固相微萃取气相色谱法测定浓海水中氯酚含量的不确定度评定

建立固相微萃取气相色谱法测定浓海水中2,4,6-三氯酚和五氯酚,并进行了测量结果不确定度评定。重点分析了样品采集、标准溶液制备、校准曲线回归、前处理方法等分量引入的不确定度,合成标准不确定度,通过乘以95%概率下的扩展因子2,获得测量结果的扩展不确定度。     

钴铈复合氧化物催化降解2,4,6-三氯酚

采用溶胶-凝胶法制备了一种疏松多孔的钴铈复合氧化物,该复合氧化物具有较大的比表面积和孔体积。并以废水中一定浓度的2,4,6-三氯酚作为模型化合物,研究自制的钴铈复合氧化物对水中的2,4,6-三氯酚的催化降解效果。研究结果表明,自制的钴铈复合氧化物所具有的氧化还原性能以及协同催化作用使其对废水中的2,4,6-三氯酚具有一定的催化降解活性。初始溶液的pH值对降解影响较大,酸性条件更有利于2,4,6-三氯酚的降解。100 mg自制的钴铈复合氧化物与10 mL 100 mg/L的2,4,6-三氯酚在25℃下恒温振荡30 h,2,4,6-三氯酚的降解率可达到86.3%,溶液中可被氧化的有机物含量下降了36.7%。     

水解-接触氧化工艺处理纺织综合废水

广东省溢达纺织有限公司纺织综合废水水质参数:pH=10～14,ρ(CODCr)=1000~1500mg/L,ρ(BOD5)=300~450mg/L,ρ(SS)=300mg/L,ρ(S2-)=3mg/L,水温40~50℃,色度400~600倍。采用水解酸化-生物接触氧化法处理,运行结果表明,处理后出水:pH=7～8,ρ(CODCr)=89mg/L,ρ(BOD5)=20mg/L,ρ(SS)=54mg/L,ρ(S2-)=0.8mg/L,色度31倍,符合排放要求。     

GFAAS测定地下水中铅的不确定度评定

对GFAAS测定地下水中铅的不确定度进行了评定。对测定过程引入的不确定度来源进行了分析,并对各不确定度分量进行了量化和合成,得出拟合校准标准曲线引入的相对不确定度分量是影响铅不确定度的主要分量,求得合成标准不确定度和扩展不确定度分别是0.44μg/L和0.88μg/L,并给出了测试结果:ρPb±U(Pb)=(40.47±0.88)μg/L。     

硅钼黄分光光度法测定可溶性二氧化硅的不确定度评定

根据国家能源局发布的标准《水电工程地质勘查水质分析规程可溶性二氧化硅-硅钼黄分光光度法》(NB/T 35052-2015),进行对可溶性二氧化硅不确定度的评定,系统分析并计算各不确定度分量和扩展不确定度。结果表明,所购买的标准溶液、标准工作曲线的拟合是影响不确定度的主要因素。通过计算得出当可溶性二氧化硅含量为8.01 mg/L时,其扩展不确定度为0.48 mg/L(k=2)。     

豆奶生产废水处理实例

采用气浮-水解酸化-五级生物接触氧化工艺处理豆奶类生产废水,在进水ρ(CODCr)=2000～4000mg/L,ρ(BOD5)=1000～1500mg/L,ρ(SS)=2000～3500mg/L,ρ(NH3-N)=38mg/L,ρ(动植物油)=250～300mg/L时,处理后出水的ρ(CODCr)<130mg/L,ρ(BOD5)<60mg/L,ρ(SS)<100mg/L,ρ(NH3-N)<20mg/L,ρ(动植物油)<20mg/L。该工艺运行便利,剩余污泥量小。     

酚试剂分光光度法测定公共场所空气中甲醛的不确定度评定

对影响酚试剂分光光度法测定公共场所空气中甲醛的因素进行辨别,根据测量不确定度评定方法,进行测定不确定度评定,通过计算和评定,得出该方法测定空气中甲醛的测量结果为0.156 mg/m~3时,取包含因子k=2(置信概率95%),扩展不确定度U=0.028 mg/m~3。从各分量对总不确定度的贡献来看,斜率分量对总不确定度的贡献最大,可通过提高人员标准溶液配制的准确性和采用更加精确和标准的量具来减小测量不确定度。     

蚌埠杨台子污水处理厂二期工程设计

蚌埠杨台子污水处理厂二期工程采用预处理-A~2O微曝氧化沟-深床滤池-紫外线消毒组合工艺处理城市污水,采用机械浓缩脱水工艺处理污泥。工程运行结果表明,在进水ρ(CODCr)=231.0~321.0 mg/L,ρ(BOD5)=85.0~142.0 mg/L,ρ(SS)=74.0~154.0 mg/L,ρ(NH3-N)=26.5~33.9 mg/L,ρ(TN)=28.9~35.6 mg/L,ρ(TP)=1.80~2.90 mg/L的情况下,出水水质指标达到或优于GB 18918—2002《城镇污水处理厂污染物排放标准》中一级A标准。介绍了工艺流程、主要处理构筑物工艺设计参数、设备性能参数,分析了工艺设计特点,简述了运行效果。     

基于QuEChERS液相色谱-串联质谱法测定茶叶中除虫脲残留量的不确定度评定

对茶叶中除虫脲残留量的液相色谱-串联质谱法(liquid chromatography-tandem mass spectrometry,LC-MS/MS)检测过程进行了研究,根据JJF 1059—1999《测量不确定度评定与表示》中有关规定,归纳测定过程中不确定度来源,并且对不确定度的各个分量进行了分析和合成。茶叶中除虫脲含量为0.503 mg/kg时,其扩展不确定度为0.028 mg/kg(k=2,P=95%)。评定结果显示,标准物质及配制基质标准曲线时产生的不确定度是不确定度的主要来源。     

连续流动注射法测定水中总氰化物的不确定度评定

总氰化物为高毒物质,侵入水体会造成水体污染。利用连续流动分析仪在线测定水中氰化物,通过分析测量过程中的不确定度来源,评定其A类和B类不确定度,计算不确定度分量、合成标准不确定度及扩展不确定度。结果表明,总氰化物测定值的合成标准不确定度u_c=0.00055 mg/L,扩展不确定度u_c=0.0011 mg/L,其中标准曲线拟合引入的不确定度对于合成不确定度的影响较大,属于主要的不确定度来源。     

石墨炉原子吸收法测定不锈钢食具镉镉元素迁移量的不确定度评估

石墨炉原子吸收法测定不锈钢食具镉元素迁移量的不确定度,依据测量不确定度的评定原理和方法,对GB/T 5009.81-2003中不锈钢食具乙酸浸泡液的镉迁移量进行不确定度来源分析,量化不确定度分量,最后得出扩展不确定度。当测量结果为0.000 30 mg/dm2,合成标准不确定度为0.000 013 mg/dm2,扩展不确定度为0.000 03 mg/dm2(包含因子k=2)。     

OPTIMIZATION OF PHOTOCATALYTIC PROCESS PARAMETERS FOR THE DEGRADATION OF 2,4,6-TRICHLOROPHENOL IN AQUEOUS SOLUTIONS

In the present study, the photocatalytic degradation of 2,4,6-trichlorophenol (2,4,6-TCP) was carried out in a batch reactor under UV light in aqueous solution for 5 h using titania P-25 (surface area 50 m²/g) as a photocatalyst and sodium hypochlorite as an oxidant. Variables studied include catalyst dose (0.25-1.25 g/L), pH (2-6), and concentration of the oxidant (3.06 × 10^-6M-15.3 × 10^-6M). The rate of degradation was studied in terms of changes in concentration of the pollutant and reduction in chemical oxygen demand. The optimal values of operational parameters leading to 2,4,6-TCP abatement were obtained by using response surface methodology. The percent degradation and COD reduction of 2,4,6-TCP was found to increase with increases in the catalyst dose up to the dose of 1.1 g/L, pH in the range of 4-4.5, and oxidant concentration of 9.95 × 10^-6M.     

水中三硝基甲苯质量控制标准物质的研制

研制了以三硝基甲苯为主要成分的水质计量用标准物质。用先密后疏的方式检验样品的稳定性,对样品的均匀性、稳定性分别采用单因素方差分析方法和线性模型进行考察,组织多个国内权威实验室对样品进行协作分析定值,并对定值结果进行合成标准不确定度和扩展不确定度评估。样品的定值结果为0.983 mg/L,扩展不确定度为0.046mg/L。均匀性指标符合国家标准物质的技术要求,稳定性可达24个月以上。可满足水质三硝基甲苯分析量值传递的需要,达到分析测试中质量保证的目的和要求。     

OPTIMIZATION OF PHOTOCATALYTIC PROCESS PARAMETERS FOR THE DEGRADATION OF 2,4,6-TRICHLOROPHENOL IN AQUEOUS SOLUTIONS

In the present study, the photocatalytic degradation of 2,4,6-trichlorophenol (2,4,6-TCP) was carried out in a batch reactor under UV light in aqueous solution for 5 h using titania P-25 (surface area 50 m²/g) as a photocatalyst and sodium hypochlorite as an oxidant. Variables studied include catalyst dose (0.25–1.25 g/L), pH (2–6), and concentration of the oxidant (3.06 × 10^?6M–15.3 × 10^?6M). The rate of degradation was studied in terms of changes in concentration of the pollutant and reduction in chemical oxygen demand. The optimal values of operational parameters leading to 2,4,6-TCP abatement were obtained by using response surface methodology. The percent degradation and COD reduction of 2,4,6-TCP was found to increase with increases in the catalyst dose up to the dose of 1.1 g/L, pH in the range of 4–4.5, and oxidant concentration of 9.95 × 10^?6M.     

自动电位滴定法测定水中总硬度的不确定度评定

依据测量不确定度的评定原理和方法,通过自动电位滴定法测定水中总硬度的实例,分析了测量重复性、取样、标准溶液浓度、标准溶液配制过程、滴定管、摩尔质量等因素对总硬度测量不确度的影响,确定不确定度数学模型,及不确定度报告的书写形式。在总硬度为103mg/L的水样测定中,测得其合成标准不确定度为0.6168mg/L,扩展不确定度为1.3mg/L。     

Mechanism of removing chlorophenolic compounds from solution by a water-insoluble cationic starch

The removal of three chlorophenolic compounds from solutions using highly crosslinked cationic starch containing a tertiary amine group was investigated. The three chlorophenolic compounds were 2-chlorophenol, 2,4-dichlorophenol and 2,4,6-trichlorophenol. The adsorption process predominated over the initial pH = 2∼6 for 2-chlorophenol, and predominated over the initial pH = 2 to 4 range for 2,4-dichlorophenol and 2,4,6-trichlorophenol. The ion-exchange process predominated at initial pH = 12 for 2-chlorophenol, and predominated over the initial pH = 10 to 12 range for 2,4-dichlorophenol and 2,4,6-trichlorophenol. Both processes coexist over the initial pH=8 to 10 range for 2-chlorophenol, and coexist over the initial pH = 6∼8 for 2,4-dichlorophenol and 2,4,6-trichlorophenol. Experimental results indicate that the adsorption process is initially pH-independent, and the ion-exchange process is initially pH-dependent. The adsorption and ion-exchange processes are concentration-dependent and correspond to the Langmuir isothermal adsorption. They are endothermic for 2-chlorophenol and 2,4-chlorophenol, and are exothermic for 2,4,6-chlorophenol. The ion-exchange capacity is larger than the adsorption capacity. Moreover, the order of the amount of three chlorophenolic compounds removed by the cationic starch is 2,4,6-chlorophenol > 2,4-dichlorophenol > 2-chlorophenol.     

Structural and Catalytic Differences between Two FADH(2)-Dependent Monooxygenases: 2,4,5-TCP 4-Monooxygenase (TftD) from Burkholderia cepacia AC1100 and 2,4,6-TCP 4-Monooxygenase (TcpA) from Cupriavidus necator JMP134

2,4,5-TCP 4-monooxygenase (TftD) and 2,4,6-TCP 4-monooxygenase (TcpA) have been discovered in the biodegradation of 2,4,5-trichlorophenol (2,4,5-TCP) and 2,4,6-trichlorophenol (2,4,6-TCP). TcpA and TftD belong to the reduced flavin adenine dinucleotide (FADH(2))-dependent monooxygenases and both use 2,4,6-TCP as a substrate; however, the two enzymes produce different end products. TftD catalyzes a typical monooxygenase reaction, while TcpA catalyzes a typical monooxygenase reaction followed by a hydrolytic dechlorination. We have previously reported the 3D structure of TftD and confirmed the catalytic residue, His289. Here we have determined the crystal structure of TcpA and investigated the apparent differences in specificity and catalysis between these two closely related monooxygenases through structural comparison. Our computational docking results suggest that Ala293 in TcpA (Ile292 in TftD) is possibly responsible for the differences in substrate specificity between the two monooxygenases. We have also identified that Arg101 in TcpA could provide inductive effects/charge stabilization during hydrolytic dechlorination. The collective information provides a fundamental understanding of the catalytic reaction mechanism and the parameters for substrate specificity. The information may provide guidance for designing bioremediation strategies for polychlorophenols, a major group of environmental pollutants.     

Liquid-liquid Extraction Methods to Determine Reductive Dechlorination of 2,4,6-trichlorophenol by Zero-valent Metals and Zero-valent Bimetals

Abstract

The reductive dechlorination of 2,4,6-trichlorophenol (2,4,6-TCP) was studied using zero-valent metals (ZVMs) and bimetals. A reliable extraction method was required to distinguish the removal by chemical transformation from the removal by physical adsorption on the ZVMs or bimetal. Three liquid–liquid extraction methods with ethyl acetate were evaluated by conducting mass recovery tests in the ZVM-chlorophenol systems. A typical liquid–liquid extraction showed low recoveries for 2,4,6-TCP and the reaction products while the modified liquid–liquid extraction involving acid addition gave increased recoveries. The Mg system needed an additional modification since the modified extraction method was not working on the Mg and Pd/Mg system. Pd/Fe and Pd/Zn gave the highest reaction rate for 2,4,6-TCP dechlorination, producing less or no chlorinated daughter compounds while the plain metals such as Fe and Zn showed much slower degradation rates for 2,4,6-TCP.