Separation Of Mixtures Research Articles

Surveys of work in events in the area of chemistry teaching and science related to the theme domestic water quality

This article was constructed from a bibliographic survey carried out during the professional master's course in the Graduate Program in Science and Mathematics Teaching (IEMCI-UFPA). The aim is to analyze the work already published on the topic of domestic water quality with a theme for the teaching of mixture separation processes. This review followed as its main criterion the bibliographic analysis of works published in national events of great relevance for the area of Science Teaching and Chemistry, delimited in a certain temporal clipping. Based on the analysis collected with the survey, it was possible to trace relevant paths for research to seek to contribute to academic production, in order to bring new reflections on the use of the theme focused on citizen education.

Novel process development and mechanism analysis of purification of polymer monomers by combining pressure swing distillation and extraction distillation

Methyl methacrylate is a new polymer material monomer, which is often used in the manufacture of plexiglass, and has very high industrial application value. Producing high purity methyl methacrylate requires a clean and effective separation process. In this work, an efficient separation method of methyl methacrylate/water/methanol azeotrope based on pressure swing distillation coupled extractive distillation is established. The best entrainer in terms of both environmental impact and effectiveness is chosen by examining the impact of relative volatility. The feasibility of pressure swing distillation and the best separation order are determined by ternary phase diagram analysis. A multi-objective optimization method is used to optimize the three designed processes, targeting gas emissions and total annual costs, thereby obtaining the best process plans and parameters. On this basis, the optimal thermal integration design of the three processes is carried out. The analysis of the four processes is conducted from the viewpoints of the energy, economy, environment and exergy. The findings demonstrate that the pressure swing extractive distillation process when combined can significantly increase economy and lessen mixture separation difficulty. Compared with the traditional process, the total annual cost, gas emission and energy loss are reduced by 8.20%, 10.46%, 11.69%, and the effective energy utilization rate is 50.31%. The development of this process is of great significance for the recovery of wastewater containing methyl methacrylate and methanol and the separation of high-purity methyl methacrylate.

Robust and flexible polyester fiber membrane with under-liquid dual superlyophobicity for efficient on-demand oil-water separation

Functional materials with under-liquid dual superlyophobicity have generated a great deal of concern from researchers due to their switchable separation ability oil-water mixtures and emulsions. Conceptually, under-liquid dual superlyophobicity is a Cassie state achievable under-liquid through the synergy of an under-liquid double lyophobic surface and the construction of a highly rough surface. However, obtaining an under-liquid dual superlyophobic surface remains difficult due to its thermodynamic contradiction and complex surface composition. Herein, we successfully prepared a functional coating by modifying the mixture of cellulose nanocrystals (CNCs) and nano-TiO2 with perfluorooctanoic acid (PFOA) via a simple method, then obtained a polyester fiber membrane with under-liquid dual superlyophobicity by roll coating method. The surface wettability of the polyester (PET) membrane was altered, transforming it from the original under-water oleophobic/under-oil superhydrophilic state to the under-water superoleophobic/under-oil superhydrophobic state after coated. The resulting membrane was applied to separate oil and water on-demand. The coated PET membrane exhibited high separation efficiency (>99 %) and high separation flux, effectively separating immiscible oil-water systems as well as oil-in-water and water-in-oil emulsions. The coated PET membrane also demonstrated the ability to perform alternate separation of oil-water mixtures through wetting, washing, and rewetting cycles, with repeated processes up to 10 times without significant reduction in separation efficiency. Furthermore, compared with the previous works, our approach offers a simpler and more convenient method for constructing under-liquid dual superlyophobic surface, making it more suitable for continuous corporate production. This study may provide inspiration for the production and application in large-scale of under-liquid dual superlyophobic membranes.

Economic, entropy generation and environmental analysis of separation of high-concentration azeotropic mixtures by an innovative extractive distillation configuration based on multi-objective optimization

The process design and optimization of separating azeotropic mixtures by extractive distillation (ED) has been a hot problem in recent years. Conventional ED process often faces challenges of high energy consumption and high costs when dealing with azeotropic mixtures containing a high content of a certain component. Therefore, an energy-efficient innovative three-column extractive distillation process (ITCED) that is capable of simultaneously performing preconcentration and extractive distillation functions within a complex distillation column for separating ethyl acetate/n-propanol/water azeotropic mixture containing a large amount of n-propanol is developed. Multi-objective optimization is conducted with the minimization of total annual cost (TAC), CO2 emissions, and entropy generation as the objective functions. According to the optimization results, the ITCED process exhibits substantial advantages compared to the conventional three-column extractive distillation process (TCED), with reductions of 34.95% in TAC, 35.84% in CO2 emissions, and 38.91% in entropy generation. Subsequently, heat pump and heat integration technologies are employed to enhance the ITCED process for the further energy conservation. As a result, compared with the TCED process, the DHP-HI-ITCED process achieves savings of 48.18% in TAC, 67.5% in CO2 emissions and 72.96% in entropy generation.

Hydrate-based technique for natural gas processing: Experimental study of pressure-dropping and continuous modes

Gas hydrate crystallization is perspective and energy-efficient technology for gas mixtures processing, including natural gas. There were compared pressure-dropping and continuous gas hydrate crystallization methods for separation of gas mixture closed to natural gas. The studied mixture has been chosen similar to the natural gas composition: CH4 (75.68 mol.%) - С2H6 (7.41 mol.%) - C3H8 (4.53 mol.%) - н-C4H10 (2.47 mol.%) - CO2 (5.40 mol.%) - H2S (1.39 mol.%) - N2 (3.01 mol.%) - Xe (0.11 mol.%). Experiments were provided in the 4 L high pressure reactor, using water solution of SDS (0.20 wt.%). The experiment conditions were 280.15 K and pressure of 4.25 MPa. The components separation factors and recovery for two modes have been researched and compared for choosing more effective options. After comparing these characteristics, it was concluded that continuous process is more productive than pressure-dropping mode. At the stage cut (θ) of 0.9, the gas components total recovery (R) for the continuous mode have exceeded the total recovery for the pressure-dropping mode by 8.15 %, and at θ = 0.8, exceeded by 6.11 %. The recovery and separation factors have the highest values for H2S, C3H8, Xe in the continuous mode: 97.62 %, 94.90 %, 84.98 % and 8.7, 10.53, 6.36, respectively. Thus, the choosing of the more effective stage cut depends on the aim of the process: the highest purity or the largest recovery.

Experimental Investigation of the Performance of a Novel Adiabatic Swirl-Flow Separation Apparatus in Air–Water Two-Phase Flow

Abstract Experiments were performed for determining the efficacy of a swirl-flow apparatus for phase separation of a premixed two-phase air–water mixture. In the experiments gas and liquid flow rates were parametrically varied. The goal of this study was to determine the ideal operating conditions for phase separation of an adiabatic mixture and to serve as a benchmark for future desalination experiments involving separation of vapor-saline water two-phase mixture generated by flash evaporation. The novel swirl-flow apparatus enables the formation of a stable air core (lighter fluid) in the middle of the separator tube due to centrifugal force induced by strategically injecting the two-phase mixture tangentially into the tubular test section. Separated air is removed by tapping into the air core using a retrieval tube that is mounted in the center of the test section. Conditions under which maximum phase-separation efficiency is obtained in the swirl-flow apparatus were identified and a correlation for the phase-separation efficiency is proposed for the range of experimental conditions explored in this study.

Study on separation of the tuber-soil binary mixture based on vibration and airflow coupling

One of the critical steps in the root crop harvesting process is screening tubers from soil. However, low screening efficiency seriously hinders the rapid development of the root crop industry. Clarifying the tuber-soil mixture separation behaviour and establishing the connection between vibration, airflow parameters, and separation index (SI) is critical to increasing screening efficiency. Corydalis Yanhusuo is employed as the research object, and the three-dimensional scale distribution and mechanical properties of tubers and soil particles are first counted. Then, a vibration and airflow coupling separation model of the tuber-soil mixture was constructed using the computational fluid dynamics and discrete element method (CFD-DEM) coupling method, and the physical parameters in the model were calibrated. A new method for calculating the SI is proposed. The relationship between vibration amplitude, frequency, airflow velocity, SI, and separation velocity was analysed. Simultaneously, the porosity change in the particle group during the separation process was investigated, and the relationship between vibration, frequency, and airflow velocity on the separation dynamics of binary mixtures was revealed by utilising data visualisation and frequency domain analysis. The platform for the vibration and airflow separation physical test was built. The separation behaviour of mixed particles in various parameters was discussed, as was the feasibility and accuracy of the numerical simulation results. The results of this study can provide theoretical support for the efficient screening of tuber-soil mixtures and further promote the rapid development of the root industry.

Micropreparative Gel Electrophoresis for Purification of Nanoscale Bioconjugates.

Conventional techniques for purifying macromolecular conjugates often require complex and costly installments that are inaccessible to most laboratories. In this work, we develop a one-step micropreparative method based on a trilayered polyacrylamide gel electrophoresis (MP-PAGE) setup to purify biological samples, synthetic nanoparticles, as well as biohybrid complexes. We apply this method to recover DNA from a ladder mixture with yields of up to 90%, compared to the 58% yield obtained using the conventional crush-and-soak method. MP-PAGE was also able to isolate enhanced yellow fluorescence protein (EYFP) from crude cell extract with 90% purity, which is comparable to purities achieved through a more complex two-step purification procedure involving size exclusion and immobilized metal-ion affinity chromatography. This technique was further extended to demonstrate size-dependent separation of a commercial mixture of graphene quantum dots (GQDs) into three different fractions with distinct optical properties. Finally, MP-PAGE was used to isolate DNA-EYFP and DNA-GQD bioconjugates from their reaction mixture of DNA and EYFP and GQD precursors, samples that otherwise could not be effectively purified by conventional chromatography. MP-PAGE thus offers a rapid and versatile means of purifying biological and synthetic nanomaterials without the need for specialized equipment.

Transport of particles through RO membrane in steady state condition

AbstractReverse Osmosis (RO) membranes are widespread nowadays for separating solvent from a solution. Experiments show that changes in relative interaction of solvent and solute with RO membrane matrix lead to changes in solvent permeation, solute rejection and fouling. Here we study microscopically separation of binary mixture through RO polymeric membrane using Molecular Dynamics simulation. We find better solvent permeation and solute rejection with increasing interaction between solute and membrane but fouling by solute inside the membrane increases. We also find that stronger solvent membrane interaction reduces fouling but with concomitant poorer solvent permeation and solute rejection.

Accelerating In Silico Discovery of Metal-Organic Frameworks for Ethane/Ethylene and Propane/Propylene Separation: A Synergistic Approach Integrating Molecular Simulation, Machine Learning, and Active Learning.

Cryogenic distillation, a currently employed method for C2H4/C2H6 and C3H6/C3H8 mixture separation, is energy-intensive, prompting the research toward alternative technologies, including adsorbent-based separation. In this work, we combine machine learning (ML) technique with high-throughput screening to screen ∼23,000 hypothetical metal-organic frameworks (MOFs) for paraffin (C2H6 and C3H8) selective adsorbent separation. First, structure-based prescreening was employed to remove MOFs with undesired geometric properties. Further, a random forest model built upon the multicomponent grand canonical Monte Carlo (m-GCMC) simulation data of training set MOFs was found to be the most successful in learning the relationship between MOF features and olefin/paraffin mixture separation. Using this technique, the separation performance of the remaining (test set) MOFs was predicted, and the top-performing MOFs were identified. We also employed active learning (AL) to evaluate its effectiveness in improving the prediction of olefin/paraffin selectivity. AL was discovered to be ∼29 times more efficient than the best-supervised ML model, as it was able to identify the top materials in limited training data and at a fraction of computational cost and time as compared to ML techniques. Among the top selected materials, framework chemistry was found to be the most important parameter. Nickel and copper (as a metal node) in a tfzd and hms topological arrangement respectively, were discovered to be a prevalent attribute in high-performing MOFs, further demonstrating the prominent significance of framework chemistry. Additionally, the top MOFs discovered were studied in detail and further compared to the previously reported MOFs. These MOFs show the highest selectivity for C2H4/C2H6 and C3H6/C3H8 mixture separation, as reported until date. The hierarchical strategy devised in this study will facilitate the quick screening of MOFs across multiple databases toward industrially significant separation processes by leveraging molecular simulations and AL.

Ultrasound-based separation of ethanol-water mixtures is economically advantageous and sustainable

Ultrasound-based separation of ethanol-water mixtures is economically advantageous and sustainable

Separation of CO2 and TFE by using diethanolamine and diisopropylamine

ABSTRACT The near-azeotrope mixture of TFE and CO2 is an important concern urging the scientific community to develop new ways for TFE/CO2 separations. In this work, for the first time, Diisopropylamine (DIPA) and Diethanolamine (DEA) are used as solvents for separating a near-azeotropic mixture of CO2 and tetrafluoroethylene (TFE). The complete separation mechanism has been analyzed using ASPEN Plus process simulator. The binary parameters for CO2, TFE, DIPA and DEA have been taken from Cosmotherm software and the pure data parameters have been taken from the literature (NIST). The validation of the processes has been completed by comparing binary parameters with literature and pure parameters with the UNIFAC data. The separation of the near-azeotropic mixture of TFE and CO2 has been investigated where, both solvents can be proposed as good candidates, however DEA is proven better performer than DIPA. In addition, CO2 emissions analysis and Total Annual Cost (TAC) analysis has been performed for the payback period of 3, 5 and 7 years, where DEA proves to be most efficient for TAC while DIPA has less CO2 emissions.

Separation of the cyclohexane-benzene mixture by the extractive distillation process using ethylene glycol as a solvent

The importance of cyclohexane lies in the fact that it is the main precursor for the production of Nylon 6 and Nylon 6.6, two of the most important synthetic fibers. Cyclohexane (CHX) is produced by catalytic hydrogenation of benzene (BZ), where cyclohexane with benzene is obtained as a product. Since CHX and BZ have close boiling temperatures, and similar molecular structures, their separation by conventional binary distillation is complicated. Thus, ethylene glycol (EG) was selected as a solvent in an extractive distillation (ED) process for the separation of the CHX-BZ mixture in Aspen Plus V9®; where the use of ethylene glycol as a solvent allowed us to obtain cyclohexane and benzene with purities of 99.91 mol%. In addition, compared to the extractive distillation with heat integration (EDHI) process that uses [C5(MIM)2][NTf2]2 + H2O as a mass separation agent; the use of EG as a solvent promotes an energy decrease of 41.14%, a saving of 55.07% in the Total Annual Cost (TAC), and a decrease of 72.38% in CO2 emissions. These outcomes underscore the efficacy of ethylene glycol as a suitable solvent in the purification of the cyclohexane-benzene mixture.

Chitinous material bioconversion by three new chitinases from the yeast Mestchnikowia pulcherrima

BackgroundChitinases are widely distributed enzymes that perform the biotransformation of chitin, one of the most abundant polysaccharides on the biosphere, into useful value-added chitooligosaccharides (COS) with a wide variety of biotechnological applications in food, health, and agricultural fields. One of the most important group of enzymes involved in the degradation of chitin comprises the glycoside hydrolase family 18 (GH18), which harbours endo- and exo-enzymes that act synergistically to depolymerize chitin. The secretion of a chitinase activity from the ubiquitous yeast Mestchnikowia pulcherrima and their involvement in the post-harvest biological control of fungal pathogens was previously reported.ResultsThree new chitinases from M. pulcherrima, MpChit35, MpChit38 and MpChit41, were molecularly characterized and extracellularly expressed in Pichia pastoris to about 91, 90 and 71 mU ml− 1, respectively. The three enzymes hydrolysed colloidal chitin with optimal activity at 45 ºC and pH 4.0-4.5, increased 2-times their activities using 1 mM of Mn2+ and hydrolysed different types of commercial chitosan. The partial separation and characterization of the complex COS mixtures produced from the hydrolysis of chitin and chitosan were achieved by a new anionic chromatography HPAEC-PAD method and mass spectrometry assays. An overview of the predicted structures of these proteins and their catalytic modes of action were also presented. Depicted their high sequence and structural homology, MpChit35 acted as an exo-chitinase producing di-acetyl-chitobiose from chitin while MpChit38 and MpChit41 both acted as endo-chitinases producing tri-acetyl-chitotriose as main final product.ConclusionsThree new chitinases from the yeast M. pulcherrima were molecularly characterized and their enzymatic and structural characteristics analysed. These enzymes transformed chitinous materials to fully and partially acetylated COS through different modes of splitting, which make them interesting biocatalysts for deeper structural-function studies on the challenging enzymatic conversion of chitin.

Molybdenum Sulfide Nanomaterial: A Potential Candidate for Separation Membranes

AbstractMolybdenum sulfide (MoS2)‐based nanocomposites have attracted significant attention for various separation processes due to their ultrathin thickness, high mechanical and chemical strength, and good functionality. Herein, the recent progresses of various fabrication, synthesis, and modification methods for separation membrane‐based on MoS2 nanocomposites are reviewed. Emphasis is given on applications of MoS2‐based membranes in the purification of wastewater, separation of gas mixtures, energy storage separator, and proton‐exchange fuel cells (PEFCs). Advantages and drawbacks of this material for separation applications are discussed. Finally, a future roadmap is suggested for this promising nanomaterial in various separation processes.

Gas Chromatographic Determination of Residual Concentrations of a Mixture of Organochlorine Pesticides in Food Products

Purpose of research. The aim of the work is to optimize the conditions for gas chromatographic determination of a mixture of eight organochlorine pesticides: aldrin, hexachlorobenzene, heptachlor, α-hexachlorocyclohexane, γ-hexachlorocyclohexane, dichlorodiphenyltrichloromethylmethane, dichlorodiphenyldichloroethane and dichlorodiphenyldichloroethylene.Methods. For chromatographic studies of organochlorine pesticides we used a Shimadzu GC-2010Plus gas chromatograph (Shimadzu, Japan) equipped with an automatic equilibrium vapor sample dispenser NT200N, electron-capture detector based on 63Ni and quartz capillary nonpolar column "Chromatek" SPB-5 (30 m, 0.32 mm, film thickness on the basis of phenyl(5%) and dimethyl(95%) polysiloxanes 0.5 μm) with an operating temperature range of 60°C 320/340°C. The chromatograms were processed in the application LabSolutions GPC.Results. On the basis of experimentally obtained data the optimal conditions for gas chromatographic determination and separation of eight-component mixture of organochlorine pesticides were selected, namely: the value of mobile phase flow division 1:10, carrier gas flow rate – 1.0 ml/min, two-stage temperature programmable column mode from 160 to 240°C with the rate of increase of 5°C/min. The metrological characteristics of the analysis and validation of the results of the proposed technique with the method of high-performance liquid chromatography were evaluated. Good reproducibility of chromatography results with the possibility of detection of organochlorine pesticides at the level of 10-6 – 10-5 μg/cm3 was proved. Application of Fisher's test has shown absence of significant differences in reproducibility of sampled populations the investigated methods of chromatographic analysis of COPCs are equally accurate. Extraction sample preparation of samples of real objects was proposed, the calculated extraction degrees >84% allow to recommend the technique for quantitative determination of analytes.Conclusion. The method of gas chromatographic analysis was tested for determination of organochlorine pesticides in samples of drinking water and baby puree (Russia) by additive method. Exceeding the norms of residual contents of organochlorine pesticides in the samples of the food products under study was not detected.

Evaluation of a Simplified Model for Three-Phase Equilibrium Calculations of Mixed Gas Hydrates

In this study, we perform an extensive evaluation of a simple model for hydrate equilibrium calculations of binary, ternary, and limited quaternary gas hydrate systems that are of practical interest for separation of gas mixtures. We adopt the model developed by Lipenkov and Istomin and analyze its performance at temperature conditions higher than the lower quadruple point. The model of interest calculates the dissociation pressure of mixed gas hydrate systems using a simple combination rule that involves the hydrate dissociation pressures of the pure gases and the gas mixture composition, which is at equilibrium with the aqueous and hydrate phases. Such an approach has been used extensively and successfully in polar science, as well as research related to space science where the temperatures are very low. However, the particular method has not been examined for cases of higher temperatures (i.e., above the melting point of the pure water). Such temperatures are of interest to practical industrial applications. Gases of interest for this study include eleven chemical components that are related to industrial gas-mixture separations. Calculations using the examined methodology, along with the commercial simulator CSMGem, are compared against experimental measurements, and the range of applicability of the method is delineated. Reasonable agreement (particularly at lower hydrate equilibrium pressures) between experiments and calculations is obtained considering the simplicity of the methodology. Depending on the hydrate-forming mixture considered, the percentage of absolute average deviation in predicting the hydrate equilibrium pressure is found to be in the range 3–91%, with the majority of systems having deviations that are less than 30%.

Controllable process to construct robust superhydrophobic membrane with tunable pore size for efficient separation of oil-water mixtures and emulsions

The increase in the discharge of industrial oily wastewater poses a threat to the environment and human health. Thus, the treatment of oily wastewater has become a focus of current research. The superhydrophobic surface derived from the lotus effect provides an effective direction for oil-water separation. Based on this, the authors reported a tunable superhydrophobic stainless steel separation mesh with a water contact angle of 155° through simple electrodeposition and modification with a fluorine-free modifier. The separation mesh with different surface morphology, by controlling different electrodeposition time and current, is able to achieve oil-water separation with super flux up to 51561 L/(m2·h) in heavy oil/water mixture and high-efficiency over 99.5% in water-in-oil emulsion. This controllable process constructs superhydrophobic membrane with tunable pore size, which is capable of separating heavy oil/water mixtures and water-in-oil emulsions depending on the process. This proposal is suggestive in the field of oil-water separation.

Selective adsorption analysis of BAPTA depressants on the surface of carbonate minerals: Insights into flotation behavior and adsorption mechanism

Flotation separation of magnesite and calcite, two carbonate minerals, poses a significant challenge due to their intrinsic surface similarities. In this study, 1,2-bis(o-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid (BAPTA) was employed as a depressant to selectively regulate the mineral surface property in magnesite-calcite flotation. Micro-flotation experiments demonstrated that successful separation of magnesite-calcite mixtures could be achieved with 40 mg/L BAPTA and 100 mg/L sodium oleate (NaOL). Contact angle measurements and Ultraviolet-Visible absorption spectrum analysis revealed that pre-adsorption of BAPTA selectively hindered the adsorption of sodium oleate onto calcite surface, effectively eliminating the surface hydrophobicity of calcite induced by sodium oleate. The Extended-Derjaguin-Landau-Verwey-Overbeek (EDLVO) theory further indicated a reduced attractive interaction energy between magnesite and calcite particles in the presence of BAPTA. X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) simulation elucidated the stronger binding affinity of BAPTA towards calcium ions. Finally, a model was established for the selective formation of cage-like chelating structures on the calcite surface by BAPTA.

Dilution-controlled deposition of mixtures of a synthetic polycation and a natural origin polyelectrolyte with anionic surfactants on negatively charged surfaces

The cosmetics industry is constantly seeking sustainable and environmentally friendly ingredients for hair care formulations to replace those traditionally derived from the petrochemical industry. In this context, the substitution of traditional cationic polyelectrolytes, such as poly(diallyldimethylammonium chloride, PDADMAC), by others of natural origin, such as chitosan, is a key challenge to achieve new formulations with a higher degree of naturality and more environmentally friendly without compromising product efficacy. This work investigates the effect of dilution on the phase separation of concentrated binary mixtures of two anionic surfactants (sodium laureth sulfate, SLES, and sodium dodecyl sulfate, SDS) with PDADMAC or chitosan. PDADMAC is a polycation of petrochemical origin, whereas chitosan is obtained from natural resources. Also, how this phase separation affects the formation of conditioning deposits on surfaces that mimic the charge and wettability of damaged hair fibers has been studied. The results show that for polymers of similar molecular weight, the substitution of PDADMAC by a highly charged chitosan is a promising alternative. The deposition is greatly enhanced for model wash formulations containing chitosan after minimal dilution. The results obtained here may pave the way to an important line of research toward improving the sustainability profile of hair care formulations without compromising consumer satisfaction.