Hydrochloric Research Articles

Synthesis, characterization and biological activity of the Cu (II)-1,3-PDTA [(Cu (II) (PDTA)] complex for the control of Erwinia chrysanthemi (soft rot) in the parsley manioc (Arracacia xanthorrhiza Bancroft)

Synthesis, characterization and biological activity of the Cu(II)-1,3-PDTA complex was performed by two synthetic routes: sodium and carbonate pathways. The Cu (II)-1,3-PDTA complex can be easily produced by the 1,3-PDTA binder, commercially available as Trilon F (BASF) which is available as sodium or acid salt for the coordination of Cu (II). The biological activity of the Cu (II)-1,3-PDTA [Cu (II)-PDTA] complex was performed to analyze the activity against the bacterium Erwinia chrysanthemi Bancroft. The bacterium is the causative agent of soft rot in the parsley maniac (Arracacia xanthorrhiza Bancroft). The bacterium was isolated from parsley manioc infected with soft rot. The metal complex sensitivity tests were performed by diffusion antibiogram. The mean values of the halos and standard deviations of the zones of inhibition were obtained for the [Cu (II) (PDTA)] and Streptomycin complexes. The concentrations of the complexes evaluated were 10-3, 10-2 and 10-1 M (equivalent to 36.3 g L-1 (3.63%), 3.63 g L-1 (0.363%) and 0.363 g L-1 (0.0363%), respectively). The halos were 25.0 ± 1.2 mm for control. For [Cu (II) (PDTA)] complexes, the obtained values were 9.5 ± 0.6, 15.0 ± 0.8 and 24.0 ± 0.8 via sodium and 12.0 ± 1.6, 25.0 ± 0.8 and 31.0 ± 1.9 via carbonate, for 10-3, 10-2 and 10-1 M, respectively. The results showed that the bactericidal activity of the Cu (II)-1,3-PDTA complex obtained by the two synthetic routes are adequate for the control of Erwinia chrysanthemi Bancroft.

The Damage Evolution of a Cr2O3-TiO2 Coating Subjected to Cyclic Impact and Corrosive Environments and the Influence of a Nickel Intermediate Layer

Cyclic impacts in corrosive environments significantly affect the service life of ceramic coatings, greatly increasing their susceptibility to cracking and delamination. This study investigated the damage evolution behavior of Cr2O3-TiO2 (CT) coatings under cyclic stress in a corrosive medium, and analyzed the effects of the nickel layer on coating stress, corrosion current, and crack propagation. The variations in corrosion potential and current were analyzed, and the formation patterns of interfacial corrosion cracks were observed. Pre-cracks were introduced on the ceramic coating surface using a Micro-Nano mechanical testing system, and cyclic impacts were applied to the samples in 5% diluted hydrochloric acid using SiC balls to induce damage evolution. The results indicate that the presence of the nickel interlayer reduced the corrosion current density from 9.197 × 10−6 A/cm2 to 8.088 × 10−6 A/cm2 and significantly decreased the stress between the coating and the substrate. The surface cracks gradually extended toward the interface under the coupling effect of corrosion and SiC ball impact. When cracks reached the interface, they provided channels for corrosive media, leading to stress corrosion cracking at the interface. The Ni intermediate layer suppressed the formation of interface cracks and greatly enhanced the impact damage resistance of the CT coating–substrate system in corrosive media.

Use of antiepileptic drugs in mental disorders

Antiepileptic drugs (AEDs) are quite often used in psychiatric practice and are considered the drugs of choice for mental disorders, primarily recurrent and bipolar depression and mania, behavioral and anxiety disorders with signs of bipolar emotional dysregulation, mental disorders with dependence on psychoactive substances. The level of evidence for the use of AEDs varies, sometimes they are used outside the recommendations of the FDA, EMA, outside the instructions of the Pharmcenter of Ukraine. Currently, mood stabilizers such as valproate, lamotrigine, carbamazepine have the highest level of evidence. Most psychotropic drugs are recommended for use in the treatment of affective disorders (antipsychotics, antidepressants, lithium salts) and attention deficit hyperactivity disorders (psychostimulants, atomoxetine) from the age of 6, which explains the widespread use of valproate and lamotrigine in pediatric practice outside direct indications. Bipolar affective disorders have a high level of comorbidity with generalized anxiety and panic disorder, which sometimes demonstrate low sensitivity to benzodiazepine therapy, but respond well to valproic acid salt therapy. The use of gabapentin in anxiety disorders is based on the results of controlled studies. Anticonvulsants are widely used in alcohol and substance abuse, addictive disorders, emotional and behavioral disorders associated with withdrawal states. The therapeutic and side effects of AEDs are closely related to behavioral disorders in epilepsy. They can improve or worsen behavioral symptoms associated with signs of emotional bipolar dysregulation and attention deficit hyperactivity disorder. It is expected that the list of AEDs will continue to grow, and new proposals for use in psychiatric practice will appear.

Simulation of Antral Conditions for Estimating Drug Apparent Equilibrium Solubility after a High-Calorie, High-Fat Meal.

The simulation of antral conditions for estimating drug apparent equilibrium solubility after a high-calorie, high-fat meal is challenging. In this study, (1) we measured the apparent equilibrium solubility of two model lipophilic drugs, ketoconazole and danazol, in antral aspirates collected at various time points after a minced high-calorie, high-fat meal and a glass of water 30 min after initiation of meal administration, and we designated one point estimate for ketoconazole and one point estimate for danazol; (2) we evaluated the usefulness of FeSSGF-V2 and FEDGAS pH = 3 in reproducing the two point estimates; (3) we evaluated potential compositions of FeSSGF-V3 that simulate the pH, the buffer capacity toward both less acidic and more acidic values, and the antral lipid and protein contents with easily accessible, commercially available products, and (4) we identified the most useful composition of FeSSGF-V3 for reproducing the two point estimates. For both model drugs, apparent solubility in FeSSGF-V2 and in FEDGAS pH 3 deviated substantially from the corresponding point estimate. For FeSSGF-V3, hydrochloric acid, acetates, and FEDGASbuffer pH 3 were evaluated for regulating the pH and buffer capacity, FEDGASgel was used for simulating the lipid content, and Régilait skimmed milk powder was used for simulating the protein content. Level III FeSSGF-V3 prepared with hydrochloric acid, 6.1% (w/v) Régilait, and 2.83% (w/v) FEDGASgel, i.e., one-sixth of FEDGASgel concentration in FEDGAS pH 3, was comparatively the most useful medium for point estimating ketoconazole and danazol apparent solubility in antral contents after water administration in the fed state, induced as requested by regulatory authorities in oral drug bioavailability studies. Level III FeSSGF-V3 prepared by using hydrochloric acid as the principal pH controlling species could be useful in the evaluation of food effects on drug absorption with in silico physiologically based biopharmaceutics modeling approaches and, also, with biorelevant in vitro methodologies.

2H-NMR as a Practical Tool for Following MOF Formation: A Case Study of UiO-66.

Developing the mechanism for MOF formation is crucial for the rapid development of new materials. This work demonstrates that Deuterium-NMR spectroscopy is the optimal inter-laboratory methodology for understanding the in-situ kinetics of metal-organic framework (MOF) formation. This method is facile, affordable, and allows for the isolation and monitoring of individual reagents by using one deuterated component while the remaining components are protonated. This study utilizes 2H-NMR, via the spectrometer's lock channel, to investigate the formation of UiO-66 as influenced by different modulators: acetic acid, benzoic acid, and hydrochloric acid. By monitoring the concentration of the deuterated linker and observing the chemical shift and peak width of deuterated water over time, key elements of the mechanism are unraveled. Paradoxically, conditions that cause the ligand to be consumed more slowly result in MOFs forming more quickly and with fewer defects. This phenomenon is attributed to the dissociative mechanism associated with the Zr(IV)-containing node.

2H‐NMR as a Practical Tool for Following MOF Formation: A Case Study of UiO‐66

Developing the mechanism for MOF formation is crucial for the rapid development of new materials. This work demonstrates that Deuterium‐NMR spectroscopy is the optimal inter‐laboratory methodology for understanding the in‐situ kinetics of metal‐organic framework (MOF) formation. This method is facile, affordable, and allows for the isolation and monitoring of individual reagents by using one deuterated component while the remaining components are protonated. This study utilizes 2H‐NMR, via the spectrometer’s lock channel, to investigate the formation of UiO‐66 as influenced by different modulators: acetic acid, benzoic acid, and hydrochloric acid. By monitoring the concentration of the deuterated linker and observing the chemical shift and peak width of deuterated water over time, key elements of the mechanism are unraveled. Paradoxically, conditions that cause the ligand to be consumed more slowly result in MOFs forming more quickly and with fewer defects. This phenomenon is attributed to the dissociative mechanism associated with the Zr(IV)‐containing node.

Microstructure and Corrosion Resistance of Composite Based on Ultra-High Molecular Weight Polyethylene in Acidic Media

In this work, the effect of an acidic environment on the structure of composite samples based on ultra-high molecular weight polyethylene (UHMWPE) modified with mineral filler in the form of diabase (DB) is studied. The stability of samples was investigated in solutions of sulfuric (H₂SO₄) and hydrochloric (HCl) acids with concentrations of 10 vol% and 20 vol% at room temperature for 16 weeks. It was found that the introduction of 10 wt% DB into the UHMWPE matrix significantly increases the resistance of the composite sample to aggressive media, which is confirmed by the minimum degree of swelling compared to pure UHMWPE and composites with higher filler content. Scanning electron microscopy (SEM) demonstrated a uniform distribution of DB in the sample structure and the absence of defects such as agglomeration and cracks. The methods of infrared spectroscopy (IRS) and X-ray structural analysis (XRD) revealed a decrease in the degree of crystallinity of the samples after acid exposure, but no significant changes in the chemical structure of the materials were recorded, which confirms their resistance to chemical degradation. The best chemical resistance was demonstrated by composites containing 10 wt% DB, which is associated with the formation of a barrier structure preventing the diffusion of acids. The obtained results indicate the promising application of UHMWPE with DB filler to create samples resistant to aggressive media.

Study on the effect of acid fracturing fluid on pore structure of middle to high rank coal

Acid fracturing fluids can effectively improve the microporous structure of coal, thereby enhancing the permeability of coal seam and the efficiency of gas drainage. To explore the effects of acid fracturing fluids on the pore structure modification of coal samples from different coal ranks, hydrochloric acid-based acid fracturing fluids were prepared and used to soak four types of medium to high-rank coal in an experiment. High-pressure mercury intrusion and liquid nitrogen adsorption techniques results demonstrated that the acid fracturing fluid can effectively alter the pore structure of coal. However, the modification effect does not exhibit a linear relationship with coal rank. The porosity of fat coal and coking coal increased by approximately 30%, while the surface area of gas coal and fat coal increased by about 20%. The new micropores produced by the acid fracturing fluid will increase the roughness of the fracture surface, but the widening of the original fracture will reduce the tortuosity of the fracture. Only the fractal dimension of lean coal has a significant change, about 6%. Overall, acid fracturing fluid has the best effect on gas coal and coking coal. The research results provide a reference for the selection and application of acid fracturing fluid in coal seam hydraulic fracturing.

Modification of Ganoderma lucidum spore shells into probiotic carriers: selective loading and colonic delivery of Lacticaseibacillus rhamnosus and effective therapy of inflammatory bowel disease.

Inflammatory bowel disease (IBD) is a chronic inflammation with a high incidence rate. Many probiotics, including Lacticaseibacillus rhamnosus (L. rhamnosus), have shown promise in IBD treatment. The therapeutic effects of most probiotics are greatly decided by the available live cells in the disease lesion, which is compromised as they pass through the gastric juice and intestinal tract, resulting in a loss of activity. To improve probiotic delivery efficiency in the intestinal tract, broken Ganoderma lucidum spore shells (bGLS) were explored as a carrier to enhance the intestinal tract delivery of L. rhamnosus SHA113, a probiotic that has been verified to have capability to treat IBD. It was found the bGLS treated with iturin A and hydrochloric acid (IH-bGLS) had much higher affinity to probiotic cells than the untreated ones. This is possibly due to the enhancement of hydrophobic and positive charge of bGLS. Furthermore, IH-bGLS demonstrated an 81% loading efficiency for L. rhamnosus SHA113 and 2.2% for Escherichia coli. More importantly, loading in IH-bGLS greatly enhanced the delivery of L. rhamnosus SHA113 cells to the colon and prolonged their retention time from 48 to over 120 h (P < 0.01). The mechanisms might be related to the enhancement of probiotic cell adhesion to the gastrointestinal mucosa, increase of mucus secretion and the upregulated expression of tight junction proteins, occludin and ZO-1, in the colon. The results of the animal experiment showed that the therapeutic effects of L. rhamnosus SHA113 on IBD were greatly enhanced when they were loaded with IH-bGLS. The novelty of this research is in the development of probiotic carriers from bGLS, which has significance in the improvement of intestinal delivery efficiency and the therapeutic effects of probiotics on IBD. This system may have attractive application in the enhancement of probiotic delivery efficiency in the intestinal tract, which is important to ensure and enhance the beneficial effects of probiotics.

Systematic optimisation of crude buccal swab lysate protocols for use with the ForenSeq™ DNA Signature Prep Kit.

The ForenSeq™ DNA Signature Prep kit has not been thoroughly tested with crude buccal swab lysates in large-scale population studies using massively parallel sequencing (MPS). Commonly used lysis buffers for swabs intending to undergo direct polymerase chain reaction (PCR) are SwabSolution™ and STR GO! Lysis Buffers, and these have been successfully used to generate population data using capillary electrophoresis (CE) systems. In this study, we investigated the performance and optimisation of SwabSolution™ and STR GO! lysates with the ForenSeq™ DNA Signature Prep workflow and addressed the challenge of failed MPS profiles in initial trials. To mitigate PCR inhibition in SwabSolution™ lysates, three optimisation methods were evaluated: dilution of lysates, addition of 5X AmpSolution® reagent, and purification with magnetic beads. For STR GO! lysates, we explored spin-column purification using the QIAamp® DNA Investigator kit, magnetic bead purification, and a pH adjustment with 1M hydrochloric acid. Our findings indicated that the addition of 5X AmpSolution® was effective for overcoming PCR inhibition in SwabSolution™ lysates, thereby maintaining a direct PCR approach. Spin-column purification, however, is recommended for STR GO! lysates to minimise MPS profile failure rates. These improvements enhance first-time success rates of crude swab lysates, and reduce the need for repeat sampling and re-sequencing, making the workflow more suitable for large-scale population studies in forensic laboratories.

Experimental study of parameters in micro-photochemical machining using maskless digital projection on flat surfaces of 100Cr6 steel

Photochemical machining (PCM) is a chemical etching process, in which a photoresist agent is used to cover parts of the workpiece that need to be protected from etching. In this study, the main goal is to create a groove on the flat surface of a workpiece made of 100Cr6 steel using the PCM process and to investigate different variables on the dimensional and geometrical accuracy of the groove. The experiments were designed using the response surface method with a central composite methodology, involving 20 experiments and three repetitions. In this study, the effects of different variables such as time of etching, the concentration of ferric chloride (FeCl3) in the etchant solution, and the weight ratio of hydrochloric acid (HCl) to FeCl3 in the etchant solution were investigated on dimensional accuracy such as length and width error and also geometrical accuracy such as out of parallelism, out of squareness, and out of straightness. Results indicate that as the etching duration increases, the length, width, out of straightness, out of parallelism, and out of squareness also increase. This error becomes substantial with longer durations. Also, with an increase in FeCl3 concentration in etchant solution, errors in length and width, out of straightness, out of parallelism, and out of squareness reduce. The optimal variables resulting in the least possible errors were an etching duration of 10.72 minutes (10 minutes and 43 seconds), FeCl3 solution concentration of 599.64 g/L, and a weight ratio of HCl to FeCl3 in the etchant solution of 0.1. The following results on the flat surface were obtained: groove length: 3,056 µm, groove width: 625 µm, groove depth: 48 µm, and surface roughness (Ra): 1.285 µm.

Effects of a chemical dispersant on the dispersibility of Moso bamboo phytoliths in a particle-size analysis

ABSTRACT Phytoliths produced by higher plants are biogenic minerals with a wide range of particle sizes that correspond to clay, silt, and sand in mineral soil. Phytoliths supplied to soils through plants’ death function as soil particles and affect soil physicochemical properties. Investigations of the functions of phytolith particles as a subset of soil particles are facilitated by fractionation and quantification of the phytoliths based on soil particle-size distribution. Fractionation is typically conducted through particle-size analysis (PSA) methods developed for soil texture analyses. However, the effects of chemicals used to achieve particle dispersion in these methods on phytolith dispersibility remain poorly understood. The objective of this study was to examine the effects of chemical dispersants on phytolith dispersibility. Based on the results, several recommendations are provided with respect to the dispersal conditions. The phytoliths used in this study were extracted from Moso bamboo leaf litter through wet digestion and dispersed by ultrasound followed by two chemical procedures: pH control using hydrochloric acid or sodium hydroxide and the addition of sodium hexametaphosphate as a dispersant. The extent of dispersion was determined by quantifying the clay-sized fraction (<2 µm) through gravity sedimentation and the pipette method. The results showed that the content of clay-sized phytoliths in dispersions remained constant from pH 3 to 9, then increased significantly at pH 10–11, likely due to phytolith dissolution, which also led to overestimation of the clay-sized fraction. This finding demonstrated that dispersion at higher pH (>10), as is often the case in PSA methods for soils, is unsuitable for phytoliths; instead, soil particles should be dispersed at pH < 9 to avoid phytolith dissolution.

Physical and chemical oceanographic conditions of the Barents and Kara Seas according to the latest expedition data

The goal of the work: assessment of summer oceanographic conditions of the Barents and Kara Seas.Materials and methods: the data presented in the work were obtained on the 96rd cruise of the R/V «Akademik Mstislav Keldysh» (July 25, 2024–August 31, 2024). During the expedition, hydrological and chemical characteristics (temperature, salinity, dissolved oxygen, silicates, mineral and organic forms of nitrogen and phosphorus and dissolved organic carbon) were measured from the surface to the bottom. Chemical analysis was carried out in the ship’s laboratory, according to certified methods for sea and fresh waters. Dissolved organic carbon samples were using a filtration through membrane filters (0.45 μn) and fixed with hydrochloric acid for further determination using high-precision TOC–L equipment in a stationary laboratory in Moscow. In total, 13 oceanological sections and 183 complex oceanological stations were completed.The practical significance of the research: assessment of the production potential of the economically significant seas of the European Arctic for Russia in the area of maximum climate changes, replenishment of the monitoring system of hydrological and biogeochemical characteristics based on ship observations in accordance with the Order of the Government of the Russian Federation of October 29, 2022 No. 3240-r.

Effect of Ni and Nb Elements on Corrosion Resistance and Behavior of TC4 Alloy in Hydrochloric Acid

Due to the development of the petroleum industry, more severe mining conditions put forward higher corrosion resistance requirements for materials. In this paper, the corrosion resistance and corrosion behavior of four TC4-xNi-yNb (x, y = 0, 0.5) alloys were investigated in a 1 mol/L HCl solution through microscopic characterization, electrochemical tests and corrosion weight loss testing. The results demonstrated that the addition of Ni and Nb elements could improve the corrosion resistance of TC4 alloy to varying degrees. The addition of niobium formed niobium oxide in the passive film, while the addition of nickel thickened the passive film without formation of nickel oxides. The improvement of corrosion resistance of TC4 by nickel is more significant. Finally, a new highly corrosion resistant alloy TC4-0.5Ni-0.5Nb is preferred.

Effect of chitosan coating and organic acid salts on quality and shelf life of black tiger shrimp stored at 0° C

Effect of chitosan coating and organic acid salts on quality and shelf life of black tiger shrimp stored at 0° C

A novel approach to assess acid diversion efficiency in horizontal wells

Using an acid to stimulate a heterogeneous carbonate reservoir during matrix acidizing may lead to over-treating the high permeability zones, leaving low permeability zones untreated. This is particularly exacerbated in long horizontal sections, necessitating the use of acid diverters for effective acid distribution across the formation. In previous studies, conventional core flooding systems were utilized where single inlet and outlet lines were used or, at best, two outlet lines for dual-core flooding. This paper proposes a new method for simulating matrix acidizing in horizontal wells by introducing five injection points and two outlet lines. The injection points are perpendicular to the core samples to simulate multiple perforations in a horizontal well while the outlet lines are parallel. Four experiments were conducted in this study using Indiana limestone cores that were 1.5 inches in diameter. For the first three tests, the length of the core was 12 inches, and the cores’ average permeabilities were 16 mD. For the fourth one, two 6-inch length cores with different average permeability (10 and 50 mD) were employed. Hydrochloric acid was used in the first experiment, while hydrochloric acid with viscoelastic surfactant (VES) was used in subsequent experiments. To the best of our knowledge, this is the first study to introduce a multi-point injection system with enhanced coverage and distribution, resulting in a more precise representation of acidizing a horizontal well.

Properties characterization and microstructural analysis of alkali-activated solid waste-based materials with sawdust and wastewater integration

Construction materials are significantly exposed to ecological hazards due to the presence of hazardous chemical constituents found in industrial and agricultural solid wastes. This study aims to investigate the use of sawdust particles (SDPs) and sawdust wastewater (SDW) in alkali-activated composites (AACs) made from a mixture of different silicon-aluminum-based solid wastes (slag powder-SP, red mud-RM, fly ash-FA, and carbide slag-CS). The study examines the impact of SDP content, treated duration of SDPs, and SDW content on both fresh and hardened properties of the AACs, including electrical conductivity, fluidity, density, flexural and compressive strengths, and drying shrinkage. The study also analyzes the microstructures and product compositions of the AACs influenced by SDW through a comprehensive analysis of microstructures and product compositions by using XRD, SEM-EDS, and FTIR. The results show that treating SDPs with a 2.5 mol/L NaOH solution for 12 hours decreases the fluidity and electrical conductivity of the AACs but improves their flexural and compressive strengths. Additionally, in the synthesis of a composite material incorporating binder materials SP, RM, and FA in a mass ratio of 10:3:18, a 2.0 mol/L NaOH solution is employed. The liquid-to-solid ratio is maintained at 20:31, and the sand-to-binder ratio is set at 3:1. The substitution of 12.28% SDW to NaOH solution improves the resistance to drying shrinkage and long-term mechanical strength development of the AACs. Interestingly, the addition of SDW does not affect the product compositions due to the generation and decomposition of organic acid salts from organic impurities in the acidic SDW during long-term curing at room temperature. These findings provide valuable insights for the sustainable recycling of bioresources and solid wastes containing silicon-aluminum in construction materials.

Chemical Solution Mitigates Stuck Inflow Control Devices in Horizontal Completion

Summary Horizontal open holes covering long reservoir sections can be benefitted by installing inflow control devices (ICDs) along the lateral to even the production contribution from the entire heterogeneous permeability profile. During the drilling and completion process, the well can be shut in for prolonged periods of time. Though the ICDs are designed to withstand the buildup of debris, they are still subjected to the accumulation of weighting and bridging materials existing in the drilling fluid, such as calcium carbonate (CaCO3). This debris deposits on the internal diameter of the valves or the flow control device, preventing proper shifting against the seats, or blocking the flow path of the devices. Recovering the function of the ICDs requires a chemical treatment. In high-permeability formations, it is undesirable to have acid contact the rock since this may compromise the mechanical integrity of the formation or trigger further solids buildup in the ICDs. Therefore, an acid designed to dissolve the solid deposits on ICDs but not penetrating the formation is required. In this study, a modified coreflood setup was designed and an acid-based chemical treatment was formulated to remove solid deposition on the ICD. The goal was to dissolve the CaCO3 scale on the ICD with minimal penetration into the formation to avoid formation softening. The core assembly simulates the geometry of the ICD completion system with a core matrix behind the ICD operating space. Calcite marble was used to represent the scale deposited on the ICDs, while Indiana limestone was used to represent the reservoir rock. Several acid formulations were tested using the custom-designed coreflood setup. One acid blend composed of a strong organic acid [methane sulfonic acid (MSA)] mixed with hydrochloric acid (HCl) and a second blend of HCl and mutual solvent (glycol-based solvent) showed the desirable effect of dissolving the scale deposits (calcite marble in this case) with minimum to no penetration into the formation matrix. The success of the two acid systems in dissolving CaCO3 deposits on the ICDs was confirmed by analyzing the pressure data during the coreflooding experiment, as well as from analyzing the post-treated core samples using computed tomography (CT) scan. Simulation of completion design in the laboratory is a key factor in testing and designing acid treatments to overcome scale problems in the field. Single-phase acid systems containing no gelling or emulsifying agents were tested and proved capable of dissolving the solids deposited on the ICDs with minimum to no formation contact. This will result in an economical and easier one-step treatment in the field, avoiding the complexity encountered with pulling the whole completion string out of the wellbore to be treated with acid on the surface and then reinstalling it back into the well.

Investigation of silica crystallization kinetics in rice husk ash for sustainable construction materials

Concrete is one of the most widely used materials in the world, and its utilization is rising drastically with the increasing population. Around 5-8% of global carbon emissions are caused by cement production. On the other hand, approximately 160 million tons of rice husk, considered agrowaste, turn into ash annually. Rice husk ash (RHA) is particularly attractive due to its high silica content and great potential to be used as a cementitious material. However, impurities such as alkali metal oxides and uncontrolled combustion reduce the quality of silica and promote its crystallization. Numerous studies have focused on obtaining active silica through acid leaching to remove impurities, but the study on the reaction kinetics of functionalized rice husk ash is very limited. In this research, 0.1M hydrochloric acid (HCl) was used to leach rice husk at temperatures of 50°C, 60°C, and 70°C for 1.5 hours. The rice husk was then burned at 800°C for 2 hours. Subsequently, the ash was examined using various analytical and computational techniques to develop an in-depth understanding of the burning process, aimed at producing functionalized amorphous silica for sustainable construction. It was observed that 99.39% silica with 95.04% amorphous content was formed by treating rice husk with 0.1M HCl at 70°C for 1.5 hours, followed by combustion at 800°C for 2 hours. Furthermore, reaction kinetics parameters were identified using the Coats-Redfern kinetic model for the two different reaction zones of the burning process.

Combining sequential extractions with bulk and micro X-ray spectroscopy to elucidate iron and phosphorus speciation in sediments of an iron-treated peat lake.

In shallow lakes, mobilization of legacy phosphorus (P) from the sediments can be the main cause for persisting eutrophication after reduction of external P input. In-lake remediation measures can be applied to reduce internal P loading and to achieve ecosystem recovery. The eutrophic shallow peat lake Terra Nova (The Netherlands) was treated with iron (Fe) to enhance P retention in the sediment. This treatment, however, intensified seasonal internal P loading. An earlier study suggested that Fe addition led to increased P binding by easily-reducible Fe(III) associated with organic matter (OM), which readily releases P when bottom waters turn hypoxic. In this complementary study, bulk and micro Fe K-edge and P K-edge X-ray absorption spectroscopy and micro-focused X-ray fluorescence spectroscopy were applied to characterize the P hosting Fe(III) pool. Combined with sequential extraction data, the synchrotron X-ray analyses revealed that a continuum of co-precipitates of Fe(III) with calcium, phosphate, manganese and organic carbon within the OM matrix constitutes the reducible Fe(III) pool. The complementary analyses also shed new light on the interpretation of sequential extraction results, demonstrating that pyrite was not quantitatively extracted by nitric acid (HNO3) and that most of the Fe(II) extracted by hydrochloric acid (HCl) originated from phyllosilicate minerals. Formation of an amorphous inorganic-organic co-precipitate upon Fe addition constitutes an effective P sink in the studied peaty sediments. However, the high intrinsic reactivity of this nanoscale co-precipitate and its fine distribution in the OM matrix makes it very susceptible to reductive dissolution, leading to P remobilization under reducing conditions.