Physico-Chemical Properties of Supported and Unsupported γ-Al2-O3 and TiO2 Ceramic Membranes

Abstract

Supported and unsupported γ-Al₂O₃ and TiO₂ ceramic membranes have been prepared by sol-gel techniques from alkoxide precursors. Several physico-chemical properties of these materials have been determined. N₂ sorption analysis has been used to determine pore size distributions and mean pore sizes. Particle sizes of sols as measured by “in situ” quasi-elastic light scattering are discussed in the light of SEM analyses of the sintered membranes prepared from these sols. Crack-free unsupported monoliths of Al₂O₃ with thicknesses up to 100 μm have been prepared. Similarly, supported Al₂O₃ and TiO₂ membranes with thicknesses of 0.5 μm have been produced. Preliminary measurements of the permselectiyities of supported membranes have also been made.     

Physicochemical Properties of Supported γ-Al2O3 and TiO2 Ceramic Membranes

Abstract

Supported γ-Al₂O₃ and TiO₂ ceramic membranes were prepared by sol-gel techniques from alkoxide precursors. Tests were conducted to measure the permeabilities of these membranes to solvent under a variety of operating conditions. Variables studied were feed temperature, length of time on stream, and feed pH. The stabilities of the membranes in harsh chemical environments were also determined. An alternative method for preparing supported ceramic membranes is also suggested.     

Permselectivity Characteristics of Supported Ceramic Alumina Membranes

Abstract

Supported gamma-Al₂O₃ ceramic membranes have been prepared by sol-gel techniques from alkoxide precursors. Permeability and rejection characteristics of these membranes have been used to determine the effect of sol concentration on membrane thickness. Rejection coefficients of poylethyleneglycols of different molecular weights and of several protein streams of possible industrial interest were also determined.

Permeabilities were also measured for several feedstocks. Initial studies of protocols for regenerating membranes have been carried out.     

Application of Ceramic Membranes to Reverse Osmosis

Abstract

Colloidal TiO₂ sols which contain stable particles that are ca. 50 Å in diameter have been produced. Scanning electron photomicrographs indicate that supported membranes which are free from flaws can be fabricated from these TiO₂ sols. These photomicrographs indicate that the membranes thus formed are approximately 1 micron thick. Furthermore, these photomicrographs indicate that total coverage of the support has been obtained.

In order to assess potential uses of ceramic membranes, it is necessary to determine if they are capable of achieving separations of industrial significance. A surface-force pore-flow model has been employed to predict the rejections expected for these TiO₂ membranes when used to process solutions containing polyethylene glycols of different molecular weights. These results were then used to predict the expected performance of these membranes when used to concentrate the permeate from the ultrafiltration of cheese whey.     

Separation of Liquid Solutions by Contained Liquid Membranes

Abstract

The technique of contained liquid membranes (CLM) for liquid solution separation is discussed. The CLM is obtained by confining the membrane liquid between two sets of microporous hollow fibers (MHF). The lumen of the hollow fiber carries the feed or the strip solution under proper phase pressure condition vis-a-vis the membrane phase. Various possible structural configurations of the CLM are illustrated with respect to the nature of microporous hollow fiber substrate, the feed solution and the liquid membrane. The contributions of different resistances to the solute transport rate are identified. Some basic experimental data obtained in small CLM permeators are presented for two systems with organic liquid membranes to illustrate how steady state separation is achieved after an initial unsteady period. The considerable advantages of the CLM structure over more traditional liquid membrane techniques such as supported liquid membrane (SLM) with respect to membrane stability, membrane regeneration and feed equilibration are pointed out.     

Freeform fabrication of ceramics

Abstract

Fabrication of ceramic objects by solid freeform fabrication (SFF) techniques is reviewed, with emphasis on ceramic versions of commercial rapid prototyping (RP) methods. A wide range of ceramics have been demonstrated, including aluminium oxide, silica, hydroxyapatite, silicon nitride, and lead zirconate titanate, with techniques based on extrusion, ink jet deposition, green tape lamination, and photopolymerisation. The quality of SFF ceramics compares well with conventionally processed ceramics.     

Stability of Supported Liquid Membranes: State of the Art

Abstract

This paper presents a state of art review on the stability of supported liquid membranes (SLM). The backgrounds of SLM instability phenomena are presented, and various mechanisms for explaining these phenomena are treated in detail. Several suggestions for stability improvement are discussed.

     

Effect of Plasticizer on Carrier-Mediated Transport of Zinc Ion through Cellulose Triacetate Membranes

Abstract

In practical applications of liquid membranes containing a mobile camer, three main types of membranes have been studied: liquid surfactant, supported liquid, and solvent polymeric membranes (2-6). In these membranes the solvent polymeric membrane which consists of a polymer film containing a plasticizer generally exhibits a low ionic permeability compared with the other types of membranes, although it has a high stability and durability. This is because the transference of the carrier in the membrane is depressed by its high viscosity and high electrical resistance. Accordingly, the ionic permeability may be improved by selecting an appropriate plasticizer.     

支撑液膜稳定性研究进展

分析了导致支撑液膜不稳定的因素及其机理。主要提出了近年来各国学者在改进支撑液膜稳定性方面所作的努力,包括对支撑液膜的结构、液膜相组成和制备工艺、膜支撑体以及膜组件改进等方面的工作。最后对支撑液膜的工业化前景进行了展望。     

Effects of Membrane Parameters on Performance of Vapor Permeation through a Composite Supported Liquid Membrane

Abstract

Support liquid membranes have been used in air dehumidification due to their inherent high mass transfer rates. In this study, the effects of membrane structural parameters on vapor permeation through a LiCl solution based supported liquid membrane are investigated. To aid in the analysis, a mass transfer model has been proposed for moisture transfer through the membrane, which is composed of a supported liquid layer sandwiched by two hydrophobic protective layers. The model takes into account of the resistance in boundary layers, in the protective hydrophobic layers, and in the supported liquid layer. It is a transient model. It also reflects the distributed nature of moisture permeation through the membrane. The results found that the emission rate exhibits a non‐uniform distribution nature on the membrane surface. The structural parameters of the support and the protective layers, such as thickness, pore diameters, and porosity, have great effects on vapor permeation.     

Pilot-Scale Evaluation of Supported Liquid Membrane Extraction

Abstract

An evaluation of a solvent extraction system employing supported liquid membranes has recently been completed by Rockwell Hanford Operations. The focus was on a pilot-scale, tube and shell arrangement configured for continuous operation. The tube bundle consisted of 333 polypropylene-iiricroporous fibers with a total surface of 3.6 m².

Results are reported for the evaluation of operating parameters such as flow rates and corresponding aqueous pressure differences, solvent impregnation techniques, and test system durability. Chemical and physical test results, including permeability data, are also reported for the systems nitrate ion/nitric acid/tertiary amine and (nonradioactive) Group IA-IIA metal/nitric acid/ phosphoric acid extractant.     

Fabrication and characterisation of boron doped barium stabilised bismuth cobalt oxide nanocrystalline ceramic composite

Abstract

In this paper, the fabrication and characterisation processes of both boron doped and undoped barium stabilised bismuth cobalt oxide nanocrystalline ceramic powders using polymeric precursor were reported. Obtained boron doped barium stabilised bismuth cobalt oxide nanocrystalline ceramic powders, which have been synthesised by polymeric precursor technique at temperatures below 900°C and at atmospheric condition, were characterised by X-ray diffraction, Fourier transform infrared and scanning electron microscopy techniques. According to X-ray results, fcc and bcc phases coexist in the samples of the nanocrystalline ceramic powders. Crystallite sizes for body centred cubic structure were calculated using Scherrer equation for both boron doped and undoped samples. In addition, lattice parameters were calculated for all samples.     

The membrane properties of alumina-coated alumina support layers and alumina-coated diatomite–kaolin composite support layers

ABSTRACT

Porous ceramic membranes are a current research focus because of their outstanding thermal and chemical stability. Recent research has utilised inexpensive natural materials such as diatomite to reduce the expense of these porous ceramic membranes. However, insufficient data exist for microfiltration applications using the diatomite-based membranes. The measured membrane properties of alumina-coated alumina support layers and alumina-coated diatomite–kaolin composite support layers have been compared. These experiments have been used to determine whether the average pore size could be reduced effectively by controlling the thickness of the alumina coating layer, while maintaining acceptable water permeability. The membrane properties of the alumina-coated alumina support layers and the alumina-coated diatomite–kaolin composite support layers were examined using the scanning electron microscopy, mercury porosimetry, and a dead-end microfiltration system.     

Fabrication of coloured zirconia ceramics by infiltrating water debound injection moulded green body

Abstract

Abstract

The authors developed a new technique combining ceramic injection moulding and liquid precursor infiltration, presenting a new strategy for fabrication of coloured zirconia ceramics. The authors’ strategy includes ceramic injection moulding 3Y‐TZP powder using a water debinding binder system, debinding moulded parts in water and drying, immersing debound parts in solutions containing different colouring ions and then sintering and creating coloured zirconia ceramics. The fabricated coloured ceramic bars exhibit a core shell structure, and the thickness of the coloured shell can be tailored by adjusting immersion time and temperature. Using solutions containing different colouring ions, ceramic bars with various colours can be prepared.     

无机陶瓷分离膜的研究与应用—陶瓷分离膜的制备技术

本文详细介绍了多种无机陶瓷分离膜的制备方法及工艺原理,并对各种膜的制备技术进行了分析与讨论,其中不少技术是近年来的新研究成果。     

Studies on Carbonate Ion Transport through Supported Liquid Membrane Using Primene JMT and Tributyl Phosphate

Abstract

A supported liquid membrane system consisting of source, receiving and membrane phases, in which mixed extractants were used in the membrane phase, was explored for the carbonate ion transport from source to receiving through membrane phase. Primary amine Primene JMT and TBP were used as extractants (carriers) in liquid membrane phase. Different experimental variables such as concentration of carbonate ion, carriers, alkali and hydrogen peroxide, stirring speed, etc have been investigated. Primary amine Primene JMT and TBP mixed carriers show the synergistic effect for the transport of carbonate ions through supported liquid membrane system. The stability of the supported liquid membrane system has been explored for 50 h. The pre-concentration of carbonate ions from dilute solutions were also demonstrated. The effect of different alkalis on the permeability coefficient of transport of carbonate ions through supported liquid membrane system has been investigated. The primary amine in combination with TBP shows more effective for the transport of carbonate ions through supported liquid membrane system in comparison with that of secondary and tertiary amines.     

Purification of Produced Water by Ceramic Membranes: Material Screening,Process Design and Economics

Abstract

Produced water, generated from underlying formations during the recovery of hydrocarbons, constitutes the largest waste stream associated with oil and gas production. Currently, over 90% of produced water is reinjected into the formation, either in support of enhanced oil recovery or for disposal. In arid areas, reclamation of produced water for beneficial uses such as irrigation or tower cooling may be an attractive alternative if the produced water can be purified to an adequate quality, specifically through the removal of dissolved components including inorganic compounds (salts, heavy metals, and radiochemicals) and organic compounds (fatty acid, aliphatic, and aromatics).

Membranes technologies show advantages in both energy efficiency and high water quality. Due to the presence of dissolved organics, reverse osmosis with organic membranes is highly limited. Research efforts focus on developing new materials that are less prone to fouling and are easy to regenerate. Novel ceramic membranes are relatively new classes of material that show promising application in produced water purification due to their extreme stability in harsh environments and optional choices for regeneration. This paper details the results of investigations of produced water purification by microporous ceramic membranes, including metal oxide membranes, clay membranes, and zeolite membranes. Techniques for membrane fabrication, process design, and economic aspects are also discussed.     

Statistical Models to Describe the Structure of Porous Ceramic Membranes

Abstract

A knowledge of the material structure of porous membranes is essential in the computation of flux–pressure differential and blinding behavior. The data provided by manufacturers on the internal pore properties, mercury porosimetry and air permeability, is of limited use since it is based for interpretation on an assumed matrix of cylindrical pores. Ceramic membranes are considered in this work for which three different types are investigated. None of these show any resemblance to structures assumed for an interpretation of this data.

The pore structure in all examples vary and it is concluded that deterministic models to describe this are not valid.

Statistical models based on random division of 2 and 3 dimensional space are proposed to describe the structure of cellular ceramic membranes (2 space model), sintered ceramic membranes and foam membranes (3 dimensional space models). The models are shown to be inter–related providing a direct comparison between the membrane structures.

The structures proposed by the models are compared and agree well with experimental data.     

Recovery and Concentration of Metal Ions. II Multimembrane Hybrid System

Abstract

The multimembrane hybrid system (MHS) has been developed and used for the transportation and separation of divalent metal ions from multicomponent solutions. The system consists of three membranes in series

ion-exchange membrane | liquid membrane | ion-exchange membrane

The experiments were performed with liquid membranes composed of di(2-ethylhexyl)phosphoric acid in kerosene and Nafion-120 perfluorosulfonic acid polymer membranes. The fluxes and separation characteristics have been determined for MHS separating a solution of Zn(II), Mn(II), Cu(II), and Ni(II) sulfates as the feed phase, and the strip phase containing sulfuric acid. The results of competitive permeation experiments have shown the selectivity order Zn(II) > Mn(II) > Cu(II) ? Co(II), Ni(II). High separation coefficients were found for Zn(II), Cu(II), and Mn(II) compared to Ni(II) and Co(II).     

Liquid Membrane Separations of Metal Cations Using Macrocyclic Carriers

Abstract

The selectivity in water and methanol solvents of macrocyclic crown ether ligands toward univalent and bivalent cations is well known. Incorporation of these ligands into chloroform liquid membranes separating water and salt solution phases results in a system showing selective cation transport. The cation transport rates of single cations across these liquid membranes have been correlated with equilibrium constant values for cation-macrocycle interaction in methanol. This correlation has been extended to binary cation mixtures of Cs⁺ with Li⁺, Na⁺, K⁺, and Rb⁺. A model for cation transport from these cation mixtures has been reduced to an equation which gives good agreement between measured and predicted transport rates across our liquid membranes.