Sample Dissolution Research Articles

Neutron-based analytical techniques for the elemental composition analysis of electronic waste samples: advantages and challenges

Recycling electronic waste (WEEE) is a fundamental aspect of the circular economy. To develop technology and assess its economic aspects, the composition characterization of the waste items is crucial. Neutron-based analytical techniques, such as the INAA, in-beam NAA, and PGAA, are applicable to measure the elemental composition of WEEE. These techniques are bulk representative and offer simultaneous determination of the relevant elements without sample dissolution. This study explores the suitability of neutron-based elemental analysis methods for measuring common WEEE items, e.g., printed circuit boards and integrated circuits. Matrix effects mostly related to the thermal neutron self-shielding, were identified and successfully corrected, ensuring accurate mass fraction measurements.

Understanding Europium and Terbium Speciation and Ion Pairing in Carbonate Complexes Using Advanced Spectroscopy Techniques

Lanthanide (Ln) elements are critical materials that are typically extracted/mined together. Their separation by solvent extraction from acidic media is well known; however, there are few studies in basic media with carbonate anions. We investigated the complexation of Eu(III) and Tb(III) carbonates as solids and solutions in alkaline K2CO3, wherein we sought to access a Tb(IV) carbonate complex through ozonolysis. L3‐edge XANES of Eu and Tb carbonate solids, colorless solutions, and a red‐hued Tb solution (obtained by ozonolysis) all showed Ln(III) cations. The absence of evidence for a Tb(IV) complex was confirmed through XAS and EPR analyses, despite the solution exhibiting a deep red color. For solids and solutions, EXAFS results indicate molecular Ln(III)‐carbonato anions. In terms of the Eu(III) carbonate coordination number, the coordination does not change upon dissolution of the solid sample. Furthermore, EXAFS for the solutions revealed evidence for the association of potassium cations with the Ln(III)‐carbonato anions. This direct observation of contact ion pairing by EXAFS at room temperature is rare. The insights into Ln(III) carbonate complexation and solution speciation afforded by XANES‐EXAFS, FT‐IR, and EPR provides perspectives that serve as benchmarks for future computational and experimental efforts focused on caustic‐side solvent extraction of Ln(III) ions.

Application of microwave digestion for complete dissolution of igneous silicate rock samples: A simple and quick sample preparation procedure

In the area of geochemical analyses of rock solutions, achieving a complete sample dissolution is a fundamental prerequisite for obtaining accurate, precise and reliable analytical results. The challenge posed by the presence of resistant minerals such as zircon, rutile, corundum, spinel, tourmaline, beryl, chromite, and cassiterite in different silicate rocks is a well-recognized challenge in geological studies. These minerals, due to their resilient nature, demand additional efforts to ensure complete dissolution during sample preparation. The prevailing conventional sample digestion methods require several days of laboratory work and the handling of large amounts of multiple types of acids, which also increase sample blanks. Until recently, there was a widely held belief that microwave-assisted digestion, where microwave radiation is transformed to heat, faced limitations in achieving complete dissolution of refractory minerals. This prevailing opinion led to skepticism about the applicability of microwave-assisted digestion for sample preparation of e.g. igneous rock samples containing these minerals. This study introduces a novel, universal and quick closed-vessel (pressurized) high-temperature microwave-assisted digestion method appropriate for dissolution of all major types of igneous silicate rock samples, including rocks containing refractory minerals. This streamlined and expeditious procedure, comprising three steps, requires only a total time of ∼9 h. The method proves its versatility by successfully dissolving both, mafic igneous samples (e.g., basalt) with low-content of resistant minerals, and felsic igneous samples (e.g., granite) with relatively high-content of resistant minerals. To validate the reliability of this procedure, 36 trace elements were analyzed: Li, Be, Sc, V, Cr, Co, Ni, Cu, Zn, Ga, Rb, Sr, Y, Zr, Nb, Cs, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, Ta, Pb, Th and U in several geological Certified Reference Materials (CRMs). The CRMs including basalts JB-3, BCR-2, BHVO-2; andesites JA-2, AGV-2; granodiorite GSP-2; granite JG-2 and alkaline granite MGL-OShBO, were digested and analyzed using triple quadrupole Inductively Coupled-Plasma-Mass Spectrometer (ICP-QQQ). The results of the analysis demonstrate remarkable consistency, closely aligning with both certified and literature values.

Fluid‐rock interaction experiments with andesite at 100°C for potential carbon storage in geothermal reservoirs

AbstractGeothermal energy extraction often results in the release of naturally occurring carbon dioxide (CO2) as a byproduct. Research on carbon storage using volcanic rock types other than basalt under both acidic and elevated temperature conditions has been limited so far. Our study uses batch reactor experiments at 100°C to investigate the dissolution of andesite rock samples obtained from an active geothermal reservoir in Sumatra (Indonesia). The samples are subjected to reactions with neutral‐pH fluids and acidic fluids, mimicking the geochemical responses upon reinjection of geothermal fluids, either without or with dissolved acidic gases, respectively. Chemical elemental analysis reveals the release of Ca2+ ions into the fluids through the dissolution of feldspar. The overall dissolution rate of the rock samples is 2.4 × 10–11 mol/(m2 · s) to 4.2 × 10–11 mol/(m2 · s), based on the Si release during the initial 7 h of the experiment. The dissolution rates are about two orders of magnitude lower than those reported for basaltic rocks under similar reaction conditions. This study offers valuable insights into the potential utilization of andesite reservoirs for effective CO2 storage via mineralization.

Exploring the evolution of microstructure and mechanical property of a γʹ-strengthened Co-based single crystal superalloy during creep and thermal exposure at 1000 °C

The study provided a systematic investigation into the creep behavior of a γʹ-strengthened Co-based single crystal superalloy Co-7Al-8W-1Ta-4Ti (at.%) under compressive creep conditions at 1000 °C and 137 MPa. Simultaneously, the microstructural changes during thermal exposure at 1000 °C were thoroughly examined. The microstructure analysis of the creep samples revealed the presence of γ/γʹ rafts, twins, stacking faults, and dislocation networks. Statistical analyses were conducted to assess the dimensions and volume fractions of γʹ, alongside Vickers hardness tests and nanoindentation experiments. Results show that γʹ dissolution in the creep samples with substantially higher dissolution rates compared to thermal exposure. Localized Co depletion and Ti enrichment in twin is observed in creep sample, potentially initiating localized phase transformations. Concurrently, lattice rotation occurred during creep, resulting in a progressive deviation of crystal orientation away from the [001] direction. Stacking faults transitioned from network-like structures to parallel configurations, and twins played a significant role in creep deformation, particularly in samples subjected to 382 h creep. The study also explored the evolution of Vickers hardness and the elastic modulus, introducing a systematic linear model to describe Vickers hardness changes during both thermal exposure and creep conditions.

Teaching Experimental Instrumental Analytical Chemistry Are we forming professionals, training operators or illuding students (and ourselves)?

Teaching Experimental Instrumental Analytical Chemistry Are we forming professionals, training operators or illuding students (and ourselves)?

Migration characteristics of constant elements in the process of coal dissolution by liquid CO2

The effect of liquid CO2 on coal dissolution plays a key role in improving coal bed methane (CBM) recovery and CO2 geological storage. In order to study the effect of liquid CO2–H2O reaction on the migration of mineral constant elements in coal, three kinds of coal samples (lignite, bituminous coal, and anthracite) with different degrees of metamorphism were selected as the research objects. The one-factor experiments of dissolution of liquid CO2 and water-bearing coal samples were carried out by simulating the temperature and pressure of the stratum. X-ray fluorescence spectroscopy (XRF) was used to test the changes in the relative content of constant elements in coal samples after liquid CO2 injection under different pressure conditions. Scanning electron microscopy (SEM) was utilized to observe the evolution pattern of the surface features of the coal before and after the dissolution of liquid CO2. A quantitative analysis of coal pore development characteristics was conducted based on low-temperature N2 adsorption/desorption experiments, and isothermal adsorption experiments were carried out before and after etching the coal samples to understand the adsorption characteristics of CH4 and CO2 by coal under different pressure conditions. The research results indicated that the migration ability of constant elements in coal showed a trend of first decreasing and then increasing with the increasing degree of coal metamorphism. Among the three selected coal samples, the migration ability of constant elements was found to be strongest in anthracite, followed by lignite and bituminous coal. Most of the element migration in coal was carried out through chemical reactions (hydrolysis, carbonation, redox), while some elements were primarily transported through physical means (such as the low-temperature impact of liquid CO2). The dissolution process expands the original pore space of coal and generates new pores, greatly increasing the coal's capacity for CO2 adsorption. These findings deepen our understanding of mineral dissolution in coal by liquid CO2 and provide important insights for achieving efficient and long-term coalbed CO2 geological storage and enhanced methane recovery techniques.

Rapid dissolution without elemental fractionation by laser driven hydrothermal processing

Traditional dissolution of geologic samples often requires a significant time investment. Here, we present an alternative method for the dissolution of geologic materials using laser-driven hydrothermal processing (LDHP). LDHP uses laser energy directed onto a submerged sample, which increases the temperature and pressure at the liquid–sample interface and drives the hydrothermal dissolution coupled with photomechanical spallation, an ablative process. This uses focused 527 nm laser energy at 40 W average power, 1 kHz pulse repetition rate, and 115 ns pulse duration. When LDHP is performed on basalt geostandards (BCR-2 and BHVO-2) using the conditions outlined, we show that LDHP does not produce significant elemental fractionation and, thus, can be considered an alternative processing method to traditional mechanical crushing and acid digestion. Additionally, it is possible using LDHP to utilize the spatially confined beam to target and selectively isolate individual phases in a rock, potentially alleviating the need for mechanical separation of inclusions that are difficult to physically isolate. Furthermore, using this outlined method of LDHP, we demonstrate full dissolution of 120 mg of obsidian in 85 minu, meaning that LDHP is a potentially very useful method when sample processing is time sensitive.

Moisture-induced limited recrystallization may not reduce the dissolution of amorphous solid dispersions: A case of nitrendipine

As a promising strategy, amorphous solid dispersion (ASD) technology has been widely studied and employed. However, moisture affects the physical stability of ASD, leading to phase separation and recrystallization. This study aims to investigate the moisture-induced physical instability of the nitrendipine (NTD) ASD systems from apparent phenomenon to molecular mechanism. The critical relative humidity (CRH) of the ASD was identified as 50% RH through a dynamic vapor sorption study. After being stored above the CRH, ASDs exhibited obvious phase separation and recrystallization, owing to water competition hydrogen bond as evidenced by molecular docking. After 75% RH exposure, the ASD underwent obvious recrystallization thereafter the dissolution was reduced. However, the dissolution of ASD samples stored at 60% RH did not decrease obviously. This study helps to understand the environment humidities for ASD physical stability and gives hints at the relation between recrystallization and dissolution in the ASD system.

Dissolution behavior of stone wool fibers in synthetic lung fluids: Impact of iron oxidation state changes induced by heat treatment for binder removal

Stone wool fiber materials are commonly used for thermal and acoustic insulation, horticulture and filler purposes. Biosolubility of the stone wool fiber (SWF) materials accessed through acellular in vitro dissolution tests can potentially be used in future as an indicator of fiber biopersistence in vivo. To correlate acellular in vitro studies with in vivo and epidemiological investigations, not only a robust dissolution procedure is needed, but fundamental understanding of fiber behavior during sample preparation and dissolution is required. We investigated the influence of heat treatment procedure for binder removal on the SWF iron oxidation state as well as on the SWF dissolution behavior in simulant lung fluids (with and without complexing agents). We used heat treatments at 450 °C for 5 min and 590 °C for 1 h. Both procedures resulted in complete binder removal from the SWF. Changes of iron oxidation state were moderate if binder was removed at 450 °C for 5 min, and there were no substantial changes of SWF’s dissolution behavior in all investigated fluids after this heat treatment. In contrast, if binder was removed at 590 °C for 1 h, complete Fe(II) oxidation to Fe(III) was observed and significant increase of dissolution was shown in fluids without complexing agent (citrate). PHREEQC solution speciation modeling showed that in this case, released Fe(III) may form ferrihydrite precipitate in the solution. Precipitation of ferrihydrite solid phase leads to removal of iron cations from the solution, thus shifting reaction towards the dissolution products and increasing total mass loss of fiber samples. This effect is not observed for heat treated fibers if citrate is present in the fluid, because Fe(III) binds with citrate and remains mobile in the solution. Therefore, for developing the most accurate SWF in vitro acellular biosolubility test, SWF heat treatment for binder removal is not recommended in combination with dissolution testing in fluids without citrate as a complexing agent.

Comparison between Microwave Digestion and Conventional Open Digestion Method for Heavy Metals determination

In the present study a comparison between microwave assisted digestion and conventional wet acid open digestion system for dissolution of bivalve tissue samples was carried out. Sample matrix decomposition was done by using a mixture of concentrated nitric acid and hydrogen peroxide. The determination of trace elements (Zn, Co, Cu, Cd and Pb) in commercially popular bivalve species from two important fish landing centers in Mumbai was used for this purpose. The recovery of heavy metals after analysis was done using certified reference material TORT 2- Lobster hepatopancreas for both the digestion methods. The results of the present study indicate that microwave digestion system for heavy metal analysis is the preferred method for rapid and good quality results. It provides better recovery and precision for heavy metal analysis. The sample preparation step is much easier by microwave digestion system compared to conventional open digestion methods for heavy metal analysis. It is particularly ideal for trace metals like lead and cadmium as they are generally present in very small concentration in biological samples. In the current study microwave digestion proved to be better method than conventional open digestion method with rapid sample digestion process and least sample contamination problem.

APMP.QM-S19: Toxic elements in seafood

Main textSeafood is one of the major food resources for human consumption in the world. The CODEX Alimentarius Commission and many jurisdictions have set maximum levels of metallic contaminants in seafood. The use of reliable methods for measurement of metallic contaminants is important in safeguarding the quality of these products and public health.The Supplementary Comparison APMP.QM-S19: Toxic Elements in Seafood was coordinated by the Government Laboratory, Hong Kong, China (GLHK). Four measurands (arsenic, cadmium, mercury and lead) in seafood were chosen. The last CCQM or RMO key comparison / supplementary comparison in the area of metallic contaminants in seafood was organized by GLHK in 2011 (APMP.QM-S5). Hence, it was timely to organize another comparison that covers different measurands. This Supplementary Comparison (APMP.QM-S19) offers different analytical challenges (e.g. in analysis of mercury and a different range of measurands) as compared to the previous comparison. Moreover, it enabled National Metrology Institutes / Designated Institutes (NMIs/DIs) that did not participate in the previous comparisons to demonstrate their measurement competencies.Nineteen institutes participated in APMP.QM-S19. Most participating NMIs/DIs employed microwave-assisted acid digestion for sample dissolution. Inductively coupled plasma mass spectrometry (ICP-MS), including triple quadrupole and sector field, were the most commonly used instrumental techniques. Results of all participating NMIs/DIs were evaluated against the supplementary comparison reference value (SCRV). The SCRV and associated uncertainty were determined from results of NMIs/DIs that participated in the supplementary comparison using methods with demonstrated metrological traceability. Median was used as estimator of the SCRVs. For arsenic, the SCRV was 1.342 mg/kg calculated from 15 participating NMIs/DIs. For arsenic, cadmium, mercury and lead, the SCRVs were 1.342 mg/kg, 0.3630 mg/kg, 0.1230 mg/kg and 0.4101 mg/kg, respectively, calculated from 15, 14, 13 and 11 participating NMIs/DIs.Participating NMIs/DIs that have successfully participated in APMP.QM-S19 have demonstrated measurement capabilities in determining inorganic elements, in a mass fraction range from 0.02 mg/kg to 50 mg/kg in high organic content matrix, including seafood of animal origin and high protein food.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Investigation on pretreatment method for the determination of rare earth elements in polymetallic mineral samples in Pan-Xi region by ICP-MS.

The polymetallic mineral samples in Pan-Xi region are rich in rare earth resources, and exploring an efficient and accurate analysis method is of great significance for their comprehensive utilization. In this study, the samples were decomposed by three methods, namely closed acid dissolution, open acid dissolution with five acid and alkali fusion with sodium peroxide, and the 15 REE were determined by inductively coupled plasma mass spectrometry (ICP-MS) with Rh and Re as internal standard correction elements. The comparative experiments were conducted using standard substances, and the results showed: (1) The detection limit of closed acid dissolution method was low with relative standard deviation (RSD) ranging from 2.51% to 9.56% and the accuracy of method (ΔlgC) ranging from 0.006 to 0.073, while the sample processing was long, and the results of some REE were low. (2) The RSD of open acid dissolution with five acid method ranged from 1.93% to 7.96%, and ΔlgC ranged from 0.004 to 0.045 with low results of the determination results of REE. (3) The alkali fusion with sodium peroxide method eliminated the influence of matrix effects by selecting instrument optimization, sample dilution, appropriate internal standard elements, etc. The RSD ranged from 1.24% to 6.49%, and ΔlgC ranged from 0.001 to 0.032. In conclusion, alkali fusion with sodium peroxide method has a fast analysis process, complete sample dissolution, and the accuracy and precision of test results can meet the requirements of specification (DZ/T0011-2015), which is most suitable for the analysis of REE in polymetallic mineral samples from Pan-Xi region.

Drill-In Fluid Optimization for Formation Damage Control Considering Salt Dissolution in Saline-Lacustrine Reservoirs

Summary Salt dissolution induced by drill-in fluid loss is a frequent occurrence in saline-lacustrine reservoirs, which can potentially result in serious formation damage. In light of this, an experimental study was conducted to investigate the salt mineral dissolution and dynamic damage in the rock samples collected from a saline-lacustrine carbonate reservoir and the response of pore-fracture structures using the in-situ drill-in fluids. The study further involved analyzing the formation-damage-control (FDC) ability of the in-situ drill-in fluids. The results indicated that although salt dissolution significantly increased the pore size of the tight matrix and the width of natural fractures, improving the conductivity of seepage channels, the increase in pore-fracture size may have greatly aggravated the drill-in fluid loss during the process. The continuous serious filtrate loss, lower pressure-bearing capacity of the plugging zone, and lower permeability recovery rate (PRR) of rock indicated poor FDC performance of in-situ brine drilling fluids for the salt-dissolved core samples. The FDC performance of drill-in fluids for saline-lacustrine carbonate reservoirs was optimized based on the response of reservoir pore-fracture structure to salt dissolution and the theory of slightly underbalanced activity. The experimental results showed that the optimized drill-in fluids had better FDC ability, with an average PRR increase of 14.04%. Field application indicated that the optimized drill-in fluids reduced the drill-in fluid loss by 76.48%, shortened the drilling cycle by 45.20%, and increased the initial production capacity per well by 7.70%. This study can provide insightful guidance to optimize the FDC performance of drill-in fluids for saline-lacustrine hydrocarbon reservoirs during drilling.

X-ray Fluorescence Analysis of Waste Sm-Co Magnets: A Rational Approach

Determination of the chemical composition of waste Sm-Co magnets is required for their efficient recycling. The non-stereotypical composition of said magnets makes an analysis extremely challenging. X-ray fluorescence spectrometry is a promising analytical tool for this task. It offers high accuracy and simplicity of sample preparation as it does not require sample dissolution. However, a serious limitation of X-ray fluorescence analysis is the spectral interference of matrix elements and impurities. In this work, a two-stage technique has been developed for the determination of the main components (Sm, Co) and impurities (Fe, Cu, Zr, Hf, Ti, Ni, Mn, Cr) in samples of spent samarium–cobalt magnets using wavelength dispersive X-ray fluorescence spectrometry. In order to overcome the main limitation of the chosen method and to maximize its capabilities of qualitative and quantitative analysis, we propose an approach to the selection of analytical lines and experimental conditions, as well as a preparation method for the calibration standards. The obtained results have been shown to have a good correlation with ICP-OES. The limits of detection are in the range of 0.001–0.02 wt%, and the limits of quantification are 0.003–0.08 wt%.

Release behavior and biodegradability of controlled‐release potassium fertilizer encapsulated in starch–alginate matrix

AbstractThis work presents the fabrication of potassium chloride encapsulated in starch–alginate matrix, crosslinked by calcium chloride to form hydrogel bead. Sixteen formulations (S1–S16) were designed in four levels sodium alginate (SA 0.5% w/v to 2.0% w/v) and potassium chloride (KCl 5% w/v to 20% w/v) with 10% w/v starch and 0.75 M calcium chloride. The analysis reviewed that a higher concentration of sodium alginate, coupled with a lower KCl concentration, results in enhanced encapsulation efficiency. Notably, hydrogel beads formulated with higher concentrations of SA exhibited a more uniform, spherical shape with compact surfaces. Higher SA concentration has lower the swelling of the beads and therefore reduces its potassium release in general. In another word, with higher SA concentration, the release rate was at a better control to the expected release timeframe. On the contrary, it was also observed that the sample's dissolution in water after 24 h increased with the rising SA content. A higher concentration of sodium alginate led to an increased biodegradation rate, with the biodegradation rate increasing by 25% as the SA concentration was raised from 0.5% to 2% over a period of 5 days. In conclusion, this study represents a preliminary exploration into the viability of encapsulating potassium within a starch/SA matrix, with the optimal ratio of starch, alginate, and potassium was found to be 10:2:5. The significance of this work lies in its potential applications within agricultural practices, particularly in drought‐prone regions, owing to its hydrogel properties. By precisely tailoring the starch, alginate, and potassium ratios, this study opens avenues for further advancements in sustainable nutrient delivery systems.

Multi-scale dissolution dynamics for carbon sequestration in carbonate rock samples

Carbon dioxide (CO2) sequestration in porous, sedimentary reservoirs is a key technology to mitigate emissions of anthropogenic CO2 and curb irreversible climate change. The abundance of carbonate formations, both as saline aquifers and hydrocarbon reservoirs, makes future CO2 storage in carbonate formations highly likely. The weak carbonic acid that forms when CO2 dissolves in water will, however, interact with highly reactive carbonate. Preferential flow paths may form during dissolution or calcite precipitation may reduce injectivity - both processes significantly impacting reservoir sweep efficiency. Hence, understanding the dynamics of the dissolution processes and their influence on flow properties is necessary to safely store CO2 in carbonate formations. Darcy and sub-Darcy scale dissolution kinetics were here assessed in carbonate core plugs with and without pre-existing highly permeable pathways, during multiphase flow and under relevant storage conditions.Darcy-scale dissolution and precipitation data (injectivity changes, effluent analysis and mass loss) confirmed that CO2 and brine co-injections altered the carbonate rock structure on Darcy scale, but could not determine the cause of change. Multi-modal imaging was applied to independently quantify structural changes with computed tomography (CT) and aqueous flow characteristics with positron emission tomography (PET), thereby determining injectivity dependence on local flow patterns. Formation of high permeability pathways, which was expected due to rock dissolution, was only observed in cores with pre-existing open fractures, where reactive flow was limited to the fracture plane. A good correlation between the two imaging modules was found: areas of higher porosity yielded a low-density CT signal (i.e. high number of voids present) and a high PET signal density (i.e. large volume of traced fluid present). Loss of injectivity suggested local changes in the flow pattern due to blocking of pore throats by moving particles or secondary precipitation or mineralization of dissolved ions. High-resolution PET imaging revealed cementation, that was also visible using micro-CT, hence determining sub-Darcy local flow obstructions that led to decreased Darcy scale injectivity. Multi-modal imaging, where core characteristics, such as large vugs and cementation, can be independently determined by complementary modalities, may therefore be a useful tool to quantify reactive flow and resulting dissolution in rock samples.

Molar masses and molar mass distributions of commercial regenerated cellulose materials and softwood dissolving pulp determined by SEC/MALLS

The molar masses and molar mass distributions of three commercial regenerated cellulose samples, viscose rayon, Tencel, and Bemliese (or cuprammonium nonwoven), have been determined by dissolution in 8% (w/w) lithium chloride/N,N-dimethylacetamide (LiCl/DMAc) and subsequent size-exclusion chromatography with multi-angle laser-light scattering detection (SEC/MALLS). Before dissolution in LiCl/DMAc, the regenerated cellulose samples were pretreated by the following three methods: (1) soaking in ethylene diamine (EDA) and subsequent solvent exchange to N,N-dimethylacetamide (DMAc) through methanol, (2) soaking in water and subsequent solvent exchange to DMAc through ethanol, and (3) soaking in water and subsequent solvent exchange to tert-butyl alcohol through ethanol and freeze dying. The pretreated samples were dissolved in 8% (w/w) LiCl/DMAc by stirring the cellulose/LiCl/DMAc mixtures for 1–3 weeks followed by dilution to 1% (w/v) LiCl/DMAc for SEC/MALLS analysis. The EDA- and water-pretreated samples gave almost the same SEC-elution pattens and molar mass plots, resulting in similar number- and mass-average molar masses. However, the freeze-dried samples gave 10%‒20% lower mass recovery ratios than those obtained for the EDA- or water-pretreated samples, probably because of incomplete dissolution of the freeze-dried samples in 8% (w/w) LiCl/DMAc. The average mass-average degree of polymerization values of viscose rayon, Tencel, and Bemliese were 340, 530, and 880, respectively. The slopes of the conformation plots were 0.58–0.62, showing that all of the molecules in the three regenerated cellulose samples were dissolved in 1% (w/v) LiCl/DMAc, forming linear random-coil conformations.Graphical abstract

Determination of the Matrix Composition of Glasses of the Ga–Ge–Te–I System by Inductively Coupled Plasma Atomic Emission Spectrometry

A procedure is developed for the high-precision determination of matrix elements of high-purity glasses of the Ga–Ge–Te–I system, containing from 5 to 15 at % Ga, from 10 to 20 at % Ge, from 69 to 75 at % Te, and from 1 to 6 at % I, using inductively coupled plasma atomic emission spectrometry. The procedure includes two stages independent of each other: determination of the ratio of the mass fractions of Ga and Te to the mass fraction of Ge (stage 1) and determination of the mass fraction of I (stage 2) in the glass sample. Based on these values, the mass and mole fractions of each matrix element of the analyzed sample were calculated. Sample preparation includes the acid dissolution (provides quantitative transfer of Ga, Ge, and Te into the solution) and alkaline opening (provides quantitative transfer of I into the solution) of samples. The accuracy of the results of analysis was confirmed by comparing the results of an analysis of model solutions and model glass samples with the calculated composition. The estimated uncertainty of the results of analysis is 0.05–0.1 at % at P = 0.95.

Study on Physical Properties and Energy Evolution of Natural Gypsum Rock under Freeze-thaw Cycles

The physical and mechanical properties, microstructure deterioration characteristics and damage mechanism of natural gypsum rock under freeze-thaw cycles were studied by using a self-developed programmed freeze-thaw experimental device, results showed: Compared with that before freeze-thaw, with the increase of freeze-thaw cycles, the surface dissolution of gypsum rock samples becomes more obvious, the longitudinal wave velocity decreases linearly, the uniaxial compressive strength and elastic modulus decrease exponentially, the compaction stage of stress-strain curve is significantly prolonged, and the plasticity of post-peak failure process is enhanced. With the increase of axial strain, the total input energy curve rises at a faster rate, and the elastic energy curve also rises, but the rising rate slows down significantly after the freeze-thaw cycle, and the dissipation energy curve gradually evolves from a smooth rise to an ' S ' type. The research results have reference significance for the construction scheme design and frost damage prevention of gypsum surrounding rock tunnels in cold regions.