Separation Method Research Articles

Development and optimization of high-performance extraction chromatography method for separation of rare earth elements

The effectiveness of commonly used extractants for chromatographic separation of rare earth elements (REEs) was compared. Columns loaded with similar molar concentrations of tributyl phosphate (TBP), di-(2-ethylhexyl) phosphoric acid (HDEHP), and N-Methyl-N, N, N-tri-octyl-ammonium chloride (Aliquat-336), with mineral acid as eluent were evaluated. Retention factors were determined, and separation efficiency was assessed based on the resolution data of the REEs acquired under the same elution conditions for each column. HDEHP demonstrated the best separation efficiency for the entire REE series (mean Rs = 2.76), followed by TBP (mean Rs = 1.52), while Aliquat-336 exhibited the lowest performance (mean Rs = 1.42). The HDEHP-coated column was then used to optimize the extraction chromatographic separation of the REEs. The primary challenge was to completely elute the heavy REEs (Tb – Lu) while maintaining adequate separation of the light REEs (La – Gd) within a reasonably short time. The stepwise gradient elution procedure improved the resolution between adjacent REEs, allowing the complete separation of the entire REE series within 25 minutes. Better separation efficiency for light REEs was achieved at higher column temperatures and a mobile phase flow rate of 1.5 mL/min in the tested domain of 20–60 °C, and 0.5–2.0 mL/min, respectively, resulting in plate heights (H) ranging from 0.011 to 0.027 mm.

High-performance Ti6Al4V surface manufacture by laser carburising-assisted grinding

High-precision Ti6Al4V surfaces with superior properties are in urgent demand in the manufacturing industry. The existing production model that separates surface strengthening from processing has limitations. Therefore, an integrated Ti6Al4V surface machining and strengthening method, laser carburising grinding, is proposed. Remelt layers containing diffusely distributed granular TiC phases are prepared on Ti6Al4V surfaces by coupling laser carburising alloying with grinding processes, improving the material surface's mechanical properties and grindability. Compared with the separated method, the surface shape accuracy is increased by 16 %, the surface hardness reaches 652 HV, and the surface wear resistance is greatly improved. The results improve the surface machining-strengthening integration theory of titanium alloy. The related technology is of great practical significance in guiding production.

Adsorption of metal porphyrins using chitosan/zeolite-X composite as an efficient demetallization agent for crude oil: Isotherm, kinetic, and thermodynamic studies

Chitosan/zeolite-X (CHS/ZX) was synthesized to serve as an effective adsorbent for metal porphyrins through adsorption processes as an alternative to traditional separation methods from crude oil. The adsorption-desorption mechanisms of vanadyl and nickel tetraphenyl porphyrin (VO-TPP and Ni-TPP) were conducted on the model solution. Compared to individual components CHS and ZX, the CHS/ZX composite exhibited a doubled capacity for metal porphyrin removal. The synthesized composite was systematically characterized using FESEM, BET, XRD, FTIR, TGA, XPS, and CHN analyses. The study investigated the impact of many factors, including temperature, initial metal-porphyrin concentration, CHS/ZX dose, and contact time, on the adsorption efficiency of metal-porphyrin using CHS/ZX adsorbents. The adsorption processes of VO-TPP and Ni-TPP on CHS/ZX were effectively assessed through various equilibrium models, such as Langmuir, Freundlich, and Dubinin-Radushkevich (D-R). The pseudo-second-order model accurately depicted the adsorption processes of both VO-TPP and Ni-TPP. Determining the point of zero charge (pHPZC) highlighted the composite's surface charge distribution. Furthermore, considering the ΔG° and ΔH° values, the adsorption processes at different temperatures are exothermic, and VO-TPP exhibits a greater adsorption capacity than Ni-TPP under similar conditions. Notably, 73.7 % of VO-TPP and 83.8 % of Ni-TPP that were adsorbed were successfully recovered.

Ultra-fast and ultra-efficient phenol removal from aqueous solution using a nano biocarbon adsorbent by RSM-CCD method: parameters, isotherm, kinetic, ANOVA.

The purpose of this research is to investigate the ability of peanut shell activated carbon (PSAC) to adsorb phenol from aqueous solutions. Phenolic wastewater in various industries and their release to the environment are environmental problems. Among the various separation methods, adsorption is an accepted method because of its efficiency, simplicity, cost-effectiveness, and possibility to use different adsorbent materials to achieve maximum adsorption efficiency. Response surface methodology (RSM) was used to minimize the required experiments, modeling, finding the optimal point, and variance analysis. Among the studied variables, pH, adsorbent dosage, and initial concentration are important. The results show that it is possible to completely remove at 300ppm of phenol concentration and 5min. Characterization of PSAC was done using Fourier transform infrared spectroscopy spectrum (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), Brunauer-Emmet-Teller (BET), and size analysis. By examining the isotherm models, it was found that the adsorption follows the Langmuir model. The maximum adsorption capacity was 250mgg-1 based on the Langmuir model. The three combined features of complete removal, ultra-fast adsorption, and high adsorption capacity are the unique features of this nano biocarbon for phenol removal.

Inverse Coefficient Problem for the 2D Wave Equation with Initial and Nonlocal Boundary Conditions

In this paper, we consider direct and inverse problems for the two-dimensional wave equation. The direct problem is an initial boundary value problem for this equation with nonlocal boundary conditions. In the inverse problem, it is required to find the time-variable coefficient at the lower term of the equation. The classical solution of the direct problem is presented in the form of a biorthogonal series in eigenvalues and associated functions, and the uniqueness and stability of this solution are proven. For solution to the inverse problem, theorems of existence in local, uniqueness in global, and an estimate of conditional stability are obtained. The problems of determining the right-hand sides and variable coefficients at the lower terms from initial boundary value problems for second-order linear partial differential equations with local boundary conditions have been studied by many authors. Since the nonlinearity is convolutional, the unique solvability theorems in them are proven in a global sense. In the works, the method of separation of variables is used to find the classical solution of the direct problem in the form of a biorthogonal series in terms of eigenfunctions and associated functions. The nonlocal integral condition is used as the overdetermination condition with respect to the solution of the direct problem. The direct problem reduces to equivalent integral equations of the Fourier method. To establish integral inequalities, the generalized Gronwall-Bellman inequality is used. We obtain an a priori estimate of the solution in terms of an unknown coefficient, that are useful for studying the inverse problem.

Harnessing the power of hollow Zein nanoparticles for enhanced antifouling and heavy metal removal of polyethersulfone membranes

This study explores the physicochemical characteristics of an innovative mixed matrix membrane made from polyethersulfone (PES) and hollow Zein nanoparticles (HZNs), which are derived from the corn storage protein, Zein. HZNs, with a mean diameter of 40 nm, were applied to address the challenges associated with metal and inorganic nanoparticles, such as their tendency to accumulate unevenly on the membrane surface. The membranes were fabricated by incorporating varying concentrations of HZNs into the PES casting solution through the nonsolvent phase separation method. The addition of HZNs enhanced the hydrophilicity and pure water flux of the membranes. It also modified the membrane structure, morphology, pore size, molecular weight cut-off (MWCO), and porosity. Increasing the HZN concentration up to 5 wt% proportionally improved the surface hydrophilicity and roughness of the membranes. Furthermore, the modified membranes exhibited excellent performance in rejecting heavy metals at an acidic pH of 4, with the 5 %-HZNs/PES membrane achieving a 100 % rejection rate without significantly affecting water flux due to Donnan exclusion. Additionally, the 5 %-HZNs/PES membrane showed a minimal irreversible fouling resistance (Rir) of 17.9 % and a fouling resistance ratio (FRR) of 82.1 %. These results indicate that the developed mixed matrix membrane holds significant promise for applications in water purification processes.

New exact solitary waves for the Sasa-Satsuma model with variable coefficients

In this paper, we investigate the variable coefficients Sasa-Satsuma model, which can describe the propagation of a light pulse in a cylindrical fiber. We study this model and obtain rich solutions using two separate methods. We obtain analytical Weierstrass elliptic function solutions using the Weierstrass elliptic function expansion method. Some Jacobi elliptic function solutions are obtained using the modified Jacobi elliptic function expansion method. When the Jacobi elliptic function degenerates, we obtain the corresponding trigonometric, hyperbolic function solutions and periodic solutions. We also try to take the coefficients of the equation as some functions and obtain some more complicated exact solutions, which have not appeared in previous studies. Finally, we simulate some waveform diagrams of the solutions using the computer software Mathematica and obtain periodic waves, bright and dark soliton, double solitons and some complex periodic waves. With these waveform diagrams, we can observe the dynamical behavior of the solutions more clearly.

Joint dereverberation and blind source separation using a hybrid autoregressive and convolutive transfer function-based model

Most frequency-domain blind source separation (BSS) methods are based on the multiplicative narrowband assumption, which is not valid in long reverberation environments. In contrast, convolutive transfer function (CTF)-based BSS methods do not rely on the narrowband assumption, and the separation performance is significantly improved compared to the traditional algorithms in long reverberation environments. However, the CTF-based BSS methods and their variants, e.g., autoregressive (AR) BSS methods, introduce modeling errors to some extent, due to the truncation or approximation during the optimization process. To address this problem, we propose a frequency-domain BSS method employing a hybrid AR and CTF model, which can provide more precise representations of the early reflections and late reverberations. Furthermore, we utilize the Gaussian noise model to deal with the BSS problem in noisy reverberant environments. We formulate the objective function using the maximum log-likelihood criterion, and derive an efficient iterative algorithm for parameter estimation with the block coordinate descent (BCD) method. Experimental results show that the proposed method has a better separation performance than the existing methods in long reverberation environments.

Optimization of the Separation and Validation Method for Ginsenoside Re and Ginsenoside Rg1 Compounds in Panax Ginseng Powder Extract Using the HPLC Method: A Systematic Literature Review

The analytical methods used to analyze ginsenoside compounds include TLC, HPTLC, HPLC, UPLC, GC and MS. The HPLC method is the most widely used analytical technique with various combinations of UV detection or with ELSD. The HPLC method is a method of separating and purifying chemical compounds or medicinal compounds. To study new information from optimization for the separation of ginsenoside Re and ginsenoside Rg1 compounds, then validate the analytical method to show that the method provides accurate results in accordance with the requirements. The data and information used in this review article come from national and international journals. The data and information search method was carried out using the literature research method. keywords: "Optimization of Separation and Method Validation of Ginsenoside Compounds using the HPLC method" with a journal publication period 2019-2023. Of the 35 research articles found, only 9 journals met the inclusion and exclusion criteria. Studies on ginsenoside compounds Re and Rg1 in ginseng plants are still not well separated. So it’s still necessary to optimize the analytical method using the HPLC method and then validate the analytical method to show that the method provides accurate results in accordance with the requirements.

Enhancing Unsupervised Outlier Model Selection: A Study on IREOS Algorithms

Outlier detection stands as a critical cornerstone in the field of data mining, with a wide range of applications spanning from fraud detection to network security. However, real-world scenarios often lack labeled data for training, necessitating unsupervised outlier detection methods. This study centers on Unsupervised Outlier Model Selection (UOMS), with a specific focus on the family of Internal, Relative Evaluation of Outlier Solutions (IREOS) algorithms. IREOS measures outlier candidate separability by evaluating multiple maximum-margin classifiers and, while effective, it is constrained by its high computational demands. We investigate the impact of several different separation methods in UOMS in terms of ranking quality and runtime. Surprisingly, our findings indicate that different separability measures have minimal impact on IREOS’ effectiveness. However, using linear separation methods within IREOS significantly reduces its computation time. These insights hold significance for real-world applications where efficient outlier detection is critical. In the context of this work, we provide the code for the IREOS algorithm and our separability techniques.

Investigations on Hydrogen Isotope Separation Factor Employing Palladium-Based Solid Metallic Membranes

At present, there are several methods for hydrogen isotope separation (in elemental form), the most important being cryogenic distillation, thermal diffusion, and gas chromatography. However, these methods have a series of drawbacks, namely, high complexity, high energy consumption, and associated costs. Taking into account these disadvantages, a promising separation method is the one based on solid metallic membranes because of its advantages like low energy consumption and reduced complexity. This method uses the difference between some of the isotopes’ properties, namely, solubility; diffusivity; and, implicitly, permeability. This work envisages the integration of an isotopic separation module, based on membrane permeation, on the exhaust gas line from the current experimental rigs employed at ICSI, to recover and store the hydrogen isotopes. We obtained a maximum separation factor of 5.66 for the lowest studied concentration of deuterium in the hydrogen isotopic mixture (0.05 atomic fraction). The results show that hydrogen isotope separation is possible using palladium/silver membranes. Still, the throughput of the permeated gas is very low, and a significant number of stages will be necessary to obtain the desired purity (above 99.5%).

Ag@SnS/PVDF membranes with self-cleaning ability driven by photocatalysis process

Coupling photocatalysis with membrane separation technology becomes one pioneering method to solve the membrane fouling. In this study, Ag@SnS photocatalyst was synthesized and blended with polyvinylidene fluoride (PVDF) to fabricate Ag@SnS/PVDF composite membranes via non-solvent induce phase separation (NIPS) method. The results show that with the addition of Ag@SnS, water flux of Ag@SnS/PVDF hybrid membranes increases due to the enhanced membrane hydrophilicity and increased porosity. The optimal hybrid membrane (MAS-2) exhibits the rejection rate of 97.0 % and 95.4 % for BSA and HA accompanied with a water permeance of 578.5 L m−2 h−1 bar−1. Moreover, MAS-2 membrane reveals excellent self-cleaning ability by photodegradation of HA on membrane surface, and its flux recovery rate (FRR) can achieve 91.7 % after UV irradiation and 95.8 % after 3 h natural sunlight irradiation via photocatalysis regeneration. The heterostructure of Ag@SnS can assist separation of photoinduced electrons and holes by transferring photoinduced electrons to Ag nanoparticles with enhanced photocatalytic activity. After three cycles, the FRR can still reach around 90.0 %, revealing its outstanding cleaning ability. Therefore, the Ag@SnS/PVDF membranes have a foreseeable potential in the field of water treatment due to its high flux performance, self-cleaning ability via photocatalysis process.

Analytical solution to some boundary value problems of elasticity in bipolar coordinates

Analytical solutions of two-dimensional statics problems of elasticity are presented in bipolar coordinates for homogeneous isotropic bodies bounded by the coordinate lines of a bipolar coordinate system. In particular, various boundary problems for an eccentric circular ring, a half-plane with circular holes, and others are considered. The equilibrium equations and Hooke’s law are expressed using bipolar coordinates. This paper does not address the static equilibrium requirement of the external load at each circular boundary of the study area. This requirement, which significantly limits the range of problems that can be solved, typically appears in papers dealing with the aforementioned problems. In addition, the proposed method for obtaining an exact (analytical) solution is much simpler compared to the traditional approach. The exact solutions are derived using the method of separation of variables. By utilizing MATLAB software, the numerical results of some boundary value problems for an eccentric semi-ring are obtained, and the corresponding diagrams are presented.

Tensor low-rank and sparse decomposition and its application in bearing fault information separation

Abstract Properly separating fault information from noisy measured signals is crucial for effective bearing health sensing. However, conventional fault information separation methods face challenges such as predefined model parameters and poor noise robustness. Additionally, with the advent of Industry Big Data, multichannel monitoring signals present significant challenges for traditional single decomposition approaches. To address these challenges and fully extract potential fault information, this paper introduces a tensor low-rank and sparse decomposition (tensor LRSD) approach for multichannel signal processing. Inspired by matrix LRSD, we construct a tensor LRSD model that adaptively decomposes the signal into a tensor sparse term containing fault information and a low-rank term representing the intrinsic signal pattern. To further enhance the decomposition performance, a maximum correlation-based selection strategy is designed. This strategy evaluates the correlation between each tensor slice and selects appropriate tensor sparse terms for fault information extraction. Simulation analysis and two experimental studies involving typical bearing failures are implemented to verify the capability and superiority of the presented tensor LRSD approach. The consequences demonstrate that the presented method outperforms conventional techniques, showcasing its capability to effectively separate fault information from noisy signals.

Separation of terbium as a first step towards high purity terbium-161 for medical applications.

Terbium-161 is a medical radiolanthanide that has a beta decay energy and half-life similar to that of lutetium-177, which makes it a promising alternative for therapeutic purposes. The production route using an enriched gadolinium-160 target necessitates the purification of terbium-161 from the untransmuted target material as well as from its stable decay product, dysprosium-161. The separation of neighbouring lanthanides is challenging due to their similar chemical properties and prominent trivalent oxidation states. In this work, the aim is to change the oxidation state of terbium, resulting in the altering of chemical properties that ease the intragroup separation. To this end, a novel separation method is investigated, involving the electrochemical oxidation of terbium (3+) to terbium (4+) followed by anion exchange chromatography. The electrolysis conditions are set to the highest achievable conversion rate, followed by a dilution step during which the pH and electrolyte concentration are slightly lowered to obtain conditions that are compatible with the separation method. XAS analysis is done to characterize the carbonato complex of both oxidation states and to further elucidate the separation mechanism. The results show that the separation approach of combining electrochemical oxidation with anion exchange chromatography is promising for the purification of 161Tb for medical use.

ScHD4E: Novel ensemble learning-based differential expression analysis method for single-cell RNA-sequencing data

Differential expression (DE) analysis between cell types for scRNA-seq data by capturing its complicated features is crucial. Recently, different methods have been developed for targeting the scRNA-seq data analysis based on different modeling frameworks, assumptions, strategies and test statistic in considering various data features. The scDEA is an ensemble learning-based DE analysis method developed recently, yielding p-values using Lancaster's combination, generated by 12 individual DE analysis methods, and producing more accurate and stable results than individual methods. The objective of our study is to propose a new ensemble learning-based DE analysis method, scHD4E, using top performers in only 4 separate methods. The top performer 4 methods have been selected through an evaluation process using six real scRNA-seq data sets. We conducted comprehensive experiments for five experimental data sets to evaluate our proposed method based on the sample size effects, batch effects, type I error control, gene ontology enrichment analysis, runtime, identified matched DE genes, and semantic similarity measurement between methods. We also perform similar analyses (except the last 3 terms) and compute performance measures like accuracy, F1 score, Mathew's correlation coefficient etc. for a simulated data set. The results show that scHD4E is performs better than all the individual and scDEA methods in all the above perspectives. We expect that scHD4E will serve the modern data scientists for detecting the DEGs in scRNA-seq data analysis. To implement our proposed method, a Github R package scHD4E and its shiny application has been developed, and available in the following links: https://github.com/bbiswas1989/scHD4E and https://github.com/bbiswas1989/scHD4E-Shiny.

Comparison study on seismic isolation design of RC frame structure based on two different codes

With the development of building seismic isolation technology and the official release of the Isolation Code in September 2021, seismic isolation design in China will now rely on two foundational codes: the Seismic Code and the Isolation Code. This paper take a ceramic jar storage of the RC frame structure as the research object, and carry out the seismic isolation design based on the separated calculation design method of the Seismic Code and the unitary calculation design method of the Isolation Code respectively, and clarify the control index of the Isolation Code is the story drift angle. The maximum displacement is reduced by 37.5%. In terms of material consumption, the Isolation Code leads to a 5.94% decrease in concrete usage, accompanied by a 13.97% increase in steel consumption, resulting in an overall cost increase of 4.98%. The findings indicate that seismic isolation design, guided by the Isolation Code, substantially mitigates the seismic response of the superstructure. The damage extent to structural members is reduced by 15–20%, promoting enhanced safety and repairability. The outcomes of this study offer valuable insights for future seismic isolation designs in RC frame structures.

Acoustofluidic separation of bacteria from platelets using tilted-angle standing surface acoustic wave

Separation of microscale objects, such as cells and bacteria, is an essential sample preparation step in various microfluidic applications in microbiology, chemistry, biology, and biomedicine. Microfluidic separation of bacteria from blood cells is highly in demand to prevent or investigate bacterial infectious diseases. Unlike red and white blood cells, platelets have a similar size distribution to that of bacteria, which makes bacteria separation from platelets technically challenging. Most previous techniques for microfluidic separation rely on size as a separation marker. These size-based separation methods are not applicable to separation of the same or similar-sized samples. Here, we propose an acoustofluidic method using tilted-angle standing surface acoustic wave (taSSAW) for label-free separation of the microscale objects of the same or similar size based on compressibility. From the experimental investigation with polymethylmethacrylate, polystyrene, and polycaprolactone microparticles of the same size, we found that less compressible objects migrated further when exposed to the taSSAW field formed within a microchannel. Based on the findings, we demonstrated that Escherichia coli (E. coli) can be separated from platelets because the taSSAW-induced acoustic radiation force acting on comparatively less compressible E. coli was greater than that applied to the platelets. Fluorescence microscopy, scanning electron microscope, hemocytometry, sodium dodecyl sulfate polyacrylamide gel electrophoresis, and polymerase chain reaction were conducted to confirm the successful positive separation of bacteria from platelets with high purity of exceeding 96 % and recovery rate of exceeding 81 %.

PROSPECTIVE DIRECTIONS FOR THE FORMATION OF THE STRUCTURE OF THE METHODS OF INVESTIGATING SELF-INTERESTED AND VIOLENT CRIMES COMMITED BY MINORS

Concepts and structural elements of the forensic method of crime investigation are considered. The role of operational investigative support in criminal proceedings is shown and a conclusion about the need to include it as a separate element in the structure of crime investigation methodology is made. It is proposed to include a list of the following structural elements in the investigation methodology of self-interested and violent crimes committed by minors: forensic classification and characteristics of crimes; identification of signs of a criminal offense and circumstances to be established at the primary stage of the investigation; typical investigative situations, versions and investigation planning; peculiarities of conducting investigative (search) actions and tactical operations; organizational and tactical features of the interaction of the investigator with the operational units during the operational and detective support of covert investigative (search) actions (discovery of evidentiary information, overcoming opposition to the investigation, ensuring the protection and safety of persons participating in criminal proceedings, searching for wanted persons); coordination activities of law enforcement agencies with state bodies, organizations, public associations and mass media regarding the prevention of criminal offenses. It was emphasized that the operational investigative support of criminal proceedings plays an important role when overcoming opposition to the investigation and organizing the safety of court and law enforcement officials, persons who provide assistance, contribute to investigative activities, persons participating in criminal proceedings, and their family members and close relatives of these persons. It was concluded that separate methods of investigating self-interested and violent crimes committed by minors should be formed taking into account their classification. At the same time, it is worth focusing attention on those categories of self-interested and violent crimes that are most often committed by minors. To do this, it is necessary to analyze the judicial and investigative practice and find out what problems arise during their investigation. The formation of separate methods of investigating self-interested and violent crimes should be based on the information established in the basic method. During the development of separate methods of investigation of self-interested and violent crimes committed by minors, it is necessary to use the forensic classification of the specified crimes not only according to the criminal law criterion, but also according to the criminalistic one.

Efficacious conditions for sorption of 85Sr (II) and 152+154Eu (III) onto natural composite beads

Radionuclides Sr-85 and Eu-152 + 154 are by-products of nuclear fission, presenting significant applications alongside potential health hazards, necessitating precise separation methods. In response, a sorption technique utilizing gypsum Alginate-Starch (GA-St) beads was innovated and meticulously characterized through advanced analytical methods including Energy Dispersive X-ray (EDX), Scanning Electron Microscopy (SEM), and Fourier Transform Infrared Spectroscopy (FT-IR). Under optimized sorption conditions, the saturation capacities reached 37.89 mg g−1 for 85Sr (II) and 75.87 mg g−1 for 152+154Eu (III) after 12 and 34 cycles, respectively. These conditions, achieved at pH 6.5 and 3.5 with equilibrium times of 1440 and 300 min for 85Sr (II) and 152+154Eu (III), respectively, underscore ambient temperature's role. The sorption mechanism conforms to the Freundlich model and pseudo nth-order kinetics, with thermodynamic assessments revealing the spontaneity and endothermic nature of the sorption processes. Desorption experiments exhibited remarkable recovery rates of 88.94 % for 85Sr (II) and 99.8 % for 152+154Eu (III) using 0.1 mol L−1 HNO3 from the loaded GA-St beads. These findings underscore the efficacy of GA-St beads as sorbents for both radionuclides, offering promising avenues for addressing challenges in nuclear waste management.