Showing papers in "Separation Science and Technology in 2006"

Ionic Liquids as Extraction Solvents: Where do We Stand?

Abstract: The unique physicochemical properties of ionic liquids (ILs) and the relative ease with which these properties can be fine‐tuned by altering the cationic or anionic moieties comprising the IL have led to intense interest in their use as alternatives to conventional organic solvents in a wide range of synthetic, catalytic, and electrochemical applications Recent work by a number of investigators has been directed at the application of ionic liquids in various separation processes, among them the liquid‐liquid extraction of metal ions Although certain IL‐extractant combinations have been shown to yield metal ion extraction efficiencies far greater than those obtained with molecular organic solvents, other work suggests that the utility of ILs may be limited by solubilization losses and difficulty in recovering extracted metal ions In this report, recent efforts to overcome these limitations are described, and progress both in achieving an improved understanding of the fundamental aspects of meta

A Review of the Use of Chitosan for the Removal of Particulate and Dissolved Contaminants

Abstract: Chitosan has unique properties among biopolymers, especially due to the presence of primary amino groups. Chitosan has been used for the chelation of metal ions in near‐neutral solution, the complexation of anions in acidic solution (cationic properties due to amine protonation), the coagulation of negatively charged contaminants under acidic conditions, and for precipitative flocculation at pH above the pKa of chitosan. The coagulation and flocculation properties can be used to treat particulate suspensions (organic or inorganic) and also to treat dissolved organic materials (including dyes and humic acid). This paper will give an overview of the principal results obtained in the treatment of various suspensions and solutions: (a) bentonite suspensions; (b) organic suspensions; (c) anionic dye solutions; and (d) humic acid solutions. Stoichiometry and charge restabilization were determined for the coagulation of humic acid, kaolin, and organic dyes with chitosan, indicating charge neutralization...

Biosorption of heavy metals by powder of green coconut shell

Abstract: Alternative processing methods are being considered more seriously, sorption and/or complexation of dissolved metals based on the chemical activity of biomass, known as biosorption, is the base of the new technology for metal removal and recovery. Different types of biomass (dead and alive) like bacteria, yeast, bark, fungi, agricultural by‐products, coconut shell, marine algae, peat, moss and aquatic mosses have been investigated for biosorption of heavy metals ions. Biosorption of each of the metal ions by coconut shell powder was investigated in this study. The biosorption capacities of coconut shell for cadmium, chromium, and arsenic were studied at different particle sizes (0.044–0.297 mm), initial metal concentration (20– 1000 mg/L), and solution pH values 2–9 in batch mode, the experimental data obtained for each metal were evaluated and fitted using adsorption models. Also, analyses were made of biomass by SEM‐EDS before and after the biosorption to confirm the presence of metal ions species.

Biofouling in Membrane Bioreactor

Abstract: A membrane bioreactor (MBR) combines membrane separation and biological treatment, normally involving the activated sludge process, in municipal wastewater treatment. Despite excellent performance over years of full‐scale operation, the interactions between microbes and the membrane in the MBR process, which determine its design and operational criteria, remain unclear. This report reviewed research regarding how numerous process parameters impact biofouling rates and, in particular, the possible contribution of microbial products to biofouling. This study also characterized different fractions of microbial products and assessed their potential affect on membrane fouling.

Separation and Preconcentration of Cesium from Acidic Media by Extraction Chromatography

Abstract: A novel extraction chromatographic resin for the separation and preconcentration of cesium from acidic nitrate media comprising an inert polymeric substrate impregnated with 1,3‐calix[4]bis‐o‐benzo‐crown‐6 (“BC6B”) in a chlorinated diluent is described. Cesium is shown to be both strongly and selectively retained by the resin at low (<1 M) acid concentrations and readily eluted from it using 6 M HNO3. Only potassium ion (at concentrations exceeding ca. 0.01 M) exerts a significant adverse impact on cesium retention. Unexpectedly, cesium uptake by the resin does not exhibit the acid dependency anticipated from liquid‐liquid extraction data. This is also the case for a resin employing a related macrocyclic extractant, calix[4]arene‐bis‐(t‐octylbenzocrown‐6) (“BobCalix”), prepared and partly characterized in an effort to overcome certain limitations of the BC6B‐based material. Despite this, the resin is shown to be well suited to the isolation of radiocesium from acidic solution for subsequent deter...

Extraction Chromatography Versus Solvent Extraction: How Similar are They?

Abstract: Over the last decade, extraction chromatography (EXC) has emerged as a versatile and effective method for the separation and preconcentration of a number of metal ions. Frequently, EXC is described as a technique that combines the selectivity of solvent extraction (SX) with the ease of operation of chromatographic methods. Despite this, the extent to which EXC actually provides the selectivity of SX and to which solvent extraction data can be used for the quantitative prediction of the retention of metal ions on an EXC column has remained unclear. To address these questions, the extraction chromatographic and solvent extraction behavior of lanthanides using three different acidic organophosphorus extractants bis‐(2‐ethylhexyl) phosphoric acid (HDEHP), 2‐ethylhexyl 2‐ethylhexylphosphonic acid (HEH[EHP]), and bis‐(2,4,4 trimethylpentyl)phosphinic acid (H[DTMPeP])) have been compared. Specifically, the rate and extent of uptake of selected lanthanides by the three extractants have been examined. In ...

Modelling Individual and Competitive Adsorption of Cadmium(II) and Zinc(II) Metal Ions from Aqueous Solution onto Bagasse Fly Ash

Abstract: The present study deals with the competitive adsorption of cadmium (Cd(II)) and zinc (Zn(II)) ions onto bagasse fly ash (BFA) from binary systems. BFA is a waste obtained from the bagasse‐fired boilers of sugar mills. The initial pH≈6.0 is found to be the optimum for the individual removal of Cd(II) and Zn(II) ions by BFA. The equilibrium adsorption data were obtained at different initial concentrations (C 0 = 10–100 mg/l), 5 h contact time, 30°C temperature, BFA dosage of 10 mg/l at pH 0 = 6. The Redlich–Peterson (R–P) and the Freundlich models represent the single ion equilibrium adsorption data better than the Langmuir model. The adsorption capacities in the binary‐metal mixtures are in the order Zn(II)>Cd(II) and is in agreement with the single‐component adsorption data. The equilibrium metal removal decreases with increasing concentrations of the other metal ion and the combined action of Cd(II) and Zn(II) ions on BFA is found to be antagonistic. Equilibrium isotherms for the binary adsorpti...

Electrolytic Reduction of Spent Nuclear Oxide Fuel as Part of an Integral Process to Separate and Recover Actinides from Fission Products

Abstract: Bench‐scale tests were performed to study an electrolytic reduction process that converts metal oxides in spent nuclear fuel to metal. Crushed spent oxide fuel was loaded into a permeable stainless steel basket and submerged in a molten salt electrolyte of LiCl–1 wt% Li2O at 650°C. An electrical current was passed through the fuel basket and a submerged platinum wire, effecting the reduction of metal oxides in the fuel and the formation of oxygen gas on the platinum wire surface. Salt and fuel samples were analyzed, and the extent of fission product separation and metal oxide reduction was determined.

Operation of membrane bioreactor with powdered activated carbon addition

Abstract: The effect of powdered activated carbon (PAC) addition to the activated sludge (AS) in a membrane bioreactor (MBR) has been investigated. The long term nature of the tests allowed the PAC to gradually incorporate into the biofloc forming biologically activated carbon (BAC). One series of tests involved 4 bench scale (2 L) MBRs operated at sludge retention times (SRTs) of 30 days with PAC inventories of 0, 1, 3 and 5 g/L and steady state biomass concentrations of 12.0±1.0 g/L. The characteristics of the mixed liquors (MLSS) from the 4 reactors were compared. Short term filtration tests, including measurement of specific cake resistance (SCR), flux decline profile, and irreversible fouling resistance in an unstirred cell and “sustainable” flux (by monitoring transmembrane pressure (TMP) rise) in a crossflow cell all showed better filtration performance for the MLSS with BAC compared with the AS alone. In terms of SCR and flux decline profile the 1 g/L PAC addition performed best, but in terms of mi...

Uptake of Fluoride by Al3+ Pretreated Low‐Silica Synthetic Zeolites: Adsorption Equilibrium and Rate Studies

Abstract: The removal of fluoride from single component aqueous solution using Al3+‐ pretreated low‐silica synthetic zeolites (Al‐Na‐HUD, Al‐HUD, Al‐F9, and Al‐A4) was studied. The effects of adsorbent mass, initial solution pH, and initial concentration on fluoride removal in a batch system were evaluated. Equilibrium data were simulated using simple isotherms such as the Freundlich (F), Langmuir‐Freundlich (LF), Redlich‐Peterson (RP) and Dubinin‐Radushkevitch (DR) isotherms. From the DR model, initial pH effects and desorption studies, it was considered that the fluoride adsorption onto the zeolites proceeded by ion‐exchange or chemisorption mechanism. In interpreting the kinetic results, reaction kinetics (using Elovich equation) and mass transfer processes (both external mass transfer and intraparticle diffusion) were considered. Equilibrium and kinetic results of fluoride adsorption onto the adsorbents demonstrated the following order of performance: Al‐Na‐HUD>Al‐F9> Al‐HUD>Al‐A4.

Fouling Control in a Submerged Flat Sheet Membrane System: Part II—Two‐Phase Flow Characterization and CFD Simulations

Abstract: Gas‐liquid two‐phase flow has been shown to be very effective in reducing fouling for different membrane modules with different feeds, including submerged flat sheet membranes used in membrane bioreactors for treatment of wastewater. Although gas‐liquid two‐phase flow occurring on the lumen side of tubular or hollow‐fiber membranes has been very well characterized the two‐phase flow regime in submerged membrane processes is different to that inside external membranes. Characterization of two‐phase flow in submerged flat sheet membrane modules has not been previously reported and hence the use of two‐phase flow in these modules has not yet been optimized. This paper reports on characterization of two‐phase flow for a submerged flat sheet membrane module with the aim of identifying the most effective flow profiles for fouling minimization. In order to better understand the fouling control process by two‐phase flow, CFD simulations were also conducted. It was found experimentally that an increase in...

Effect of Sludge Retention Time on Membrane Bio‐Fouling Intensity in a Submerged Membrane Bioreactor

Abstract: The submerged membrane bioreactor (sMBR) is being increasingly applied for municipal and industrial wastewater treatment. This paper examines the role of sludge retention time (SRT), an important operating parameter of the MBR as it affects the biological characteristics of the sludge and therefore influences membrane fouling. Well controlled runs were carried out at short SRT (10days) and moderate SRT (30days) in a 30 L submerged MBR equipped with KUBOTA flat‐sheet membranes. At steady operation, the mixed liquor suspended solids (MLSS) stabilized at approximately 5–6 g/L and 8.5–10 g/L for SRT 10 and 30days respectively. The DGGE profiles suggested a shift in the dominant bacterial community with the prolonged SRT. The soluble microbial products (SMP) were 9.3 mg/L and 5.4 mg/L at the SRTs of 10days and 30days respectively. The total amount of extracellular polymeric substance (EPS) extracted from the floc and the supernatant was approximately constant at the two SRTs under the same organic loa...

Partitioning Behavior of Penicillin G in Aqueous Two Phase System Formed by Ionic Liquids and Phosphate

Abstract: An aqueous two‐phase system (ATPS) was presented with hydrophilic ionic liquid 1‐butyl‐3‐methylimidazolium chloride ([Bmim]Cl) and NaH2PO4 aqueous solution in this paper. The partitioning behavior of penicillin G in the ATPS was investigated. Concentrations of NaH2PO4, penicillin G, and [Bmim]Cl were evaluated to determine their effects on the partition coefficient and extraction yield of penicillin G. It was found that both of partition coefficient and extraction yield strongly depended on the concentration of [Bmim]Cl, penicillin and NaH2PO4. A high extraction yield of 93% was achieved with the following parameters: NaH2PO4 · 2H2O 40% (wt%), penicillin 45000∼50000 u/ml, [Bmim]Cl 20∼21% (wt%). The [Bmim]Cl/NaH2PO4 system was also applied in a real filtration of penicillin G fermentation broth and the extraction yield was averaged at 91.5%. It is worthy noting that the working pH value of ATPS was at the range of 5∼6, no emulsification and protein denaturation could be observed.

Biosorption of Zinc from Aqueous Solutions by Rice Bran: Kinetics and Equilibrium Studies

Abstract: Rice bran, an agricultural by‐product, was used for the removal of zinc ions from aqueous solution. The work considered the determination of zinc‐biomass equilibrium data in batch system. These studies were carried out in order to determine some operational parameters of zinc sorption such as the time required for the Zinc‐biosorbent equilibrium, the effects of biomass particle size, pH, and temperature. The results showed that pH has an importance effect on zinc biosorption capacity. The biosorbent size also affects the zinc biosorption capacity. The sorption process follows pseudo‐second‐order kinetics. The intraparticle diffusion may be the rate‐controlling step involved in the adsorption zinc ions onto the rice bran up to 30 min. The equilibrium data could be best fitted by the Langmuir sorption isotherm equation over the entire concentration range (40–160 mg/dm3). Thermodynamic parameters, such as ΔG°, ΔH°, ΔS°, have been calculated. The thermodynamics of zinc ion/rice bran system indicate s...

Fouling Control in a Submerged Flat Sheet Membrane System: Part I – Bubbling and Hydrodynamic Effects

Abstract: Submerged flat sheet membranes are mostly used in membrane bioreactors for wastewater treatment. The major problems for these modules are concentration polarization and subsequent fouling. By using gas‐liquid two‐phase flow, these problems can be ameliorated. This paper describes a study of the use of gas‐liquid two‐phase flow as a fouling control mechanism for submerged flat sheet membrane bioreactors. The effect of various hydrodynamic factors such as airflow rate, nozzle size, intermittent filtration, channel gap width, feed concentration, imposed flux, and the use of membrane baffles were investigated. Experiments conducted on model feeds showed that fouling reduction increased with air flow rate up to a given value and beyond this flowrate no further enhancement was achieved. The effect of bubbling was also found to increase with nozzle size at constant airflow. Using intermittent filtration as an operating strategy was found to be more effective than continuous filtration and it also reduce...

Membrane¿Based Hybrid Processes: A Review

Abstract: It has been widely recognized that membrane separation processes can offer many advantages over conventional mass transfer processes. A large number of membrane separation processes are currently being practiced in various sectors of industries. Despite the advantages, membrane processes often suffer from shortcomings when used individually. To overcome such limitations, membrane‐based hybrid processes have been developed to maximize the productivity of the target separation processes. In this review, the membrane hybrid processes reported in the literature are classified into several categories and chosen examples of the processes are presented to show the general trends in the development of membrane‐based hybrid processes.

Effect of membrane surface properties during the fast evaluation of cell attachment

Abstract: The biofouling potential is one of the important factors to design and to select membranes for water and wastewater treatment. In this investigation, the effect of membrane surface properties during the attachment of S. cerevisiae cells was examined using a laboratory‐scale membrane filtration cell enabling direct microscopic observation of microbial cell deposition. The experimental results from 6 commercially available membranes showed that the initial adhesion rate, k d , was affected by the zeta potentials, hydrophobicity, and roughness of membrane surfaces. The k d value was significantly lower at the membrane which had more negative, hydrophilic, and smooth surfaces. The results will be helpful to minimize the time for selecting membranes in different situations, and for testing the performance of newly designed membranes.

Development of a Precipitation Based Separation Scheme for Selective Removal and Recovery of Heavy Metals from Cadmium Rich Electroplating Industry Effluents

Abstract: The treatment of electroplating wastes is a serious worldwide problem, because of their high content of many different heavy metals. Chemical precipitation based treatment methods could be an impor...

Method and Apparatus for Precision In‐Line Sampling of Distillate

Abstract: In this short note we present a method and describe a simple apparatus for use with simple, fractional, and steam distillation operations in which the operator requires a precise measurement of instantaneous distillate composition as the distillation proceeds. There are many examples in which such a measurement will play a critical role. One such example is in the measurement of boiling or distillation curves, where one desires an explicit measure of distillation process temperatures as a function of distillate volume fraction. The ability to augment temperature‐volume distillation curves with composition information is very helpful. The optimization of critical distillation conditions for the separation of sensitive solutes is another example in which instantaneous distillate composition is of value. The purification of reactants before a reaction is still another example. In all of these cases, it is the instantaneous composition that emerges from the condenser that is needed, rather than the i...

Biofilm Structure and Extracellular Polymeric Substances in Low and High Dissolved Oxygen Membrane Bioreactors

Abstract: This paper discusses the effect of dissolved oxygen (DO) on the biofilm structure in membrane bioreactor (MBR) and their consequence on membrane permeability and EPS. Two MBRs under high DO (6.0 mg/L, HDO) and low DO (<0.1 mg/L, LDO) were operated in parallel under same hydrodynamic conditions. The microbiological aspects in MBR systems were explored through a series of analysis techniques including PCR‐DGGE, gel filtration chromatography (GFC), confocal laser scanning microscope (CLSM), and image analysis. The rate of membrane fouling for the LDO MBR was 5 times faster than that for the HDO MBR. The microbial communities between HDO and LDO MBR were quite different, which is likely to be the reason for different structures and permeabilities of the biofilms. The specific biofilm resistance in HDO MBR was lower to that in LDO MBR. This is attributed to relatively lower porosity and higher amount of EPS for the biofilm in LDO MBR. The distributions of cell and EPS were not uniform in the biofilms ...

Adsorption characteristics of benzaldehyde, sulphanilic acid, and p-phenolsulfonate from water, acid, or base solutions onto activated carbon cloth

Abstract: Adsorption of benzaldehyde (BA), sulphanilic acid (SA), and sodium salt of p‐phenolsulfonic acid (p‐PhS) from water, acid, or base solutions onto activated carbon cloth (ACC) was studied by in‐situ UV‐spectrophotometric method. Kinetics of adsorption was followed over 90 min and the data were fitted to first order rate law. The order of rate of adsorption was found to be BA>SA≈p‐PhS in water, BA>p‐PhS>SA in 1 M H2SO4 and BA>SA >> p‐PhS in 0.1 M NaOH. Competitive adsorptions of BA and SA from an equimolar mixture in 1 M H2SO4 and of BA and p‐PhS from an equimolar mixture in H2O were studied for exploring the possibilities of separation of binary mixtures. It was found that p‐PhS was not adsorbed at all from 0.1 M NaOH solution. Adsorption isotherms of BA, SA, and p‐PhS at 30°C were derived and the data were fitted to the Langmuir and Freundlich models. The Freundlich model was found to represent the experimental data better than the Langmuir model.

Sustainable Flux Fouling in a Membrane Bioreactor: Impact of Flux and MLSS

Abstract: The long term sustainable flux behavior of a submerged membrane bioreactor operated under a steady state conditions at a range of mixed liquor suspended solids (MLSS) concentrations has been examined. Comparison of fouling rates at a number of imposed fluxes has been made between long term filtration trials and short term tests using the flux step method. Results indicate an exponential relationship between fouling rate and flux for both long and short term trials, although the value was an order of magnitude lower during long term tests. Moreover, operation during long term trials is characterised by a period of pseudo stable operation followed by a catastrophic rise in TMP at a given critical filtration time (tfilt) during trials at 6 g · L−1. This time of stable operation, tfilt, is characterised by a linear relationship between fouling rate and flux. Results have been compared with the literature. Data for membrane fouling prior to the end of tfilt yielded a poor fit with a recently proposed ...

Low temperature liquid state synthesis of lithium zirconate and its characteristics as a CO2 sorbent

Abstract: In this study, a new preparation method providing greatly improved CO2 sorption is introduced. Li2ZrO3 sorbent was prepared by low temperature co‐precipitation and compared in CO2 sorption performance with a sorbent prepared by the conventional high temperature solid‐state reaction method. The two sorbents were characterized using scanning electron microscopy, X‐ray diffraction and thermo‐gravimetric analysis. The Li2ZrO3 powder prepared by the relatively simple co‐precipitation method showed significantly better performance than the one prepared by solid‐state reaction with respect to both kinetics and CO2 sorption capacity. Extensive study of the powder prepared by co‐precipitation has been performed at various conditions.

Biosorption of Zinc on Palm Tree Leaves: Equilibrium, Kinetics, and Thermodynamics Studies

Abstract: The efficiency of using palm tree leaves to remove zinc ions from aqueous solution was studied. Adsorption isotherms, kinetics, and thermodynamics studies were conducted. The influence of different experimental parameters, such as equilibrium pH, shaking rate, temperature, and the presence of other pollutants such as chelating agents on the biosorption of zinc on palm tree leaves was investigated. Batch biosorption experiments showed that palm tree leaves used in this study proved to be suitable for the removal of zinc from dilute solutions where a maximum uptake capacity of 14.7 mg/g was obtained at 25°C. Zinc biosorption on palm tree leaves was found to be highly pH dependent. The biosorption process was found to be rapid with 90% of the adsorption completed in about 10 min. Dynamics studies of the biosorption of zinc on palm tree leaves showed that the biosorption process followed the pseudo second‐order kinetics with little intraparticle diffusion mechanism contribution. The equilibrium resul...

Irreversible Fouling in MF/UF Membranes Caused by Natural Organic Matters (NOMs) Isolated from Different Origins

Abstract: For more efficient use of membrane technology in water treatment, it is essential to understand more about the fouling that requires chemical cleaning to be eliminated (i.e., irreversible fouling). In this study, five different MF/UF membranes and four types of organic matter collected from different origins were examined in terms of the degree of irreversible membrane fouling. Experimental results demonstrated that the extent of irreversible fouling differed significantly depending on the properties of both the membrane and organic matter. Among the tested membranes, UF membranes made of polyacrylonitrile (PAN) exhibited the best performance in terms of prevention of irreversible fouling. In contrast, MF membranes, especially one made of polyvinylidenefluoride (PVDF), suffered significant irreversible fouling. Conventional methods for characterization of organic matter such as specific ultraviolet absorption (SUVA), XAD fractionation, and excitation‐emission matrix (EEM) were found to be inadequ...

Bacterial Community Structure on Membrane Surface and Characteristics of Strains Isolated from Membrane Surface in Submerged Membrane Bioreactor

Abstract: In order to investigate the bacterial community structure and the characteristics of bacteria on the membrane surface, a submerged membrane bioreactor treating municipal wastewater was continuously operated under two different conditions. Bacterial community structures were examined by PCR‐denaturing gradient gel electrophoresis and PCR cloning of 16S rRNA genes. Bacterial strains isolated from membrane surface were identified and their growth curve, EPS concentration and hydrophobicity were measured. The structures of bacterial communities in the suspended solids and on the membrane surface were obviously different, and γ‐Proteobacteria more selectively adhere and grow on the membrane surface than other microorganisms. Most of the membrane isolates grew slowly as compared with the strains isolated from the suspended solids. Also, the membrane isolates were higher cell surface hydrophobicities, higher EPS concentrations, and higher ratios of protein to carbohydrate within the EPSs than the isolat...

Extracellular Polymeric Substances in Fouling Layer

Abstract: Membrane biofouling via microbial products limits the feasibility of utilizing membrane bioreactor (MBR) for treating wastewater. Fouling layer would be built up when activated sludge was filtered with a mixed cellulose ester membrane. This study probed the three‐dimensional distributions of protein, α‐polysaccharide, and β‐polysaccharide in fouling layer using fluorescently labeled lectins and fluorescein isothiocyanate (FITC) as staining agents in combination with confocal laser scanning microscopy (CLSM). These extracellular polymeric substances (EPS) distributed heterogeneously in the fouling layer, with α‐polysaccharide being concentrated close to the membrane surface. The flow pattern yielded in the fouling layer determines the filtration resistance of biofouling.

Chitin Extraction from Black Tiger Shrimp (Penaeus monodon) Waste using Organic Acids

Abstract: In chitin extraction from black tiger shrimp shell waste, HCl is the commonly used decalcifying agent However, it is considered a harsh chemical An alternate was found by using organic acids Conditions for deproteinization were: 1 M NaOH at 95°C for 6 h and solid‐to‐solvent ratio of 1∶15 (w/v) Demineralization involved treatment with 025 M HCl at ambient temperature for 30 min with agitation The optimal solid‐to‐acid ratio was 1∶30 (w/v) and this led to 865±12% purification of chitin With the same conditions, the optimal ratio of mixed acids (025 M HCOOH and 025 M C6H8O7 at 1∶2 (v/v)) was 1∶28 (w/v) with chitin purification of 881±18%

Behavior of Membrane Scaling During Crossflow Filtration in the Anaerobic MBR System

Abstract: Fouling of membrane bioreactor (MBR) has been studied intensively. Because of the high concentration of carbonates, scaling can be a serious problem in anaerobic bioreactor, which attracts little attention. In this study, the wastewater was treated with an anaerobic process followed by either a submerged or a side‐stream aerobic membrane reactor. The wastewater was spiked with calcium to investigate the effect of scaling on membrane filtration. Very little scaling was detected in the external membrane system (the side‐stream MBR). Results from chemical cleaning of internal membrane system indicated that the flux decline caused by membrane scaling was far more severe than that by membrane fouling. However, the flux decline from membrane scaling can be effectively recovered by the chemical cleaning of EDTA and NaOCl.

Separation of Ionic Liquid Dispersions in Centrifugal Solvent Extraction Contactors

Abstract: Separations of dispersions formed by mixing immiscible organic room‐temperature ionic liquids (IL)/hydrocarbon/and aqueous systems using a centrifugal solvent‐extraction contactor have been successfully demonstrated in proof‐of‐concept testing. This accomplishment is significant in that physical property factors that are typical of ionic liquid systems (e.g., similar densities of the bulk phases, low interfacial tensions, and high viscosities) are typically unfavorable for dispersion separation, particularly in continuous processes. Efficient separation of dispersions containing ionic liquid solvents is essential for utilization of these compounds in liquid‐liquid extraction applications to maximize both solute transfer efficiency and solvent recovery. Efficient solvent recovery is of particular concern in IL applications because of the high cost of most IL solvents. This paper presents the results of initial experiments with three hydrophobic ionic liquids to determine how their physical propert...