Acid Dissolution Research Articles

Long-term variation, solubility and transport pathway of PM2.5-bound iron in a megacity of northern China

Although particulate Fe has a significant impact on human health, atmospheric chemical reactions, air quality, climate change, and ecosystems, there is a lack of long-term continuous hourly observation on particulate Fe in the megacity of Beijing, limiting research on these issues. To address this gap, this study continuously measured hourly concentrations of Fe in PM2.5 from October 2018 to October 2022 in Beijing. The results indicate an overall decline in Fe concentrations, consistent with previous studies in Beijing. This decline can be attributed to multiple factors, such as reduced coal consumption, restrictions on biomass burning, increased use of clean energy, advanced technologies for industrial emission reduction, and efforts to control fugitive dust. Seasonal variations in Fe concentrations were similar across the various years, with higher mean concentrations in spring, fall, and winter, and lower levels in summer. Daily variations in PM2.5-bound Fe concentrations exhibited two peaks, influenced by changes in emission intensity and the evolution of the planetary boundary layer. The solubility of PM2.5-bound Fe exhibited a wide range, varying from 4 % to 95 %, surpassing previously reported source-specific values. This variability can be attributed to acid dissolution effects and complexation behaviors. Nonparametric wind regression analysis identified distinct hotspots (higher concentrations) in the northwest wind sector at wind speeds of approximately 5–15 km/h, which are associated with blowing dust and dust storms. Additionally, the potential source contribution function analysis identified high-potential source areas were precisely located in the northwestern, western, and southern regions of Beijing, rather than primarily in the southern areas recorded in a previous study. This research provides valuable insights for studying the health effects and migration and transformation of nutrient elements, particularly particulate Fe, in Beijing.

A New Method for Measuring the Effective Length of Acid-Fracturing Fractures

Acid fracturing as an important stimulation technique, provides strong technical support for the exploration breakthrough and efficient development of carbonate oil and gas reservoirs. Accurately predicting the effective length of acid-fracturing fractures is of great significance for guiding the acid-fracturing design and improving the stimulation effect of acid fracturing. This article fully considers the essential requirement that the long-term conductivity of acid-fracturing fractures is not zero within the effective length segment. Based on the principle of the same acid concentration and acid dissolution amount, the long-term conductivity testing experiment of acid-fracturing fractures under different residual acid concentrations was designed and carried out with the consideration of the common ion effect. The critical acid concentration with long-term conductivity of 0 was obtained. This method overcomes the shortcomings of the existing methods that result in the overestimation of the effective length of acid-fracturing fractures due to inaccurate values of residual acid concentration or short-term conductivity as the determining criterion. The experimental results show that the higher the acid concentration, the deeper the acid etching groove, and the higher the initial conductivity of acid-fracturing fractures. The long-term conductivity decline rate of different acid concentrations is above 80%, which means that using short-term conductivity as an evaluation indicator alone will overestimate the effective length of acid-fracturing fracture and the yield-increasing effect of acid-fracturing treatment. In the case presented in this paper, the critical acid concentration for acid-fracturing fracture with long-term conductivity of 0 is 4%, and the effective length of acid-fracturing fractures is 120 m.

Acid dissolution of LiF/(NH4)3AlF6 mixtures obtained in the fluorination of α-spodumene with NH4HF2: Modeling and optimization

Lithium is an essential element in the current energy paradigm shift. Therefore, Li extraction from mineral sources has become a scientific and technological priority. Industrially, the mineral α-spodumene is heated to 1100 °C to obtain phase β and then digested with concentrated sulfuric acid at 250 °C. As an alternative, the extraction of Li from α-spodumene with molten NH4HF2 has been proposed as an efficient alternative method at low temperature (∼160 °C). However, the LiF obtained requires an acid leaching step to be solubilized and to separate the Li from other products. This research presents the modeling and optimization of the acid leaching operating parameters of the LiF/(NH4)3AlF6 mixture. This mixture was obtained by processing α-spodumene with NH4HF2 at low temperatures. The solids were characterized by XRD, SEM/EDS, and the Rietveld method. The leaching operating parameters investigated were solid/liquid ratio, sulfuric acid concentration, and leaching time. (NH4)3AlF6 dissolution and Li extraction were analyzed and modeled separately using artificial neural networks and least squares, respectively. The optimization stage of the process leads to (NH4)3AlF6 dissolution of 99% and Li extractions of 93%, working with 6% (v/v) sulfuric acid solution and an S/L ratio of 30 g/L for 24 min

A method for predicting fracture conductivity based on three‐dimensional spatial morphology features

AbstractThe distribution of fracture clearance is an important factor that determines the conductivity of carbonate fractures. In this paper, the morphological analysis of acid fractures and the evaluation of acid fracture conductivity were carried out to test the characteristics of acid fracture clearance and the conductivity of acid fractures under the conditions of different acid rock reaction rates. Combined with the distribution rule of fracture clearance and the calculation formula of acid fracture conductivity under closure stress, the calculation formula of acid fracture conductivity of carbonate rocks is established and verified, and the influence rule of the distribution of fracture clearance on the conductivity of acid fractures is simulated and calculated. The results show that with the increase of the closure pressure, the conductivity of the fracture with a closure pressure of 60 MPa is about 94% lower than that of the fracture with a closure pressure of 10 MPa. The increase in acid dissolution rate is beneficial to improve the fracture conductivity under various closure stresses, and the acid dissolution is beneficial to reduce the influence of the closure stress on the fracture conductivity of acid dissolution. When the confining pressure is 10 MPa, the acid corrosion rate increases from 0.0001 to 0.0004 g/cm2 s, and the conductivity of the acid corrosion fracture increases from 27 to 420 μm2 cm. As the dissolution rate of acid solution increases, the proportion of large clearance on the fracture surface increases, the average value of total clearance increases, and the proportion of contact on the fracture surface decreases.

Highly efficient deborylative hydroxylation of boronic acids through a metal and base-free process using pectin as a reusable carbocatalyst: The positive effect of hydrogen-bond donating groups

Phenols are important organic compounds with a broad range of application in pharmaceuticals, polymers, and agrochemicals. A metal- and base-free pectin-catalyzed methodology has been introduced for the sustainable ipso-hydroxylation of aryl and heteroaryl boronic acids to phenols using 30% H2O2 as a benign oxidant. Pectin (Pec, galacturonic acid ≥74.0%) was chosen as an inexpensive and available polysaccharide with numerous extraction sources. Control experiments using high methoxy pectin (HM-Pec, 70-75% esterification) confirmed that the abundant carboxylic acid and hydroxyl groups on the Pec surface act as catalytically active sites to improve the oxidation process by adsorbing the substrates via hydrogen bonding. The use of H2O:EtOH (1:1 v/v) as a solvent system instead of H2O enhanced the reaction yield, substrate scope and separation of catalyst by improving the dissolution of less soluble arylboronic acids in water such as 1-naphthylboronic acid and 2-naphthylboronic acid and preventing the gel formation of Pec nanoparticles. The reaction endured a broad substrate scope for aryl and heteroaryl boronic acids with good to excellent yields (75-99%). Pec showed an excellent reusability up to 6 runs with negligible loss of activity which verified by FT-IR, XRD and FESEM of recycled catalyst. More importantly, as a metal- and base-free catalyst system, the present research gave a comparable result to previous homogeneous and heterogeneous catalyst systems in view of reaction time, yield, oxidant loading, and number of reusability cycles.

Biocompatible, Europium-Doped Fluorapatite Nanoparticles as a Wide-Range pH Sensor.

The development of a simple, biocompatible, pH sensor with a wide range of detection, using a single fluorescent probe is highly important in the medical field for the early detection of diseases related to the pH change of tissues and body fluids. For this purpose, europium-doped fluorapatite (FAP: Eu) nanoparticles were synthesized using the coprecipitation method. Doping with the rare earth element europium (Eu) makes the non-luminescent phosphate mineral fluorapatite, luminescent. The luminous response of the sample upon dissolution in hydrochloric acid (HCl), in highly acidic to weakly basic media, makes it a potential pH sensor. A linear variation was observed with an increase in pH, in both the total intensity of emission and the R-value or the asymmetry ratio. The ratiometric pH sensing enabled by the variation in R-value makes the sensor independent of external factors. The structural, optical, and photoluminescent (PL) lifetime analysis suggests a particle size-dependent pH sensing mechanism with the changes in the coordinated water molecules around the Eu3+ ion in the nanoparticle. Given its exceptional biocompatibility and pH-dependent fluorescence intensity for a wide range of pH from 0.83 to 8.97, the probe can be used as a potential candidate for pH sensing of biological fluid.

Open acid dissolution-Ammonia solution extraction-ICP OES rapid determination of 7 trace metal elements in soil.

To overcome the corrosion of hydrofluoric acid on the ICP OES injection system in the acid dissolution system, this paper makes some improvements based on the traditional open digestion. The improved method does not require the complete removal of hydrofluoric acid. After appropriate digestion of the sample with a mixed acid, the solution can be transferred to a colorimetric tube containing ammonium hydroxide solution to give the final volume for analysis. In this paper, two-point standard curves are plotted using soil standards and process blanks, which is not only convenient but also overcomes the interference of the matrix effect. Through continuous experiments, the preferred ratio of mixed acid is 3 mL nitric acid + 5 mL hydrofluoric acid, and the concentration of ammonia solution is 0.5%. The spectral lines of the measured elements V (292.4), Cr (283.5), Co (228.6), Ni (231.6), Cu (324.7), Zn (213.8) and Pb (220.3) were determined. The method quantification limits of the seven measured elements V, Cr, Co, Ni, Cu, Zn and Pb were 0.909, 4.32, 0.269, 0.261, 0.968, 3.69 and 2.64 μg g-1, respectively, and the precision was 3.5%, 5.2%, 4.8%, 2.4%, 6.1% and 4.5%, respectively. After processing six national standard materials according to the experimental method, the measured values of each measured element were basically in agreement with the certified values, indicating that this method is fully feasible for the measurement of V, Cr, Co, Ni, Cu, Zn and Pb in soil. This method greatly improves the efficiency of pretreatment and is particularly suitable for analysing large batches of samples.

Evolution characteristics and exploration targets of Permian clastic rock reservoirs in Bohai Bay Basin, East China

Based on core observation, thin section examination, fluid inclusions analysis, carbon and oxygen isotopic composition analysis, and other approaches, the structural and burial evolution histories were investigated, and the diagenetic evolution process and genetic/development models were systematically discussed of the Upper Paleozoic Permian clastic rock reservoirs in the Bohai Bay Basin, East China. The Bohai Bay Basin underwent three stages of burial and two stages of uplifting in the Upper Paleozoic. Consequently, three stages of acid dissolution generated by the thermal evolution of kerogen, and two stages of meteoric freshwater leaching occurred. Dissolution in deeply buried, nearly closed diagenetic system was associated with the precipitation of authigenic clay and quartz, leading to a limited increase in storage space. Different structural uplifting–subsidence processes of tectonic zones resulted in varying diagenetic–reservoir-forming processes of the Permian clastic reservoirs. Three genetic models of reservoirs are recognized. The Model I reservoirs with pores formed in shallow strata and buried in shallow to medium strata underwent two stages of exposure to long-term open environment and two stages of meteoric freshwater leaching to enhance pores near the surface, and were shallowly buried in the late stage, exhibiting the dominance of secondary pores and the best physical properties. The Model II reservoirs with pores formed in shallow strata and preserved due to modification after deep burial experienced an early exposure-open to late burial-closed environment, where pore types were modified due to dissolution, exhibiting the dominance of numerous secondary solution pores in feldspar and the physical properties inferior to Model I. The Model III reservoirs with pores formed after being regulated after multiple periods of burial and dissolution experienced a dissolution of acidic fluids of organic origin under a near-closed to closed environment, exhibiting the dominance of intercrystalline micropores in kaolinite and the poorest physical properties. The target reservoirs lied in the waterflood area in the geological period of meteoric freshwater leaching, and are now the Model II deep reservoirs in the slope zone–depression zone. They are determined as favorable options for subsequent exploration.

Divergent Geochemical Pathways of Carbonate Aquifer Evolution in a Classic Karst Terrain: (1) Polygenetic Cave Development Identified Using Longitudinal Groundwater Geochemistry

Carbonic acid and sulfuric acid speleogenesis describe a dichotomy between epigenetic and hypogenetic caves and carbon and sulfur cycling in karst, but do not acknowledge the global spectrum of cave formation. This paper, part one of a two-part investigation, tests and revises speleogenetic models from a classic karst landscape using dissolved ion concentrations δ13CDIC, and δ34S in water samples collected at four sites across the Bluespring and Lost River karst basins in the Mitchell Plateau, Indiana, USA. Analyses revealed elevated sulfur in both karst basins but differently sourced; H2S (δ34S = −14.2‰) evolved from petroleum seeps in Bluespring Caverns accounted for up to 61% of sulfur in the cave stream, while evaporite beds (δ34S = [+14.50‰, +17.91‰]) of the St. Louis Limestone contributed up to 100% of sulfur at Orangeville Rise, a terminal spring of the Lost River karst basin. These results have implications for carbon–sulfur cycle linkages, particularly the potential acceleration of carbon flux from sulfuric acid dissolution in otherwise epigenetic settings. We suggest a new paradigm for speleogenesis in the North American midcontinent—speleogenesis in the Mitchell Plateau and similar settings is not epigenetic or hypogenetic, but instead polygenetic with competing chemical processes varying across space and time.

Research on mechanisms and effects of microbial agent applied in scaling control of circulating cooling water

Scaling control is vital for the safe operation of circulating cooling water system. Biological treatment involves the addition of microbial agent; it employs the metabolism of functional strains, and it is a novel, efficient and environmentally friendly method used to control scaling. In this study, microbial agent (including Nitrosomonas, Nitrospira, Bacillus cereus, Bacillus subtilis and Pseudomonas) were selected to investigate their anti-scaling mechanisms and the effects of employing biological methods. The anti-scaling efficiency of the microbial agent was found to be approximately 55.34–61.29%. The anti-scaling mechanisms of the functional strains included (a) acid production and solubilisation, (b) acid production and dissolution, (c) CaCO3 lattice distortion and (d) biosorption of scaling ions. Our study provides a deeper understanding of the anti-scaling mechanisms of functional strains and will assist in the advanced development and application of microbial agent in scaling control.

Does Media Choice Matter When Evaluating the Performance of Hydroxypropyl Methylcellulose Acetate Succinate-Based Amorphous Solid Dispersions?

Hydroxypropyl methylcellulose acetate succinate (HPMCAS) is a weakly acidic polymer that is widely used in the formulation of amorphous solid dispersions (ASDs). While the pH-dependent solubility of HPMCAS is widely recognized, the role of other solution properties, including buffer capacity, is less well understood in the context of ASD dissolution. The goal of this study was to elucidate the rate-limiting steps for drug and HPMCAS release from ASDs formulated with two poorly water soluble model drugs, indomethacin and indomethacin methyl ester. The surface area normalized release rate of the drug and/or polymer in a variety of media was determined. The HPMCAS gel layer apparent pH was determined by incorporating pH sensitive dyes into the polymer matrix. Water uptake extent and rate into the ASDs were measured gravimetrically. For neat HPMCAS, the rate-limiting step for polymer dissolution was observed to be the polymer solubility at the polymer-solution interface. This, in turn, was impacted by the gel layer pH which was found to be substantially lower than the bulk solution pH, varying with medium buffer capacity. For the ASDs, the HPMCAS release rate was found to control the drug release rate. However, both drugs reduced the polymer release rate with indomethacin methyl ester having a larger impact. In low buffer capacity media, the presence of the drug had less impact on release rates when compared to observations in higher strength buffers, suggesting changes in the rate-limiting steps for HPMCAS dissolution. The observations made in this study can contribute to the fundamental understanding of acidic polymer dissolution in the presence and absence of a molecularly dispersed lipophilic drug and will help aid in the design of more in vivo relevant release testing experiments.

Electrochemical recycling of diamond and precious metals from used diamond tools

The recycling of used diamond tools, which contain a large amount of unused diamond particles and precious metals, can not only realize the reuse of resources, but also reduce the pressure of environmental protection. In this paper, diamond particles were recovered by acid dissolution of aqua regia, and the current density, complexing agent concentration and pH value of the acid dissolution system were adjusted to recover Cu and Co by electrodeposition. Scanning electron microscope and energy spectrometer were used to study the changes of the composition and morphology of the plated layers, and the effects of the parameters such as current density, complexing agent concentration and pH on the organization and composition of the alloy plated layers were analyzed. The results showed that at the current density of 40 mA/cm², pH 4.5 and complexing agent concentration of 10 g/L, uniformly distributed, dense and moderately thick Cu-Co alloy plating was obtained, and the weight percentages of Cu and Co reached the peak respectively. The Cu and Co in the waste diamond tools can be recovered under this condition with good recovery effect.

Facile and complete sulfuric acid leaching of zinc ferrite assisted by copper powder: Leaching mechanism and kinetics investigation

Zinc ferrite is a dominant phase in mass solid wastes generated from zinc or iron production, which causes the obstacle of metal recovery and recycling. A facile and efficient sulfuric acid leaching process of zinc ferrite assisted by copper powder was proposed in this study. The effects of factors on the leaching of zinc ferrite and copper were investigated. The results showed that zinc ferrite and copper were coupled and leached. The complete dissolution of zinc ferrite was obtained with wide ranges of leaching conditions. The shortest time for the complete dissolution of zinc ferrite was 10 min at 80 ℃ under the conditions: copper to zinc ferrite molar ratio of 1.5, sulfuric acid concentration of 100 g/L, liquid to solid ratio of 30 mL/g, and copper powder of + 38.5–20 μm. The least consumption of copper to realize the complete dissolution of zinc ferrite was 27.15%. The leaching kinetics was studied by the shrinking core model. It was found that zinc ferrite leaching assisted by copper was controlled by surface chemical reaction. The apparent activation energies for zinc, iron, and copper are 56 kJ/mol, 56 kJ/mol, and 50 kJ/mol, respectively. Characterization of the leaching residues and determination of iron and copper species in the leaching solution showed galvanic corrosion took place between zinc ferrite and copper, enhancing their acid dissolution.

Application of Acid Fracturing Technology to Improve Water Yield of Deep Carbonate Geothermal Wells

To achieve the “carbon peak” goal, green and low-carbon energy development is the key. The development and utilization of geothermal resources and the development of deep carbonate geothermal wells in China are analyzed. Based on the principle of chemical reaction between hydrochloric acid and the main components of carbonate rock, four rock samples from geothermal wells were dissolved with 15% and 20% hydrochloric acid, respectively. The comparison showed that 15% hydrochloric acid was more economical and effective. The percolation capacity of acid dissolution fractures was tested through percolation capacity experiments, and the optimal amount of acid solution was determined to be 2-8 PV. It was verified that acid dissolution helps improve fracture percolation capacity. Through the on-site testing of acid fracturing technology in the Xiong’an New Area, it has been verified that the on-site implementation of multi-stage acid fracturing has a significant effect on increasing production. Finally, conclusions are drawn. The method of using acid solution dissolution to increase the water yield of deep carbonate geothermal wells is feasible, and the multi-stage acid fracturing technology is suitable for deep wells and can increase the water output of geothermal wells, which has good promotion value.

Composite material with enhanced recyclability as encapsulant for photovoltaic modules

Encapsulation of photovoltaic cells was carried out using a transparent glass fiber reinforced composite with enhanced chemical recyclability based on a matrix of an epoxy resin containing cleavable functional groups. The current-voltage curves showed a decrease of 6.3% on the short-circuit current (Isc) after encapsulation of the cell, lower than the one observed for the reference non-recyclable standard epoxy composite. Its performance stability under thermal cycling, ultraviolet (UV), and damp-heat exposure was evaluated and compared with the one of the reference standard epoxy. Both resins showed good stability performance under UV exposure and thermal cycling accelerated aging. Moreover, a power loss below the 5% allowed by the photovoltaic standard was observed for the recyclable resin after 1000 h of damp-heat exposure, even the pronounced loss of 4.7% in power remains a concern. Regarding the recyclability, the composite was dissolved in acetic acid dissolution and glass fiber fabrics were successfully recovered. A new module was manufactured with these fabrics, showing this time a loss of 12% in Isc comparing with the non-encapsulated cell. Further work will consider improving the moisture barrier properties of the composite, and adjusting the recycling conditions to allow component recovery valid for new modules.

Design Principles for Transition Metal Nitride Stability and Ammonia Generation in Acid

Transition metal nitrides have shown great promise for reducing or eliminating the use of expensive precious-metal-based catalysts (e.g., Pt) in proton exchange membrane fuel cells and electrolyzers, but the use of these nitrides in such technologies is severely hindered by their dissolution at acidic pHs [1-2]. More importantly, the decomposition of transition metal nitrides in acid generates ammonia from the protonation of lattice nitrogen, giving rise to many false positives in previous reports of nitride catalysts for electrochemical nitrogen reduction to ammonia. For example, while nitrides such as VN [3], NbN [4], and Mo2N [5] have been computationally predicted to catalyze the reduction of nitrogen to ammonia, the experimentally observed ammonia has been attributed to the decomposition of nitrides in acid [6-8]. To tackle this challenge, motivated by our previous work [9-12] on the design principles of transition-metal-oxide-based catalysts, we established the stability descriptors of transition metal nitrides in acid. Such stability descriptors not only offer a fundamental understanding of nitride dissolution but also provide new guiding principles to optimize the intrinsic stability of nitrides for diverse acidic applications.In this work [13], combining ab initio calculations with synchrotron X-ray spectroscopies, we identified electronic-structure-based design principles governing the extent and kinetics of nitride dissolution and ammonia production in acid. We found that lowering the nitrogen 2p band center of transition metal nitrides with respect to the Fermi level leads to weakened metal-nitrogen bonds, increased labile metallic character, and a reduced barrier for the protonation of lattice nitrogen to produce ammonia, correlating with faster dissolution kinetics of nitrides in acid. Moreover, increasing the solubility of dissolved metal ions in acid was found to be critical in preventing surface oxide passivation to ensure the complete conversion from transition metal nitrides to ammonia. Based on these observations, a new mechanistic picture was formulated, where the initial protonation step of lattice nitrogen is critical to trigger nitride dissolution, and this proposed reaction scheme was supported by the pH-dependent dissolution kinetics of nitrides in acid.These design principles and mechanistic insights for producing ammonia and dissolving metal cations from the decomposition of nitrides in acid are essential for a variety of clean energy applications. For instance, such design principles can be leveraged to boost the stability of nitride catalysts for proton-exchange membrane fuel cells and electrochemical ammonia synthesis, where the dissolution of nitrides in acid has hindered their functions. Moreover, these descriptors for nitride dissolution and ammonia formation in acid provide emerging opportunities for designing novel nitride chemistries for distributed, on-demand ammonia generation. As nitrides represent an exciting, yet markedly unexplored chemical space, this work provides a blueprint to design multinary nitrides in such a vast materials space for various acidic applications, including electrocatalysis and beyond.

Activation behavior of the novel CO2 foaming agent for mining on fly ash

Although there have been many research results on the chemical activation of fly ash (FA) as a supplementary cementitious material (SCM) in cementitious materials. However, there is a lack of research on the use of CO2 foaming agent (sodium bicarbonate and potassium aluminum sulfate) to activate fly ash. In this experiment, the effects of CO2 foaming agent, sodium bicarbonate, and potassium aluminum sulfate on the activity of FA mixed paste were investigated. The mechanism of FA activation by activator was revealed by selective acid dissolution, QXRD, BSE-EDS statistical analysis, and quantitative analysis of TGA. The results showed that the remaining fly ash amounts of MG, SBG, and PASG after 28 days were 17.5%, 25.9%, and 43.3% lower than those of the control group, respectively. In addition, potassium aluminium sulphate promoted hydration to generate more CH to activate the FA. Sodium bicarbonate promoted hydration and produces more CH to activate FA by generating nano-CaCO3. The mixture of sodium bicarbonate and potassium aluminum sulfate took advantage of both nano-CaCO3 and potassium aluminum sulfate to promote silicate hydration to provide CH. As a result, the two synergistically activate FA. The above results show that CO2 foaming agents can be used not only as foaming agents to prepare lightweight materials, but also as chemical activators to activate solid waste. This will have a high practical application value.

A 3D-Printed Electrochemical Immunosensor Employing Cd/Se ZnS QDs as Labels for the Rapid and Ultrasensitive Detection of Salmonella typhimurium in Poultry Samples

Salmonella is one of the leading causes of foodborne illnesses worldwide, with poultry products being a major source of contamination. Thus, the detection of salmonella in commercial poultry products is crucial to minimize the effects on public health. Electrochemical sensors are promising tools for bacteria detection due to their sensitivity, simplicity, and potential for on-site analysis. In this work, a three-dimensional (3D) printed electrochemical immunosensor for the determination of Salmonella typhimurium in fresh chicken through a sandwich immunoassay employing biotinylated anti-S. typhimurium antibody followed by streptavidin labeled with Cd/Se ZnS quantum dots (QDs) is presented. The device features three carbon-black polylactic acid electrodes and a holder, and the quantification of S. typhimurium is performed by anodic stripping voltametric (ASV) determination of the Cd(II) released after acidic dissolution of the QDs. To enhance sensitivity, an electroplated bismuth film was deposited on the working electrode, achieving a detection limit of 5 cfu/mL in a total assay time of 25 min, whereas 5 h of sample pre-enrichment was required for the detection of 1 cfu/25 mL of chicken rinse and chicken broth. The method is accurate, with %recovery values ranging from 93.3 to 113% in fresh chicken samples, and repeatable with intra- and inter- assay coefficient of variations <2 and 5%, respectively, indicating the suitability of the proposed immunosensor for the detection of S. typhimurium at the point-of-need.

Elucidating the chemical interaction effects of herb pair Danshen-Chuanxiong and its anti-ischemic stroke activities evaluation

Ethnopharmacological relevanceSalvia miltiorrhiza Bunge (Danshen) and Ligusticum chuanxiong Hort. (Chuanxiong) is the core herb pair in traditional Chinese medicines (TCMs) formulae for treating ischemic stroke. However, the synergistic effect of Danshen-Chuanxiong against anti-ischemic stroke and its compatibility mechanism remains unclear. Aim of the studyThis study aimed to uncover the compatibility mechanism of Danshen-Chuanxiong against ischemic stroke through chemical profiling, pharmacodynamics evaluation, network pharmacology and experimental validation. Materials and methodsUltra-high performance liquid chromatography (UHPLC) combined with quadrupole time-of-flight tandem mass spectrometry (QTOF-MS) and UHPLC connected with tandem triple quadrupole mass spectrometry (QQQ-MS) were utilized to conduct the chemical interaction analysis. Then the synergistic effects of Danshen-Chuanxiong against ischemic stroke were comprehensively evaluated by the middle cerebral artery occlusion reperfusion (MCAO/R) mice model, zebrafish ischemic stroke model and glutamic acid-induced PC12 cells injury model. Afterwards, network pharmacology and molecular docking were applied to dissect the significant active compounds and potential mechanisms. Finally, the key target proteins were experimentally validated by Western blot. Results83 compounds were characterized in Danshen-Chuanxiong by UHPLC-QTOF-MS analysis, and 4 compounds were tentatively identified for the first time. The quantification results (24 accurately identified compounds) in 13 proportions of Danshen-Chuanxiong revealed that Danshen significantly increased the dissolution of most phthalides (from Chuanxiong), while Chuanxiong facilitated the dissolution of most phenolic acids (from Danshen) in solution. The anti-ischemic stroke effects of Danshen-Chuanxiong were significantly better than Danshen or Chuanxiong in attenuating infarct size, reducing brain edema and neurological scores in MCAO/R mice. Also, compared with single herbs, this herb pair exerted better effects of suppressing the incidence of cerebral thrombosis in zebrafish, and increasing the cell viability of glutamic acid-induced PC12 cells. In network pharmacology, 7 effective compounds (rosmarinic acid, chlorogenic acid, salvianolic acid B, (Z)-ligustilide, ferulic acid, caffeic acid, tanshinone IIA) and 5 hub targets (AKT, TNF−α, IL-1β, CASP3 and BCL2) as well as 4 key pathways were predicted. Western blot results showed that Danshen-Chuanxiong exert therapeutic effects mainly through decreasing the protein expressions of TNF-α, IL-1β and Cleaved-CASP3, elevating the levels of p-AKT and BCL2. ConclusionsThis work provided an integration strategy for uncovering the synergistic effects and compatibility mechanism of Danshen-Chuanxiong herb pair for treating ischemic stroke, and laid foundation for the further development and utilization of this herb pair.

Acid-Soluble Drilling Fluid in the Northern Carbonate Reservoir of the Yishan Slope in the Ordos Basin

The carbonate reservoir in the northern Yishan slope of the Ordos Basin presents significant challenges to gas field exploration and development. With its low pressure, limited porosity, low permeability, and abundance of micro-fractures, the reservoir is resistant to acid dissolution. Once solid particles block these fractures during drilling and completion, serious reservoir damage ensues. To address these obstacles, we engineered an acid-soluble, solid-free drilling fluid system in the lab. This involved incorporating sodium carboxymethyl cellulose, heat-resistant starch, fungicides, and lubricants. Contrasted with the commonly used potassium ammonium based drilling fluid system, our innovative solution showed notable improvements. Specifically, the density decreased by 0.04 to 0.06 g/cm3, and the solid content decreased by 4.0% to 6.50%, while the acid-soluble rate surged from 8.50% to 95.45%. In addition, the reservoir permeability recovery value saw an increase from 51.50% to 95.88%. In practical field application, we employed this novel drilling fluid system in ten horizontal wells. Following acid fracturing and reconstruction, these wells registered a 75.94% increase in gas production compared to nearby wells. Our findings demonstrate that the proposed system effectively mitigates the incursion of solid-phase particles into the reservoir while enhancing acidification during acid fracturing. This results in the swift removal of plugging, restoration of formation permeability, and improved well production. Our research thus introduces a drilling and completion fluid system of high efficiency with superior reservoir protection performance, potentially offering substantial benefits to the development of carbonate rock salt gas reservoirs.