Membrane-based Solvent Extraction Research Articles

Removal of phenol from wastewater by different separation techniques

Application of membrane techniques (pervaporation and membrane-based solvent extraction) and adsorption tothe removal of phenol from solutions modelling wastewater from phenol production by cumene oxidation processwas investigated. The transport and separation properties of composite membranes PEBA, PERVAP 1060 and PERVAP 1070 in pervaporation of water-phenol mixtures were determined. It was found that the best removal efficiency ofphenol was obtained using the PEBA membrane. MTBE, cumene and the mixture of hydrocarbons were applied in the membrane-based phenol extraction. Extra-Flow contactor with Celgard X-30 polypropylene hollow-fiber porousmembranes was used in the experiments. MTBE was found the most efficient extractant. Adsorption of phenol on the different Amberlite resins was also investigated. Among the Amberlite resins of various grades used, the Amberlite XAD-4 had the best properties in the phenol removal from the aqueous solutions. It was shown that regeneration of the adsorbent bed could be effectively performed with sodium hydroxide solution.

Membrane based solvent extraction and stripping of a heterocyclic carboxylic acid in hollow fiber contactors

Simultaneous membrane based solvent extraction (MBSE) and membrane based solvent stripping (MBSS) in HF contactors of a heterocyclic carboxylic acid (HCA) of industrial importance from sulphate solutions with solvent containing trioctylamine (TOA) were studied. An effective transport of HCA was achieved. The proposed reaction-diffusion model gives a much better fit to experimental values than the diffusion model. The mean values of the lumped rate constants of extraction and stripping reactions for HCA are 2.19.10 −6 and 5.92.10 −6 m.s −1, respectively. The mass-transfer resistances based on reaction kinetics play a decisive role in MBSE and MBSS of HCA and participate in their overall resistances by about 65 and 40%, respectively.

Membrane-based solvent extraction of sulfur aroma compounds: influence of operating conditions on mass transfer coefficients in a hollow fiber contactor

Membrane-based solvent extraction is proposed to recover sulfur aroma compounds from an industrial effluent. It consists in transferring the aroma compounds from water into an organic solvent by contacting the two phases inside the pores of a membrane. Mass transfer experiments were performed using a crossflow hollow fiber membrane module, with hexane and miglyol as stripping solvents and synthetic aqueous feed phases with three diluted sulfur compounds. Selective extraction of the aroma compounds is due to the high partition coefficients of aroma compounds between water and the selected solvents. Diffusion inside the organic-filled pores is negligible using hexane, but becomes very important using miglyol, due to its high viscosity. Both tube and shell side compartments are able to receive the feed phase. For these two configurations, mass transfer coefficients are equivalent using hexane as a stripping solvent, but a larger interfacial area is offered when the aqueous feed phase flows in the shell.

Recovery of aroma compounds from tomato industry effluent using membrane-based solvent extraction

This work focuses on a non-destructive process for recovering valuable aromatic fractions from an odorous tomato industry aqueous effluent. Non-dispersive solvent extraction of four selected aroma compounds, chosen as key aroma, was, at first, carried out on very diluted model aqueous solutions. Mass transfers from water to n-hexane and from water to Miglyol (two solvents widely used in aromatic industry) were studied using a cross-flow designed hollow fibre membrane contactor. The influence of physico-chemical properties of the aroma compounds studied and the influence of the solvent viscosity on mass transfer are discussed. The results obtained with model solutions have been validated on the industrial process effluent.

Analysis of concentration boundary layer in thallium (III) extraction with butyl acetate using membrane modules of different length

The development of concentration boundary layer (CBL) inside the hollow fibers, based on the experimental data from membrane-based solvent extraction of thallium (III) from chloride-containing acidic solutions with butyl acetate, was investigated. The experiments have been performed using three laboratory made contactors, consisting of hydrophobic polypropylene or polyvinylidene fluoride fibers of different length. The feed solution flowed inside the fibers, while the organic phase was pumped counter-currently at the module shell side. The influence of aqueous flow rate on the mean mass transfer coefficient in the aqueous phase was investigated. The tube-side Sherwood number was proportional to the Graetz number raised to powers ranging between 0.4 and 0.81. A model for the determination of CBL thickness and entry length was developed and used for the numerical analysis of the process. The entry length, i.e. the axial distance from the fiber inlet at which CBL reaches the axis of the fibers, was directly proportional to the aqueous phase flow rate and inversely proportional to the number of fibers in a module.

Factors influencing transport through liquid membranes and membrane based solvent extraction

Based on experimental data from pertraction through liquid membranes and membrane based solvent extraction (MBSE) or solvent stripping (MBSS) of butyric acid (BA), phenylalanine (Phe), and heterocyclic carboxylic acid (HCA), the influence of the formulation of the membrane phase, kinetics of the acid/carrier complex decomposition, composition of the donor phase, and hydrodynamic conditions on pertraction and MBSE is discussed. The analysis of mass-transfer resistance including the resistance based on reaction kinetics in pertraction through bulk and supported liquid membranes and in MBSE and MBSS in hollow fibre contactors is presented. It has been found that mass-transfer resistance based on the reaction kinetics on the stripping interface represents about 38% of the overall resistance in pertraction of BA and about 60% in MBSS of BA from the complex with trioctylamine extractant. Aggregation and/or formation of a microemulsion at the concentration of DEHPA in the membrane phase above 1 kmol·m–3 substantially decrease the transport rate of Phe through the layered liquid membrane. Competitive transport of HCl decreases greatly the transport of HCA through liquid membrane with TOA as a carrier while the influence of the co-transport of H2SO4 is very small. Transport of the mineral acid from chloride media is much higher than from sulphate media.

Factors influencing transport through liquid membranes and membrane based solvent extraction

Based on experimental data from pertraction through liquid membranes and membrane based solvent extraction (MBSE) or solvent stripping (MBSS) of butyric acid (BA), phenylalanine (Phe), and heterocyclic carboxylic acid (HCA), the influence of the formulation of the membrane phase, kinetics of the acid/carrier complex decomposition, composition of the donor phase, and hydrodynamic conditions on pertraction and MBSE is discussed. The analysis of mass-transfer resistance including the resistance based on reaction kinetics in pertraction through bulk and supported liquid membranes and in MBSE and MBSS in hollow fibre contactors is presented. It has been found that mass-transfer resistance based on the reaction kinetics on the stripping interface represents about 38% of the overall resistance in pertraction of BA and about 60% in MBSS of BA from the complex with trioctylamine extractant. Aggregation and/or formation of a microemulsion at the concentration of DEHPA in the membrane phase above 1 kmol m -3 substantially decrease the transport rate of Phe through the layered liquid membrane. Competitive transport of HCI decreases greatly the transport of HCA through liquid membrane with TOA as a carrier while the influence of the co-transport of H 2 SO 4 is very small. Transport of the mineral acid from chloride media is much higher than from sulphate media.

Recovery of sulfur aroma compounds using membrane-based solvent extraction

This work focuses on a non-destructive process for recovering valuable aromatic fractions from the food industry’s odorous wastewaters. Non-dispersive solvent extraction of three sulfur aroma compounds, dimethyldisulfide, dimethyltrisulfide and S-methyl thiobutanoate, was carried out from very diluted aqueous solutions representing real effluent. The mass transfer from water to n-hexane was studied using a cross-flow designed hollow fiber membrane contactor. A preliminary study showed high affinity of solutes for n-hexane, with constant partition coefficients at infinite dilution between water and hexane in a 90–560 range. The influence of tube and shell side hydrodynamics on mass transfer was studied, with the aqueous phase on the tube side, and the organic phase on the shell side. The diffusion of solutes from the bulk aqueous phase to the aqueous–organic interface controlled the separation and contributed, under the conditions tested, to more than 97% of the overall mass transfer resistance. A resistance-in-series model overestimated overall mass transfer coefficients. The main explanation is the inaccuracy of the Lévêque correlation used at low Reynolds numbers. The choice of a correlation for predicting mass transfers in the solvent phase did not affect the estimation, since the corresponding mass transfer resistance was negligible. Mass transfer fluxes obtained experimentally by membrane-based solvent extraction were greater for the three aroma compounds than those obtained by pervaporation.

Effect of mass transport resistances in multicomponent membrane extraction on the overall mass fluxes

An effect is studied of all the individual mass transport mechanisms on the overall mass fluxes during membrane extraction, i.e. for the process that is both energy efficient and easy to operate. In multicomponent systems each of the constituent mechanisms is defined by an appropriate matrix of mass transfer coefficients. The method developed to assess the relative importance of the individual transport mechanisms is validated using multicomponent extraction, studied experimentally by Kubaczka, Burghardt and Mokrosz (1998, Membrane-based solvent extraction in multicomponent systems. Chemical Engineering Science, 53, 899–917), as a test case. If resistances to mass transfer, identified by the method as insignificant, are omitted from the simulations, the agreement between numerical predictions and experiment is not impaired. It is also demonstrated that the accuracy of calculating mass fluxes in membrane extractors became worse when the variation of diffusivities with concentration along the diffusion path is neglected, and also, when the effect of the membrane on interrelationships between the mass fluxes (referred to the stationary system of coordinates) is not taken into account.

Membrane-based solvent extraction in multicomponent systems

Extraction with the use of a porous membrane which forms an interphase between two bulk phases and provides the physical surface for mass transfer is, in a number of applications, more efficient than that carried out in conventional devices. The present study focuses on the development of a general mathematical model of membrane extraction in multicomponent systems. The general method of calculating mass transfer resistances in porous membranes that allows for the effect of hindered diffusion in the membrane pores has been proposed. The appropriate system of kinetic and balance equations for the process takes into account the mass transfer resistance on both sides of the membrane and in the membrane itself, as well as the variation of diffusion coefficients with concentration. The mathematical model proposed was experimentally verified. The measurements and the appropriate calculations are described in detail. The results reveal that it enables successful simulation of the process in which aromatic hydrocarbons are separated out from aliphatic compounds using tetraethylene glycol; the average accuracy of the simulation of the outlet extractor concentrations was 15%.

Membrane-based solvent extraction and stripping of lactate in hollow-fibre contactors

This work reports lactate extraction with Aliquat 336, an ion-exchange carrier, using membrane contactors with hydrophobic microporous membranes. The overall mass-transfer coefficients were evaluated by either assuming a constant distribution coefficient or using the equilibrium equation. The mass-transfer coefficients calculated using the equilibrium relationship between C f ∗ and C O, proved to be more rigorous, since the variation of the distribution coefficient with solute concentration is accounted for throughout the extraction process. Assuming the resistance in series model, the membrane resistance was identified as the limiting step on the mass-transfer process. In order to increase the membrane mass-transfer coefficient, it is necessary to increase the diffusion coefficient of the lactate-amine complex; this can be achieved by reducing the viscosity of the organic phase either through a temperature increase or reduction of the carrier concentration. Using a plate-and-frame module with a well-defined hydrodynamic characterization of both phases, the mass-transfer coefficients can be rigorously evaluated; these were compared with the values obtained with hollow-fibre modules. Simultaneous extraction and stripping of lactate was accomplished using two hollow-fibre modules in series. This configuration assures that saturation of the carrier does not occur, as it is permanently regenerated; furthermore, the carrier concentration can be reduced while still maintaining the mass-transfer rate, thus decreasing the associated operating costs of the process.

Downstream Processing of Lactic Acid by Membrane-Based Solvent Extraction∗

Abstract Lactic acid has extensive use in the food and chemical industry. About half the lactic acid used in the world is produced by fermentation of carbohydrates using lactic acid bacteria. The recovery of lactic acid from the fermentation broth is more difficult than the fermentation itself. In the present work a study of membrane-based solvent extraction as a separation unit for the continuous downstream processing of lactic acid from fermentation broth was carried out. The experiments were performed using simulated fermentation broths made of lactic acid in acetate buffer or distilled water as the feed solution. The effects of membrane material, organic carrier, and pH of the feed solution on membrane extraction efficiency were investigated. A separation degree of 35% was obtained by using a polyether-etherketone (PEEK-WC 14%) membrane with 5% trioctylamine as the organic carrier in n-heptane. The experimental results obtained with the simulated system encourage the use of membrane-based solvent extraction with a real fermentation broth.

Removal of hexachlorocyclohexane isomers from water by membrane extraction into oil

Abstract Semi-volatile organic contaminants such as pesticides, PAHs and PCBs, as well as their more volatile counterparts, are being found in ground and surface waters with increasing frequency. It has been shown that removal of the volatile organic contaminants such as carbon tetrachloride and trichloroethene can be performed by membrane-based solvent extraction using a non-volatile oil as the solvent. The membrane is microporous polypropylene, coated to prevent wetting of the membrane pores by the oil phase. Solutes volatilize from water into the gas-filled membrane pores and are transferred to and concentrated in the oil phase. The hollow fiber shape of the membranes leads to a high specific surface area, and a very rapid removal rate; limited in most cases only by diffusion of the contaminant through water to the membrane surface. In this paper the applicability of this technology for removal of less volatile compounds from water is assessed. It is shown that the pesticide lindane (γ-hexachlorocyclohexane) and two other isomers of hexachlorocyclohexane can be removed from water at a rate similar to that of the volatile species. A transport model presented earlier is updated to include transfer through the membrane by surface diffusion, a mechanism proposed to explain the rapid transfer of species of low volatility. The model predicts rapid removal from water of a wide range of organic compounds.

Membrane-based solvent extraction for selective removal and recovery of metals

A membrane-based solvent extraction process was developed for selective removal and recovery of metals from aqueous solutions. The process utilizes microporous membranes as an interface between an aqueous solution and organic solvents containing liquid ion exchangers. Metal ions are transported from the aqueous solution to the organic phase at the interface created in the pores of membrane. The organic solvent, which is loaded with metal ions in the extraction module, is regenerated in contact with the stripping solution in the stripping module. One important feature of this process is the stability of the membrane system, which results from using an aqueous—organic separator to remove aqueous solution from the organic circulating line. This process was evaluated for enrichment of copper using solvents containing LIX 64N. The process is applicable to selective recovery of metals from ore leachates or metal-containing wastewater.