Reduction of amine mist emissions from a pilot-scale CO2 capture process using charged colloidal gas aphrons

In the CO₂ capture process from coal-derived flue gas where amine solvents are used, the flue gas can entrain small liquid droplets into the gas stream leading to emission of the amine solvent. The entrained drops, or mist, will lead to high solvent losses and cause decreased CO₂ capture performance. In order to reduce the emissions of the fine amine droplets from CO₂ absorber, a novel method using charged colloidal gas aphron (CGA) generated by an anionic surfactant was developed. The CGA absorption process for MEA emission reduction was optimized by investigating the surfactant concentration, stirring speed of the CGA generator, and capture temperature. The results show a significant reduction of MEA emissions of over 50% in the flue gas stream exiting the absorber column of a pilot scale CO₂ capture unit.     

On the effect of gap size between baffle outer diameter and tube inner diameter on the mixing characteristics in an oscillatory‐baffled column

We report our experimental investigation on the effect of gaps between baffle outer diameter and inner tube diameter on the mixing characteristics, in terms of mixing time and axial dispersion coefficient, in a batch oscillatory‐baffled column. Local concentration profiles are measured using conductivity probes at two locations along the height of the column. The mixing time was determined based on the equilibrium concentration concept, and the axial dispersion coefficient was obtained by solving the axial dispersion governing equation. Comparison of mixing time between the ‘push‐fit’ and ‘loose‐fit’ baffle arrangements was carried out and the results showed that the existence of a gap of various sizes between the baffle outer and the tube diameters lengthened the time at which the state of uniform mixing is achieved in such a device. © 1999 Society of Chemical Industry     

Growing Innovative Calcium Carbonate Morphologies by Utilizing the Colloidal Gas Aphron System as a Surfactant-Based Template Method

Many studies have been conducted to study the various polymorphs and morphologies of calcium carbonate crystals in nature and living organisms. In this experimental work, a novel method has been employed to crystallize calcium carbonate by using colloidal gas aphron dispersion. The polymorph and morphology of prepared particles were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectrometry techniques. SEM and XRD analyses demonstrated that the morphology of synthesized CaCO₃ can be changed from spherical (vaterite phase) to novel rod and plate-like shapes (mixture of vaterite and calcite phases) with changes in the surfactant concentration. The quantitative examination results of different calcium carbonate polymorph orientations showed that the precursor concentrations had no significant effect on the orientation of calcite phase, but rather they affected the orientation development of vaterite phase at a higher surfactant concentration.     

Comparison of Soil Washing Using Conventional Surfactant Solutions and Colloidal Gas Aphron Suspensions

Abstract

Surfactants have proven to be an effective way of augmenting the removal and mobilization of organics from contaminated soil. A more recent and innovative technology to aid the removal of contaminants from soil is the use of colloidal gas aphron (CGA) suspensions. The performance of CGAs and surfactant solutions in washing soils contaminated with 2,4-dichlorophenoxy acetic acid (2,4-D) was investigated and compared with the process of washing soils with aqueous solutions of surfactants as in conventional surfactant flushing. In general it was observed that there was no significant difference in the performance of the two processes of soil washing for a highly soluble compound like 2,4-D. However, the surfactant consumption per gram of 2,4-D recovered from the soil was higher for conventional washing than for CGA solutions. CGAs also had a significant advantage over surfactant solutions in that at low flow rates, the pumping of CGAs showed lower pressure drops across the soil column.     

Flow patterns and oil—water dispersion in a 0.38 m diameter oscillatory baffled column

We report our experimental flow visualization observations of flow patterns and experimental oil‐water dispersion measurements in an oscillatory baffled column (OBC) of an internal diameter 380 mm. Both types of experiments were carried out covering an identical range of oscillation frequencies, amplitudes, orifice diameters and baffle spacings. The flow visualization observations show that eddy mixing has been achieved in the pilot OBC and the intensity of which is largely dependent on the operational and geometrical parameters tested, which is similar to that in a smaller scale OBC. The scale‐up correlation was found to be linear. The oil‐water dispersion measurements show that the degree of the dispersion depends significantly on the oscillation frequency and amplitude with an increase in either leading to an increase in dispersion. The effect of the orifice diameter on the oil—water dispersion is also evident, but the effect of the baffle spacing is much weaker. Based on the experimental data we have established a correlation relating the degree of oil—water dispersion to the power input to the system. We have also compared the power requirement to achieve a complete dispersion in the pilot OBC with that in a bench scale OBC of 50 mm diameter and found that the energy dissipation is more economical in the large scale application.     

FLOTATION OF Cu(Ⅱ) BY COLLOIDAL GAS APHRONS(CGA)

Colloidal gas aphrons(CGAs) were first defined by Sebba( J.Colloid Interface Sci .,1971,35(4):643) as micro bubbles(25—300?μm).These microbubbles do not coalesce easily and are markedly different from conventional soap bubbles in their stability and flow properties.CGAs are composed of a gaseous inner core surrounded by a thin surfactant film, which are created by intense stirring of a surfactant solution. CGA dispersion typically contains about 65% gas. CGA suspensions have viscosity similar to water, which make them suitable for pumping without deterioration in quality. Two important considerations in the application of CGA suspensions are: ① their colloidal size, resulting in a large surface area to volume ratio, and ② the existence of a double film of surfactant encapsulating the gas that retards the coalescence of the bubble. CGA suspensions are found very effective for separating hydrophobic organic compounds and heavy metal ions. In this paper, flotation of Cu(Ⅱ) by colloidal gas aphrons has been conducted in order to explore a new method for separating heavy metal ions from dilute solution. The effects of CGA flow rate, amounts of CGA introduced to the system, surfactant concentration on the flotation efficiency have been systematically investigated. The optimum flotation condition is determined. The results show that flotation efficiency at pH=5—6 has an optimum value to CGA flow rate and amount. When pH is greater than 7, the flotation efficiency can be as high as 99% at the optimum condition.     

利用胶质气体泡沫气浮Cu(Ⅱ)

引　言Ｓｅｂｂａ[1,2 ] 曾报道 ,表面活性剂水溶液在高速搅拌 (>50 0 0ｒ·ｍｉｎ- 1)下混合会生成直径为 10～ 10 0μｍ的微泡沫 (ｍｉｃｒｏｆｏａｍｓ) ,这些微泡沫由气体内核和一层薄皂膜组成 ,称为胶质气体泡沫 (ｃｏｌｌｏｉｄａｌｇａｓａｐｈｒｏｎｓ ,简称ＣＧＡ) .ＣＧＡ的气含率在 6 0 %～70 %之间 .ＣＧＡ不同于传统意义上的泡沫 ,具有胶体的性质 ,且可以用泵输送到设备中去 ,因此可以利用ＣＧＡ进行气浮分离 .近年来 ,许多研究者对ＣＧＡ的气浮分离开展了研究工作 .Ｊａｕｒｅｇｉ和Ｖａｒｌｅｙ[3] 以及Ｎｏｂｌｅ和Ｖａｒｌ…     

Formation of polymeric microspheres using electron beam radiation

Polymeric particulates are currently being produced by a variety of different techniques. This new approach illustrates the formation of cross-linked polymeric microspheres by incorporating trimethylolpropane propoxylate triacrylate (a radiation-sensitive monomer) into a polyaphron system and exposing it to electron beam radiation. Polyaphrons are essentially a collection of droplets encapsulated in a very thin aqueous film dispersed in a aqueous matrix. This film gives extreme stability to the system, which allows for extremely high dispersed-phase concentrations. The formation of polyaphrons requires the presence of a surfactant in both the dispersed (monomer) and continuous (aqueous) phases. The effects of monomer-phase concentration, monomer- and acqueous-phase surfactant concentration, aqueous-phase surfactant type, and preparation temperature were studied to gain an understanding of the conditions that promote the formation of polymeric microspheres with a narrow size distribution. Polymeric microspheres ranging from 2 to 40 microns in diameter were formed with monomer concentrations as high as 67 vol % without any aphron bridging occurring or need for agitation to keep the monomer-phase dispersed in the aqueous matrix. In addition, the ability to reduce the wettability of the microspheres is demonstrated through incorporation of a polymerizable fluorinated acrylate in the dispersed phase.     

An L9 orthogonal design methodology to study the impact of operating parameters on particulate emission and related characteristics during pulse-jet filtration process

This study embodies experimental characterization of emitted particulate and filtration performance under varied situation in a pulse-jet cleaning process. Tests were conducted under simulated condition in a filtration apparatus consisting four bags. The effect of four different factors such as fabric punch density, baffle plate height, air to cloth ratio and cycle time have been investigated on the key parameters; emission, pressure drop along with PM_2.5 and average particle diameter of emitted particulate matter in a pulse-jet filtration process. Experimental investigation based on L₉-orthogonal design shows that emission is reduced with the increases in punch density and pulse cycle time; but it increases up to a certain extent with the increase in air to cloth ratio. However baffle plate height has no effect on the emission. On the other hand pressure drop across the tube sheet increases with the material consolidation, air to cloth ratio and pulse cycle time; but the above parameter first decrease with the increase in baffle plate height. PM_2.5 (based on the number distribution) is found to be mainly affected by the baffle plate height and cycle time; as it first increases and then decrease with the increase in baffle plate height but it shows reverse trend with the increase in cycle time. Average particle diameter based on number volume is found to be mainly affected by the baffle plate height and cycle time. With the increase in time of filtration, both emission and pressure drop tend to increase without affecting PM_2.5 and average particle diameter based on number volume.     

Evaluating Cu(II) Removal From Aqueous Solutions with Response Surface Methodology by Using Novel Synthesized CaCO3 Nanoparticles Prepared in a Colloidal Gas Aphron System

Removal of heavy metals from water and wastewaters has recently gained a great deal of attention due to their serious environmental problems. In this study, novel synthesized calcium carbonate nanoparticles, prepared in a colloidal gas aphron (CGA) system, were used as adsorbents for the removal of Cu²⁺ ions from aqueous solutions under different conditions. A developed pseudo-second-order (PSO) model well described the adsorption kinetics of the process. Langmuir and Freundlich adsorption isotherms have been examined and the maximum adsorption capacity from the Langmuir isotherm equation was found to be 666.67?mg Cu/g adsorbent. The effects of temperature, Cu²⁺ initial concentration, and CaCO₃ dosage on the removal capacity were also investigated using the three-level Box–Behnken experimental design method. The response surface modeling results demonstrated that under certain experimental conditions (i.e., T?=?26°C, [Cu²⁺]?=?200?mg/L, and [CaCO₃]?=?0.5?g/L), maximum removal capacity value (393.52?mg/g) was achieved.     

一种分散稳定剂的合成及应用

文章合成了一种阴离子型分散聚合稳定剂;特性粘数2～4dL/g,浓度20%,表观粘度200～300mPa·s该稳定剂兼有高分子和表面活性剂的特点,具有优异的分散稳定作用;使用该稳定剂合成的聚丙烯酸分散液,分散粒子总比表面积0.28m2/g,表面积平均粒径19.33μm,体积平均粒径为228.82μm。稳定期大于半年。     

Extraction of erythromycin‐A using colloidal liquid aphrons: I. Equilibrium partitioning

Colloidal liquid aphrons (CLAs) are surfactant‐stabilised solvent droplets which have recently been explored for use in pre‐dispersed solvent extraction (PDSE). In this work, the equilibrium partitioning of a microbial secondary metabolite, erythromycin, has been studied using both CLAs (formulated from 1% (w/v) Softanol 120 in decanol and 0.5% (w/v) SDS in water) and surfactant‐containing, two‐phase systems. The equilibrium partitioning of erythromycin was found to be strongly influenced by the extraction pH, and exhibited a marked change either side of the pK_a of the molecule. A modified form of the Henderson–Hasselbach equation could be used as a simple design equation to predict the equilibrium partition coefficient (m_eryt = C_org /C_aq) as a function of pH. For extraction experiments with dispersed CLAs where pH > pK_a, m_eryt values as high as 150 could be obtained and the erythromycin could be concentrated by factors of up to 100. Experiments were also carried out in surfactant‐containing, two‐phase systems to determine the effect of individual surfactants used for aphron formulation on erythromycin partitioning. For extraction at pH 10 neither the Softanol (a non‐ionic surfactant) nor SDS (an anionic surfactant) had any influence on the equilibrium erythromycin partition coefficients. For stripping at pH 7, however, it was found that recovery of erythromycin from the organic phase decreased with increasing concentration of SDS, although again the Softanol had no influence on the equilibrium. The effect of SDS was attributed to a specific electrostatic interaction between individual erythromycin and SDS molecules under stripping conditions. The m_eryt values and concentration factors achievable in the two‐phase systems were considerably less than those for the PDSE experiments. The physical properties of the two‐phase systems, ie density, viscosity, interfacial tension, etc, and the equilibrium distribution of the surfactants were also determined in relation to subsequent studies on the kinetics of erythromycin extraction. © 2000 Society of Chemical Industry     

纳米TiO2流体表面改性及对真空闪蒸制冰的影响

利用电镜扫描法、紫外分光光度法及烘干称重法对纳米TiO₂流体的分散稳定性进行了综合评价,研究了表面活性剂种类及浓度对其分散稳定性的影响。将纳米TiO₂流体引入真空闪蒸制取冰浆系统,研究了纳米TiO₂浓度、表面活性剂浓度及对吸附作用下纳米TiO₂流体真空闪蒸制冰的影响。结果表明,表面活性剂类型对纳米TiO₂流体分散稳定性的影响很大,复合型的分散稳定性最佳,其次是阴离子型;纳米粒子及表面活性剂可以增强真空下纳米TiO₂流体的成核效果,增大含冰率,降低过冷度;表面活性剂浓度是影响真空闪蒸制冰系统压力及闪蒸率的重要因素,系统压力及闪蒸率均随着表面活性剂浓度的增大而增大;另外,确定了在吸附作用下真空闪蒸制冰系统中使用纳米TiO₂流体的最佳条件。在最佳条件下,含冰率为18.35%,过冷度为0.51℃,热导率为0.920W/(m·K),对比蒸馏水有较大改善。吸附作用下真空闪蒸制冰可行性较高,制取冰浆效果优良。     

Controlling the dispersion of multi-wall carbon nanotubes in aqueous surfactant solution

The sonication-driven dispersion of multi-wall carbon nanotubes (MWCNTs) in aqueous surfactant solution has been monitored by UV-vis spectroscopy and transmission electron microscopy. Time dependent sonication experiments reveal that the maximum achievable dispersion of MWCNTs corresponds to the maximum UV-vis absorbance of the solution. With higher surfactant concentration the dispersion rate of MWCNTs increases and less total sonication energy is required to achieve maximum dispersion. Dispersion of higher MWCNT concentrations requires higher total sonication energy. For effective dispersion the minimum weight ratio of surfactant to MWCNTs is 1.5-1. The surfactant molecules are adsorbed on the surface of the MWCNTs and prevent re-aggregation of MWCNTs so that a colloidal stability of MWCNT dispersions could be maintained for several months. The maximum concentration of MWCNTs that can be homogeneously dispersed in aqueous solution is about 1.4 wt%.     

Characterisation of colloidal gas aphrons for subsequent use for protein recovery

Colloidal gas aphrons (CGAs) were first reported by Sebba (J. Colloid Interface Sci., 35 (4) (1971) 643) as micro bubbles (10–100 μm), composed of a gaseous inner core surrounded by a thin surfactant film, which are created by intense stirring of a surfactant solution. Since then, these colloidal dispersions have been used for diverse applications (clarification of suspensions, removal of sulphur crystals, separation of organic dyes from wastewater, etc.). However, there have been no reports, as yet, of their direct application for protein recovery. In this study, CGAs are created from an anionic surfactant (AOT) and are characterised in terms of stability and gas hold-up for a range of process parameters relevant to their proposed use for protein recovery, at a later stage. A statistical experimental design was developed in order to study the effect of different factors (surfactant concentration, salt concentration, pH, time of stirring and temperature) on the stability and gas hold-up of CGAs. The analysis of results from the experimental design provides predictive statistical models. Stability was found to depend mainly on salt and surfactant concentration. Several interactions are shown to be significant including the time-temperature interaction. Gas hold-up was found to depend mainly on salt and surfactant concentration and time of stirring. Also, results from power measurements are presented and the minimum energy for the formation of CGAs, for one set of solution properties, is determined.     

Axial dispersion in a pulsed plate column

A technique involving the indicator colour change in an acidbase reaction has been used to measure axial dispersion coefficients in a 15 cm diameter pulsed column. Data have been obtained mainly for single phase (aqueous) flow with two different types of plate at two different spacings. With coarsely perforated plates, the dispersion coefficient is proportional to (amplitude)² times frequency, but semicircular unperforated baffle plates show a dependence on amplitude times frequency. These results are critically compared with published data, and two types of flow regime for axial dispersion are indicated.     

Dispersion of tracer gas supplied at the distributor of freely bubbling fluidised beds

The dispersion of tracer gas, continuously injected beneath an isolated area of the distributor plate, has been determined from time averaged concentration measurements in freely bubbling three dimensional air fluidised beds. The concentration profiles at different levels and for a series of flow rates have been plotted dimensionlessly showing them to be substantially alike in shape, this plot has been well fitted with a simple expression [1]. The tracer dispersion at points within the bed has been successfully predicted using a single phase model, depending mainly on the radial dispersion coefficient. The radial dispersion coefficient has been found to be roughly constant at all levels in the bed (except near the bottom where it is high), but increases rapidly, from a value near molecular diffusion, with an increase in the excess gas flow (U — U_m.f.). Within the experimental range considered, it appears that the Peclet number is inversely proportional to the average bubble diameter.     

A Study on Dispersion and Antibacterial Activity of Functionalizing Multi‐walled Carbon Nanotubes with Mixed Surfactant

The dispersibility in aqueous phase and antibacterial activity of multi‐walled carbon nanotubes (MWNT) with mixed surfactant functionalization has been studied. The ratio of 3:7 between hexadecyltrimethylammonium bromide and octylphenol ethoxylate (TX100) showed the highest dispersing power for MWNT. The use of mixed surfactants formed stable MWNT dispersions at lower total surfactant concentration compared to their concentrations when used alone. UV–Vis spectroscopy, transmission electron microscopy and Fourier transform infrared spectroscopy were employed to characterize the dispersion of MWNT in the aqueous phase. The result indicated that the surfactant molecules had been successfully adsorbed onto the surface of the MWNT. Bacterial toxicity assay showed that the mixed surfactant‐functionalized MWNT had a strong antibacterial activity and concentration dependence to Staphylococcus aureus. Based on the consideration of the cost and environmental impact, the use of mixed surfactant (CTAB‐TX100) should be more favorable for the stable dispersion of MWNT and the improvement of antibacterial activity than that of an individual surfactant. These observations suggested that the mixed surfactant‐functionalized MWNT might be a promising antibacterial agent for removal and inactivation of biological contaminants in water treatment applications.     

Atomic force microscopy characterization of ultrathin polystyrene films formed by admicellar polymerization on silica disks

Atomic force microscopy was used to study the characteristics of polymer films formed via admicellar polymerization (the polymerization of monomers solubilized in adsorbed surfactant aggregates). The investigated system included cetyltrimethylammonium bromide (C₁₆TAB) as a cationic surfactant, styrene, 2,2′‐azobisisobutyrilnitrile as an initiator, and polished silica disk substrates. Our goal was to examine changes in the properties and morphology of the formed polymer films due to changes in the surfactant and monomer feed levels. Normal tapping and phase‐contrast modes in air were used to image the nanoscopic and microscopic morphologies of the polystyrene‐modified silica. The root‐mean‐square roughness of the surface before and after modification was statistically analyzed and compared. The images were captured with loading‐force set‐point ratios of 0.2–0.9, and this allowed us to examine the stability of the polystyrene films. In the first series, for which the feed ratio of C₁₆TAB to styrene was kept constant and the total feed concentration was varied, a uniform layer of a polystyrene film was observed along with some nanometer‐size aggregates at high feed concentrations of both C₁₆TAB and styrene. These droplets eventually agglomerated with the film beneath and formed larger macrodroplets in a ring arrangement. At lower concentrations, droplets and holes were observed that eventually agglomerated to form a bicontinuous thin film. In the second experimental series, the concentration of C₁₆TAB was kept constant, and the feed ratio of C₁₆TAB to styrene was varied. A smooth thin film was observed at high concentrations of styrene. This film could be deformed and/or removed to expose the silica surface beneath. At lower styrene loadings, the polystyrene film became unstable and formed dropletlike aggregates, possibly because of either the uneven adsolubilization of the styrene monomer within the admicelle or the dewetting effect during washing and drying. The structure of the polystyrene film formed on a smooth silica disk was very dependent on the amount of the surfactant fed to the system; this contrasted with the results on precipitated silica. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 36–46, 2003     

Synthesis and characterization of intercalated ladder‐like poly(vinylsilsesquioxanes)/organically modified montmorillonite nanocomposites

In this paper, ladder‐like poly(vinylsilsesquioxanes) (LPVS)/organically modified montmorillonite (OMT) nanocomposites have been synthesized by ultrasonic dispersion and solution blending method. The structures of nanocomposites are characterized by small angle X‐ray scattering (SAXS) and high‐resolution transmission electronic microscopy (TEM). These results indicate that LPVS have already entered the galleries of OMT layers and intercalated LPVS/OMT nanocomposites have been formed. The effects of different reaction conditions, including solution concentration and the advantage of ultrasonic dispersion, are discussed. The intercalated nanocomposite is further treated at 250.0°C for 2 h in order to eliminate surfactant in OMT. On the basis of the SAXS and TGA results, it has been found that the treated product remains in its intercalated structure and presents better thermal stability, which provides potential usage in polymer composites. POLYM. COMPOS., 27: 660–664, 2006. © 2006 Society of Plastics Engineers