Enhanced naphthalene solubility in the presence of sodium dodecyl sulfate: effect of critical micelle concentration

Surfactants can increase the solubility of non-polar compounds, and have been applied in areas such as soil washing and treatment of non-aqueous phase liquids (NAPLs). This investigation explored the feasibility of removing vapor phase polycyclic aromatic hydrocarbon (PAH) from gases using an anionic surfactant. The solubility of vapor phase naphthalene was measured herein using gas chromatograph (GC) with a photon ionization detector (PID). The measurement results indicated that surfactant molecules were not favorable to micelle formation when temperatures increased from 25 degrees C to 50 degrees C. Regardless of whether solutions were quiescent or agitated, equilibrium naphthalene apparent solubility increased linearly with surfactant concentrations exceeding critical micelle concentration (CMC). The pH effects on naphthalene apparent solubility were small. Agitation increased naphthalene apparent solubility and lumped mass transfer coefficients. Furthermore, lumped mass transfer coefficients decreased with increasing surfactant concentration owing to increase in interfacial resistance and viscosity and decreased spherical micelle diffusion coefficients. Finally, the net absorption rate increased because the solubilization effects of micelles exceeded the reduction effects of mass transfer coefficient above the CMC. The enhanced naphthalene apparent solubility from the addition of surfactant can be expressed by an enrichment factor (EF). The EF value of naphthalene for the surfactant solution at 0.1 M with agitation at 270 rpm relative to quiescent water could reach 18.6. This work confirms that anionic surfactant can improve the removal efficiency of hydrophobic organic compound (HOC) from the gas phase.     

Development of supercritical carbon dioxide extraction with a solid phase trap for dioxins in soils and sediments

A method involving supercritical fluid extraction (SFE) with a solid phase trap containing activated alumina was investigated for the rapid analysis of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and dioxin like polychlorinated biphenyls (DL-PCBs) in soils and sediments. The samples were extracted by using supercritical carbon dioxide with water (2% versus CO(2) flow velocity) being used as an entrainer at a pressure of 30 MPa and a temperature of 130 degrees C for 50 min. The extracts were adsorbed on an activated alumina trap that was maintained at a temperature of 150 degrees C, and then, PCDD/DFs and DL-PCBs were eluted with 20 ml of hexane at 60 degrees C. After concentration, they were measured with a high-resolution gas chromatograph interfaced to a high-resolution mass spectrometric detector. The average concentrations of PCDD/DFs and DL-PCBs corresponded to the results obtained by the conventional method, and the reproducibility of this SFE method was below 21% of the relative standard deviations for all samples. The total time required for the analysis of the pretreatment of this method was only 2 h.     

Kinetics of the extraction of pyrene using carbon dioxide in dense phase

Bath extraction experiments of pyrene from two spiked soils with different textural composition (sandy, sandy-clay) were performed with near-critical and supercritical CO(2) at different pressures (7.5, 15, 20, 25 MPa) and temperatures (40, 50, 60 degrees C) in order to obtain mass transfer rate data. An empirical equation whose parameters depend on type of soil but are independent of pressure and temperature is proposed. The comparison between individual mass transfer coefficients shows that the extraction is controlled by the resistance within the particle. Effective diffusivities between 0.4 and 6.0 x 10(-10) m(2)/s are deduced.     

The negative rejection of H+ in NF of carbonate solution and its influences on membrane performance

Nanofiltration (NF) experiments were conducted with simulated solution containing bicarbonate hardness and with three membranes: NF90, NF270 and NF-. The operating pressure was kept at 1.0 MPa, the water sample temperature was kept at 25 degrees C, the velocity on membrane surface was approximately 1 m s(-1) and the feeding pH values were 6.0, 6.5, 7.0, 7.5 and 8.0. Except for sampling, both the concentrate and the permeate were cycled to the feeding tank in order to keep the concentration constant. Experimental results demonstrated that the flux of NF90 membrane was slightly affected by the feeding pH, while the flux of NF270 and NF membranes was augmented when the feeding was acidified. The permeate pH of each membrane was always lower than the concentrate pH, indicating that the H(+) was negative rejected. This phenomenon was observed not only in the filtration of carbonate solution, but also in the filtration of the NaCl solution and the tap water. It is assumed that the small positive H(+) can easily permeate the NF membranes having negative charges. The more charges the membrane has, the more H(+) is negative rejected. High permeability of H(+) can speed decomposition of HCO(3)(-) into CO(3)(2-) and then accelerate CaCO(3) crystallization on membrane surface, which is unfavorable for membrane performances. In NF processes, it is better to considerate the membrane's selection and the feeding's pretreatment simultaneously, and it is beneficial for preventing scaling when selecting the membranes with less negative charges if only the water qualify can meet the demands.     

NaNO(2)/FeCl(3) catalyzed wet oxidation of the azo dye Acid Orange 7

A combination of ferric chloride and sodium nitrite significantly improved the wet oxidation of the azo dye Acid Orange 7 (AO7) in acid aqueous media (pH 2.6) under moderate conditions (T=150 degrees C; oxygen pressure=0.5 MPa). To evaluate the catalytic system, wet oxidation of AO7 was carried out at temperatures between 90 and 150 degrees C and oxygen pressures ranging from 0.1 to 0.5 MPa. The effect of initial solution pH from 2.6 to 11.4 and the amount of catalyst on the degradation of AO7 were also investigated. AO7 initial concentration was kept 200 mg L(-1). The degradation process was monitored by UV-visible spectroscopy, HPLC, IC (ion chromatography), GC-MS and TOC analysis. At 150 degrees C and 0.5 MPa oxygen pressure, 56% TOC was removed after 4h of treatment, while no obvious TOC removal were achieved without catalyst at the same experimental condition. The main degradation products were some small organic acids: formic acid, acetic acid, pyruvic acid, oxalic acid, succinic acid (identified and quantified by IC) and phthalic acid (identified by GC-MS).     

预涂动态膜强化渗透与截留性能研究

以二氧化钛粉体材料为涂膜剂,陶瓷管为基膜制备预涂动态膜,引入通量增强系数Zi和截留增强系数Fi研究了预涂动态膜制备条件对其强化渗透与截留性能的影响,并用SEM电镜对预涂动态膜和基膜表面形貌进行表征。结果表明:制备的预涂动态膜表面均匀密实,其孔径低于基膜平均孔径。预涂动态膜的渗透与截留性能随涂膜液pH值的增加而增加,在跨膜压差低于0.2 MPa、错流速度低于1.5 m/s,涂膜时间少于30 m in和涂膜液浓度低于0.4 g/L范围内,提高这些参数值有利于提高预涂动态膜的渗透与截留性能,超出此范围时,提高这些参数值对增强其渗透与截留性能的效果已不明显,其中错流速度的影响相对小些。跨膜压差为0.2 MPa,错流速度为1.5 m/s,涂膜时间30 m in,涂膜液浓度和pH值分别为0.4 g/L和10.2时为最佳制备条件。     

Effect of carbon dioxide concentration on biomass production and partitioning in Betula pubescens Ehrh. seedlings at different ozone and temperature regimes

Seedlings of Betula pubescens were grown at two CO(2) concentrations, in combination with either two O(3) concentrations or two air temperatures, during 34-35 days at 24 h day(-1) photoperiod in growth chambers placed in a greenhouse. Increasing the CO(2) concentration from 350 to 560 micromol mol(-1) at 17 degrees C air temperature increased the dry weight of the main leaves, main stem, branches and root. The mean relative growth rate (RGR) was increased 10% by CO(2) enrichment, while increasing the O(3) concentration from 7 to 62 nmol mol(-1) decreased the RGR by 9%. The relative biomass distribution between the different plant components was not significantly affected by the CO(2) concentration irrespective of the O(3) concentration. No significant interactions between CO(2) and O(3) concentration were found except on leaf size, which was stimulated more by elevated CO(2) concentration at high, compared to low, O(3) levels. In another experiment, elevated CO(2) (700 micromol mol(-1)) significantly increased the dry weight of the different plant components, and more at 20 degrees C than at 15 degrees C. Raising the CO(2) concentration increased the RGR by 5 and 10% at 15 and 20 degrees C, respectively. CO(2) enrichment increased the branch dry weight relatively more than the dry weight of the other plant parts. Increasing the CO(2) concentration or temperature increased the plant height and stem diameter, however, no interactions between CO(2) and temperature were found.     

Solvent and surfactant enhanced solubilization, stabilization, and degradation of amitraz

In an effort to help with the development of effective dip vat management and waste disposal strategies this study determined how solution properties such as pH, buffer composition, ionic strength, temperature, solubility in organic solvents and the addition of commonly used solubilizing agents influenced the hydrolysis of amitraz. Amitraz degrade by means of hydrolysis described by a pseudo-first order rate process and a type ABCD pH rate profile. Hydrolysis increased with temperature and was fastest at low pH, slowest at neutral to slightly alkaline pH, and slightly increased above pH 10. However, buffer concentration and ionic strength influenced the hydrolysis rate and had to be accounted for before constructing a pH rate profile. Hydrolysis seems to depend on the dielectric constant of solvent mixtures and was fastest in water, slower in propylene glycol and ethanol solutions, and slowest in DMSO mixtures. In surfactant solutions, anionic micelles enhanced and cationic micelles retarded the hydrolysis rate. The magnitude of micellar effects decreased with increasing concentrations of the surfactants. The increased solubility and faster hydrolysis of amitraz in the sodium lauryl sulfate solutions showed that anionic surfactants potentially could be used for cleaning up amitraz spills, because it both solubilized the drug and catalyzed hydrolysis.     

Effects of potassium alkalis and sodium alkalis on the dechlorination of o-chlorophenol in supercritical water

Effects of potassium alkalis and sodium alkalis on the dechlorination of o-chlorophenol (o-CP) in supercritical water (SCW) were studied in this paper under the conditions of 450 degrees C and 25 MPa. Experimental results indicated that the dechlorination of o-CP can be accelerated significantly by all alkalis investigated. The dechlorination of o-CP proceeded mainly via two pathways: hydrodechlorination and hydrolysis. Both of the two pathways can be promoted by alkalis, and the dechlorination of o-CP can be accelerated by both the cations and hydroxide ion dissociated from alkalis. The overall dechlorination of o-CP can be accelerated by cations via promoting the hydrodechlorination pathway, while, hydroxide ion via promoting the hydrolysis pathway. In addition, the hydrodechlorination can be accelerated faster by sodium alkalis than that by potassium ones, while, the hydrolysis can be promoted faster by potassium alkalis. This difference may be caused by the different charge density between potassium ion and sodium ion, and the different solubility and dissociation constant between potassium alkalis and sodium alkalis in SCW. Dechlorination of o-CP with addition of alkalis prior to supercritical water oxidation (SCWO) process not only can avoid the reactor corrosion caused by the generated hydrochloric acid in direct SCWO of o-CP, but also can reduce the formation of toxic chlorinated byproducts compared with direct SCWO process or SCWO of o-CP with addition of alkali.     

Iron-induced decomposition of perfluorohexanesulfonate in sub- and supercritical water

Decomposition of perfluorohexanesulfonate (PFHS), a bioaccumulative analogue of perfluorooctanesulfonate (PFOS), in sub- and supercritical water was investigated. Although PFHS was only slightly reactive in pure subcritical water at 350 degrees C, it decomposed to F(-) and SO(4)(2-) ions when the temperature was increased to 380 degrees C, at which temperature the water became supercritical state. Addition of zerovalent iron to the reaction system dramatically accelerated PFHS decomposition to F(-) ions in both sub- and supercritical water: for example, when the initial PFHS concentration was 741microM, the F(-) yields at 350 degrees C were 4.13-16.0 times as high as those in the absence of iron, depending on the amount and the particle size of the iron powder. After the reactions, small amounts of CO(2) and CF(3)H were also detected in the gas phase; these increased with temperature, and the amount of CF(3)H increased markedly when the reaction was carried out in supercritical water. Increasing the specific surface area of the iron powder markedly increased PFHS consumption and F(-) formation in the aqueous phase, which indicates that the reactions occurred on the iron surface and that the increased specific surface area was a key factor in accelerating the decomposition of PFHS to F(-) ions.     

An assessment of the suitable operating conditions for the CeO2/gamma-Al2O3 catalyzed wet air oxidation of phenol

It has been shown that the CeO2/gamma-Al2O3 catalyst is a feasible alternative to CeO2 for the catalytic wet air oxidation (CWAO) of phenol because it remains an effective catalyst and yet is cheaper to prepare. In this study, we found that the optimal cerium content in the CeO2/gamma-Al2O3 catalyst was 20 wt.%, regardless of catalyst loading. Furthermore, at 180 degrees C, with a phenol concentration of 1000 mg l(-1), and an O2 partial pressure of 1.0M Pa or 1.5M Pa, the optimal catalyst loading was 3.0 gl (-1). The efficacy of CWAO of phenol improved with O2 partial pressure, although the effects of O2 pressure were more significant between 0.5 MPa and 1.5 MPa than between 1.5 MPa and 2.0 MPa. After 2 h of reaction, approximately 100% phenol conversion and 80% total organic carbon (TOC) removal was recorded at 180 degrees C, 1000 mg l(-1) of phenol and 3.0 g l(-1) of catalyst. Because these percentages subsequently leveled off, it is suggested that 2 h is a suitable time over which to run the reaction. The efficacy of CWAO of phenol decreased as initial phenol concentration was raised (from 400 to 2500 mg l(-1)), with the exception of phenol conversion after about 2 h, for which 400 mg l(-1) produced the lowest phenol conversion figure. Higher phenol concentrations require both catalyst loading and O2 partial pressure to be increased to maintain high performance. For example, for 2000 mg l(-1) and 2500 mg l(-1) phenol, nearly 100% phenol conversion and 90% TOC removal after 4 h of reaction at 180 degrees C required 4.0 g l(-1) of catalyst and 2.0 MPa.     

Kinetics and mechanism of oxidation of tetrachloroethylene with permanganate

The kinetics, reaction pathways and product distribution of oxidation of tetrachloroethylene (PCE) by potassium permanganate (KMnO4) were studied in phosphate-buffered solutions under constant pH, isothermal, completely mixed and zero headspace conditions. Experimental results indicate that the reaction is first-order with respect to both PCE and KMnO4 and has an activation energy of 9.3+/-0.9 kcal/mol. The second-order rate constant at 20 degrees C is 0.035+/-0.004 M(-1) s(-1), and is independent of pH and ionic strength (I) over a range of pH 3-10 and I approximately 0-0.2 M, respectively. The PCE-KMnO4 reaction may proceed through further oxidation and/or hydrolysis reaction pathways, greatly influenced by the acidity of the solution, to yield CO2(g), oxalic acid, formic acid and glycolic acid. Under acidic conditions (e.g., pH 3), the further oxidation pathway will dominate and PCE tends to be directly mineralized into CO2 and chloride. Under neutral (e.g., pH 7) and alkaline conditions (e.g., pH 10), the hydroxylation pathway dominates the reaction and PCE is primarily transformed into oxalic acid prior to complete PCE mineralization. Moreover, all chlorine atoms in PCE are rapidly liberated during the reaction and the rate of chloride production is very close to the rate of PCE degradation.     

有机改性膨润土的稳定性研究

利用十六烷基三甲基溴化铵(HDTMAB)对膨润土进行有机改性,研究了不同振荡时间、振荡强度、温度、pH以及盐溶液浓度下改性后有机膨润土的稳定性。结果表明,表面活性剂用量为0.6CEC时,改性的膨润土比较稳定。在同一环境因素下,当表面活性剂用量大于0.6CEC时,有机膨润土的稳定性均随着改性剂用量的增加而降低。振荡时间、振荡强度以及反应温度对有机膨润土稳定性影响不明显;酸性条件下会降低有机膨润土的稳定性,而中性、碱性条件下,有机膨润土的稳定性会提高;对于0.6CEC改性的有机膨润土,当NaC l、CaC l2的浓度由0.2 mol/L增加到0.6 mol/L时有机膨润土的稳定性得到了显著的提高,浓度继续增大,稳定性下降。所以当外界NaC l或CaC l2浓度为0.6 mol/L时,0.6CEC改性的有机膨润土相对0.8CEC以及1.0CEC改性的膨润土稳定,可用做废水处理的吸附剂,且无二次污染。     

Supercritical fluid extraction of polycyclic aromatic hydrocarbons from marine sediments and soil samples

Supercritical fluid extraction (SFE) was used to extract polycyclic aromatic hydrocarbons (PAH) from a certified sample of marine sediment. This sample contains a great number of organic pollutants that are present in low concentrations. The extractions were carried out at 50 and 80 degrees C, at a pressure varying from 230 to 600 bar and using CO2 in the supercritical phase and the effect of three organic modifiers (methanol, n-hexane and toluene), added at 5%/vol, at the same temperature and pressure conditions, were then considered. PAHs were characterized by GC-MS and the recover yield was estimated for 6 PAHs that were representative of those present in the sample, according to their molecular weight and to the number of condensed rings. The analytical conditions giving the best recovery efficiency were used on an unpolluted soil sample spiked with 11 PAHs of environmental importance at a concentration similar to that certified for the sediment sample. An increase in the yield of recovered PAHs, using methanol as co-solvent, was observed while higher temperatures caused a negative effect on the quantity of recovered pollutants. The recovery yield for PAHs from the spiked soil sample was measured and found to be greater than 90%. Better recoveries were obtained for those compounds with higher molecular weight.     

Chlorpyrifos degradation in Turkish soil

Degradation of chlorpyrifos was evaluated in laboratory studies. Surface (0-15 cm) and subsurface (40-60 cm) clay loam soils from a pesticide-untreated field were incubated in biometer flasks for 97 days at 25 degrees C. The treatment was 2 micrograms g-1 [2,6-pyridinyl-14C] chlorpyrifos, with 74 kBq radioactivity per 100 g soil flask. Evolved 14CO2 was monitored in KOH traps throughout the experiment. Periodically, soil subsamples were also methanol-extracted [ambient shaking, then supercritical fluid extraction (SFE)], then analyzed by thin-layer chromatography. Total 14C and unextractable soil-bound 14C residues were determined by combustion. From the surface and subsurface soils, 41 and 43% of the applied radiocarbon was evolved as 14CO2 during 3 months incubation. The time required for 50% loss of the parent insecticide in surface and subsurface soils was about 10 days. By 97 days, chlorpyrifos residues and their relative concentration (in surface/subsurface) as % of applied 14C were: 14CO2 (40.6/42.6), chlorpyrifos (13.1/12.4), soil-bound residues (11.7/11.4), and 3,5,6-trichloropyridinol (TCP) (3.8/4.8). Chlorpyrifos was largely extracted by simple shaking with methanol, whereas TCP was mainly removed only by SFE. The short persistence of chlorpyrifos probably relates to the high soil pH (7.9-8.1).     

TiO2/EP光催化降解水体中微污染磺胺嘧啶的研究

制备了膨胀珍珠岩（EP）为载体的TiO2催化剂（TiO2/EP）,对使用较为广泛的抗生素磺胺嘧啶（SDZ）进行了光催化降解研究,探讨了TiO2的负载量、溶液的初始浓度、初始pH、无机离子（HCO3^-、SO4^2-和Cl^-）和腐殖酸（HA）对SDZ降解效果的影响。结果表明：SDZ的光催化降解符合一级反应动力学方程;当TiO2最佳负载量为20 wt%,SDZ浓度为5 mg/L,pH=6.7,紫外光照射强度为1 000μW/cm^2,反应时间为45 min时,SDZ的降解率达到96%;HCO3^-在低浓度时能促进SDZ的光催化降解,高浓度时促进作用不明显;SO4^2-和Cl^-对SDZ的光催化降解有轻微的抑制作用;HA对SDZ光催化降解有显著的抑制作用,浓度越高,抑制作用越强。UV-TiO2/EP是一种去除水体中微污染SDZ的有效方法。     

Glazed tiles manufactured from incinerated sewage sludge ash and clay

Sewage sludge incineration is applied extensively in highly populated cities as a final sludge treatment. In this study, incinerated ash was utilized as an additive to clay to manufacture glaze tiles. Four different amounts of ash (0, 15, 30, and 45%) were added, and five glaze concentrations (0.03, 0.06, 0.1, 0.15, and 0.2 g/cm2) were applied on the surface of biscuit tiles to study the effects of ash additive and glaze concentration on properties of fired samples. Sewage sludge was dehydrated and incinerated into ash at 800 degrees C. Subsequently, tile specimens were manufactured and fired at 800 degrees C to make biscuit tiles. Fritted glazes and iron oxide were used as the fundamental glaze and colorant, respectively. Finally, glaze was applied on the surface of biscuit tiles and then fired at 1050 degrees C to sinter them into glazed tile specimens. Tests were performed to analyze properties, including water absorption, firing shrinkage, weight loss on ignition, abrasion resistance, bending resistance, acid-alkali resistance, and aging resistance on specimens of glaze tile. To further understand more about the microstructural behavior of glazed tile specimens, analysis of energy dispersive spectrometer, scanning electron microscopy, and X-ray were carried out in this study.     

Absorption and reaction kinetics of amines and ammonia solutions with carbon dioxide in flue gas

The removal system for the absorption of CO2 with amines and NH3 is an advanced air pollution control device to reduce greenhouse gas emissions. Absorption of CO2 by amines and NH3 solutions was performed in this study to derive the reaction kinetics. The absorption of CO2 as encountered in flue gases into aqueous solutions of monoethanolamine (MEA), diethanolamine (DEA), and NH3 was carried out using a stirred vessel with a plane gas-liquid interface at 50 degrees C. Various operating parameters were tested to determine the effect of these variables on the absorption kinetics of the reactants in both gas and liquid phases and the effect of competitions between various reactants on the mass-transfer rate. The observed absorption rate increases with increasing gas-liquid concentration, solvent concentration, temperature, and gas flow rate, but changes with the O2 concentration and pH value. The absorption efficiency of MEA is better than that of NH3 and DEA, but the absorption capacity of NH3 is the best. The active energies of the MEA and NH3 with CO2 are 33.19 and 40.09 kJ/mol, respectively.     

表面活性剂对多壁碳纳米管吸附Pb~(2+)的影响

多壁碳纳米管(MWNT)在吸附有毒气体和重金属离子方面具有极高的应用价值.针对MWNT对水溶液中Pb2+的净化吸附进行了研究,从吸附量,吸附速率、动力学角度考察了表面活性剂、Pb2+浓度对MWNT吸附Pb2+的影响.结果表明,司班-60、吐温-20、阿拉伯树胶等表面活性剂的加入,促进了MWNT在溶液中的分散,导致在Pb2+摩尔浓度为3～18 mmol/L的Lang-muir和Freundlich等温吸附方程中的吸附常数(K)变大,使得MWNT对Pb2+的吸附速率和平衡吸附量都得到提高;随着溶液中Pb2+浓度的增大,MWNT对其吸附量渐至饱和,随后由于Pb2+的位阻作用.吸附量下降;在这3种表面活性剂中,由于司班-60具有相对较小的分子量,其分散的MWNT在Pb2+摩尔浓度为14 mmol/L时,吸附量最大,为230 mg/g.     

Cosolvent-enhanced chemical oxidation of perchloroethylene by potassium permanganate

A laboratory study was conducted to examine cosolvent-enhanced in-situ chemical oxidation (ISCO) of perchloroethylene (PCE) using potassium permanganate (KMnO4). The conceptual basis for this new technique is to enhance permanganate oxidation of dense non-aqueous phase liquids (DNAPLs) with the addition of a cosolvent, thereby increasing DNAPL solubility while avoiding mobilization. Among 17 cosolvent candidates screened, tertiary butyl alcohol (TBA) and acetone were the most stable in the presence of KMnO4, both of which increased PCE aqueous solubility significantly, and therefore are suitable to be used as cosolvent in this study. Batch experiments indicated that the second-order rate constant for PCE oxidation by potassium permanganate was 0.043+/-0.002 M(-1) s(-1) in the purely aqueous (no cosolvent) solution. In the presence of 20% cosolvent (volume fraction=fc=0.2), the rate constant decreased to 0.036+/-0.003 M(-1) s(-1) with TBA and to 0.031+/-0.002 M(-1) s(-1) with acetone. However, in the presence of free-phase PCE, chloride ion concentration from PCE oxidation in acetone/water solutions (fc=0.2) was about twice that in aqueous solutions, indicating that the increase in PCE solubility more than compensated for the decrease in reaction rate constant, such that the oxidation efficiency of PCE was increased with cosolvent. A complete chlorine mass balance was observed in the aqueous system, whereas approximately 70% was obtained in TBA/water or acetone/water (fc=0.2). In soil columns containing residual DNAPL and subjected to isocratic flushing with step-wise increases in f(c) cosolvent, TBA at fc=0.2 resulted in PCE mobilization, whereas acetone at fc相似文献