activities of lyophilized laccase and laccase entrapped in RMs were compared using an oxidative reaction. Laccase hosted in an anionic RM effectively catalyzed the oxidative reaction in various organic solvents, while lyophilized laccase exhibited no such catalytic activity. To optimize the preparation and reaction conditions for laccase in RMs, we examined the effects of pH of water pools of RMs, the concentrations of both enzyme and surfactant for the preparation of RMs, the hydration ratio (Wo), and the reaction temperature on laccase catalytic activity in organic media. Laccase entrapped in RMs exhibited the highest catalytic activity in isooctane under the following conditions: bis-2-ethylhexyl sulfosuccinate sodium salt (AOT) of 100 mM, pH 6.0, Wo=40, and reaction temperature of 60 degrees C. Under the optimum conditions, environmental pollutants such as bisphenol A, 2,4-dichlorophenol and 2,4,6-trichlorophenol were effectively degraded in 3 h.     

Adsorption of aromatic compounds from water by treated carbon materials

Carbon materials with different textural and surface chemistry properties have been studied to analyze their behavior in removing aromatic compounds (phenol, o-chlorophenol, p-nitrophenol, aniline, and phenol compound mixtures) from water. A mesoporous high surface area graphite and a microporous activated carbon with (HSAGox and ACox) and without (HSAGT and ACT) oxygen surface groups, were used as adsorbents. Apparent surface areas, surface oxygen groups, and zero points of charge have been determined. The adsorption behavior of single compounds on ACT depends on the relation between the molecular and the pore sizes. The aniline, the nitrophenol, and the chlorophenol interact with the oxygen surface groups of oxidized graphite, while there is no evidence of any type of interaction of the phenol with these groups. The adsorption of the organic compound mixtures on the thermally treated samples is determined by the acid-base character of the adsorbate-adsorbent, whereas on the oxidized carbons, the controlling forces are the specific interactions between organic molecules and the oxygenated groups. Selectivity coefficients for the different mixtures are presented over the entire range of adsorption.     

普洱生茶在贮藏过程中香气成分的变化

为了考察普洱生茶贮藏前后的品质变化,在不同贮藏温度度进行贮藏,对其进行感官评价,并进行气相色谱- 质谱分析。结果表明：普洱生茶在(25 ± 1)℃贮藏3 个月与8 个月的香气成分变化显著,而在(35 ± 1)℃条件下贮藏3 个月与8 个月所产生的香气成分种类和含量变化不显著,但与贮藏前相比,变化显著。贮藏8 个月后,(25 ± 1)℃和(35 ± 1)℃条件下贮藏的茶样中同时检测出15 种新出现的香气成分,主要为β - 紫罗兰酮环氧化物、茉莉酮、邻苯二甲酸二辛酯、苯酚衍生物。结果表明,贮藏时间和温度对普洱生茶香气成分变化有重要作用,8 个月的贮藏对改善普洱生茶的香气有显著效果。     

Identification of migrants from nitrile-butadiene rubber gloves

Polyvinyl chloride gloves containing di(2-ethylhexyl) phthalate are restricted for food contact use. In their place, disposable gloves made from nitrile-butadiene rubber (NBR) are used in contact with foodstuffs. Some unknown substances were found to migrate into n-heptane from NBR gloves. By GC/MS, HR-MS and NMR, their chemical structures were confirmed to be 2,2,4-trimethyl-1,3-pentanediol diisobutyrate (used as a plasticizer), 4,4'-butylidenedi(6-tert-butyl-m-cresol), a mixture of styrenated phenols consisting of 2-(alpha-methylbenzyl)phenol, 4-(alpha-methylbenzyl)phenol, 2,6-di(alpha-methylbenzyl)phenol, 2,4-di(alpha-methylbenzyl)phenol and 2,4,6-tri(alpha-methylbenzyl)phenol (used as antioxidants), and 2,4-di-tert-butylphenol, which seems to a degradation product of antioxidant. Migration levels of these compounds were 1.68 micrograms/cm2 of 2,4-di-tert-butylphenol, 2.80 micrograms/cm2 of 2,2,4-trimethyl-1,3-pentanediol diisobutyrate, 46.08 micrograms/cm2 of styrenated phenols and 4.22 micrograms/cm2 of 4,4'-butylidenedi(6-tert-butyl-m-cresol) into n-heptane, respectively. The content of total styrenated phenols was 6,900 micrograms/g in NBR gloves.     

基于主成分分析和HS-SPME-GC-MS技术综合评价不同品种芒果品质特性

为表征台农、象牙和金煌三种芒果的品质特性,本文通过测定其主要品质指标,利用主成分分析法(PCA),构建芒果主要品质综合评分模型,并采用HS-SPME-GC-MS技术对其挥发性风味物质进行分析,综合评价其品质。结果表明,金煌的可溶性固形物、总糖含量和糖酸比最高,分别为19%、24.18 mg/g和10.86;台农的V_C和总酚含量最高,分别达9.52 mg/100 g和1.03 mg/g;主成分分析结果表明,台农的综合得分最高,其次为金煌,象牙的综合得分最低。HS-SPME-GC-MS技术从三种芒果中共检测出116种挥发性风味物质,主要包括烯烃类、酚类和醛类等8类物质。台农和象牙的挥发性化合物以烯烃类为主,相对含量分别为45.52%和58.12%,金煌中以酚类物质为主,相对含量为56.88%。通过ROAV分析法共确定了15种关键风味化合物,其中台农和象牙香气贡献最大的物质为(E,Z)-2,6-壬二烯醛,金煌香气贡献最大的是3-己烯醛。台农呈柑橘香、甜香等芳香气味,象牙具有黄瓜香特征风味,而金煌含有特殊的木香气味,该风味主要由2,4-二叔丁基苯酚所贡献。综合分析认为,台...     

Synergy of combining sonolysis and photocatalysis in the degradation and mineralization of chlorinated aromatic compounds

Merits of using advanced oxidation processes such as sonolysis and photocatalysis as well as a combination of the two have been explored using model herbicides such as 2,4-dichlorophenoxy acetic acid and 2,4-dichlorophenoxypropionic acid and the chlorinated phenols 2,4-dichlorophenol and 2,4,6-trichlorophenol. Whereas sonolysis is quite effective in the initial degradation of chlorinated aromatic molecules, complete mineralization is difficult to achieve. Photocatalysis is selective toward the degradation of polar compounds but causes the build up of undesirable chemical intermediates. In contrast to sonolytic degradation, photocatalysis is very effective toward achieving complete mineralization. By simultaneously carrying out high-frequency sonolysis and photocatalysis we have succeeded in achieving faster and complete mineralization with no build up of toxic intermediates even at very low catalyst loadings. The synergy of combining the two advanced oxidation processes is discussed.     

Chlorophenol stress affects aromatic amino acid biosynthesis-a genome-wide study

Chlorophenols are a class of chemicals commonly used in preservatives, disinfectants, algaecides, herbicides and pesticides. However, there is a growing evidence that these compounds are a threat to human health. This is alarming as many chlorophenols are common pollutants found in the global environment at potentially biohazardous levels. Despite chlorophenols being abundant, widely used and poisonous, we know relatively little about their mechanism of toxicity in eukaryotes. Thus, we performed genome-wide growth screens using Saccharomyces cerevisiae to understand the molecular basis of chlorophenol toxicity. Of ～4850 single gene knockout strains tested, 393 mutants showed growth sensitivity to treatment with 4-chlorophenol (4-CP), 2,4-dichlorophenol (2,4-DCP) or pentachlorophenol (PCP). Only eight mutants showed growth hypersensitivity to all the three treatments and harboured deletions in genes important for aromatic amino acid biosynthesis (ARO1, ARO7) or mitochondrial protein synthesis and respiration (ATP5, ISA1, RML2, GET2, SLS1, MRPL38).     

Biodegradation of p-nitrophenol by aerobic granules in a sequencing batch reactor

In this study, aerobic granules to treat wastewater containing p-nitrophenol (PNP) were successfully developed in a sequencing batch reactor (SBR) using activated sludge as inoculum. A key step was the conditioning of the activated sludge seed to enrich for biomass with improved settleability and higher PNP degradation activity by implementing progressive decreases in settling time and stepwise increases in PNP concentration. The aerobic granules were cultivated at a PNP loading rate of 0.6 kg/ m3 x day, with glucose to boost the growth of PNP-degrading biomass. The granules had a clearly defined shape and appearance, settled significantly faster than activated sludge, and were capable of nearly complete PNP removal. The granules had specific PNP degradation rates that increased with PNP concentration from 0 to 40.1 mg of PNP/L, peaked at 19.3 mg of PNP/(g of VSS) x h (VSS = volatile suspended solids), and declined with further increases in PNP concentration as substrate inhibition effects became significant. Batch incubation experiments show that the PNP-degrading granules could also degrade other phenolic compounds, such as hydroquinone, p-nitrocatechol, phenol, 2,4-dichlorophenol, and 2,6-dichlorophenol. The PNP-degrading granules contained diverse microbial morphotypes, and PNP-degrading bacteria accounted for 49% of the total culturable heterotrophic bacteria. Denaturing gradient gel electrophoresis analysis of 16S rRNA gene fragments showed a gradual temporal shift in microbial community succession as the granules developed from the activated sludge seed. Specific oxygen utilization rates at 100 mg/L PNP were found to increase with the evolution of smaller granules to large granules, suggesting that the granulation process can enhance metabolic efficiency toward biodegradation of PNP. The results in this study demonstrate that it is possible to use aerobic granules for PNP biodegradation and broadens the benefits of using the SBR to target treatment of toxic and recalcitrant organic compounds.     

Phenolic antioxidants inhibit the triplet-induced transformation of anilines and sulfonamide antibiotics in aqueous solution

Recent studies have shown that dissolved organic matter (DOM) may inhibit the excited triplet-induced oxidation of several aromatic water contaminants, in particular those containing an aniline functionality. Such an inhibition was ascribed to antioxidant moieties of DOM. The present study was conducted with the aim of verifying whether well-defined antioxidants could act as inhibitors in analogy to DOM. Various substituted phenols exhibiting antioxidant character were able, at micromolar concentration, to slow down the photoinduced depletion of several anilines and sulfonamides in aerated aqueous solution containing 2-acetonaphthone as the photosensitizer. A concomitant accelerated degradation of the phenols in the presence of such contaminants was observed. This reinforces the hypothesis of reduction of oxidation intermediates of the contaminants by the phenols. Phenol (unsubstituted) was found to be a useful inhibitor even in the case of DOM-photosensitized transformations. Phenolic antioxidants are proposed as diagnostic tools to investigate the aquatic photochemistry of aromatic amines.     

大麦酚类化合物及相关酶类的研究进展

大麦作为重要的粮食作物和啤酒酿造原料,其中的酚类化合物及其相关酶类（如酚类合成酶——苯丙氨酸解氨酶,酚类氧化酶——过氧化物酶和多酚氧化酶）对大麦的生长发育起重要的调节和保护作用,而在大麦的加工过程中会影响产品质量,如过氧化物酶和多酚氧化酶的氧化产物（苯醌和聚合产物）直接影响食品的质量。本文综述了大麦籽粒中酚类化合物及相关酶的种类和功能,并分析了对食品工业和啤酒酿造的影响。     

Volatile components of raw and smoked black bream (Brama raii) and rainbow trout (Oncorhynchus mykiss) studied by means of solid phase microextraction and gas chromatography/mass spectrometry

Solid phase microextraction followed by gas chromatography/mass spectrometry of raw and smoked black bream and rainbow trout was carried out. The volatile components of the raw fish belong to a limited number of groups of compounds. Raw black bream has a higher presence of acids than raw trout, while the latter contains more alcohols, hydrocarbons, esters and phenol derivatives; both contain similar concentrations of saturated aldehydes. The volatiles of the smoked fish basically comprise the compounds also detected in the raw fish together with others produced during the processing. Smoke components detected in both smoked fish species were mainly phenol, guaiacol and syringol derivatives, ketones, acetic acid and some polycyclic aromatic hydrocarbons. Smoked black bream contained a higher number and higher concentrations of smoke components than smoked rainbow trout. Large variations in concentrations of smoke components in the smoked fish samples indicated that the smoking process had not been totally homogeneous. The presence of autoxidatively derived compounds, such as unsaturated aldehydes, was mainly detected in some smoked bream samples, showing that this degradation process is not occurring homogeneously. The usefulness of the applied techniques for the study of volatile components of raw and smoked fish is shown. © 2002 Society of Chemical Industry     

氧化还原酶及其在纺织染整中的应用

介绍了酶的分类以及主要氧化还原酶,如过氧化氢酶、漆酶、葡萄糖氧化酶、过氧化物酶等的特点和作用机理,详细介绍了氧化还原酶在纺织染整加工中的应用和存在的问题。     

Enrichment and characterization of chlorinated organophosphate ester-degrading mixed bacterial cultures

Chlorinated organophosphate ester (OPE)-degrading enrichment cultures were obtained using tris(2-chloroethyl) phosphate (TCEP) or tris(1,3-dichloro-2-propyl) phosphate (TDCPP) as the sole phosphorus source. In cultures with 46 environmental samples, significant TCEP and TDCPP degradation was observed in 10 and 3 cultures, respectively, and successive subcultivation markedly increased their degradation rates. 67E and 45D stable enrichment cultures obtained with TCEP and TDCPP, respectively, completely degraded 20 muM of the respective compounds within 6 h and also the other, although the degradation rate of TCEP by 45D was relatively slow. We confirmed chloride ion generation on degradation in both cases and the generation of 2-chloroethanol (2-CE) and 1,3-dichloro-2-propanol (1,3-DCP) as metabolites of TCEP and TDCPP, respectively. 67E and 45D also showed dehalogenation ability toward 2-CE and 1,3-DCP, respectively. Addition of inorganic phosphate did not significantly influence their ability to degrade the chlorinated OPEs but markedly increased their dehalogenation ability, which was maximum at 0.2 mM of inorganic phosphate and decreased at a higher concentration. Denaturing gradient gel electrophoresis analysis showed that dominant bacteria in 67E are related to Acidovorax spp. and Sphingomonas spp. and those in 45D are Acidovorax spp., Aquabacterium spp., and Sphingomonas spp. This analysis indicated the relationship of the Sphingomonas- and Acidovorax-related bacteria with the cleavage of the phosphoester bond and dehalogenation, respectively, in both cultures. This is the first report on bacterial enrichment cultures capable of degrading both TCEP and TDCPP.