Electrostatic Coalescence: Reactor,Process Control,and Important Parameters

Abstract

An optimal breakage of liquid membrane emulsions is desirable for the industrial application of liquid membrane extraction. The electrostatic emulsion breakage process was investigated with regard to its parameters. The results show that the breakage efficiency increases with the applied field strength, frequency, and the achievable polarization of the membrane phase molecules. An on-line measurement of the applied field strength allows control of the process efficiency.     

Multichannel Flow Electrophoresis in an Alternating Electric Field

Abstract

Investigation on the mass transfer behavior of multichannel flow electrophoresis (MFE) has confirmed the existence of concentration polarization in the separation process, which is characterized by a reduction of the relative protein migration flux corresponding to an increase in the protein concentration in the feed. The mobility of bovine serum albumin (BSA) in a gel membrane, as interpreted from its elution curve, was about one-sixth of its mobility in solution as determined by high capillary electrophoresis. This indicates that accumulation of charged protein onto the membrane surface occurs in MFE. An alternating electric field was applied instead of the steady one in MFE. The negative part of the alternating electric field reduced the polarization layer periodically. The effectiveness of this method was demonstrated by an over 40% increase of BSA migration flux at pH 6.9 in an optimized alternating electric field. The separation outputs of BSA and hemoglobin bovine blood conducted in an optimized alternating electric field at pH 6.0 were about 26 and 32% higher than their respective outputs obtained in a steady electric field. Because of its proven efficiency for reducing concentration polarization and its ease of operation, the use of an alternating electric field is a promising application in other membrane separation processes.     

Enhanced Coalescence of Emulsion in an Electric Field

Abstract

The action of an electric field on an emulsion produced effects like drop disintegration and promoted coalescence. High and low field intensities modify droplet displacements due to electrostatic forces. In this investigation a water-in-oil type of emulsion was prepared using distilled water and soap as the surfactant. After mixing, these emulsions were separated under an applied direct current high voltage electric field at a fixed 2.09 kV applied output voltage across the system. The time of coalescence, upper plate position, mixing time, and dispersion/coalesced phase volume interface are the parameters considered to influence the coalescence parameter and dispersion band hold-up. The results show that the prepared emulsion can be separated back into its bulk phases by using electric fields. The degree of separation depends on the applied voltage.     

Membrane Aging and Related Phenomena in Liquid Surfactant Membranes Process

Abstract

The membrane aging phenomenon and its influences on the kinetics of cobalt(II) permeation by the liquid surfactant membranes (LSM) process has been studied. The experimental results showed that the emulsion formulated from the internal aqueous phase and the membrane (organic phase) of a certain age has far-reaching consequences on the kinetics of metal extraction and emulsion stability. The investigations have revealed that there exists an optimal age and composition of the membrane in which the highest extraction (synergism) and the lowest emulsion swelling are achieved. Analytical and instrumental examinations of the membrane phase during aging have shown various chemical and physical changes as a result of the surfactant decomposition, reaction products precipitation and self-association, and macroemulsion formation.

     

Selective Separation of Gallium from Acidic Leach Solutions by Emulsion Liquid Membranes

Abstract

The separation and concentration of gallium from acidic leach solutions, containing various other ions such as iron, cobalt, nickel, zinc, cadmium, lead, copper, and aluminium, by an emulsion liquid membrane (ELM) technique using tributyl phosphate (TBP) as carrier has been presented. Liquid membrane consists of a diluent, a surfactant (ECA 4360J), and an extractant (TBP), and 0.1 M HCl or 0.1 M H₂SO₄ were used as the stripping solution. The important variables governing the permeation of gallium and their effect on the separation process have been studied. These variables were membrane type and composition, mixing speed, diluent type, surfactant concentration, extractant concentration, HCl concentration in the feed, acid type of stripping phase, feed concentration, and treatment ratio. The optimum conditions were determined. It was possible to selectively extract 96.0% of gallium from the acidic leach solutions, containing Fe, Co, Ni, Zn, Cd, Pb, Cu, and Al, at the optimum conditions.     

The Effect of Pulsed Direct Current Field on the Membrane Flux of a New Style of Membrane Bioreactor

The effect of a pulsed direct current electric field on the membrane flux of an antifouling Membrane Bioreactor (MBR) designed and built in the laboratory was studied. The results showed that a pulsed direct current electric field had a significant effect on the membrane flux. The average membrane flux when using a pulse direct current electric field was between that of a steady electric field and that of no electric current under a trans‐membrane pressure drop of ΔP = 0.1 MPa and a pulsed direct current electric field strength of 20 V/cm. There was an optimum value of pulse intensity and pulse duration for the membrane flux. The shorter the pulse interval time was, the higher the frequency of power‐on, and the higher the average stable membrane flux of the MBR. This may have resulted from the fact that charged coarse particles and colloids account for 80 % of COD_cr and BOD₅ in urban domestic sewage. These particles and colloids moved away from the membrane surface at a certain electrical field strength, gradually thinning the particle sedimentary layer, reducing the membrane filtration resistance, and increasing the membrane flux significantly. However, the formation of a sedimentary layer on the membrane surface needed a significant amount of time and an appropriate pulse frequency while the MBR is powered on. This could save energy while keeping the membrane clean.     

Liquid Membranes: Advancing Reaction Zone Model for Finite Reactions

Abstract

An advancing reaction zone model has been proposed for a multiple emulsion liquid membrane for the case of simple permeation with finite reaction at the inner interphase. The model has been numerically solved and the effect of different system parameters on the rate of extraction and on the concentration profiles in the emulsion globule has been discussed.     

Separation and Concentration of Phenylalanine by Emulsion Liquid Membrane in a CSTR Extraction Process

Abstract

The extraction and concentration of phenylalanine by the continuous CSTR emulsion liquid membrane (ELM) separation process has been evaluated. We discussed the influence of operating conditions on the separation and concentration efficiencies of phenylanine. It was found that the extraction rate of phenylalanine increased as the amount of emulsion used and the internal concentration of H⁺ increased. However, the concentration ratio of phenylalanine increased as the emulsion amount and acid concentration increased only up to a certain limit and then declined with further increases of these. The reduction of the concentration ratio is due to the swelling of the emulsion drops. Two effects, swelling owing to osmotic pressure and swelling caused by the entrainment of water due to mechanical agitation, are responsible for the swelling of emulsion drops. A mass transfer model for analyzing the extraction of phenylalanine by liquid surfactant membrane is presented. The model assumes that the extraction and stripping reactions are reversible, and that the reaction equilibrium exists in both the internal and the external interfaces. The scheme for mass transfer is based on a hollow sphere model. The phenomena of osmotic swelling, mechanical entrainment, and breakage are all considered in the mathematical treatment. The effects of operation parameters on the extraction efficiency and concentration ratio are discussed by simulation.     

Electrostatic enhancement of coalescence of water droplets in oil: a review of the technology

The technology for electrostatic enhancement of coalescence of water droplets in oil emulsions is critically reviewed. Historically, the electrostatic coalescer was invented for the petroleum-related industries in California [US Patent 987 115 (1911)]. Nowadays, this technology is generally considered for the separation of an aqueous phase dispersed in a dielectric oil phase with a significantly lower dielectric constant than that of the dispersed phase. Various designs have been introduced, with most using alternating current (AC) electric fields with mains frequency (50 or 60 Hz). The direct current (DC) electric field has been less common in the past as compared to the AC. In 1981, the concept of pulsed DC electric fields was introduced, together with insulated electrodes [Trans. IChemE 59 (1981) 229–237; UK Patent 217 1031A (1986)]. Since then, this has become more common in the electrocoalescence technology. Pulsed DC and AC fields are especially useful, when the aqueous phase content of the emulsion is high, to prevent short-circuiting between the pair of electrodes. Processing of oil from old wells is a good example, where the volumetric water content could vary significantly. Reported work by some workers indicates the existence of an optimum frequency, which depends on the electrode coating material, its thickness and the liquid emulsion composition. This is however, a contentious issue which has not been completely resolved. The characteristics and geometry of the electrode system (generally cylindrical or plate) influence the performance of the electrostatic coalescer, and are closely related to the type of the applied electric field and the emulsion used. There are basically two types of electrode: uninsulated electrode and insulated electrode. Combination of electrocoalescence and mechanical separation (e.g., centrifugal force) has also been introduced. Heating and the addition of chemicals have been shown to further enhance the electrocoalescence of water droplets. Other methods that can be combined with the electrical treatment are filtration, methods employing high pressure and temperature, and mixing. This review paper also looks at some of the current specific industrial applications using the electrocoalescence technology. Besides the oil and petroleum industries, this technology has potential applications in the edible oil industries such as palm oil, sunflower oil and vegetable oil processing. Most of the currently available equipment is very big and bulky, having a large inventory of emulsion. Therefore, we see the future trend for new developments to be in the direction of inventing small portable devices, incorporating features such as optimum electric fields and combined electrical and centrifugal forces to further enhance the separation of water-in-oil emulsions. Furthermore, a better understanding of the fundamentals of electrocoalescence will enable a better design of the geometry of the electrodes, of the flow field with respect to the electric fields, the type of dispersion used and the type of the applied electric field.     

Membrane Recovery in Liquid Membrane Separation Processes

Abstract

The use of conventional electrostatic coalescers with bare metal electrodes for the separation of rich water-in-oil emulsions often causes the formation of a sponge-like emulsion. This effect was eliminated by the use of insulated electrodes in a coalescer that allow the application of high electric fields at the oil/water interface, resulting in a clean separation of oil from water.     

Coupling Electrophoresis with Ultrafiltration for Improved Processing of Plasma Proteins

Abstract

The feasibility of coupling electrophoresis with ultrafiltration (electroultrafil-tration) in order to increase the flux and improve the selectivity of the ultrafiltration process was demonstrated experimentally for protein solutions. An electric field controlled the build-up of retained proteins at the membrane surface. Electroultrafiltration fluxes were 3 to 5 times greater than normal ultrafiltration fluxes. Retention and separation factors were also higher. The effects of important process variables were studied.     

Emulsion polymer derived nanocomposite: a review on design and tailored attributes

ABSTRACT

Recently, fabrication of polymeric nanocomposite via emulsion polymerization process has become a research spotlight. This review highlights the capability of emulsion polymerization technique to produce polymeric nanocomposite with tailored nanostructures, advanced properties, and high performance. Initially, overview on emulsion polymerization is presented. Afterward, advances in nanocomposites through the use of nanoparticles in emulsion polymerization have been elaborated. Main focus is given on the influence of graphene, carbon nanotube, carbon black, nanoclay, and inorganic nanoparticles on the essential features of emulsion polymerized nanocomposite. These materials have wide-ranging applications in coatings, adhesives, foaming/anti-foaming agents, packaging, paper/textiles, construction, and drug delivery fields.     

On the Splitting of d.c. Contribution to the Dielectric Loss. Case of Poly(monocyclohexylitaconate)

Abstract

The splitting of the d.c. conductivity on the low frequency side of the dielectric loss has been performed by using the complex dielectric polarizability α, instead of the permittivity. Data dealing with the dielectric loss for poly(monocyclohexylitaconate) have been used to compare both methods. The dielectric relaxation peaks in M″ and α″, are in general in good qualitative agreement. There is a small shift which is attributed to the fact that M is a modulus and α a compliance.     

流花油田老化油高频/高压脉冲交流电场破乳脱水研究

在测定老化油乳化液粘度-温度曲线、含水率反相点曲线的基础上,采用静态静电聚结破乳实验装置研究了油水反相特性对电场破乳脱水效果的影响,使用自主搭建的动态破乳脱水特性快速评价装置研究了高频/高压脉冲交流电场下电场强度和频率对老化油乳化液破乳脱水效果的影响. 结果表明,流花油田老化油反相点含水率约为40%,油水反相过程中乳化液粘度增加,电场破乳脱水难度增大;老化油乳化液含水率为30%时,最优电场强度1.25 kV/cm、电场频率2.5 kHz下破乳后的离心脱水率为97.8%,远高于工频电场下的离心脱水率(4.2%),高频/高压电场破乳比工频/高压电场破乳优势明显.     

Liquid Emulsion Membrane (LEM) Process for Vanadium (IV) Enrichment: Process Intensification

Abstract

A liquid emulsion membrane (LEM) system for vanadium (IV) transport has been designed using di‐2‐ethylhexyl phosphoric acid (D2EHPA), dissolved in n‐dodecane as carrier. The selection of extractant, D2EHPA, was made on the basis of conventional liquid‐liquid extraction studies. The work has been undertaken by first carrying out liquid‐liquid extraction studies for vanadium (IV) to get stoichiometric constant (n), and equilibrium constant (K_ex), which are important for process design.

Transport experiments were carried out at low vanadium (IV) concentration (ppm level). The studies on liquid emulsion membrane included i) the influence of process parameters i.e. feed phase pH, speed of agitation, treat ratio, residence time and ii) emulsion preparation study i.e., organic solvent, extractant concentration, surfactant concentration, internal strip phase concentration. When the strip phase concentration was 2 mol/dm³ (H₂SO₄) and feed phase pH 3 better extraction of vanadium was obtained. Higher V_m/V₁ gave higher extraction of vanadium (IV). A simplified, design engineer friendly model was developed.     

New Matrix Materials for Molten Electrolyte Membranes

Abstract

An electrochemical flue gas desulfurization process has been developed and shown to remove 98+% of SO₂ from simulated flue gas (0.3% SO₂) by flow past an electrolyte-filled membrane. An applied electric field preferentially removes SO₂ and produces a concentrated by-product stream of SO₃. The only reagent required for the process is electricity; this permits the process to have favorable economics.

The electrolyte is retained by a matrix of inert powder which forms a membrane. The matrix is designed to retain the molten electrolyte and prevent electrode pore flooding; flooding reduces interfacial area and increases the electrical requirements. New membrane formulations have been tested for increased electrolyte retention; the preparation of membranes with borosilicate glass or zeolites as the matrix is presented. The capillary action of the zeolite is higher than that of the porous electrodes. This enables the process to operate with a higher mass transfer area, allowing higher current densities. Polarization is compared with that of a MgO-based membrane.     

Two-Component Emulsion Liquid Membranes with Macromolecular Carriers of Divalent lons

Abstract

Experimental investigations are presented on the application of poly-[poly(ethylene glycol) phosphate] (PEGP) as a macromolecular, multisite, carrier of ions in an emulsion liquid membrane system. This polymer acts as a mobile carrier and surfactant-stabilizing W/O/W emulsion. The transport properties of PEGP have been checked for systems composed of (a) a feed phase containing Ni(II), Co(II) or Cu(II) ions; (b) an organic phase, i.e., PEGP dissolved in 1,2- dichloroethane; and (c) 1 M sulfuric acici as a receiving solution. Fast and effective membrane extraction of Ni(II) has been found for membranes with PEGP of molecular weight 22,000. It has been proved that the affinity of PEGP toward the studied ions is reversed in comparison with that for poly(ethylene glycol). The affinity order of PEGP toward the tested ions is Ni(II) > Co(II) > Cu(II).     

Study on Competitive Transport of Heavy Metal Ions Through Liquid Surfactant Membrane

Abstract

In the present work an attempt has been made to develop a mathematical model for competitive transport of Cr(VI) and Mo(VI) through liquid surfactant membrane from acidic solution using Alamine‐336 and Caustic Soda as extractant and stripping reagent respectively. A reaction front has been assumed to exist within the emulsion globule in the proposed model. It has been assumed that, an instantaneous and irreversible reaction takes place at the membrane‐internal stripping phase interface between the solute and internal stripping reagent. Experiments on simultaneous extraction of Cr(VI) and Mo(VI), in batch mode, from aqueous solutions of Potassium Dichromate and Ammonium Molybdate have been carried out with the initial concentration of the solutes between 50–100 mg/l. Experiment on emulsion stability has also been performed to arrive at a reasonably stable emulsion composition. Effect of initial solute concentration on distribution coefficient has also been found experimentally and fitted by a semiemperical model that has been used in the computer simulation of the simultaneous extraction process. It has been found that the experimental results are within reasonably close proximity with the simulated curves.     

Recovery of Nitrophenols from Aqueous Solutions by a Liquid Emulsion Membrane System

Abstract

The application of liquid emulsion membrane technology to the extraction of nitrophenols from aqueous solutions is discussed. The effects of various parameters such as hydrophilic lipophilic balance of the surfactants, speed of agitation, water volume fraction in the water-in-oil emulsion, treatment ratio, and the concentration of surfactant on the extraction of p-nitrophenol are studied, and a suitable formulation for a liquid emulsion membrane is developed. The same formulation was used to extract o-nitrophenol and 2,4-dinitrophenol, and the results are compared with those of p-nitrophenol. The swelling of the emulsion during extraction is minimized by the addition of cyclohexanone to the membrane phase. The demulsification of the emulsion phase after extraction is also carried out by a chemical demulsification technique. Acetone is used for demulsification.