Microemulsion Liquid Membranes. I. Application to Acetic Acid Removal from Water

Abstract

A separation technique utilizing nonionic microemulsions as emulsion liquid membranes has been successfully applied to the removal of acetic acid from an aqueous feed phase. The surfactant systems were carefully characterized in order to assure that they were truly microemulsions. The effects of mixing intensity, feed concentration, treat ratio, and microemulsion viscosity on the separation kinetics were investigated. The microemulsions did not typically display leakage and had negligible swell over 5-minute duration. The reversible phase behavior of the microemulsion was utilized to demulsify the liquid membrane phase and recover the acetate ion via a temperature change of approximately 40°C. Material balances closed to within 10% and rates of separation were faster than the sampling rates when the microemulsion was fully dispersed in the aqueous feed phase.     

乳状液膜处理含醋酸废水的实验研究

对煤油-司班80-液体石蜡-氢氧化钠乳状液膜处理含醋酸废水溶液的过程作了系统研究,分析了影响醋酸脱除率的各个因素,探讨了内水相浓度、乳水比、油内比以及传质搅拌速率的最佳组合方案。实验结果表明,内水相的浓度2 mol/L,油内比1∶1,乳水比1∶6,传质搅拌速率250 r/min,废水中醋酸脱除率可达96%以上。     

液膜法处理H酸废水的多级萃取工艺研究

以Span-80、FSN-100为复合表面活性剂、三辛胺为流动载体,研究了三级逆流萃取时不同乳水比（Rcw）对废水COD去除率指标的影响,同时对逆流萃取后萃取相的破乳情况进行了考察,结果表明液膜法处理H酸废水的多级萃取工艺有较好的适应性。     

膜法处理H酸废水的初步研究

采用磺化聚醚砜中空纤维管膜萃取技术处理含H酸的水溶液，研究了流动方式、溶液pH、温度以及初始浓度对萃取效率的影响。实验结果表明，在水走壳程，有机相走管程，两相并流流动时，提高水相流速和有机相流速都会影响萃取效率。在两膜器串联、两相并流的情况下，可使初始质量浓度为2000mg·L^-1的溶液降至30mg·L^-1，证明了膜萃取去除H酸废水的可行性和高效性。     

Removal of Aniline from Wastewater Using Hollow Fiber Renewal Liquid Membrane

Hollow fiber renewal liquid membrane (HFRLM) method was proposed based on the surface renewal theory for removal of aniline from waste water. The system of aniline + D2EHPA in kerosene + HCl was used. Aqueous layer diffusion in the feed phase is the rate-control step, and the influence of lumen side flow rate on the mass transfer is more significant than that on the shell side. The resistance of overall mass transfer is greatly reduced because of the mass transfer intensification in the renewal of liquid membrane on the lumen side. The driving force of mass transfer can be considered as a function of distribution equilibrium, and the overall mass transfer coefficient increases with the increase of pH in the feed solution, HCl concentration and D2EHPA concentration, and decreases with the increase of initial aniline concentration. A mass transfer model is developed for HFRLM based on the surface renewal theory. The calculated results agree well with experimental results. The HFRLM process is a promising method for aniline wastewater treatment.     

Separation of Palladium and Silver from a Nitric Acid Solution by Liquid Surfactant Membranes

Abstract

The recovery of palladium from a nitric acid solution containing silver has been conducted by application of liquid surfactant membranes (LSMs) containing LIX 860, a β-hydroxyoxime, as a mobile carrier in a stirred tank. The extraction equilibria of palladium and silver using several different extractants were also studied. Palladium was selectively extracted from a silver-containing liquor with LIX 860 while it was also observed that both palladium and silver were extractable with a sulfur-containing extractant. The recovery of palladium with LIX 860 was selectively achieved by using perchloric acid solution as the LSM internal phase dosed with thiourea. In the LSM operation, the effects of several chemical parameters on the selective recovery of palladium were studied. The use of hydrochloric acid as an internal receiving phase prevented the transport of silver into the emulsion due to the formation of silver chloride in the external feed solution. Commercially available Span 80 was found suitable for the selective extraction of palladium as a surfactant in LSM operation. Under optimum conditions, palladium was successfully separated from silver and concentrated into a receiving phase in W/O emulsions.     

十二烷基苯磺酸乳化液膜法净化湿法磷酸除镁

采用乳化液膜技术对湿法磷酸进行净化处理,针对磷酸-镁体系,选用带磺酸基团(-S03H)的十二烷基苯磺酸作为萃取剂,在其不同浓度下对pH=0.27的磷酸体系中的镁离子进行净化实验,得到了乳化时表面活性剂十二烷基苯磺酸的临界浓度。最佳实验条件:十二烷基苯磺酸在有机相中的临界浓度为摩尔分率10%,最佳油水体积比为1/3,最佳乳化转速为5400 r/min,最佳乳化时间45 s。     

Separation of Cobalt and Nickel with Phenylphosphonic Acid Mono-4-tert-octylphenyl Ester by Liquid Surfactant Membranes

Abstract

The separation of cobalt and nickel with liquid surfactant membranes (LSMs) was carried out in a stirred cell using a newly synthesized extractant. The effect of a surfactant on the kinetics of cobalt and nickel extraction was investigated to elucidate the role of a surfactant used in LSMs. The extraction equilibrium of these metals was also examined. Further, the interfacial tension between the organic and aqueous phases was measured to elucidate the adsorption equilibrium of a surfactant. It was found that the interfacial activity of the extractant is as high as that of a surfactant. In the extraction equilibrium study of these metals, extraction equilibrium constants were obtained for cobalt and nickel for the following equations:

Co²⁺ + 2(HR)₂=CoR₂(HR)₂ + 2H⁺ Ni²⁺ + 3(HR)₂=NiR₂2(HR)₂ + 2H⁺ The effects of the extractant and surfactant on the extraction rate of cobalt and nickel in LSMs were studied. The results were analyzed by a proposed model with an interfacial reaction, and rate constants were obtained for each metal. It was found that the new extractant has a very strong extractability for each metal compared with a conventional commercial extractant such as 2-ethylhexylphosphonic acid mono-2-elhylhexylester (commercial name, PC-88A) or di(2-ethylhexyl)phosphoric acid (D2EHPA). Further, a surfactant strongly affected the extraction rate and the separation of these metals, and a cationic surfactant was selected.     

乳化液膜法处理有机萘磺酸类废水的应用及稳定性

介绍了乳化液膜法处理含有机萘磺酸类工业废水的分离技术 ,分析了萃取过程中表面活性剂种类和浓度、内相浓度、外相pH等因素对膜稳定性的影响 ,论述了增强液膜稳定性的措施 ,并提出了该技术的研究进展和应用前景     

吸附-热再生法回收废水中醋酸的研究

针对浓度为3%的醋酸废水,选用YK-15椰壳炭为吸附剂,采用吸附和分步热再生法从废水中分离醋酸,达到了废水处理和醋酸回收的双重目的.系统地考察了动态吸附和分步热再生的工艺条件,结果表明,在温度为30℃,废水流速为7.3×10-5 m·s-1的适宜条件下,YK-15椰壳炭对醋酸的动态吸附容量为161.0 mg·g-1,穿透点处废水的处理能力为4.7 g(废水)·g-1(活性炭).对吸附剂进行分步热再生的适宜条件是,第一步控制温度为110～130℃,脱除吸附柱内35%～40%的残余水,以浓缩醋酸.第二步继续升温至320℃,脱附并回收醋酸,醋酸的脱附率可达96%以上,收率为87%,回收醋酸的浓度为30%左右.吸附–脱附的循环实验表明,活性炭的吸附和脱附性能稳定,数据重现性好.     

乳状液膜法从铀矿的硫酸浸出液中提取铀的研究

本文研究了以双丁二酰亚胺为表面活性剂,三正辛胺为载体,磺化煤油为溶剂,碳酸钠为膜内相组成的乳状液膜体系,从矿石硫酸浸出液中提取铀.考察了各种因素对膜稳定性和铀提取率的影响,提出了适宜的工艺条件.结果表明,此乳状液膜体系对铀具有迁移速度快,提取效率高,选择性和稳定性好的优点.铀的提取率可达99.4%.     

Similarity Solutions of Marangoni Convection Boundary Layer Flow with Gravity and External Pressure

This study is focused on a steady dissipative layer, which is generated by Marangoni convection flow over the surface resulted from an imposed temperature gradient, coupled with buoyancy effects due to gravity and external pressure. A model is proposed with Marangoni condition in the boundary conditions at the interface. The similarity equations are determined and approximate analytical solutions are obtained by an efficient transformation, asymptotic expansion and Pade approximant technique. For the cases that buoyancy force is favorable or unfavor-able to Marangoni flow, the features of flow and temperature fields are investigated in terms of Marangoni mixed convection parameter and Prantl number.     

乳状液膜法处理三氯乙醛废水的研究

本工作是用乳状液膜法处理三氯乙醛废水的初步实验.实验系将氢氧化钠水溶液包以煤油作为液膜,处理含有50—200ppm的三氯乙醛水溶液.实验考察了影响三氯乙醛渗透的一些因素,在适当的条件下可以脱除95%以上的三氯乙醛.并计算了该液膜体系的总包传质系数,结果表明它趋向于一个恒定值.     

稀硝酸作吸收剂的气态膜法回收废水中氨氮

利用稀硝酸作吸收剂研究了基于聚四氟乙烯(PTFE)中空纤维微孔疏水膜的气态膜分离过程用于脱除/回收废水中氨氮并制取硝酸铵的可行性和长期操作稳定性。在相同的操作条件下对用PTFE、聚丙烯(PP)和聚偏氟乙烯(PVDF)制得的3种膜接触器的除氨性能进行了系统的比较,并研究了料液进口浓度、流速、温度条件对3种膜接触器传质性能的影响。实验数据表明中空纤维膜内径和壁厚是影响传质过程的最主要因素,且总传质系数K、膜侧传质系数kM、管程液相传质系数kL均随温度的升高而显著增加。室温下长期实验结果显示:PVDF膜运行7 d后发生严重泄漏,PP膜稳定运行20 d后传质系数显著下降,PTFE膜运行30 d时性能仍然保持稳定。表明具有良好耐硝酸氧化性的PTFE膜为气态膜法脱除/回收废水(或化工料液)中氨氮并制取硝酸铵的工业化应用提供了基本保障。     

活性炭UF膜分离污水中COD的实验研究

试验考察了粉末活性炭的投加对超滤膜运行性能的影响,结果表明:随粉末活性炭投量的增加膜稳定运行时间延长,通量下降率降低。粉末活性炭的投加对膜过滤阻力影响不大。在此基础上又对PAC-UF组合系统去除有机物的效果进行了进一步研究,主要是对比研究了不同PAC投加量对5种不同配置水样中有机物的去除效果。得出如下结论:在相同PAC投加量下,CODMn值大的水样的CODMn平均去除率高,且出水CODMn值相近。说明了PAC-UF组合系统出水稳定,受水质差异的影响不大。     

Facilitated Transport through a Liquid Surfactant Membrane with Continuous Phase Resistance: Role of Drop-Size Distribution

Abstract

An advancing reaction front model with drop-size distribution has been proposed for the case of facilitated transport through a liquid surfactant membrane. The model takes into account the continuous phase and outer liquid membrane phase resistances along with diffusion through a composite emulsion drop. The computed results are found to be in excellent agreement with the experimental data of Ho et al. The outer liquid membrane phase resistance seems to be an important parameter in controlling the overall extraction rate. Analytical solutions to model equations for uniform drop size are also presented in this study. The model is also capable of predicting the effect of various parameters on the overall extraction rate for the limiting cases of inverse Biot modulus tending to zero and infinity.     

Effect of Electrolyte and Temperature on Volatile Organic Compounds Removal from Wastewater Using Aqueous Surfactant Two-Phase System of Cationic and Anionic Surfactant Mixtures

Abstract

Benzene, toluene, ethylbenzene, and xylene are frequently observed contaminants in industrial wastewaters causing concerns about environmental and health effects. An aqueous surfactant two-phase (ASTP) extraction system using mixtures of cationic and anionic surfactants have been shown to be a promising surfactant-based separation technique to concentrate solutes such as proteins and dyes from aqueous solution. A phase separation of a surfactant solution occurs at certain surfactant compositions and concentrations, forming two isotropic phases. One is rich in surfactant aggregates (surfactant-rich phase) and the other is lean in surfactant aggregates (surfactant-dilute phase). Most of the organic contaminants tend to solubilize and concentrate in the surfactant-rich phase, leaving the surfactant-dilute phase containing only small amounts of contaminants as remediated water. The effect of NaCl addition on the critical micelle concentration (CMC) and the extraction ability of ASTP formed by mixtures of cationic surfactant (dodecyltrimethylammonium bromide; DTAB) and anionic surfactant (alkyl diphenyloxide disulfonate; DPDS) at 50 mM total surfactant concentration with a 2:1 molar ratio of DTAB:DPDS was investigated; the CMC of the mixture slightly decreases with increasing NaCl concentration. The extraction and preconcentration of benzene are greatly enhanced by added NaCl. The higher the degree of hydrophobicity of contaminants, the greater the extraction into the surfactant-rich phases. At 1.0 M NaCl addition, about 95% of xylene, 92% of ethylbenzene, 90% of toluene, and 79% of benzene are extracted into the surfactant-rich phase within a single stage extraction and the contaminant partition ratios can be as high as 395 for xylene, 273 for ethylbenzene, 206 for toluene, and 84 for benzene, which are greater than those obtained from the conventional ASTP extraction system using nonionic surfactants.     

Preparation of Peracetic Acid from Acetic Acid and Hydrogen Peroxide: Experimentation and Modeling

Based on the kinetic equations and equilibrium constants, some mathematic models were developed for calculating peracetic acid (PAA) concentration, equilibrium conversion rate of hydrogen peroxide, etc. The effects of several parameters on PAA synthesis were investigated by experimentation and modeling. The equilibrium constants determined from the forward and reverse rate constants at 293, 303, 313 and 323 K were 2.91, 2.81, 2.72 and 2.63, respectively. The models could predict the values of equilibrium concentration of PAA with average relative deviation of less than 10%. Both of the experimental and model-calculated results demonstrated that temperature and catalyst loading were the most important factors affecting the rate of PAA synthesis, but high temperature led to the decrease of equilibrium concentration of PAA. According to the model, the reaction could achieve equilibrium within 24 h when operated at 303 K with 1%~1.5%(w) sulfuric acid as catalyst. Additionally, when using anhydrous acetic acid and 30% hydrogen peroxide to prepare PAA, the volumetric ratio of the two solutions should be in the range of 1.2~1.5 in order to obtain the highest equilibrium concentration of PAA. This study can serve as a step towards the further optimization of PAA synthesis and some other related investigations.     

Development of Liquid Membrane Pertraction for the Removal and Recovery of Chromium from Aqueous Effluents

Abstract

Liquid membrane pertraction combines the loading and stripping steps of solvent extraction into a single unit operation, allowing the continuous removal and concentration of a given species. In this paper the feasibility of applying liquid membrane pertraction to the recovery of chromium (Cr(VI) from aqueous effluents with the objective of reducing levels to below allowable discharge limits has been examined. A continuous laboratory-scale liquid membrane pertractor was constructed to solve a variety of problems associated with the treatment of Cr(VI)-bearing streams. Various operational factors such as feed velocity, strip velocity, membrane velocity, and composition of the inlet feed were then examined. Satisfactory continuous runs lasting up to 22 days were achieved. Chromium levels in synthetic waste could be reduced from 200–300 mg/L down to 1 mg/L, well within most allowable discharge limits. Experiments showed that the strip phase can be concentrated with inlet Cr(VI) concentrations of 2000 ppm Cr(VI), with indications that it should be possible at even higher concentrations.