利用某尾矿制备纳米SiO2

采用固相熔融法从尾矿中提取SiO2,利用超声辅助化学沉淀法制备纳米SiO2。分别研究了NaOH与尾矿质量比、反应温度、反应时间对SiO2提取率的影响,以及溶解水量、HCl浓度、终点pH、超声波功率和超声波频率对纳米SiO2性能的影响,研究表明,当NaOH与尾矿的质量比为1.4∶1,温度为325℃时灼烧25 min后用100 mL水溶解,滴加1.6 mol/LHCl酸化沉淀,终点pH调至8.5,在超声功率100 W,超声频率28 Hz的条件下,尾矿中SiO2提取率达到98.0%,产物中SiO2含量为98.40%,平均粒度为18 nm,得到的产品符合国家标准。     

气液两相旋流喷嘴雾化特性

为提高烟尘净化用喷嘴的雾化性能,提出一种气液两相旋流喷嘴,用CFX软件对该喷嘴内部流场模拟的结果表明,强烈的气旋作用使液流呈环状,使气液混合流在达到喷嘴末端时易于破碎成雾。在实验室条件下,利用Winner313型喷雾激光粒度分析仪对喷嘴进行了雾化粒度测定,分析发现雾滴中位径与气液比的关系呈幂函数衰减,这一规律将有助于在工程应用时确定喷嘴工况。     

Interaction of bisphenol A with dissolved organic matter in extractive and adsorptive removal processes

The fate of endocrine disrupting chemicals (EDCs) in natural and engineered systems is complicated due to their interactions with various water constituents. This study investigated the interaction of bisphenol A (BPA) with dissolved organic matter (DOM) and colloids present in surface water and secondary effluent as well as its adsorptive removal by powdered activated carbons. The solid phase micro-extraction (SPME) method followed by thermal desorption and gas chromatography-mass spectrometry (GC-MS) was utilized for determining the distribution of BPA molecules in water. The BPA removal by SPME decreased with the increased DOM content, where the formation of BPA-DOM complexes in an aqueous matrix was responsible for the reduced extraction of BPA. Colloidal particles in water samples sorbed BPA leading to the marked reduction of liquid phase BPA. BPA-DOM complexes had a negative impact on the adsorptive removal of BPA by powered activated carbons. The complex formation was characterized based on Fourier transform infrared (FTIR) and ultraviolet-visible (UV-Vis) spectroscopy, along with the calculation of molecular interactions between BPA and functional groups in DOM. It was found that the hydrogen bonding between DOM and BPA would be preferred over aromatic interactions. A pseudo-equilibrium molecular coordination model for the complexation between a BPA molecule and a hydroxyl group of the DOM was developed, which enabled estimation of the maximum sorption site and complex formation constant as well as prediction of organic complexes at various DOM levels.     

Validation and use of in vivo solid phase micro-extraction (SPME) for the detection of emerging contaminants in fish

A variety of emerging chemicals of concern are released continuously to surface water through the municipal wastewater effluent discharges. The ability to rapidly determine bioaccumulation of these contaminants in exposed fish without sacrificing the animal (i.e. in vivo) would be of significant advantage to facilitate research, assessment and monitoring of their risk to the environment. In this study, an in vivo solid phase micro-extraction (SPME) approach was developed and applied to the measurement of a variety of emerging contaminants (carbamazepine, naproxen, diclofenac, gemfibrozil, bisphenol A, fluoxetine, ibuprofen and atrazine) in fish. Our results indicated in vivo SPME was a potential alternative extraction technique for quantitative determination of contaminants in lab exposures and as well after exposure to two municipal wastewater effluents (MWWE), with a major advantage over conventional techniques due to its ability to non-lethally sample tissues of living organisms.     

The toxicity of composted sediments from Mediterranean ports evaluated by several bioassays

This work investigates the ecotoxicological evaluation of contaminated dredged sediments from French Mediterranean navy harbour (A), commercial port (B) and two composite specimens (C) and (D) coming from the mixture of A and B with other port sediments. The toxicity of elutriates from these sediments is estimated using embryo-toxicity test, Microtox® solid phase test, LuminoTox, phytotoxicity tests and genotoxicity test. Bioassay responses are not clearly correlated with chemical contamination in the whole sediment and vary as a function of tested organisms. The highest contaminated samples (A and C) are almost always more toxic than the less contaminated samples (B and D). Among composite sediments, the mixture effect with other sediments is not efficient to decrease toxicity in sample C, suggesting that other parameters influence toxicity level such as particle size or organic matter content. These parameters should be taken into consideration in order to improve the efficiency of the mixture process and produce composite sediments with low toxicity.     

Removal of carotene-like colored compounds by liquid-liquid extraction during polycyclic aromatic hydrocarbons analysis of plant tissue

Plants contain a wide variety of chemicals, some of which may have similar chromatographic behavior to polycyclic aromatic hydrocarbons (PAHs). During solid phase extraction (SPE) with Si-gel for instance, the co-elution of carotene-like colored compounds with PAHs has been observed. In this paper, liquid–liquid extraction was applied for the separation and subsequent analysis of PAHs from plant extracts. PAHs containing 2–6 rings, which include naphthalene, phenanthrene, pyrene, benzo[a]pyrene and benzo[ghi]perylene, were used as representative target chemicals. Carotene-like compounds extracted from Komatsuna (Brassica campestris) shoot by acetone followed by Si-gel treatment were incorporated as undesired components in the model matrix. Results showed the feasibility of employing either acetonitrile or 2% (w/v) KOH–methanol as solvents for high PAHs recovery and low extraction of colored fraction. For acetonitrile, 86.9–93.5% of each PAH could be recovered after three extraction cycles (relative standard deviation, RSD < 1.6%) with only about 10% co-extraction of colored fraction. For 2% KOH–methanol, PAHs recoveries ranging from 79.3% to 83.1% after five cycles (RSD < 1.5%) were achieved while the percent extraction of colored fraction was also low at 10%. The relatively higher selectivity of the solvents for PAHs over the colored fraction as well as the solubility of the matrix solution in the solvent may have contributed to these results. On this basis, liquid–liquid extraction is very useful for the pre-treatment of plant extracts for PAHs analysis.     

Biodegradation of mono-alkyl phthalate esters in natural sediments

Mono-alkyl phthalate esters (MPEs) are primary metabolites of di-alkyl phthalate esters (DPEs), a family of industrial chemicals widely used in the production of soft polyvinyl chloride and a large range of other products. To better understand the long term fate of DPEs in the environment, we measured the biodegradation kinetics of eight MPEs (-ethyl, -n-butyl, -benzyl, -i-hexyl, -2-ethyl-hexyl, -n-octyl, -i-nonyl, and -i-decyl monoesters) in marine and freshwater sediments collected from three locations in the Greater Vancouver area. After a lag period in which no apparent biodegradation occurred, all MPEs tested showed degradation rates in both marine and freshwater sediments at 22 °C with half-lives ranging between 16 and 39 h. Half-lives increased approximately 8-fold in incubations performed at 5 °C. Biodegradation rates did not differ between marine and freshwater sediments. Half-lives did not show a relationship with increasing alkyl chain length. We conclude that MPEs can be quickly degraded in natural sediments and that the similarity in MPE degradation kinetics among sediment types suggests a wide occurrence of nonspecific esterases in microorganisms from various locations, as has been reported previously.     

Determination of phenolic and steroid endocrine disrupting compounds in environmental matrices

BACKGROUND, AIM AND SCOPE: Many pollutants have received significant attention due to their potential estrogenic effect and are classified as endocrine disrupting compounds (EDCs). EDCs comprise many classes of organic compounds. The development or optimization of analytical protocols for the simultaneous determination of EDCs in environmental samples is an analytical challenge because these compounds exhibit different physicochemical characteristics, they occur in the aquatic environment in relatively low concentrations and, furthermore, environmental samples are considered as complex matrices. The aim of this study is the development of analytical methods for the simultaneous determination of phenolic and steroid EDCs in aqueous and solid samples. The target compounds are 4-nonylphenol, 4-octylphenol, their ethoxylate oligomers (mono- and di-ethoxylates of nonylphenol and octylphenol), bisphenol A, the estrogens (estriol, estrone, 17beta-estradiol, 17alpha-estradiol) and the synthetic steroids (mestranol and 17alpha-ethynylestradiol). MATERIALS AND METHODS: Solid phase extraction employing Oasis HLB cartridges and different elution solvents was used for the recovery studies of the target compounds from various types of water samples (ultrapure water, artificial seawater, river water and seawater). Ultrasonic assisted extraction was applied for the recovery of the target EDCs from the solid samples. The recoveries were assessed using various solvents for the extraction and the elution of EDCs from different SPE cartridges used for clean up. Gas chromatography-mass spectrometry after derivatization with N,O-bis(trimethylsilyl)-trifluoroacetamide was employed for the determination of these compounds. RESULTS AND DISCUSSION: The recovery rates of three elution solvents (methanol, acetone and ethylacetate) for the extraction of target EDCs from artificial seawater were assessed after preconcentration on SPE cartridges. Acetone showed better recoveries and was further tested for its extraction efficiency in different water types (river water, seawater). Ultrasonic assisted extraction was used for the recovery of target EDCs from solid matrices. Acetone, methanol, mixture of acetone-methanol (1:1) and ethylacetate were used as extraction solvents. Ethylacetate and the mixture of acetone-methanol (1:1) exhibited better extraction efficiencies. An additional clean up step was necessary for sediment samples. Different SPE cartridges were employed for clean up of the extracts (Oasis HLB, C18, Florisil, silica, combination of silica and alumina). Florisil cartridges were finally used. The proposed methods were further validated on the determination of target EDCs in field collected samples (river water, seawater, wastewater, total suspended solids and sediments) from the major area of Thessaloniki, Greece. CONCLUSIONS: Efficient and accurate integrated methods for the simultaneous determination of alkylphenols (nonylphenol, octylphenol), their ethoxylate oligomers (mono- and di-ethoxylate of nonylphenol and octylphenol), bisphenol A and steroids (estriol, estrone, 17beta-estradiol, 17alpha-estradiol, mestranol and 17alpha-ethynylestradiol) in aqueous and solid samples were developed. The proposed methods were applied for the determination of the target compounds in representative environmental samples in the area of Thessaloniki, Northern Greece. RECOMMENDATIONS AND PERSPECTIVES: This study confirms the occurrence of selected EDCs in inland and marine waters in the area of Thessaloniki, Northern Greece. Since there is no previous data on the occurrence of the target EDCs in the major area, an extended survey is in progress to evaluate the occurrence and fate of these compounds.     

Analysis of a gas-phase partitioning tracer test conducted in an unsaturated fractured-clay formation

The gas-phase partitioning tracer method was used to estimate non-aqueous phase liquid (NAPL), water, and air saturations in the vadose zone at a chlorinated-solvent contaminated field site in Tucson, AZ. The tracer test was conducted in a fractured-clay system that is the confining layer for the underlying regional aquifer. Three suites of three tracers were injected into wells located 14, 24, and 24 m from a single, central extraction well. The tracers comprised noble gases (traditionally thought to be nonsorbing), alkanes (primarily water partitioning), perfluorides (primarily NAPL partitioning), and halons (both NAPL and water partitioning). Observations of vacuum response were consistent with flow in a fractured system. The halon tracers exhibited the greatest amount of retardation, and helium and the perfluoride tracers the least. The alkane tracers were unexpectedly more retarded than the perfluoride tracers, indicating low NAPL saturations and high water saturations. An NAPL saturation of 0.01, water saturation of 0.215, and gas saturation of 0.775 was estimated based on analysis of the suite of tracers comprising helium, perfluoromethylcyclohexane and dibromodifluoromethane, which was considered to be the most robust set. The estimated saturations compare reasonably well to independently determined values.