Performance Of Separation Process Research Articles

The Impact of Adsorption Property Modification by Crosslinkers on Graphene Oxide Membrane Separation Performance

The health risks associated with the presence of heavy metals in drinking water can be severe. To address this issue, membrane separation technology is one of the consolidated alternatives. Inorganic, porous membranes were found in applications where low energy consumption is highly desirable. The selectivity of these membranes is attained by functionalisation. Graphene oxide functionalised membrane technology is promising for removing heavy metal ions. This work summarises, discusses and presents the relationship between adsorption and overall membrane separation process performance for heavy metal ions removal from wastewater when a graphene oxide-functionalised membrane is used. The separation performance depends on the hydrophobic interactions of the membrane and the solute. The electrostatic interaction between the negatively charged membrane surface and positively charged metal ions facilitates the adsorption, leading to the rejection of these metal ions. The influences of the chemical nature of the modifiers of graphene oxide layers are highlighted.

Beneficent impact of mixed molecular magnet/neodymium powder for facilitating ethanol dehydration in the pervaporation process

The focus of the study concerned the application of alginate membranes enriched with a mixture of Magnequench Fine Powder (MQFP) and a Molecular Magnet [Fe4(acac)6(Br-mp)2] (MM) in different proportions to improve ethanol dehydration via pervaporation. The paper concentrated on how the combined fillers affected the membranes ability to transport the ethanol/water solution components. It was observed that the integration of MM into MQFP not only improved the magnetic properties but also provided a uniform distribution of the filler in the alginate matrix. By merging the properties of two different fillers, we achieved membranes with outstanding separation process performance. This efficiency was unattainable using each filler separately, highlighting the synergistic effect of combining the two fillers. The membrane with 1 wt% MQFP and 9 wt% MM proved to be the most efficient, with the highest Pervaporation Separation Index and separation factor, reaching 40974 kg⋅m−2⋅h−1 and 12735.14, respectively.

Understanding the phase and solvation behavior of fluorinated ionic liquids

• Effect of perfluoroalkyl chains on the properties and phase equilibria of FILs. • VLE of FILs show the need of optimal fluorine density to enhance gas absorption. • LLE of FILs reveal high surfactant behavior in water and improved PFCs solubility. • SLE of FILs uncover formation of eutectic mixtures with complex phase behavior. • FILs show huge relevance in GHGs capturing processes and biomedical applications. Fluorinated ionic liquids (FILs) are defined as molecules having fluorinated tags equal to or longer than 4 carbon atoms in the anion and/or cation structures. They present nanosegregated domains making them 3-in-1 solvents with exceptional properties, including an attractive solubility power. This work is an important contribution towards understanding the current research on the phase behavior of FILs, which may be used as task-specific materials for industrial applications. An overview of the main works published in the last two decades is presented, concerning gas solubility in FILs, the application of membranes to improve the gas absorption in FILs, and the use of modeling approaches to ease the application of FILs in gas capture and separation processes, with emphasis on the relationship between the structural properties and their performance. Contributions concerning the liquid-liquid and solid-liquid equilibria behavior of FILs, including the liquid-liquid equilibria (LLE) of FILs in water and perfluoroalkanes, and the solid-liquid equilibria (SLE) of solid FILs in water and mixtures of FILs are also presented. Regarding the absorption of gases in FILs, a careful analysis of the published works reveals that: (1) an optimal density of fluorine atoms in FILs structure is required to positively impact the absorption of different gases, (2) the functionalization of membranes can be also a useful method to improve the performance in separation processes, and (3) modeling tools can ease the screening of the features that promote the absorption of gases by FILs. The study of FILs LLE showed a rich phase behavior with water and perfluoroalkanes and the enhanced surfactant power of FILs, which is highly dependent on the length of the hydrogenated and fluorinated side chains. Finally, studying the SLE of FILs mixtures allowed the formation of deep eutectic systems that enlarges the applicability of FILs.

Experimental and theoretical assessment of CO2 capture by adsorption on clinoptilolite

Clinoptilolite is a low-cost and abundant natural zeolite with a high CO2 selectivity, which is abundant in many regions around the world, but with limited industrial use. By combining experimental and theoretical (molecular simulation) approaches, the present work aims at contributing with fundamental data to assist the design of adsorption processes based on this zeolite. A sample of naturally occurring (raw) clinoptilolite was characterized by TGA, XRD, XRF, N2 adsorption isotherms at −196 °C and CO2 at 0 °C. Single-component (CO2, N2, CH4 and O2) and binary (CO2/CH4 and CO2/N2) equilibrium isotherms were measured gravimetrically. Column dynamics experimental data were obtained in order to validate a fixed-bed model, which was then used to evaluate the performance of separation processes. Molecular simulation (MS) was used to build a predictive zeolite model validated with experimental data for CO2, N2, CH4 and O2 able to investigate adsorption of mixtures and gas diffusion. TGA results demonstrated structural stability up to 600 °C with the X-ray diffraction pattern revealing clinoptilolite as the main phase, together with cristobalite and other silicon phases as contaminants. The textural properties obtained from N2 adsorption isotherms at −196 °C of the studied sample were comparable to those reported in the literature, though inaccurate for the actual clinoptilolite structure, which poses significant diffusional resistance for N2 at such temperature. IAST combined with Sips model was used to predict the behavior of mixtures. The proposed clinoptilolite MS model was used to verify the suitability of IAST in predicting mixture equilibrium on clinoptilolite and to predict the selectivity of CO2 over O2. The MS model was able to assess the equilibrium effects in the adsorption of the CH4-N2 mixture and to confirm the relationship between the diffusivity of gases and the positioning and nature of cations in the structure. The fixed-bed model highlighted the different performances of the raw and exchanged clinoptilolite samples, including the theoretical Na-clinoptilolite crystal predicted by the MS model. Together with experimental data, the MS model can be used to aid the design of separation processes of such gas stream with multiple components using clinoptilolite.

Modeling Metal Influence on the Gate Opening in ZIF-8 Materials

Zeolitic imidazolate frameworks (ZIFs) undergo pressure-induced phase transitions that are peculiar to each ZIF. The phase transition is associated with the rotation of the imidazolate, and it is accompanied by an increase of their pore openings, affecting ZIFs performance in separation processes. This phenomenon is known as the gate opening or the swing effect. Here we report the metal dependence of the ambient pressure and high pressure (HP) phases of ZIF-8(M) with M = Mg, Fe, and Zn, determined by using periodic Kohn–Sham density functional models. We show that the substitution of Zn with Mg or Fe has a big influence on the gate opening energy, which significantly decreases, an opposite trend than what was previously reported upon functionalization of the linker. The lowest energy phase of ZIF-8(Fe) is different than for ZIF-8(Mg) and ZIF-8(Zn), and its structure is significantly closer to the HP phase. Multireference wave function methods have been used to study the electronic structure of ZIF-8(Fe), confirming the metal center to be high spin (S = 2) divalent iron in antiferromagnetic coupling. The high-spin nature of the iron species coupled with a band gap in the visible light range makes ZIF-8(Fe) an interesting material for catalysis and photocatalysis.

Development of H2 selective silica membranes: Performance evaluation through single gas permeation and gas separation tests

To prove the usefulness and achieve penetration of microporous ceramic membranes in gas separation applications of industrial interest, their behavior needs to be validated and predicted at relatively realistic conditions. In this respect, the present study employed hybrid silica (HybSi) membranes, modified by chemical vapor infiltration (CVI) in order to render them more selective to hydrogen in hydrogen/carbon dioxide binary mixtures, which are representative to effluent streams of methane or biogas steam reforming/water gas shift processes. Experimental studies with a single modified membrane exhibited high hydrogen permeance (1.5.10−7 mol.m−2.s−1.Pa−1, at 250 °C) and H2/CO2 permselectivity (H2/CO2 = 61.3, at 250 °C). Gas separation tests with binary gas mixtures revealed that high hydrogen purity values (>99%) can be reached at different process conditions. The mathematical model, also developed in this study in order to interpret the experimental results, can reliably predict hydrogen separation process performance over a wide range of operating conditions and also serve as a tool for subsequent optimum process engineering purposes.

LABORATORY RESEARCH RESULTS OF ONION SEPARATION ON A BAR ELEVATOR WITH AN ADJUSTABLE TILT ANGLE

Existing machines for harvesting root crops and onions do not provide qualitative indicators of root crops pile separation, which leads to a violation of agrotechnical requirements when harvesting them [1, 2]. It is necessary to search for new solutions to increase the quality indicators of root crop separation, namely to increase the completeness of separation and reduce damage. The article presents the design of the onion set harvesting machine, equipped with a bar elevator with an asymmetric arrangement of shakers. We described the methodology and results of laboratory studies to determine the quality indicators of heap onion sets separation on an experimental bar elevator. The results of laboratory tests of the onion set harvesting machine equipped with a bar elevator with an adjustable blade angle showed a high-quality performance of separation process at optimal values of parameters: translational speed of the bar elevator blade vEL = 1.55 ... 1.68 m s, the supply of onions heap Qb?- 19.7 ... 27.1 kg s and inclination angle of the blade bar elevator is in the range аг= 15.1... 21.9 degrees. The use of a bar elevator with an adjustable angle of inclination of the blade allows to increase the completeness of onion sets separation by 20%, and reduce damage to the bulbs by 11%.

Nanofiltration of binary palm oil/solvent mixtures: Experimental and modeling

Purification by using membrane technology has been recently considered as an alternative method to the conventional purification of crude vegetable oil. Although there are studies regarding the application of membrane technology on the purification of crude vegetable oil, the research on the separation process performance by considering transport models is scarce. Therefore, in this work, an investigation on the performance of organic solvent nanofiltration (OSN) for palm oil and solvent mixtures was carried out. In order to describe and predict the membrane separation performance, the integration of membrane transport model with experimental data is required. Parameter estimation of transport model parameters was conducted to correlate a chosen transport model to the experimental data. In this research, the effect of concentration polarization was also included in the mass transfer of triglycerides, whereby a combined film theory/ solution diffusion transport model was employed. The results revealed that the permeation flux of palm oil and acetone mixtures in SolSep NF 030,306 nanofiltration membrane increased with increasing stirring speed but decreased with increasing feed viscosity. The rejection of triglyceride, on the other hand, increased with increasing feed concentration, however, the rejection did not show any significant trending with the change in operating pressure. This study served as the first attempt to investigate the performance of organic solvent nanofiltration of palm oil by using a solvent resistant membrane through both experiments and membrane transport modeling.

Characterisation of Romakon™-PM pervaporation membranes for the separation of dilute aqueous alcohol mixtures

Thin-film composite pervaporation membranes with selective layer from pyromellitic dianhydride -4,4′ oxydianiline polyimide on porous poly(amide-imide) support (Romakon™-PM) for treatment of water/ethanol mixtures with exceeding water content (>50 wt% water) are characterised by the use of scanning electron microscopy, atomic force microscopy and X-ray diffraction. Membranes showed high values of flux, separation factor and PSI (up to 774) in the selected feed mixture composition range. The influence of the support and structural features of the polyimide in the coating layer on the transport properties is discussed. The membranes are successfully tested in terms of pervaporation dehydration of beer. The influence of the permeate temperature on the separation process performance is discussed.

Coordinatively Unsaturated Metal Site-Promoted Selective Adsorption of Organic Molecules on Supported Metal-Organic Framework Nanosheets.

Metal-organic frameworks (MOFs) are a class of customizable porous material, which have shown good performance in separation processes, because of their large surface area and molecular recognition property. Although the effects of chemical structure of MOFs on their separation performance were extensively studied, the exploration of their surface properties was still limited. This work demonstrated a MOF nanosheet with large amount of coordinatively unsaturated metal sites, Cu(BDC) (copper(II) benzenedicarboxylate), where the unsaturated Cu sites were utilized to selectively adsorb organic molecules with Lewis basicity. This work also investigated the direct growth of Cu(BDC) on the cellulose substrate, where the MOF nanosheets were immobilized on the cellulose substrate, enabling the composite material for practical applications. The heterogeneous nucleation and growth of MOF nanosheets on the cellulose were achieved by tuning the basicity of solution and reaction temperature. We believe this direct growth approach can be applied to other MOF composite materials for separation and purification purposes, as well as other applications involving molecular recognition properties of MOFs, such as sensing, catalysis, and enzyme immobilization.

Design analysis of low pressure distillation column for cryogenic air separation

Cryogenic air separation units are widely used in industry, which consume a large energy and need to produce a huge amount of need of nitrogen, oxygen and argon products with high purity. High purity distillation columns are critical unit operations in cryogenic air separation plants. In this paper the low pressure distillation column is investigated by using a steady state model. The first principles mathematic model of the column is firstly developed, and the pressure, temperature and static liquid nitrogen, oxygen and argon concentrations in the upper column are presented. The obtained results give important information on the variation of temperature, pressure, component concentrations and molar flows within the distillation column. The study highlighted the importance of considering air as ternary mixture. The separation process performance is significantly influenced by the location of side draw of argon and reflux ratio at the top of the column

A practical perspective of fluid (gas or liquid) - Solid adsorption equilibrium

The fluid (gas or liquid) – solid adsorption equilibrium is a core thermodynamic property of an adsorbate-adsorbent system for establishing the efficiency of separation of a fluid mixture by an adsorptive process and for selection of an optimum adsorbent for a specified separation duty. The shape of an equilibrium adsorption isotherm of a pure gas or those for the components of a gas mixture are determined by the nature of the adsorbate-adsorbent pair, the system temperature, the porosity of the adsorbent, and the energetic heterogeneity of the adsorbent. The same factors also determine the shape of an equilibrium isotherm of a binary liquid mixture. The published literature on this subject is vast. The purpose of this article is not to review the literature but to provide a systematic practical perspective of the subject.Analytical models for fluid-solid adsorption isotherms facilitate numerical simulation of separation process performance using mathematical process models. However, the practically viable isotherm models must obey several physical and thermodynamic constraints. A selection of such isotherm models for pure and multi-component gas and binary liquid mixtures is presented. It may not, however, be possible to a priori chose a reliable isotherm model for a system of interest without extensively testing the model using experimental isotherm data for that system. The same conclusion applies to theoretical concepts for (a) predicting multi-component gas-solid adsorption equilibria from the corresponding pure gas adsorption equilibria, (b) coalescing adsorption isotherms of different pure gases at different temperatures and (c) coalescing isotherms for adsorption of trace components from a mixture (gas or a liquid) into a single characteristic curve on a given adsorbent for predictive purposes.

Generalizing Countercurrent Processes: Distillation and Beyond

AbstractThe implementation and exploitation of countercurrent movement between different phases is a well‐established principle to enhance the performance of separation processes. The improvements are essentially due to the establishment and application of more favorable driving forces compared to co‐current operation. The success of dedicated multistage countercurrent distillation processes has been a key motivator for the development of many other principles of countercurrent separation processes. This promoting aspect was strongly supported by the availability of graphical solutions of the underlying mass balance equations, e.g. the McCabe‐Thiele diagram. Selected applications of countercurrent separation processes are presented, which demonstrate extensions exploiting spatial and temporal sub‐structures and additional phase changes.

Effect of mineralogical composition and kerogen content on oil shale natural floatability

ABSTRACTMineralogical composition is one of the important factors that affect the performance of separation processes. In the current study, two oil shale samples, from El-Nakhil and El-Bieda localities, differ in their mineralogical composition, were subjected to flotation tests. Chemical analysis, differential thermal analysis (DTA), thermo-gravimetric analysis (TGA), and microscopic examination are among the used characterization techniques. In addition, their responses for upgrading by flotation were conducted as a function of pH, solid-liquid ratio, stirring speed and different particle sizes. The characterization results indicated that the kerogen content in El-Nakhil sample was 30% while in El-Beida sample was 10%. On the other hand, the flotation results indicated that El-Bieda responses better than that of El-Nakhil in terms of the difference in kerogen % between the original sample and the concentrated ones. The difference in flotation results of two samples can be explained by the difference in kerogen morphology as well as its interaction with surrounding matrix. In El-Bieda the kerogen has a laminated structure but in El-Nakhil it appears as laminated liptinitic component, in addition to the higher carbonate content in El-Nakhil sample in comparison to higher clay content in El-Bieda sample.

Desalination characteristics of TFN-RO membrane incorporated with ZIF-8 nanoparticles

Nanoparticle addition to membranes is advancing the performance of separation processes and improving the flux without jeopardizing the selectivity. However, fouling-resistance improvement of RO membranes is still needed in the desalination industry. The objective of this paper is to investigate the addition of ZIF-8 to the membrane selective-layer and its effect on the improvement of membrane fouling-resistance. SEM images of ZIF-8 nanoparticle showed a rhombic dodecahedral shape with an apparent uniform size of around 80nm and BET surface area of 735m2/g while membrane images showed a typical ridge and valley structure of aromatic polyamide (PA). The contact angle of the best performing membrane PZ4 (33.2°) was much lower than that of the control membrane (62.8°) suggesting higher surface-hydrophilicity. The permeate flux of PZ4 increased 53% compared to the control PA membrane under brackish water conditions while maintaining high salt rejection of 99.4%. Under fouling conditions with BSA, the control PA membrane lost more than 50% of its initial flux while PZ4 lost only 13% after 4h of continuous operation. This study showed that ZIF-8 nanoparticles can significantly enhance the polyamide fouling-resistance and in the case of PZ4 membrane, the fouling was remarkably reduced by more than 75%.

Preparation of high-performance Al2O3/PES composite hollow fiber UF membranes via facile in-situ vapor induced hydrolyzation

The preparation of inorganic/organic composite membranes has been demonstrated to bring together the advantages of ceramic and polymeric materials. However, the fabrication of inorganic/organic thin-film composite membranes in hollow fiber configuration has rarely been reported due to the complexity of existing methods. A facile and economic method, in-situ vapor induced hydrolyzation process, was proposed for preparation of Al2O3/Polyethersulfone (PES) thin-film composite hollow fiber ultrafiltration (UF) membranes. The amphiphilic copolymer of PEO-PPO-PEO was introduced to bridge the Al2O3 nanoparticles and PES substrate, resulting in a more stable deposition of Al2O3 on the substrate. The surface morphology and pore size of Al2O3/PES membranes could be precisely tuned by controlling the addition of aluminum precursors. The resultant membrane presented a MWCO of 22kDa and a high pure water permeability (PWP) of 280Lm−2h−1bar−1 due to the completely coated surface hydrophilic Al2O3 ceramic layer. In addition, the as-prepared thin film composite membrane exhibited a lower membrane contact angle than most other mixed matrix inorganic/organic composite membranes. Due to the higher surface hydrophilicity, the composite membranes showed improved antifouling properties to humic acid (HA). This in-situ vapor induced hydrolyzation process was demonstrated to be promising for fabricating thin-film inorganic/organic composite hollow fiber membranes with high performance in separation processes.

Controlling the Intermediate Structure of an Ionic Liquid for f-Block Element Separations.

Recent research has revealed molecular structure beyond the inner coordination sphere is essential in defining the performance of separation processes; nevertheless, such structure remains largely unexplored. Here we apply small-angle neutron scattering (SANS) and X-ray absorption fine structure (XAFS) spectroscopy to investigate the structure of an ionic liquid system studied for f-block element separations. SANS data reveal dramatic changes in the ionic liquid microstructure (∼150 Å) which we demonstrate can be controlled by judicious selection of counterion. Mesoscale structural features (>500 Å) are also observed as a function of metal concentration. XAFS analysis supports formation of extended aggregate structures, similar to those observed in traditional solvent extraction processes, and suggests additional parallels may be drawn from further study. Achieving precise tunability over the intermediate features is an important development in controlling mesoscale structure and realizing advanced new forms of soft matter.

Numerical investigation of coalescing plate system to understand the separation of water and oil in water treatment plant of petroleum industry

ABSTRACTThe most widely utilized process of produced water treatment is considered to be use of coalescing or corrugated plate systems in the oil industry because these systems have promising results in the acceleration of the separation process. Even use of corrugated plate systems seem to be effective in separation processes, the geometrical parameters of the plate system could greatly influence the performance of separation process. In this study, a two-dimensional computational fluid dynamics model for coalescing plates was developed to investigate Reynolds number and plate hole shape on separation efficiency. Spacing between plates was set to 12 mm while fluid mixture’s Reynolds number varied between 5 and 45 for the computational model. Hole profile and dimensions were determined to be cylindrical, rectangular and ellipse shapes as 10, 15 and 20 mm based on hydraulic diameter definition, respectively. Furthermore, when hole profiles of coalescing plates were chosen to be ellipse and rectangular shapes, separation efficiency nearly stayed constant regardless of hole dimension. The study also reported that change of oil fraction from 5% to 15% caused approximately 30% increase in the separation efficiency. The investigation also revealed Reynolds number of the mixture was inversely proportional to the separation efficiency. It was also found that the highest separation efficiency was obtained for a cylindrical shape with a hole diameter of 15 mm when distance between plates was 12 mm and Reynolds number was 18.

Membrane Distillation: Principles, Applications and Perspectives

Membrane Distillation (MD) is a membrane-based operation able to give 100% theoretical ions rejection and to efficiently work with high concentrated brines. Both features make MD of interest for the purification of wastewater, the production of ultra-pure water and the concentration of brines produced in desalination. MD, also integrated with other membrane operations, can be a valuable way to improve the performance of separation processes.

A framework for the integration of solvent and process design with controllability assessment

This work presents a systematic framework for solvent design and selection based on optimum economic and controllability separation process performance. Solvents are initially designed in a solvent-process screening stage where conceptual process models are optimized to identify solvent options and process features of optimum economic performance. The integration of solvent and process design is facilitated computationally by a data mining approach which allows a reduced number of solvents to be evaluated in process design optimization. Highly performing solvents identified in the first stage are introduced into rigorous separation process design, supported again by the proposed data mining approach. At this stage detailed process models enable identification of operating process characteristics which can be used as targeted set-points in a subsequent control design problem. Selected solvents and design configurations which are able to match the targeted set-points are then investigated for their performance in compensating the effects of multiple and large in magnitude process disturbances. A non-linear sensitivity analysis approach is employed that calculates the optimum steady-state effort for the solvent-process design-control structure configuration. The focus of the work is maintained in the formal mathematical presentation and implementation of the data mining procedure and the controllability assessment of different solvents as well as in the use of rigorous process design models. In this respect alternative solvents and process designs are evaluated based on their economic and static controllability performance.