Sorption of Cd(II) onto kaolin as a soil component and desorption of Cd(II) from kaolin using rhamnolipid biosurfactant

In this study, a microbial surfactant, rhamnolipid, was investigated for its potential to enhance recovery of Cd(II) from kaolin, a representative soil component. The study was divided into two parts. In the first part, the sorption of Cd(II) ions to kaolin was investigated as a function of pH and initial Cd(II) ion concentration. Kaolin was also shown to be a good sorbent for treatment of Cd(II) ions from waste waters. The equilibrium sorption capacity for Cd(II) ions was measured and extrapolated using the Langmuir, Freundlich, Redlich-Peterson, and Koble-Corrigan sorption models. The best correlation between experimental and model predicted equilibrium uptake was obtained using the Kolbe-Corrigan sorption model. The values of parameters of the Koble-Corrigan model were determined as A=11.13 (mmol(1-b)kg(-1)L(b)); B=0.39 (L(b)mmol(-b)); b=0.48. In the second part, the desorption of Cd(II) from kaolin was investigated as a function of pH, rhamnolipid concentration, and the amount of sorbed Cd(II) by kaolin. The highest Cd(II) desorption efficiency by rhamnolipid biosurfactant from kaolin was obtained at pH 6.8, at an initial Cd(II) ion concentration of 0.87 mM (4.42 mmol Cd(II)/kg kaolin) and at a rhamnolipid concentration of 80 mM and found to be 71.9% of the sorbed Cd(II).     

Sorption of polycyclic aromatic hydrocarbons on electrospun nanofibrous membranes: sorption kinetics and mechanism

Five types of nanofibrous membranes were prepared by electrospinning poly(?-caprolactone) (PCL), poly(d,l-lactide) (PDLLA), poly(lactide-co-caprolactone) (P(LA/CL)), poly(d,l-lactide-co-glycolide) (PDLGA) and methoxy polyethylene glycol-poly(lactide-co-glycolide) (MPEG-PLGA), respectively. These electrospun nanofibrous membranes (ENFMs) were used to adsorb anthracene (ANT), benz[a]anthracene (BaA) and benzo[a]pyrene (BaP) from aqueous solution, and the sorption kinetics and isotherms of these PAHs on the five ENFMs were investigated. The pseudo-second-order model (PSOM) can well describe the sorption kinetics of the three PAHs on five ENFMs, and the partition-adsorption model (PAM) can interpret the sorption processes of PAHs on the ENFMs. PCL ENFMs, which had the largest surface areas (8.57 m² g⁻¹), exhibited excellent sorption capacity for ANT at over 4112.3 ± 35.5 μg g⁻¹. Moreover, the hydrophobicity and pore volume of ENFMs significantly affected the sorption kinetics and sorption capacity of the PAHs. The main sorption mechanisms of three PAHs on the PDLLA ENFMs included hydrophobic interactions and pore-filling, while those of PCL, P(LA/CL) and PDLGA ENFMs were dominated by the hydrophobic interactions. The sorption mechanisms of MPEG-PLGA ENFMs primarily included pore-filling, hydrogen bonding interactions and hydrophobic interactions. Additionally, π-π bonding interaction was also deduced to be involved in all of ENFMs sorption systems.     

纳米PET树脂及其工程塑料应用

通过双螺杆挤出机熔融共混技术 ,将蒙脱土 (MMT)以纳米尺度分散在聚对苯二甲酸乙二醇酯 (PET)基体树脂中制得纳米复合PET树脂。蒙脱土在与PET树脂结合前 ,先经过有机化处理。X 射线衍射结构分析表明 ,蒙脱土层间距依次按照纯蒙脱土、有机化蒙脱土、PET复合蒙脱土的顺序从 1 3nm增大到 2 3nm ,直至 3 1nm。透射电子显微镜图象显示 ,纳米分散的层状硅酸盐的片层厚度平均在 30nm左右。纳米复合PET具有良好的熔体强度、快速结晶、良好机械强度等性能 ,是开发耐热、增强、阻燃工程塑料的良好基础树脂。     

从二氧化碳制备生物可降解塑料——机会与挑战

从CO2制备塑料成为目前化学化工领域备受关注的研发方向,其原因一方面在于CO2作为化工资源的规模化利用,另一方面则是所得到的塑料具有生物可降解性能,为解决长期制约生物降解塑料发展的性价比难题提供了难得的机遇。本报告介绍了二氧化碳基塑料研发方面的最新进展,指出生物降解只是二氧化碳基塑料的诸多性能之一,但不是实现其规模化应用的决定因素。不断提高其性价比,使其与普通塑料相比有竞争力,是二氧化碳基塑料面临的最大挑战。二氧化碳基塑料的性价比取决于其高效合成和性能改善的程度,一方面其高效制备受制于催化剂活性、聚合工艺、聚合后处理技术等因素,其中提高催化活性是降低其成本的核心。另一方面,二氧化碳基塑料的玻璃化温度较低(35℃左右)、且为无定型结构,存在尺寸稳定性差(40℃以上)和低温脆性(18℃以下)的问题,能否在保持生物降解性能的前提下,解决低成本的高温增强和低温增韧难题,是二氧化碳基塑料改性的关键。     

国内外汽车用塑料概况及新的成型方法

概括介绍了国内外汽车用塑料的历史、现状及未来发展趋势。讨论了汽车用塑料的应用、品种和新的成型方法。     

Sorption and degradation of bisphenol A by aerobic activated sludge

Laboratory-scale batch experiments were conducted to investigate the sorption and degradation of bisphenol A (BPA) at μg/L range in an aerobic activated sludge system. The sorption isotherms and thermodynamics indicated that the sorption of BPA on sludge was mainly a physical process in which partitioning played a dominating role. The values of sorption coefficient K_oc were between 621 and 736 L/kg in the temperature range of 10–30 °C. Both mixed liquor suspended solid (MLSS) and temperature influenced BPA sorption on sludge. The degradation of BPA by acclimated activated sludge could be described by first-order reaction equation with the first-order degradation rate constant of 0.80 h⁻¹ at 20 °C. The decrease of initial COD concentration and the increase of MLSS concentration and temperature enhanced BPA degradation rate. The removal of BPA in the activated sludge system was characterized by a quick sorption on the activated sludge and subsequent biodegradation.     

膨胀石墨对重油和生物体液的吸附-来自中国的研究

膨胀石墨(简称EG)是通过将残留石墨层间化合物(简称GIC)快速加热到约1000℃而分解、膨胀制得的。这种材料具有较大比表面积和较强表面活性,因此,EG可以吸附重油和粘稠性有机液体。本文综述了清华大学研究组近年来所进行的膨胀石墨吸附重油和生物体液的研究成果。     

气相色谱法测定盐酸美金刚原料药中有机溶剂残留量

目的:用毛细管柱气相色谱法建立测定盐酸美金刚原料药中二氯甲烷、乙腈、乙醚、乙醇的残留量的方法。方法:采用内壁涂有5%苯基-95%聚二甲基硅氧烷的毛细管柱(DB-5毛细管色谱柱30m×0.53mm×1.5μm),以氮气为载气,流速1.0ml/min。柱温箱:50℃保持12min,然后以30℃/min升温至230℃,至少保持12分钟。分流直接进样,进样口温度230℃,进样量:1.0μl。FID检测器,检测器温度280℃。按内标法计算残留溶剂的含量。结果:在考察的浓度范围内呈现良好的线性关系(二氯甲烷r=0.99885、乙腈r=0.99975、乙醚r=0.99659、乙醇r=0.99985),方法的精密度良好,回收率较为理想。结论:该法适用于盐酸美金刚原料药中二氯甲烷、乙腈、乙醚、乙醇的残留量的检测。     

Effect of solvents quality on determination of particle size and polydispersity of nanoparticles

Nanotechnology is of great interest to researchers and industrialists and nanocolloidal carrier systems for drug delivery have been studied in great detail, but while much research has been carried out on the preparation of nanoparticles using a variety of techniques employing various solvents, no attention has been given to the quality of solvents used in the process of nanoparticles characterization. The present investigation aimed to study the effect of solvents quality on the chitosan nanoparticles characterization for average particle size (Z) and polydispersity index (P.I.). Particle size distribution study showed that the number of particles contributed by solvents significantly affects both the Z and P.I. of the nanoparticulate suspensions leading to ambiguous results. While the Z decreases upon dilution with organic solvents, the phosphate buffer and water causes a net increase in Z because of the introduction of larger extraneous nanoparticles. The P.I. was found to increase with dilution because of the differences in the size of the polymeric nanoparticles and the nanoparticles introduced by the solvent upon dilution. The study thus recommends use of the highest quality of solvents in nanoparticles manufacturing and characterization process to avoid the generation of erroneous results.     

Silicone emulsion-enhanced recovery of chlorinated solvents: batch and column studies

Batch and column experiments were conducted to investigate the feasibility of flushing with silicone oil emulsion for the removal of chlorinated solvents, including trichloroethylene (TCE), perchloroethylene (PCE) and 1,2-dichlorobenzene (DCB). In the batch experiments, solubilization potentials of emulsion and effects of surfactants as additives were examined. The emulsion prepared with 2% (v/v) silicone oil could solubilize 90.7% of 10,000 ppm TCE, 97.3% of 4000 ppm PCE and 99.7% of 7,800 ppm DCB. Results of one-dimensional column studies indicated that aqueous solubility and sorption of contaminants determined the flushing efficiency. The addition of surfactants below their critical micelle concentration (CMC) did not affect the removal of chlorinated solvents in batch and column experiments. The results of this study show that flushing with oil-based emulsion can be applied to treat the chlorinated solvents.     

Sorption behavior of tetrabromobisphenol A in two soils with different characteristics

Sorption of tetrabromobisphenol A (TBBPA) in soil influences its fate and transport in the environment. The sorption behaviors of TBBPA in two soils with different characteristics were investigated using batch equilibration experiments in the study, and the impacts of ionic strength and pH on the sorption were also evaluated. The results showed that the fast sorption rather than the slow sorption played a main role in the sorption process. The nonlinear sorption isotherms of TBBPA in the soils were observed and the Freundlich model could describe the sorption behavior of TBBPA well. The calculated K_F were 78.5 and 364.6  (mg/kg)(mg/L)⁻ⁿ for LN soil (loamy clay) and GX soil (silt loam), respectively. Soil organic matter (SOM) played a main role in the sorption of TBBPA, which contributed about 90% to the sorption in the soils. The desorption hysteresis of TBBPA was revealed in the single-cycle sorption and desorption experiments. The sorbed amount of TBBPA decreased with the increase in solution pH and increased with the increase in ionic strength. It was found that the effects of ionic strength on the sorption were mainly caused by the change of solution pH.     

特种工程塑料-我国拥有强势自主创新知识产权的新一代塑料急待产业化

根据国内外文献资料总结了特种工程塑料领域的发展历程和现状,分析了产生这种差距的原因,并提出今后应采取的对策。     

Sorption of SPADNS azo dye on polystyrene anion exchangers: Equilibrium and kinetic studies

The sorption of SPANDS from aqueous solution onto the macroporous polystyrene anion exchangers of weakly basic Amberlyst A-21 and strongly basic Amberlyst A-29 in a batch method was studied. The effect of initial dye concentration and phase contact time was considered to evaluate the sorption capacity of anion exchangers. Equilibrium data were attempted by various adsorption isotherms including the Langmuir, Freundlich and Dubinin–Radushkevich (D–R) models. A comparison of kinetic models applied to the adsorption rate constants and equilibrium sorption capacities was made for the Lagergren first-order, pseudo second-order and Morris–Weber intraparticle diffusion kinetic models. The results showed that the adsorption isotherm is in the good agreement with the Langmuir equation and that the adsorption kinetics of SPADNS on both anion exchangers can be best described by the pseudo second-order model.     

麦秆纤维/氨基树脂模塑料的制备与性能研究

以麦秆纤维为增强材料、氨基树脂为基体制备了麦秆纤维/氨基树脂模塑料.利用碱、乙酸、偶联剂KH550、KH370处理了麦秆纤维,研究了经不同方法处理的麦杆纤维对模塑料流动性、模塑收缩率、力学性能的影响.结果表明:麦秆纤维的处理效果对模塑料的性能影响很大,以添加偶联剂KH550的碱麦秆纤维模塑料综合性能最优,流动性提高了1...     

Prediction of solubility of long-chain hydrocarbons in various solvents using UNIFAC

The UNIFAC group contribution model has been widely used in the prediction of phase equilibria of various fluid mixtures. We have applied the method to predict the solubility of various long-chain hydrocarbon solids in a number of solvents of industrial importance. The calculated solubilities are compared with measured values and also with the predictions of the regular solution theory of Hildebrand and Scatchard. Some disagreements were found between the measured solubilities and the predicted values of both theories. Overall the UNIFAC scheme appears to be superior to the regular solution theory.Paper presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A.     

Application and exploration of friction stir welding/processing in plastics industry

Friction stir welding (FSW) is a green, pollution-free, low-energy technology with high manoeuvrability. Thermoplastic plastics have extensive applications in the present industry because they offer excellent physical and corrosion properties, high degree freedom of processing and design. In this paper, the current state of FSW/P in plastics industry, including tool improvement, welding methods, process parameters optimisation, metal and polymer joining as well as composites fabrication, has been addressed. Although it presents a major challenge, FSW/P has a great potential to produce defect-free joint and fabricate composites in polymer materials.     

Soil vapor extraction of chlorinated solvents at an industrial site in Brazil

This study presents the design, monitoring and remediation strategy for a soil vapor extraction (SVE) system installed at an industrial site contaminated with a mixture of organic compounds, in particular 1,2 dichloroethane, carbon tetrachloride and chloroform. The unsaturated zone at the site is very deep and presents near ideal conditions for SVE, with the contaminated portion of the porous media characterized by alluvial deposits of a well graded sand followed by a capillary barrier at 28 m of depth, which limited DNAPL downward migration. The soil cleanup time and the optimal removal rates of mass, considering different values of vacuum/discharge applied in the SVE system, have been estimated through the use of numerical sensitivity analysis. Results of the pilot-scale testing activities allowed for the calibration of flow and contaminated mass transport models and the determination, in a preliminary phase, of the infiltrated mass of different compounds.     

Sorption of metal ions on lignite and the derived humic substances

The study presents results of sorption of metal ions (Pb2+, Zn2+, Cu2+, and Cd2+) onto lignite mined in South Moravia, Czech Republic, and solid humic substances (humin and humic acid) derived from it. The efficiency of these sorbents has been studied as a function of contact time, solution pH, and metal concentration. The sorption efficiencies were higher for humin and lower for humic acid samples than for the original lignite. With its high sorption capacities of several mmol/g, particularly for Pb2+ and Cd2+, the South Moravian lignite can provide a cheap source material for preparation of sorbents utilizable in removal of toxic metals from wastewaters.     

Structural transition of a homopolymer in solvents mixture

The present work is aimed at studying the thermodynamic behaviour of a polymer in solvents mixture. Dynamic light scattering is used to measure the hydrodynamic radius of polyvinylpyrrolidone (M_w = 360,000 g/mol), in water/methanol solvents mixture, versus the mixed solvents composition at 25 °C. Then, we show that the polymer conformation adopts the Coil–Globule–Coil structure when the methanol molar fraction X_A is varied. This transition is attributed to solvent quality change which result from water and methanol complex formation. The polymer contraction rate calculated for each composition takes its maximum value at X_A = 0.17. Hildebrand theory assuming the solvents mixture as an equivalent solvent was used to analyze the change in mixed solvents quality. These changes can be attributed to dispersive forces in solvents mixture.