Polycarboxylic Acids Research Articles

Improvement of dispersants on nano carbon black-modified cement paste: performance, microstructure and carbon footprint

The agglomeration of nano carbon black (NCB), driven by its high specific surface energy, limits the fundamental performance of cementitious materials and hinders the broader application of functional cementitious materials in engineering domains. NCB-modified cement (NC) has a low snow-melting efficiency, resulting in high energy consumption and excessive CO2 emissions. Herein, this study innovatively proposed a method of using dispersants to overcome the above issue and systematically introduced the effects of three dispersants, polycarboxylic acid superplasticizer (PCE), tannic acid (TA), and sodium dodecyl sulfate (SDS), on NC. The dispersity of dispersant-NCB suspension was analyzed firstly, and then the performance of fresh paste, mechanical properties, resistivity, snow-melting speed and LCA of NC were explored. Experimental results indicated that, in terms of suspension stability, SDS was the most effective, followed by TA, while PCE exhibited the least efficacy. Furthermore, all three dispersants improved the fluidity of NC to varying degrees. However, PCE and TA demonstrated a retardation effect on the setting time, whereas SDS facilitated a reduction in the setting time of NC. From the point of view of mechanical properties, the use of these dispersants not only augmented the mechanical strength of the NC but also decreased its electrical resistivity. The uniform dispersion of SDS at the microstructural level of NCB had also been found. When the PCE content is 0.2%, TA content is 0.4%, and SDS content is 0.4%, the mechanical strength and resistivity of NC were the best. NC with dispersant TA melted snow three times faster than the control group, reducing snow-melting energy consumption. Moreover, LCA analysis showed that the addition of dispersants also reduced carbon emissions.

Effect of nano‐SiO2 dispersion on the mechanical properties and frost resistance of modified cement paste

AbstractThe dispersion of nano‐SiO2 (NS) in cement plays a critical role in enhancing the properties of cementitious materials. In this study, the combination of ultrasonic dispersion and polycarboxylic acid water reducing agent (PCE) was used to significantly improve the dispersion of NS. The effects of ultrasonic dispersion time, NS content, and PCE content on dispersion quality were investigated, alongside their impact on mechanical properties, electrical resistivity, and frost resistance. The results demonstrated that this synergistic method optimized the dispersion of NS, leading to superior mechanical properties and frost resistance. With an ultrasonic dispersion time of 40 min, NS content of 1.0 wt.%, and PCE content of 0.75 wt.%, the cement paste achieved its optimal performance. Compared to non‐dispersed samples, compressive strength increased by 33.7%. After 75 freeze–thaw cycles, the mass loss was 2%, the relative dynamic elastic modulus was 99.15%, and the strength loss was 13.74%.

Unraveling the Distribution of Black Carbon in Chinese Forest Soils Using Machine Learning Approaches

AbstractBlack carbon (BC) is a highly persistent yet poorly understood component of forest soil carbon reservoirs, while its inventory, distribution, and determining factors in forest soils on a large geographic scale remain unclear. Here, we characterized soil BC across 68 Chinese forest sites using benzene polycarboxylic acid method and developed machine learning (ML) models to predict and interpret potential impacts of soil organic matter (SOM) properties, soil physiochemical properties, meteorological conditions, wildfire history, and microbial diversity on BC. Results revealed that SOM properties were the most critical in predicting BC, complemented by the negative impact of mean annual temperature and alkaline mineral composition. The superior prediction accuracy for BC with higher condensed aromaticity (more benzene hexa‐ and penta‐carboxylic acid monomers) likely results from its simpler sources and greater resistance to transformation. This study introduces an effective ML model for predicting and interpreting soil BC inventory to better understand BC cycling.

Novel Electrospun Zwitterionic Nanofibers for Point‐Of‐Care Nucleic Acid Isolation Strategies Under Mild Conditions

AbstractNucleic acid (NA) testing at the point‐of‐care requires efficient NA extraction followed by post‐NA amplification to achieve necessary detection sensitivity. Nanofibers (NFs) are demonstrated to be an ideal solid surface in an NA extraction process but necessitate harsh conditions that interfere with the subsequent NA amplification process. It is demonstrated that novel, pH tunable, zwitterionic NFs composed of uncharged nylon doped with the weakly basic, cationic polyallylamine hydrochloride and the weakly acidic anionic polycarboxylic acid to address the issue. Unlike the other cationic polymers investigated, e.g. polybrene and polyaniline, these polymers allow efficient NA extraction in Tris‐ethylenediamine tetra‐acetic acid buffer under mild conditions (pH 4.5 containing 0.1% Tween 20 for adsorption, and pH 10 with 50 mM NaCl for elution). Adsorption and elution yields over 95% and 70%, respectively, are achieved. It also discovered a correlation between material morphologies and the NA extraction suggests that the combination of polymer chemistries and nanofiber morphologies facilitates efficient NA extraction at low concentrations (ng range) within a short time period (<10 min). Considering the simple protocols and instrument‐free operation the as‐developed NFs are highly attractive for use in sample‐to‐answer NA testing in point‐of‐care settings.

Amino polycarboxylic acids-modified abiraterone derivatives as potential injectable anti-prostate cancer agents

Abiraterone (Abi), an effective cytochrome oxidase P450 C17 (CYP17) inhibitor, inhibits androgen synthesis in testes, adrenal glands, and prostate tumors. However, their low bioavailability and dissolution rate due to their poor solubility and toxic side effects have hindered their clinical applications. In this study, water-soluble and injectable Abi derivatives were developed by introducing amino polycarboxylic acids into Abi, and their antiproliferation effects in vitro, mechanism of action, antitumor activities in vivo, pharmacokinetics, and toxicity were investigated. Compared to Abi, the water-soluble derivative Abi-DTPA exhibited excellent antitumor activity in vitro and in vivo. It decreased cell migration, invasion, and mitochondrial membrane potential. A mechanistic study revealed that it still targeted the CYP17 enzyme and increased the expression levels of apoptosis-related proteins, including cleaved caspase 9, cleaved PARP, and cleaved caspase 3. Abi-DTPA was the main form in the plasma and exhibited lower toxicity after intravenous administration. These findings suggest that Abi-DTPA can be used as a novel injectable anti-prostate cancer agent.

Bio-functionalized conductive poly(acrylic acid):poly(3,4-Ethylenedioxythiophene)-Prussian blue hybrid transducer for biosensors and bioelectronics interfaces

This study presents an innovative organic-inorganic hybrid transducer of poly(acrylic acid) (PAA), poly(3,4-ethylenedioxythiophene) (PEDOT) and Prussian blue (PB) nanocatalysts. The transducer demonstrated functionality conducive to enzyme conjugation and exhibited favorable electrochemical properties for biosensor signal transduction. Fabricated by a one-tube chemical redox method, the PAA:PEDOT-PB transducer showed long-term electrocatalytic and structural stability. The performance of the transducer was characterized by high transduction activity and low charge transfer resistance, particularly for H2O2 reduction. It achieves a linear detection range from 1.0 μM to 4.0 mM, with a sensitivity of 494 ± 10 μA mM−1 cm−1 and a LOD of 0.34 μM. The PAA:PEDOT-PB transducer featured a high density of carboxyl groups (DCOOH = 14.64 ± 0.05 μmol cm−2) that promoted the immobilization of the H2O2-dependent oxidase enzyme lactate oxidase (LOx) with an EDC/S–NHS coupling agent. The LOx-PAA:PEDOT-PB transducer was developed for lactate biosensing. The transducer provided high LOx-enzyme affinity (KMapp = 1.47 ± 0.05 mM), and a rapid response time (10 s) for lactate detection across a concentration range of 5.0 μM to 4.0 mM, showing a sensitivity of 223 ± 3 μA mM−1 cm−1 and an LOD of 1.45 μM. The LOx-PAA:PEDOT-PB transducer was integrated with a flexible screen-printed electrode, incorporating a wireless, battery-free near-field communication potentiostat module to measure lactate in artificial sweat on a skin model via smartphone. The PAA:PEDOT-PB transducer could enable connections with multiple bio-recognition molecules through polycarboxylic acid groups, providing potential avenues for the development of advanced biosensors.

Amino polycarboxylic acid complex agent modified Fe0 enhanced activation of H2O2 double decomposition pathways for tetracycline removal under neutral condition

The summary of this study explores the modification of Fe0 with amino polycarboxylic acid complex agents (APCAs) to enhance H2O2 catalysis for tetracycline (TC) removal under neutral conditions. The ethylenediaminetetraacetic acid-modified Fe0/H2O2 system (EDTA-Fe0/H2O2) achieved a removal efficiency of 90.2 % for 50 mg/L TC, significantly higher than the 23.9 % efficiency of the traditional Fe0/H2O2 system. The removal rate of various pollutants by the EDTA- Fe0/H2O2 process is 2.9 to 8.4 times higher than that of the Fe0/H2O2 process. After four cycles of use, the removal rate of TC by the EDTA-Fe0/H2O2 system can still reach 76.3 %. Additionally, the effect of treating TC in natural freshwater can also achieve 80.1 %. Characterization revealed that EDTA-Fe0 had a larger Fe(II) proportion, better hydrophobicity, and lower corrosion potential than Fe0, indicating higher activity. Quenching experiments and electron paramagnetic resonance tests confirmed that •OH was the major reactive species. Shell-isolated nanoparticle-enhanced Raman spectroscopy indicated the presence of *OOH species, suggesting the involvement of a dioxygen coordination reaction. Density functional theory calculations showed that both dioxygen and single oxygen coordination H2O2 decomposition pathways played significant roles, and EDTA-Fe0 exhibited high catalysis ability for H2O2 in both pathways. Analysis of the relationship between APCAs’ group structure and APCAs-Fe0 properties indicated that the number of carboxyl groups was crucial for enhancing catalytic activity, while the number of amino groups also impacted antibiotic removal efficiency. Overall, this study provides a solid theoretical foundation for further Fe0 applications and suggests a new method to improve TC removal.

Impact of different water-reducing agents on the properties of limonite self-compacting conductive concrete

The application environment for concrete is becoming increasingly complex, accompanied by an intensification of its functional requirements. This paper presents a method for developing self-compacting concrete with conductive properties using limonite and graphite as the concrete conductive phases. In the process of concrete preparation, the limonite is initially treated by a pre-wetting method to prevent the surface depression caused by the addition of limonite during the concrete curing process. The second stage of the process involved optimising different proportions of limonite and graphite and different dosages of water-reducing agent, defoamer and dispersant to prepare concrete. The influence of different dosages of limonite and graphite and different dosages of water-reducing agent on the mechanics and electrical conductivity of concrete was studied in order to obtain self-compacting conductive concrete with performance indicators meeting the requirements of self-compacting and electrical conductivity. The results demonstrate that the mechanical and electrical properties of self-compacting conductive concrete prepared with polycarboxylic acid superplasticizer and retarding superplasticizer combined with superplasticizer are satisfactory, and the composite superplasticizer can function in conjunction with dispersant. The self-compaction index, slump expansion, expansion time T50 and J-ring expansion of fluid concrete meet the requisite standards. Once the concrete has reached the designated curing age, its compressive strength and flexural strength align with the anticipated design expectations, while its resistivity meets the stipulated conductivity index requirements.

Two new 3D cobalt(II) coordination polymers constructed by semi-rigid carboxylic acid ligand: Syntheses, structures and properties

Two novel coordination polymers, {[Co2(L)(H2O)5]·H2O}n (1), and {[Co5(L)2(H2O)6(μ3-OH)2]·2C3H7NO·2H2O}n (2) (H4L = 3, 3′, 5, 5′-diphenyl ether tetracarboxylic acid, C16H10O9) have been synthesized by assembling semi-rigid aromatic polycarboxylic acids with transition-metal cobalt salts, and structurally characterized by elemental analysis, thermogravimetric analysis, IR spectrum, powder X-ray diffraction, and single crystal X-ray diffraction analysis. Structural analysis showed both the L ligands in CP 1 and CP 2 were regarded as 4 connection points, while the binuclear clusters in CP 1 and the pentanuclear clusters in CP 2 were regarded as 4 connection points and 8 connection points, respectively. Finally, both CP 1 and CP 2 were 3D network structures connected by two nodes (4, 4-connected for CP 1 and 4, 8-connected for CP 2). In addition, temperature-dependent susceptibilities have been measured in the range of 2 to 300 K, indicating that both CP 1 and CP 2 have antiferromagnetic coupling between adjacent Co(II) ions. Finally, Electrochemical experiments show that the CP 1 and CP 2 have good electrochemical behaviors.

Experimental Study on Improving the Performance of Cement Mortar with Self-Synthesized Viscosity-Reducing Polycarboxylic Acid Superplasticizer

In this study, a viscosity-reducing polycarboxylic acid superplasticizer (VRPCE) was synthesized using methylallyl polyoxyethylene ether (HPEG), acrylic acid (AA), and maltodextrin maleic acid monoester (MDMA) as the main raw materials. The influences of the VRPCE on the microscopic properties of cement paste were studied by gel permeation chromatography (GPC), total organic carbon test (TOC), zeta potential, laser particle size analysis, XRD, MIP, TG, and SEM. Finally, the effects of the VRPCE on the macroscopic properties of cement mortar were evaluated through flow time, slump flow, compressive strength, shrinkage, and creep. The results showed that the VRPCE can improve the hydration degree of the cement, optimize the pore structure, increase the porosity, improve the fluidity, compressive strength, and creep, and decrease the shrinkage resistance of the cement mortar.

RhizoMAP: a comprehensive, nondestructive, and sensitive platform for metabolic imaging of the rhizosphere

BackgroundElucidating the intricate structural organization and spatial gradients of biomolecular composition within the rhizosphere is critical to understanding important biogeochemical processes, which include the mechanisms of root-microbe interactions for maintaining sustainable plant ecosystem services. While various analytical methods have been developed to assess the spatial heterogeneity within the rhizosphere, a comprehensive view of the fine distribution of metabolites within the root-soil interface has remained a significant challenge. This is primarily due to the difficulty of maintaining the original spatial organization during sample preparation without compromising its molecular content.ResultsIn this study, we present a novel approach, RhizoMAP, in which the rhizosphere molecules are imprinted on selected polymer membranes and then spatially profiled using matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging (MSI). We enhanced the performance of RhizoMAP by combining the use of two thin (< 20 μm) membranes (polyester and polycarbonate) with distinct MALDI sample preparations. This optimization allowed us to gain insight into the distribution of over 500 different molecules within the rhizosphere of poplar (Populus trichocarpa) grown in rhizoboxes filled with mycorrhizae soil. These two membranes, coupled with three different sample preparation conditions, enabled us to capture the distribution of a wide variety of molecules that included phytohormones, amino acids, sugars, sugar glycosides, polycarboxylic acids components of the Krebs cycle, fatty acids, short aldehydes and ketones, terpenes, volatile organic compounds, fertilizers from the soil, and others. Their spatial distribution varies greatly, with some following root traces, others showing diffusion from roots, some associated with soil particles, and many having distinct hot spots along the plant root or surrounding soil. Moreover, we showed how RhizoMAP can be used to localize the origin of the molecules and molecular transformation during root growth. Finally, we demonstrated the power of RhizoMAP to capture molecular distributions of key metabolites throughout a 20 cm deep rhizosphere.ConclusionsRhizoMAP is a method that provides nondestructive, untargeted, broad, and sensitive metabolite imaging of root-associated molecules, exudates, and soil organic matter throughout the rhizosphere, as demonstrated in a lab-controlled native soil environment.

Preparation of modified ether polycarboxylic acid water reducing agent and evaluation

Water reducing agent as an important admixture. It is used to decrease the initial water content in cement paste, improving its fluidity. Polycarboxylic acid water reducing agent (PCE) is a high-performance type with advantages such as low dosage, high water reduction rate, environmental friendliness, and a simple synthesis process. In this study, the third monomer (TPEG-SAA-SHES) was synthesized by modifying isopentenol polyoxyethylene ether (TPEG) with sodium hydroxyethyl sulfonate (SHES). Subsequently, a modified ether polycarboxylic acid-based water reducing agent (PCE-S) was synthesized with TPEG and acrylic acid (AA). The experimental conditions for the synthesis of PCE-S were optimized through orthogonal tests. The synthesized PCE-S showed a certain degree of improvement in the initial net slurry flow compared to PCE, with a maximum enhancement of 19.64%. The adsorption increased by 18.25% when the TSS dosage was 5%. PCE-S enhances the hydration products of cement, increasing the compactness of the structure. The product is environmentally friendly, safe, and durable, effectively reducing the dosage of additives and helping to cut costs. It lays the foundation for the next industrialized mass production.

Physical and Chemical Characterization of Aerosols Produced from Experimentally Designed Nicotine Salt-Based E-Liquids.

Nicotine salt-based e-liquids deliver nicotine more rapidly and efficiently to electronic nicotine delivery system (ENDS) users than freebase nicotine formulations. Nicotine salt-based products represent a substantial majority of the United States ENDS market. Despite the popularity of nicotine salt formulations, the chemical and physical characteristics of aerosols produced by nicotine salt e-liquids are still not well understood. To address this, this study reports the harmful and potentially harmful constituents (HPHCs) and particle sizes of aerosols produced by laboratory-made freebase nicotine and nicotine salt e-liquids. The nicotine salt e-liquids were formulated with benzoic acid, citric acid, lactic acid, malic acid, or oxalic acid. The nicotine salt aerosols had different HPHC profiles than the freebase nicotine aerosols, indicating that the carboxylic acids were not innocent bystanders. The polycarboxylic acid e-liquids containing citric acid, malic acid, or oxalic acid produced higher acrolein yields than the monocarboxylic acid e-liquids containing benzoic acid or lactic acid. Across most PG:VG ratios, nicotine benzoate or nicotine lactate aerosols contained the highest nicotine quantities (in %) and the highest nicotine yields (per milligram of aerosol). Additionally, the nicotine benzoate and nicotine lactate e-liquids produced the highest carboxylic acid yields under all tested conditions. The lower acid yields of the citric, malic, and oxalic acid formulations are potentially due to a combination of factors such as lower transfer efficiencies, lower thermostabilities, and greater susceptibility to side reactions because of their additional carboxyl groups serving as new sites for reactivity. For all nicotine formulations, the particle size characteristics were primarily controlled by the e-liquid solvent ratios, and there were no clear trends between nicotine salt and freebase nicotine aerosols that indicated nicotine protonation affected particle size. The carboxylic acids impacted aerosol output, nicotine delivery, and HPHC yields in distinct ways such that interchanging them in ENDS can potentially cause downstream effects.

Preparation of p-isopropylphenol polyoxyethylene ether and evaluation of its performance in concrete

P-isopropenylphenol polyoxylates (IPP-PE) were obtained by alkoxylation reaction using p-isopropylphenol phenol (IPP) and ethylene oxide (EO) as raw materials, and P-PCE polycarboxylic acid superplasticizer was obtained by free radical polymerization of ipp-PE and acrylic acid (AA) under the action of initiator and chain transfer agent. The effects of reaction temperature, acid-ether ratio, amount of chain transfer agent and initiator, and reaction time on the dispersion properties of superplasticizer were studied, and the molecular structure and microscopic morphology of the superplasticizer were characterized by FTIR,1HNMR, and SEM, and the influence of superplasticizer on concrete properties was evaluated by concrete performance tests. The test results determined that the optimal synthesis process of polycarboxylic acid superplasticizer was as follows: reaction temperature 40 °C, n(AA):n(IPP-PE)=6:1, chain transfer agent and initiator were 0.4% and 0.6% of the mass of large monomer, respectively, and the reaction time was 4.5h. The experimental results of the concrete performance test showed that the workability of concrete mixed with the self-made superplasticizer was excellent, and the initial and 1h longitudinal flowability of the superplasticizer reached 228 mm and 215 mm, respectively. The water reduction rate reached 36%, the 28d compressive strength reached 56.8 MPa, the initial slump reached 226 mm, and it had a certain retarding and air entrainment effect.

Influence of Admixture Source on Fresh Properties of Self-Consolidating Concrete.

The study presented herein was intended to (1) compare the optimum (minimum) dosage requirements of four different sources of polycarboxylate-based high-range water-reducing admixtures (HRWRAs) and viscosity-modifying admixtures (VMAs) in attaining slump flows of 508 mm, 635 mm, and 711 mm, and a visual stability index (VSI) of 0 (highly stable concrete) or 1 (stable concrete), and (2) assess the flowability/viscosity, stability, passing ability, and filling ability of the resulting self-consolidating concretes. The test results showed that the optimum dosage requirements to obtain a uniform slump flow and visual stability index varied among the four selected admixture sources. The required dosage amount for HRWRAs was highest for the polycarboxylate-ester (PCE) type and lowest for the polycarboxylate-acid (PCA) type. Acceptable flowability plastic viscosity dynamic and static stability, passing ability, and filling ability of self-consolidating concrete can be achieved with the proper dosing of the four studied admixture sources.

Effects of biodegradable dispersants on the separation flotation of chalcopyrite and serpentine

The presence of serpentine slime coating on the chalcopyrite surfaces severely affects the chalcopyrite floatability. In this study, three biodegradable polymers, namely polyaspartic acid (PASP), polyepoxy succinic acid (PESA), and hydrolyzed polymaleic (HPMA) were used as dispersants to disperse the chalcopyrite and serpentine particles. The micro-flotation experiments demonstrated that the application of dispersants in the flotation effectively reduced the negative impact of serpentine over a wide pH range, restoring the recovery rate of chalcopyrite to about 85%. The XPS analysis revealed that the dispersants could be adsorbed onto the mineral surfaces through the binding of carboxyl groups with the magnesium or copper sites. As a result, the surface potentials of serpentine changed from positive to negative, while that of the chalcopyrite became even more negative, resulting in a strong electrostatic repulsion between them, which effectively eliminated the covering of the serpentine on the chalcopyrite surface. The AFM force measurements indicate a weak interaction of the polycarboxylic acids dispersants with the surface of chalcopyrite. Consequently, the adsorption of dispersants on the chalcopyrite surface has an insignificant impact on the subsequent adsorption of collectors, which is further supported by the adhesion force measurements between the air bubble and mineral surfaces. Therefore, the application of polycarboxylic acid dispersants in the flotation significantly enhanced the floatability of chalcopyrite in the presence of the serpentine fines.

Biochar data into structure: A methodology for generating large-scale atomistic representations

A well-defined methodology for constructing appropriate atomistic representations of biochar will aid in visualizing the structural features and elucidating biochar behavior with molecular dynamics (MD) simulations. Such knowledge will facilitate engineering biochars tailored to specific applications. To achieve this goal, we adapted modeling strategies applied in coal science by employing multi-cross-polarization 13C nuclear magnetic resonance, ultimate analysis, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy to identify functional groups. Helium density, surface area, and porosity were used to assess structural features. Biochar's aromatic cluster size distribution was proposed based on data from the benzene polycarboxylic acid method. The computational framework reduces bias by incorporating chemical information derived from density functional theory, reactive MD simulations, and advanced characterization data. The construction approach was successfully applied to cellulose biochars produced at four temperatures, obtaining independent representations with a relative error on the atomic contents of <10 % for oxygen and nitrogen and <5 % for carbon and hydrogen. The atomistic representations were validated using X-ray diffraction, electron spin resonance data, and laser desorption/ionization Fourier-transform ion cyclotron resonance-mass spectrometry. The code will assist others in overcoming structural creation barriers and enable the utilization of the generated structures for further simulations.

Preferential extraction of degraded organic matter and mineral protection of aromatic structures based on molecular marker analysis

The humic fractions were sequentially extracted from soils to study the heterogenous properties of soil organic matter (SOM). However, the bulk characteristics of these samples, such as elemental compositions and functional groups, could not fully reveal their diverse compositions. We sequentially extracted humic acids (HAs) from a sediment, and analyzed its molecular markers (benzene polycarboxylic acids (BPCAs), lignin-derived phenols, free lipids and bound lipids) to illustrate the diverse compositions of SOM. Our results suggested that the investigated HAs were derived from terrestrial C3 plants as reflected by the range of their δ13C values (−27.08 ‰ in HA1 to −27.85 ‰ in HA6), more specifically, non-woody tissue of angiosperm and belowground part as suggested by lignin and lipid markers. With the increasing times of extraction, the relative abundances of lignin-derived phenols, free lipids, and bound lipids increased, while those of the condensed aromatics (as indicated by BPCAs) decreased. We also observed that with the increasing times of extraction, the carbon preference index (CPI) increased, the ratios of acids to aldehydes of vanilly units (Ad/Al)v and δ13C of HAs decreased, suggesting that the extensively degraded organic compositions were selectively extracted because of their favored dissolution. Our results emphasize that the complete extraction of organic compositions is essential to ensure reliable analysis on SOM properties and turnover. The distribution of individual BPCAs suggested that the highly condensed aromatics were preferentially extracted. These might be attributed to the less condensed aromatics were more strongly associated with mineral particles, which is important for the protection of aromatic carbons in the environment.

Comparative study of polycarboxylic acids for sustainable crosslinking of silk fabrics: Evaluating flame retardancy and physical performances

For protein fibers, polycarboxylic acids represent a green strategy to enhance durability without using formaldehyde. This study evaluated the physical and flame retardant properties of silk fabrics treated with three formaldehyde-free crosslinkers: citric acid (CA), 1,2,3,4-butanetetracarboxylic acid (BTCA), and 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA). Results showed that these acids bond with silk protein through esterification and amidation, improving washing durability. Particularly, PBTCA integrates phosphorus into silk, boosting flame retardancy. While BTCA led to the highest weight gain and improved wrinkle recovery, it negatively impacted the tensile strength and softness of silk fabrics. Conversely, PBTCA adeptly balanced enhanced wrinkle resistance with minimal effects on tensile strength and softness, and least affected the silk fabrics' whiteness, thus preserving its aesthetic appeal. All crosslinkers improved flame retardancy, but PBTCA displayed superior performance, achieving a limiting oxygen index of 32.4 % at an 80 g/L concentration. In vertical burning tests, PBTCA treated silk fabrics showed reductions in damage length and demonstrated self-extinguishing properties, qualifying them for a higher flame retardant grade. Phosphorus in PBTCA promotes char formation during combustion, essential for effective flame retardation and smoke reduction. This research highlights the exceptional potential of silk treated with PBTCA, showcasing its suitability for demanding applications.

Dual-carbon isotope analysis of benzene polycarboxylic acids for tracking black carbon across different environments

Black carbon (BC) is ubiquitous in the environment and is a significant component of the refractory carbon pool. However, its sources, biogeochemical processes, and environmental residence times are poorly understood. One important reason is that the technical protocols for isolating/analyzing BC vary across different matrices, thereby bringing inconsistency among studies on BC in different environment media. Benzene polycarboxylic acids (BPCA), produced by nitric acid oxidation of the condensed aromatic structure that is common in BC and BC-like substances, has been proven to be a useful molecular proxy for tracking BC in the Earth's surface. Here, we introduce a new technical approach for the compound-specific dual-carbon isotope (δ13C and Δ14C) analysis of BPCA. The BPCA compounds are isolated using preparative liquid chromatography, in which trifluoroacetic acid is used in the mobile phase instead of phosphoric acid. This allows complete removal of solvent from the isolated BPCA fraction, so that conversion of BPCA isolates into CO2 can be done by conventional oxidation methods for off-line Δ14C analysis with accelerator mass spectrometry. Liquid chromatography (void column)-stable carbon isotope ratio mass spectrometry is employed to measure δ13C of the isolated BPCA, leaving as much BPCA carbon amount as possible for 14C analysis. Blockage of oxidation chamber due to incomplete oxidation of other organic acids in the samples is avoided thanks to preliminary isolation of BPCA. We tested the approach by applying it to solid and dissolved BC species in a suite of environmental reference materials, including maize char, coal, riverine natural organic matter (NOM 2R101N), marine sediment (SRM 1941b), urban dust (SRM 1649b), and coke-polluted soils. We assessed the offsets of BPCA-δ13C and BPCA-Δ14C values caused by procedural carbon contaminations to correct measured carbon isotopic values. Paired δ13C-Δ14C data of individual BPCA were plotted to validate and demonstrate the ability of this dual carbon isotope technique in tracking BC across different environmental matrices. We observed slightly different δ13C-Δ14C signatures among individual BPCA, indicating that the less condensed BC may have younger apparent radiocarbon ages.