Chemical Composition Distribution Research Articles

The chemical composition, classification, and geographical distributions of soda-saline lakes in Eastern Tanzania's rift valley

Study regionSoda-Saline Lakes in eastern Tanzania's rift valley. Study focusThis study examined the chemical composition, classification, and geographical distribution of soda-saline lakes in the eastern Tanzania rift valley. New hydrological insight of the regionThe results revealed that lake water pH ranged from 9.0 to 10.2, EC ranged from 2843 to 109,800 µS/cm, and Na+ dominated over other cations with mixed dominance of HCO3- + CO32-, Cl-, and SO42-. The study also revealed that lakes Balangida and Balangida Lelu had higher sulphate levels than the other lakes, presumably due to sulfate-rich bedrock and local agricultural input. The study suggests that trace elements and heavy metals in lake water depend on their geology, past usage, and specific environmental conditions. The saturation index (SI) showed that the lakes were oversaturated with dolomite, calcite, and aragonite but undersaturated with anhydrite, gypsum, and halite. Lakes Natron and Manyara are classified as soda types, lakes Balangida and Eyasi are classified as soda-saline types; and lakes Singidani, Kindai, Mikuyu, Balangida Lalu, and Sulunga are classified as saline types. The geographical distribution patterns showed that soda-type and soda-saline lakes were most common in northern Tanzania (Arusha and Manyara). In contrast, saline-type lakes were common in the central regions between Dodoma and Singida. The dominant volcanic nature in the northern part possibly influences soda and soda-saline types.

Application of near-infrared hyperspectral imaging for determination of cheese chemical composition

Cheeses vary in chemical composition as they have different applications according to the technological features; some hard cheeses are consumed fresh while melting is a desirable characteristic for others. The conventional reference methods for determination of cheese composition and quality are accurate, but include physical-chemical analyses that are time-consuming and require use of chemical reagents. The objective of this work was to apply near-infrared hyperspectral imaging (NIR-HSI) as a fast method for prediction and visualization of spatial distribution of chemical composition of different types of cheeses (mozzarela, requeijão do norte, minas meia cura, coalho, prato). Moisture, fat, protein, and free oil were measured, and used as reference for prediction models, while spectral information extracted from images in the range of 928–2524 nm were used as predictors. Partial Least Squares (PLS) regression models were built with full spectra and using only few selected regions with higher importance, which were applied to the images to build chemical maps and visualize the spatial variation of the cheese composition. The regression models were able to predict moisture (R2P = 0.92, RMSEP = 1.1%); fat (R2P = 0.84, RMSEP = 1.5%); protein (R2P = 0.80, RMSEP = 1.8%); and free oil (R2P =0.64, RMSEP = 0.5%) for an external set of samples, while requiring a small number of latent variables (LVs) (between 3 and 4). The chemical maps allowed visualization of the spatial distribution for each attribute, demonstrating that the composition may vary within sample. The study demonstrated the potential of NIR-HSI for the determination of cheese composition and possible application to cheese quality control.

Studying on mineralogical and petrological characteristics of Gara Djebilet oolitic iron ore, Tindouf (Algeria)

Demand for iron ore worldwide has been steadily increasing which leads to the extraction of iron ore deposits with more complex mineralogies and higher levels of silicon and phosphorus impurities. This is the case in Algeria with the iron ore deposit of Gara Djebilet, Tindouf; where it has recently been exploited to ensure the sufficiency of iron ore required to produce iron and steel products. This deposit has remained unexploited for several decades due to inadequate knowledge of its mineralogy, treatment, and economic assessments. The aim of this study is to find out the microstructure, chemical composition, and mineralogical distribution of valuable minerals and impurities, to understand the efficient processing methods for this specific iron ore. The characterization of representative ironstone samples taken from the studied area was carried out using optical microscopy, X-ray fluorescence spectrometer (XRF), petrographic microscope, X-ray diffractometer (XRD), and scanning electron microscope (SEM) coupled with energy dispersive X-ray spectroscopy (EDS). The results of the mineralogical analyses confirmed that it is an oolitic fine-grained ore consisting of gangue minerals principally composed of quartz, apatite, and iron-rich concentric cored structures. Chemical analyses of the ore indicate that it contains 56.58 wt% Fe with 7.98 wt% SiO2, 7.09 wt% Al2O3, and minor amounts of P2O5, CaO, MgO, and TiO2 compounds. The phosphorus associated was present in both ooids and groundmass, indicating that the ore has a complex texture with very rich and diverse mineralogy. For that, two potential scenarios were proposed for processing of the studied iron ore.

The Characterization of Residues Related to the Roasting– Leaching–Electrowinning Zinc Production Route for Further Metal Extraction

Super-hot acid leach residue is generated during zinc production in the roasting–leaching–electrowinning route, where both primary and secondary resources are used as feed material. This residue may contain valuable metals, such as lead, zinc, and iron, as well as precious metals, such as gold and silver. Four materials, namely super-hot acid leach residue, a residue formed when super-hot acid leach residue is selectively leached for lead with triethylenetetramine, as well as flotation concentrate, and flotation tailings formed in a selective silver flotation process with super-hot acid leach residue as the feed material were characterized to obtain a deeper understanding of possible further metal extraction. These four materials were characterized for chemical composition, mineralogy, and mineral distribution via chemical analyses, X-ray diffraction, and energy-dispersive scanning electron microscopy, respectively. The scanning electron microscope images showed that the materials have large variations in particle size distribution and composition. The results showed that the main lead phase in super-hot acid leach residue is lead sulfate, whereas it is mostly converted to lead sulfide during the selective lead leaching of the super-hot acid leach residue. The remaining lead sulfate is found in a solid solution with barium sulfate. Extracting lead from super-hot acid leach residue via triethylenetetramine leaching resulted in increased concentrations of gold and silver by 41% and 42%, respectively. The identified silver phases in super-hot acid leach residue may correspond to silver sulfide, silver chloride, and elementary silver, where silver sulfide was the most commonly occurring silver phase. After leaching this selectively for lead with triethylenetetramine, similar silver phases were identified, but silver sulfide and silver chloride occurred to a similar extent. Additionally, silver copper sulfide was detected. The presence of different silver phases might pose a challenge to reaching high silver recovery during leaching as the optimum leaching conditions differ somewhat. Furthermore, elemental sulfur, with a tendency to coat gold and silver particle surfaces, which is indicated to be present in all materials except the silver flotation tailings, may hinder metal extraction.

Fe-catalyzed low-temperature hydrothermal liquefaction of coffee shells: Influence of operating parameters on bio-oil yield, distribution of bio-oil products

Coffee shells were hydrothermally liquefied under FeCl3 catalysis to produce crude bio-oils at temperatures ranging from 190 to 300 °C. This study investigated the impact of operational parameters (hydrothermal temperature, residence time, Fe3+ catalyst concentration, extraction solvents) on the bio-oil yield. Optimized hydrothermal conditions resulted in a conversion rate of 68.47 % for coffee shells, leading to an 11.51 % yield of light bio-oil extracted from the aqueous phase and a 35.99 % yield of heavy bio-oil from the solid phase. The chemical composition and distillate distribution of the bio-oil were determined through organic element analysis, GC-MS analysis, and TG/DTG analysis. The light bio-oil primarily consisted of furfural derivatives and phenolic derivatives; however, it only accounted for approximately 14.50 % of the total energy recovered from the feedstock. The components present in heavy bio-oils varied depending on the extraction solvents used but mainly comprised fatty acids and their derivatives. Acetone extraction yielded the highest amount of bio-oil; however, its high O/C ratio reduced its higher heating value (HHV). Ethanol extraction also resulted in higher yields but TG/DTG analysis indicated that these fractions contained more refractory volatiles and solid residues compared to other solvents used for extraction. In comparison, n-hexane extraction had a lower yield than both previous methods but offered a lower O/C ratio and higher HHV instead. Our study demonstrated that Fe-catalyzed hydrothermal liquefaction is an efficient method for obtaining value-added compounds and hydrocarbon fuels from coffee shells.

Characterization of Coal Combustion Products from Malaysian Power Plant for Building Materials Applications

Coal combustion by Products (CCPs) are produced during coal combustion in the process of electric generation. Without proper handling system, this will cause serious problems towards human and environmental. Nevertheless, with proper treatment, these ashes are applicable in many areas specially building construction materials. Coal Bottom Ash, Coal Fly Ash and Cenosphere are three main wastes produced from power plant. The aim of this study is to determine the characteristics of samples collected from different parts of Malaysia Power Plant. Characterization testing involved included surface morphology, chemical composition (oxides), chemical components, amorphousness, and particle size distribution testing. From this study, CBA have more angular-shaped particles compared to CFA which is smoother surface morphology. However, Cenosphere shown the most uniform and spherical shaped particles. EDS testing shown Existing CBA have highest Carbon content (46%) while Cenosphere is lowest (11.38%). The percentage oxides contents for all samples demonstrate more than 70% of Total SiO2 + Al2O3 + Fe2O3. Hence, all ashes considered as Class F (pozzolanic). CBA, SFA, CFA and cenosphere has significantly more amorphous phases of silica and alumina, and this will increase the concrete strength. Due to agglomeration of ashes on ash pond, the cumulative PSDs results shown that the particle size of the existing sample obtained larger than the new sample. Minimum particles size of SFA (New Dry) is 2 µm while SFA (Existing 2) is 20 µm. From characteristic determination above, it shown that each type of ashes has its own uniqueness and capability to be applied wide range of applications.

Study on the Effect of Niobium on the High Temperature Oxidation Resistance of Ferritic Stainless Steel

More and more cars are installing urea selective catalytic reduction (SCR) systems to solve the problem of exhaust emissions, which often operates at high temperatures in the exhaust system and is prone to failure of the exhaust pipe due to high-temperature oxidation. And niobium containing ferritic stainless steel has been widely used in the manufacturing of automotive exhaust pipes. In order to extend the service life of ferrite stainless steel exhaust pipes, niobium plays a crucial role as an added alloying element. The solid solution and precipitation of niobium in ferritic stainless steel will give ferritic stainless steel more excellent high temperature resistance. The precipitation of Nb can change the organizational structure in steel and refine the grains. However, if the content is not properly controlled, large particles of (Nb, Ti) C will precipitate, which will reduce the high temperature oxidation resistance. In this paper, the high temperature oxidation behavior of two kinds of ferritic stainless steels with different Nb content at 700 °C, 800 °C and 900 °C was studied. The microstructure of the oxide film on the surface of the material, the thickness of the oxide layer on the cross section, the distribution of chemical composition, the existence form and distribution of Nb element were analyzed by SEM, EDS, XRD and TEM. The results show that the higher the niobium content, the better the high temperature oxidation resistance, and the higher the temperature, the more obvious the high temperature oxidation resistance of niobium. This is because the high Nb content steel is easy to precipitate NbN and other Nb-containing precipitates at the grain boundary, which is helpful to the high temperature resistance. In the case of less Nb content, its ability to generate (Nb, Ti) C precipitates and coarsen at high temperatures reduces its high-temperature resistance.

Ti-rich carboborides in the multi-component high-boron alloy: morphology and elemental distribution

In the article, the characterization of the morphology, chemical composition, and elemental distribution in the Ti-based carboboride M(C,B) in (wt.%) Fe-0.72C-2.75B-5.05W-5.57Mo-10.35Cr-2.60Ti multi-component alloy is fulfilled. The study was performed using optical microscopy, SEM, TEM, and energy-dispersive X-ray spectroscopy. It was found that the carboboride M(C,B) is present in the structure in the form of the equiaxed polygonal particles of a 0.5-7.3 mm mean size. The particles are divided into “duplex” and “uniform” ones. The duplex particles consists of the Ti-rich (75 wt. % Ti) “core” (Ti(C,B)) and the Ti-depleted (47.3 wt. % Ti) “shell” ((Ti,W,Mo,V)(C,B)). The uniform particles are characterized by an even distribution of the elements having a chemical composition close to the “shell”. The ratio of B:C (at. %) is 1:2.5, 1:3.3, and 1:3.2 for the “core”, “shell” and the uniform particle respectively. The chemical formulas of the duplex/uniform M(C,B) inclusions and the mechanism of their formation are proposed.

High-performance supercapacitive polyazomethines: Room temperature synthesis and their characterizations

A room temperature synthesized polyazomethine (PAZ) series via polycondensation route comprising monomer as 5-[4-(5-formylfuran-2-yl)phenyl]furan-2-carbaldehyde (III) and various diamines to engineer PAZ-1 to PAZ-5 polymers. Physico-chemical properties of as-prepared PAZ series have confirmed by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray analysis (EDAX), transmission electron microscopy (TEM) and spectroscopic techniques. In FTIR, –CH=N– peak at 1600 cm−1 attributed to the successful conversion of dicarbaldehyde (III) and diamines into polyazomethine. The amorphous nature of PAZ series is depicted by XRD diffractograph. The marigold like morphology of polyazomethines has revealed in FESEM and TEM images. The chemical composition and elemental distribution on PAZ surface has mapped using EDAX technique. The electrochemical activity of as-prepared polyazomethine electrodes has investigated by cyclic voltammetry (CV), galvanostatic charge discharge (GCD) and electrochemical impedance spectroscopy (EIS) techniques. The supercapacitive performance of PAZ-1 to PAZ-5 electrodes in various electrolytes as NaOH, KOH, Na2SO4, and LiCl by varying concentrations, the PAZ-2 electrode exhibits elevated specific capacitance (Cp) of 831 Fg−1, specific energy (SE) 22.99 Whrkg−1, specific power (SP) 82.87 KWkg−1 in optimum 1 M NaOH electrolyte. The distinguished PAZ-2 electrode after successive 500 cycles has delivered exceptional stability, 71.65 % in 1 M NaOH.

Influence of Si content on thermoelectric properties of Mg2(Sn,Si) films by sputtering

Mg2(Sn,Si) films with different Si content were prepared by magnetron sputtering. The phase composition, surface and cross-sectional morphology, chemical composition and element distribution, carrier concentration, carrier mobility, electrical conductivity, Seebeck coefficient and power factor of the deposited Mg–Sn–Si films were studied. The results show that the deposited films are composed of Mg2(Sn,Si) solid solution phase and a small amount of metal Mg phase. The room temperature carrier concentration decreases and mobility increases with increasing Si content in deposited Mg–Sn–Si films, respectively. The room temperature electrical conductivity and Seebeck coefficient decreases and increases with increasing Si content, respectively. The deposited Mg2(Sn,Si) films with moderate Si content possess the maximum power factor value of 2.76 mW m−1 K−2 at 303 °C and its room temperature figure of merit reaches the highest value of 0.44. The thermal conductivity decreases with increasing Si content, indicating that the lattice distortion caused by Si doping can reduce the thermal conductivity of the deposited films.

Structural, defense enzyme activity and chemical composition changes in the xylem of Aquilaria sinensis during fungus induction

Agarwood is a dark resinous wood, of high quality and in a short period, can be formed after inoculation with the efficient fungus in Aquilaria sinensis. However, the action site and mechanism of the fungus inducing the agarwood formation remain unclear. In this work, the efficient fungal infection was used to induce agarwood formation on A. sinensis, and samples were collected according to inoculation time. Subsequently, the xylem structure, histochemistry, defense enzyme activities, and the accumulation and in-situ distribution of chemical composition were investigated. The transition layer (TL) was the critical layer for the continuous accumulation of agarwood, and began to appear in the injection of fungal inducers for 15 days (15D). The parenchyma cells of the xylem rays and interxylary phloem were the main action site of fungus in the formation and accumulation of agarwood. The sesquiterpenes and 2-(2-phenylethyl) chromones (PECs) were mainly accumulated in the agarwood layer (AL) and decay layer (DL), while their relative contents were highest in the injection of fungal inducers for 30 days and 180 days (30D and 180D), respectively. Among them, PECs appeared earlier than sesquiterpenes, and both were flindersia-type PECs. They were mainly concentrated in the cell corners and intercellular layer of the cell wall. In addition, Redundancy analysis (RDA) and Mantel test revealed that the different layer percentage (DLP), phenylalanine ammonia lyase (PAL), and starch grains (SG) were the drivers of PECs, and catalase (CAT) was the driver of sesquiterpenes. Therefore, this study will provide a theoretical foundation for revealing the mechanism of fungus-induced agarwood formation and inducing high-quality and high-yielding agarwood in the future.

Ab initio modelling of transport phenomena in multi-component mixtures of rarefied gases

The direct simulation Monte Carlo method based on ab initio potentials is applied to model transport phenomena in binary, ternary and quaternary mixtures of noble gases. To this end, the Couette and Fourier problems are solved over the whole range of the rarefaction parameter spanning the near free-molecular, transitional, and slip flow regimes. Moreover, analytical solutions are obtained in the limits of the free-molecular and continuous medium regimes of flow. As a result, the shear stress, heat flux through multi-component mixtures, distributions of velocity, temperature, and mole fractions of each species are calculated as a function of the gas rarefaction. An analysis of these data points out the properties which are strongly affected by the chemical composition. It is found that the largest deviations of characteristics of mixtures from those of a single gas are observed for the binary mixture of helium and krypton, while their deviations for the ternary and quaternary mixtures are smaller. A temperature variation in a mixture leads to non-uniform distributions of chemical composition due to the thermal diffusion phenomenon. Such redistributions are analyzed in both problems and their effect on the heat and momentum transfer is evaluated. The reported results can be used to evaluate the main factors determining transport phenomena in practical applications such as vacuum systems, microfluidics, gas separation technology, space research etc.

Integrity evolution during dissimilar welding of TWIP steel

The integrity evolution induced by manufacturing involving dissimilar TWIP and mild steel weld spots was investigated. Focus was given to the effect of manufacturing parametrization on controlling the dilution of the alloying elements and the resulting weld integrity. Samples manufactured with different conditions were characterized by chemical and phase composition, morphology, and mechanical properties. The findings showed that the distribution of chemical composition and metallurgical features are sensitive to the welding parameters. The influence of manufacturing on weld morphology was noticed. Manganese distribution is affected by the welding cycle, thus leading to austenite destabilization and brittle behavior upon a quasi-static tensile shear strength test. A processing set was proposed to control manganese dilution and martensite transformation.

Chemical Characterization of Rural Organic Aerosol in the North China Plain Using Ultrahigh-Resolution Mass Spectrometry

Atmospheric organic aerosol (OA) affects air quality and human health. However, compared with urban areas, the chemical composition and temporal distribution of OA in rural regions are still not well understood. In this study, one-year atmospheric particles with an aerodynamic equivalent diameter of ≤2.5 μm (PM2.5) were collected at a rural site in Quzhou County, the North China Plain (NCP), from August 2020 to July 2021. OA in PM2.5 samples were analyzed with an ultrahigh-performance liquid chromatograph (UHPLC) coupled to an ultrahigh-resolution Orbitrap mass spectrometer in negative mode (ESI−). The results show that the chemical composition and properties of OA varied in different seasons. According to the hierarchical cluster analysis, the molecular formulas of winter OA were close to those in spring, whereas the chemical composition of OA in summer and autumn was similar. The O/C ratio of summer OA was the highest at 1.21, followed by that in autumn (0.92) and spring (0.87), while the winter OA had the lowest O/C ratio of 0.64. It indicates that, compared to the other three seasons, OA underwent more intense oxidation processes in the summer. Moreover, winter OA contained more aromatic compounds with a relative peak abundance fraction of 40%, which may be related to anthropogenic sources (e.g., coal burning) in the winter in the NCP. In addition, biomass burning is considered an important source of OA in the rural region of Quzhou County, the NCP, in all seasons.

Phosphate activated geopolymer-based coating with high temperature resistance for sub-ambient radiative cooling

Passive sub-ambient daytime radiative cooling (SDRC) is an energy-free method enabling heat dissipation away from buildings or infrastructures to cold outer space (∼3 K). However, although organic coatings (based on polymer matrices) have been proven to be a cost-effective means to achieve the SDRC effect by incorporating various functional fillers, organic coatings may have environmental concerns and aging problems. Herein, an inorganic phosphate activated geopolymer-based (PAGP) SDRC coating was synthesized using nano-silica (SiO2) particles and barium sulfate (BaSO4) sheets as the modifiers. The synthesized coating could achieve high infrared emissivity of 0.9634 and solar reflectance of 0.9471, which was also found to exhibit high-temperature resistance and optical stability up to 1000 °C due to its covalently bonded structure and electrically neutral system. The chemical composition, surface morphology, and elemental distribution of the coating were characterized by XRD, FTIR, SEM, BET, and EDS. The evolution of condensed structures and weight loss analysis during the high-temperature treatment was conducted by TGA and XRD to analyze the dehydration process and phase change during the heat process. The outdoor field tests showed a maximum sub-ambient temperature reduction of 3.8 °C by the developed coating without any energy input under direct sunlight in Hong Kong. Furthermore, the energy-saving performance of the PAGP-based SDRC coating is analyzed under different climatic conditions in China with the aid of EnergyPlus. Simulation results demonstrated that the PAGP-based SDRC coating can significantly save the cooling load in all five selected cities, which shows great potential in building energy conservation and carbon emission reduction.

Influence of Catalytic Infrared Radiation on the Protective Properties of Industrial Epoxy Primers.

The application of organic coatings is a common way of protecting metal substrates against corrosion. To dry the coating faster, catalytic infrared radiation (IR) can be applied. This paper aims to assess the differences in the physical, chemical, and corrosion properties of primer coatings dried with catalytic infrared radiation, compared to the same coatings dried under atmospheric conditions. Corrosion properties were characterized using humidity and a salt spray chamber, as well as electrochemical impedance spectroscopy (EIS), preceded by open circuit potential (OCP) measurement. Pencil hardness, cross-cut, and pull-off adhesion tests were used to compare the properties of examined primers before and after testing in the corrosion acceleration chambers. The microstructure and distribution of chemical composition were studied by scanning electron microscope (SEM) with energy-dispersive X-ray spectroscopy (EDX) together with Fourier-transform infrared spectroscopy (FTIR). Phase transitions in the coating were determined by differential scanning calorimeter (DSC). Infrared-dried primers achieved a higher curing degree. Therefore, their mechanical and corrosion properties are superior when compared to the same coatings dried under atmospheric conditions.

Effect of square wave potential polarity and amplitude on property of trivalent chromium conversion coating applied on Zn−Al hot-dip coating

The formation of Cr(III) chemical conversion coating (TCC) on Zn−Al hot-dip coating was unraveled and cathode or anode square wave potential (φp) was applied during the TCC construction progress in terms of comparatively investigating the effectiveness of φp. Corrosion resistance of TCC in chloride-containing solution was obtained by EIS and polarization curve measurements, combined with the discussion of macro/micro-morphology using 3D microscope and chemical composition distribution analysis using XPS, AES, FTIR and Raman spectra. The results showed that the cathode φp enhanced the corrosion resistance and reduced the content of Cr(VI) on the surface of freshly-prepared TCC better than anode φp. Besides, the hydrophobicity of TCC and adhesion to epoxy primer were also improved due to the reconstruction of the micro−nano structure.

Lignin fractionation towards improved rosin emulsification behavior and advanced liquid packaging board sizing performance

The heterogeneity of lignin, due to its intricate chemical composition and inconsistent molecular weight distribution across various sources, would result in inconsistent materials with unpredictable characteristics, thus presenting a significant obstacle and impeding the advancement of lignin-based products. The need for innovative rosin/lignin-based sizing agents for liquid packaging board (LPB) products has yet to be fulfilled, stimulating ongoing research efforts in this area. Herein, to tackle the urgent challenge posed by the lignin inhomogeneity and its effect on sizing performance, we propose a comprehensive approach for the production of fractionated lignin-modified rosin sizing agents for liquid packaging board (LPB) with improved sizing characteristics. This study first fractionated three lignin components from wheat straw-derived lignin and utilized them as adaptable surfactants in the manufacture of cationic dispersion rosin sizing agents. The resulting agents were analyzed and evaluated for their utilization in LPB sizing process, exhibiting improved homogeneity, molecular weight, and hydrophilic group content. The obtained fractionated lignin-modified rosin sizing agents displayed outstanding sizing performance and desirable stability. Additionally, these agents enhance the mechanical and optical properties of LPB products. This study proposed a novel and valorized approach to apply lignin biomass with a fractionation and sustainable method to prepare series lignin-modified rosin sizing agents and their great potential in liquid packaging board applications.

Use graphene coated silica core shell particles to provide rapid, precise, and equivalent chemical composition distribution analysis for polyolefin materials by high temperature thermal gradient interaction chromatography

High temperature thermal gradient interaction chromatography (HT-TGIC) has been widely used to measure chemical composition distribution due to its applicability to separate crystalline and non-crystalline amorphous polyolefin materials. The compatibility of HT-TGIC with various detectors (infrared (IR), light scattering (LS), and viscometer) has also allowed a comprehensive analysis of molecular architecture of polyolefin and recycled plastics. The introduction of an easy-to-fabricate graphene coated onto non-porous silica particles as HT-TGIC column in 2020 showed a superior chromatographic performance over the traditional graphite column. A reduction in peak broadness (∼47 %) under identical experimental conditions was demonstrated in that research. This paper similarly uses a graphene column but with the focus on optimization of experimental parameters (concentration, and thermal cooling and heating rates etc.). Equivalent chemical composition distribution (CCD) data to that obtained by the incumbent graphite column over a wide range of polyolefins products was achieved, in addition to a shortened analysis time from 120 min down to 88 min per sample. The materials studied included semicrystalline linear low-density polyethylene (LLDPE), elastomers, terpolymers, model blends to mimic recycled plastics. The results also suggest that the elimination of substrate pores enable a better HT-TGIC separation. Coupling the ease and reproducibility of the graphene column fabrication process enables long term chromatographic robustness. This not only results in equivalent CCD data compared to the traditional graphite column but also a 27 % reduction in analysis time. These results demonstrate a substantial advancement of technology in the high throughput industrial laboratory setting where fast testing turnaround time is critical. In addition, simple fabrication with commercially available silica particles and graphene nanopowder provides a cost-effective approach to make HT-TGIC columns reproducibly.

Characterization of chemical composition distribution of ethylene-propylene-diene terpolymers by room temperature liquid adsorption chromatography and comparison to statistical approach

The chromatographic analysis of ethylene-propylene-diene (EPDM) terpolymers has hitherto been carried out only at high temperature, 120–160 °C. However, EPDM terpolymers are amorphous which could potentially allow to study their chromatographic behavior at room temperature (RT). To verify this hypothesis, cloud point measurements were realized to determine prospective solvent candidates. The identified solvents enabled injecting EPDM and model ethylene propylene norbornene terpolymers at RT.The retention of EPDM terpolymers on porous graphitic carbon (PGC) is a function at least two adsorbing comonomer components, ethylene and diene, in all tested chromatographic systems. This makes it difficult to characterize the chemical composition distribution (CCD) of terpolymers, which is of immense technical interest. Therefore, a modified form of LAC (LACm) was employed for determining the CCD of EPDM terpolymers using the identified solvents. Finally, the CCD obtained using different experimental methods was compared to the CCD determined using Monte Carlo simulations.