Bicarbonate Solution Research Articles

Study on Preparation and Heat Insulation Properties of Solidified Foams for Forest Fire Prevention and Control

ABSTRACT For effective prevention and control of forest fires, a new type of solidified foam was prepared by using composite foaming agent, foam stabilizer, sodium silicate, sodium bicarbonate solution, loess and cement as raw materials. The optimal ratio of solidified foam surfactant, foam stabilizer, gel agent, crosslinking agent and powder was investigated experimentally. Its thermal insulation performance was tested and its thermal insulation mechanism was analyzed. The results showed that when the surfactant ratio was SDS: AES = 2:1, the concentration was 0.8%, the concentration of foam stabilizer dodecyl alcohol, gelling agent WG and crosslinking agent NaHCO3 were 0.08%, 10% and 2%, respectively. When the powder ratio is loess: cement = 4:6, water-cement ratio 0.6 and foam content 8 V, the comprehensive performance of solidified foam is the best. The solidified foam is heated at different temperatures, and the temperature rise is the slowest. When it is heated at 400°C, the highest temperature is 71.92°C, which is 75.89°C lower than the highest temperature of gel foam. The fire retardant material has excellent stability and can block heat for a long time. In the process of fire extinguishing, it can effectively isolate oxygen, reduce heat transfer efficiency, and inhibit the spread of fire.

Influence of Coir Fibre Preparation on Mechanical Properties of Coir Fibre/Epoxy Resin Composites

Polymer composites have been utilized across various industries, especially in transportation, for many years. With a growing emphasis on sustainable production resources, the industry increasingly favours composite materials reinforced with natural fibres or particles. Unlike conventional fibres such as glass, carbon, or aramid, natural fibres typically have low compatibility with polymer matrices, often necessitating pretreatment to enhance bonding. In this study, coir fibres were physically and chemically treated with sodium bicarbonate solutions at varying concentrations (5–15%) and immersion durations (0–5 days). The treated fibres were then mixed into epoxy resin and poured into moulds to produce test specimens for evaluating mechanical properties. The fibre content in the composites ranged from 10 to 20%. Statistical analysis revealed that immersion time significantly affects all mechanical properties tested (tensile modulus, tensile strength, strain, and impact strength). Solution concentration significantly influences tensile modulus and strain, while fibre content significantly affects tensile modulus and strength. The conducted optimization shows that the best mechanical properties are achieved with the minimum tested coir fibre content of 10%. Maximum stiffness and strength can be expected with the longest immersion time of 5 days in the highest solution concentration of 15%. The best strain and impact strength properties, however, are observed at the lowest solution concentration of 5%.

Electrochemical exfoliation of graphite using aqueous ammonium hydrogen carbonate solution and the ability of the exfoliated product as a hydrogen production electrocatalyst support

Electrochemical exfoliation of graphite has attracted much attention as a practical mass production of two-dimensional graphene-like materials. There is an increasing desire to find new and improved methods to create unique exfoliated products with excellent functionality. We used aqueous ammonium hydrogen carbonate solution as a new electrolyte for anodic oxidative exfoliation of graphite. The exfoliated product has a porous two-dimensional structure, and it can be dispersed in water for over five years. The oxidized and defected porous surface serves as an ideal support for molecular metal complexes, effectively functioning as heterogeneous electrocatalysts for hydrogen production.

Chloride removal and bicarbonate replacement by isotonic sodium bicarbonate-based continuous hemodiafiltration: a novel method to correct severe metabolic acidosis.

Previous reports highlighted the efficacy of hemofiltration utilizing isotonic sodium bicarbonate solution as replacement fluid for severe metabolic acidosis. This approach corrects metabolic acidosis by eliminating chloride and supplementing bicarbonate. Here, we present the results of an in vitro study aimed at determining the effect of Isotonic sodium bicarbonate-based Continuous HemoDiafiltration (IBB-CHDF). Conventional Continuous HemoDiaFiltration (CHDF) and IBB-CHDF utilized aqueous solutions mimicking blood's electrolyte composition. To assess the efficacy and safety, we compared serial changes in pH, HCO3-, Na+, and K+ concentrations. Blood flow rate was 100mL/min, and the dialysis fluid flow rate maintained 1.0 L/h for both CHDF and IBB-CHDF. Replacement flow rates ranged from 0.5 to 1.5 L/h for CHDF and 0.1 to 1.5 L/h for IBB-CHDF. At a replacement flow rate of 0.5 L/h with IBB-CHDF, bicarbonate increased from 14.7 mEq/L to within the physiological range (25.9mEq/L), whereas in conventional CHDF, the post-treatment bicarbonate concentration did not increase (16.5mEq/L). The maximum bicarbonate concentration achieved was 22.0mEq/L at a replacement flow rate of 1.5 L/h in conventional CHDF. Notably, in IBB-CHDF, the sodium concentration remained constant at 150mEq/L, 10mEq/L higher than conventional CHDF, and did not escalate despite increasing the replacement flow rate. IBB-CHDF effectively corrects metabolic acidosis without inducing sodium and water overload by eliminating excess chloride while providing bicarbonate.

Synergistic Effect of Influence Factors on Ammonia Volatilization in Fertilizer Solution: A Laboratory Experiment

Ammonia volatilization, which is one of the main ways that nitrogen gas is released from farmland, restricts promotion of the utilization of nitrogen fertilizer and contains some potential environmental risks. To investigate the general pattern of ammonia volatilization under actual paddy field conditions, we designed an indoor simulated system to measure the amount of ammonia volatilized within a single time period by controlling the pH and concentration of NH4+ (c(NH4+)) in the solution, the gas–liquid interfacial gas velocity, and the ambient temperature. In this paper, the influence of these factors, the synergistic effect on ammonia volatilization, and their quantitative relationship are discussed. We used solutions of ammonium bicarbonate (SAB) and diammonium phosphate (SDP) for the simulation experiments, and the results showed that there is a significant linear relationship between the amount of ammonia volatilization and c(NH4+). The correlation coefficients were between 0.9214 to 0.9897 and 0.8932 to 0.9904 for SAB and SDP, respectively. The quantitative relationship between temperature and pH and the influence factor (CIF) and the initial ammonia volatilization fluxes (IAVFs) was analyzed by the least-squares method, and the degrees of polynomial were one and two, respectively. The regression equations of the SAB and SDP among the amount of ammonia volatilization with the concentration of ammonium nitrogen, the temperature, and the pH were calculated by using MATLAB. Considering the effects of temperature and pH on the CIF and IAVFs under individual conditions, we used a binary cubic model to fit the relationship between temperature and pH to the CIF and IAVFs. The simulation results showed that the correlation coefficients between the CIF and IAVFs for SAB were 0.9980 and 0.9680, respectively, and the correlation coefficients were 0.9946 and 0.9708 for SDP, respectively. The quantitative equation took into account the coefficient of determination and degrees of polynomial, and the ammonia volatilization fluxes can be calculated by using these equations.

Computational evaluation of phosphonium ILs as CO2 absorbents for electrochemistry

Since phosphonium-based ionic liquids (ILs) are suitable electrolytes for electrochemical reduction, a computationally informed analysis of these ILs was conducted to assess their ability to absorb CO2. In this work, theoretical and experimental approaches were mixed with a focus on gas solubility, transport properties, and structural characterization. The calculations included free energy of solvation (ΔG), the Henry constant (Kh), and short-range energies (Coulomb plus Lennard–Jones). Two ILs, [P1444][TFSI] and [P1444][FSI], were selected for further evaluation because of their lower Kh values. The enthalpy and entropy of the solvation process for these selected ILs were computationally determined; both ILs were found to have a favourable enthalpy of solvation for gas dissolution, and [P1444][TFSI] had a lower penalty for solvation (less negative entropy). Moreover, the analysis revealed competition among the ions interacting with the gas. The structural characterization of the [P1444][TFSI] and [P1444][FSI] with the CO2 systems involved radial and spatial distribution functions. The gas was likely enveloped by an anion cage, and oxygen and fluorine exhibited greater interactions with the carbon atom of CO2 than nitrogen. The viscosity and density were also calculated for the two systems, and the addition of CO2 only caused a slight change on these values. Experiments on viscosity and density confirmed the computational results; here, compared with those of neat ionic liquids, an approximate 4 % decrease in the viscosity of CO2-saturated systems was observed. Finally, the actual CO2 solubility in [P1444][TFSI] was experimentally determined to be 120 mM; this value was nearly four times greater than those of typical aqueous bicarbonate solutions.

Electrochemical Deterioration of a Gold Thin Film in Bicarbonate Solution: Correlative Optical, Nano-Mechanical, and Chemical Considerations.

The electrochemical dissolution of metals in liquid electrolytes is of great concern for various electrochemical technologies. However, it is also the focus for boosting metal recovery processes, e.g., from electronic wastes, one of which is the extraction of gold (Au) using eco-friendly electrolytes. To shed more light on the possibility and improvement of such metal leaching, this work presents the investigation of electrochemical deterioration of a Au nanofilm coated on a silicon (Si) support─ubiquitous materials in electronic components─in aqueous potassium bicarbonate (KHCO3) electrolyte, a solution widely used in food products. In addition to the time-dependent in situ Raman spectra revealing the reduced reflectivity of Au associated with its molecular degradation, the significant role of the electric double layer (EDL) at the metal/electrolyte interface is also indicated. Analyzing surface adhesion maps and force-distance spectra acquired using atomic force microscopy and spectroscopy (AFM/AFS), metal degradation is related to nanoscale worm-shaped reconstructed surface features that act as local sites of reduced refractive index. Complemented by the non-negligible fraction of K observed on the treated Au surfaces using scanning electron microscopy and energy dispersive spectroscopy (SEM/EDS), an electrochemical framework of metal degradation is proposed, depicting the electric-field-induced transport of K+ and H+ ions toward the Au surface regardless of bias polarity and implying the formation of ternary gold hydrides. The consideration of faradic current in the EDL circuit also suggests the occurrence of ternary gold oxides. Such determination is reinforced by the attributability of the polar and electrostatic characteristics of the worm-like features to residual negatively charged anionic clusters of the hydrides and the oxides. The analysis process and the new understanding of metal degradation provide a potential route for inspecting other metal/solution systems.

Composite of Hydrolyzed PAN and β-Cyclodextrin Forms a Nanofiber Membrane with an Excellent Removal Effect on Various Cationic Dyes and Copper Ions.

The presence of dyes and heavy metals in wastewater represents a significant environmental and public health hazard, necessitating the development of efficient materials for their removal. In this study, we modified hydrolyzed polyacrylonitrile (PAN-H) and combined it with β-cyclodextrin (β-CD) by using an electrostatic spinning technique to fabricate composite nanofibrous membranes for water treatment applications. The resulting PAN-H/β-CD nanofiber membranes exhibit spindle-shaped fibers and porous structures with a high density of charged functional groups, which significantly enhance their selective adsorption capacity compared to pure PAN fibers. Furthermore, post-treatment with a sodium bicarbonate solution further improved this capacity, resulting in the membranes demonstrating a remarkable adsorption efficiency for cationic dyes. The adsorption process conformed to the Langmuir and pseudo-second-order kinetic models, with maximum adsorption capacities of 216.94 mg/g for methylene blue (MB), 471.59 mg/g for malachite green (MG), 299 mg/g for crystal violet (CV), and 43.95 mg/g for copper ions. The selective adsorption of these positively charged contaminants, particularly cationic dyes and metallic copper, indicates that PAN-H/β-CD membranes have significant potential for the treatment of wastewater containing similar pollutants.

Investigating reactive transport and precipitation patterns of calcium carbonate in fractured porous media

HypothesisUnderstanding calcium carbonate (CaCO3) precipitation in various polymorphs from nanoparticle size (amorphous calcium carbonate) to microparticle size (vaterite, aragonite, dendrite, calcite) is important for practical applications, including carbon geo-storage (e.g., basalt formations), hydrogen storage, groundwater management, and soil stabilization. Our hypothesis suggests that the interplay of Péclet numbers (Pe), Damköhler numbers (Da), and Supersaturation Index (SI) significantly impacts the evolution of CaCO3 precipitation in fractured porous media in terms of mixing patterns, spatiotemporal evolution, crystal morphology, crystal size, and clogging behavior. ExperimentsThis study takes a novel approach to explore the colloidal formation and precipitation dynamics of CaCO3 within a fractured microfluidic system. Here, calcium chloride (CaCl2) and sodium bicarbonate (NaHCO3) solutions were injected and reacted under varied Pe (0–11), Da (0–1), and SI (2–5). FindingsOur analysis revealed distinct precipitation patterns and mixing types, such as transverse, longitudinal, and incomplete mixing, providing insights into the behavior in fractured porous media. We systematically analyzed the temporal and spatial evolution of precipitation, demonstrating how Pe, Da, and SI dictate precipitation rates and spatial distribution. Additionally, the study uncovered a range of CaCO3 polymorphic forms, illustrating their evolution and coexistence. Morphological changes and crystal sizes were examined to decode nucleation and growth processes. Significantly, our findings highlight the relationship between precipitation and clogging in the fractured medium, offering a deeper understanding of reactive transport in complex porous environments. These insights are crucial for enhancing carbon containment security and storage efficiency in underground formations, improving groundwater remediation techniques, and developing novel construction materials through controlled precipitation processes.

Mechanical, free vibration, electrical, and water absorption properties of vinyl ester composites reinforced with Phoenix sp. fibers: Influence of eco‐friendly sodium bicarbonate treatment

AbstractEnvironmentally sustainable and eco‐friendly natural fiber‐reinforced polymer composites have become the materials of interest in replacing synthetic fibers. However, weak interfacial interaction between hydrophilic natural fibers and hydrophobic polymer matrix limits their commercial applicability. Improving the interfacial interaction using environmentally friendly chemical treatments would be beneficial for both industries and the environment. In this study, vinyl ester‐based composites were made by incorporating Phoenix sp. fibers in different content (5, 10, 15, 20, and 25 wt%) and lengths (5, 10, 15, and 20 mm). To improve the interfacial interactions, the fibers were treated with eco‐friendly sodium bicarbonate solution at different durations (24, 120, and 240 h) prior to reinforcing. The fabricated composites were characterized by mechanical, free vibration, electrical resistance, and water uptake properties. The results reveal that both fiber content and fiber length have a significant effect on the above properties. Specifically, the composites incorporated with 20 wt% of 15 mm length fibers offered better properties. Further, the composites added with 120 h treated fibers have the maximum tensile strength (61.35 MPa) and modulus (4.13 GPa), flexural strength (152.63 MPa) and modulus (10.24 GPa), impact strength (24.67 kJ/m2), and natural frequency (56.72 Hz). This improvement is mainly due to the improved interfacial bonding, which was evidenced in morphological analysis. Based on the findings, the eco‐friendly treated sustainable Phoenix sp. fibers could be used as a promising reinforcement material for fabricating light weight polymer composites for various industrial applications.Highlights Various properties of Phoenix sp. fiber/epoxy composites were investigated. Interfacial bonding is enhanced through eco‐friendly chemical treatments. Vibration behavior of composites improved due to high stiffness of treated fibers. Composites with treated fibers have excellent electrical and water resistance.

Safety and pharmacokinetic properties of a new formulation of parenteral artesunate in healthy Thai volunteers

BackgroundParenteral artesunate is the first-line therapy for severe malaria. Artesunate, in its current formulation, must be prepared immediately before administration by first dissolving in sodium bicarbonate solution and then diluting in saline. A novel solvent for rapid and stable single step reconstitution of artesunate was recently developed showing improved solubility and stability. This study aimed to compare the safety and pharmacokinetic properties of the currently available and newly developed parenteral formulation of artesunate in healthy Thai volunteers.MethodsThis was an open-label, randomized, 4 periods, 4-treatments, 24-sequence, single-dose, cross-over study in 72 male and female healthy Thai volunteers. Frequent pharmacokinetic samples were collected in all volunteers at each dose occasion. Observed concentration–time profiles were analysed with a non-compartmental approach followed by a bioequivalence evaluation.ResultsBoth intramuscular and intravenous administrations of the new parenteral formulation of artesunate were safe and well-tolerated, with no additional safety signals compared to the currently used formulation. The pharmacokinetic properties of artesunate and its active metabolite, dihydroartemisinin, were well-characterized, and showed rapid conversion of artesunate into dihydroartemisinin. Intramuscular administration of the newly formulated artesunate resulted in almost complete bioavailability of dihydroartemisinin. The pharmacokinetic properties were similar between the old and new formulation.ConclusionsThe new and more easily prepared formulation of artesunate was safe and well-tolerated, with similar pharmacokinetic properties compared to the currently used formulation. Dihydroartemisinin, the active metabolite responsible for the majority of the anti-malarial effect, showed equivalent exposure after both intravenous and intramuscular administration of artesunate, suggesting that both routes of administration should generate comparable therapeutic effects.Trial registration: The study was registered to clinicaltrials.gov (#TCTR20170907002).

Preservation Potentials of Siderite in Low‐Temperature Brines Relevant to Mars

AbstractThe scarce carbonate record on the Martian surface is one of the fundamental unsolved issues for paleoclimate and environmental evolution. Whether carbonates first formed and then dissolved due to a transition in global environments or whether Mg–Fe carbonates never extensively formed due to geochemical kinetics thresholds remains unknown. In this study, we experimentally examined the preservation potential of siderite in Mars‐relevant fluids, including ultrapure water, H2O2, NaClO4, NaClO3, NaCl, Na2SO4, NaHCO3, and Na2SiO3 solutions, at 277 K. The effects of the water/rock ratio at WR10 and WR100 on dissolution rates were also investigated. We found that siderite dissolution and subsequent oxidation and hydrolysis of leached Fe did not substantially acidify the solutions. The siderite dissolved relatively rapidly in the chloride and chlorate solutions and slowly in the silica or bicarbonate solutions. In a circum‐neutral to slightly alkaline aqueous environment with oxidative species, the mobility of leached Fe was limited, leading to the formation of goethite or lepidocrocite, which clustered on the siderite surface. The longest lifetime of 1‐mm siderite grains was found in the Na2SiO3 solution at WR100, which was estimated to range from 198 ka to 198 Ma. Water‐limited, silica‐rich, and oxidative aqueous environments benefit siderite preservation on the Martian surface. Our results support that the lack of voluminous siderite on Mars may be primarily due to the inhibition of its formation rather than alteration and dissolution after its presence, consistent with the recent detection of Mg–Fe carbonate at Gale Crater and Jezero Crater.

Analysis of wettability and contact angle of sodium bicarbonate impregnated wooden surfaces

Scots pine and spruce wood samples were vacuum impregnated with 3, 5, and 9% sodium bicarbonate solution. Contact angle measurements were made by dropping 0.05 mL of pure water and 3% saltwater solution onto the material’s surface. The surface roughness of each sample was measured, and that of Scots pine control samples was higher than that of spruce samples, but the surface roughness values of spruce wood were higher in the samples impregnated with sodium bicarbonate. When pure water or saltwater solution was dropped onto the samples, it was observed that as the waiting times increased, the contact angle value decreased, the droplet height decreased, and the droplet width increased. It was found that the contact angles were higher in the control samples of both tree species than in the samples of 5% and 7%. The contact angles of 9% impregnation solution, pure water, and salt water were higher than the control samples. As the solution ratio increased on the surfaces impregnated with sodium bicarbonate, the contact angle also increased, and the wettability behavior decreased accordingly. Sodium bicarbonate solution is effectively used in the impregnation process for pine and fir woods, making the materials more resistant to water under outdoor conditions. This solution significantly reduces the risk of deformation of wood by increasing the contact angle and reducing its water absorption properties.

Cobalt(II) Complex Constructed from Pyrazinecarboxamide and Aromatic Carboxylic Acid: Synthesis, Single Crystal XRD Along with Computational Study

A cobalt (II) mononuclear complex was synthesized by two-nitrobenzoic acid and pyrazine-two- carboxamide ligands in the presence of sodium bicarbonate and aqueous solution of cobalt acetate tetrahydrate. The synthesized cobalt(II) complex was characterized by single crystal X-rays diffraction. The coordination geometry of the cobalt complex was octahedral with water molecules occupying the axial sites. A lot of intermolecular interactions were in response to stabilize the supramolecular assembly which were inspected by Hirshfeld surface analysis. Enrichment ratios were calculated to find the pair of atoms having the highest propensity to form crystal packing interactions. Void analysis was conducted to forecast how the crystal would respond to applied stress. Interaction energy calculations were carried out using the B3LYP/6-31G(d,p) electron density model to identify which energy types most significantly contributed to the supramolecular assembly. Moreover, the energy data obtained from DFT calculations showed an average level of stability of the molecule. The moderate HOMO-LUMO energy gap suggested reactivity, while a high electrophilicity index indicates a strong tendency for electron-accepting reactions.

Development of Enteric Diclofenac Sodium Microparticles Through a Spray-Drying Process Facilitated by Different Aqueous Dispersion Systems

The objective of this study was to prepare enteric diclofenac sodium microparticles using an aqueous dispersion system via spray-drying. Two aqueous-based solvent systems, phosphate buffer at pH 7.0 and ammonium hydrogen carbonate solution, were employed as the feed dispersion media in the spray-drying process based on the solubility characteristics of Eudragit® L100. At a drug-to-polymer ratio of 1:1, the optimal solids concentration in the feed dispersion was determined to be 2% w/v, as it enabled an approximately 5-30 µm smooth-surfaced spherical microparticle with a high production yield. Diclofenac sodium was efficiently encapsulated within the microparticles, existing as solid dispersion in a partially amorphous form. Notably, the spray-drying conditions utilized in this study obviated the need for further heating for microparticles prepared using ammonium hydrogen carbonate solution, as the residual ammonium could be completely eliminated during the spray-drying process. The two-stage biorelevant drug release profile of enteric microparticles demonstrated their ability to inhibit drug dissolution under acidic conditions while facilitating drug release under basic conditions. The phosphate buffer-based microparticles exhibited greater protection efficiency under acidic conditions compared to ammonium hydrogen carbonate-based systems, despite residual alkaline salt being present in the microparticles. These results validate the potential of the developed microparticles for use as an enteric drug delivery system.

Effect of static magnetic field on corrosion of X70 pipeline steel in dilute sodium bicarbonate solutions

This paper focuses on the effect of a 0.1 T static horizontal magnetic field on the corrosion of X70 pipeline steel in 0–0.05 mol/L sodium bicarbonate solutions. The weight loss data indicate that the magnetic field reduces the average corrosion rate during immersion within 48 h in all the test solutions. The magnetic field tends to increase the average corrosion rates for the immersion time of 72 h and 96 h. The magnetic field increases the proportion of magnetite in corrosion products formed on the specimen of immersion in 0.05 mol/L sodium bicarbonate solution for 168 h. The open-circuit potentials (OCP) are in the active zone of the E-pH diagram within 48 h immersion with 0 T and 0.1 T magnetic field. A 0.1 T magnetic field delays the process for the electrode to enter the passive zone of the E-pH diagram. The linear polarisation resistance (LPR) data shows that the resistance of the active zone with 0.1 T magnetic field is larger than that with 0 T. The electrochemical impedance results also indicate that the electrode is in an active state when the potential is below −700 mVSCE and in a passive state when the potential is above −200 mVSCE.

Functional and mechanistic assessment of plant-available soil phosphorus greatly improved the multisite diagnosis of maize yield response

Context or problemPlant-available soil phosphorus (P) is commonly assessed by chemical extractions with the purpose of diagnosing and advising fertilizer P application. However, for a given crop, this approach only poorly predicts yields obtained from several experimental sites. To solve this major drawback, a functional and mechanistic evaluation has been developed to mimic dominant processes involved in the absorption of phosphate ions. Objective or research questionIn this study, we investigated the predictive ability of a mechanistic approach to diagnose maize (Zea mays L.) yields, in comparison to the common Olsen's method (0.5 M bicarbonate solution). MethodsThe processes-based assessment consists of parameterizing relationships between amount of diffusible phosphate ions (Pr) at the solid-to-solution interface equilibrating the phosphate ions concentration in solution (CP) with time (t). We parameterized [Pr vs. (CP, t)] relationships for stored and archived soil samples (plough layer) of nine long-term field experiments (LTFEs) on increasing rates of P applications including the zero-P treatment (P0). LTFEs were located in different soils (Luvisol, Podzol, Arenosol, Calcosol) with large variations in physico-chemical properties. We also used LTFEs database of maize yields. ResultsThe CP values ranged from 0.02 to 3.86 mg P L−1 for 40 (LTFE×year of maize cropping) combinations. The (Pr=v×CPw×tp) equation closely described the [Pr vs. (CP, t)] datasets, with (v, w, p) parameters being soil specific. Maximum yields ranged from 5.5 to 14.7 t DM ha−1 depending on LTFEs and years. Yields decreased significantly only in P0, and did not differ for other P rates. The relationship between the relative maize yield and CP was sites-specific with CP thresholds to obtain a relative yield of 0.95 ranged from 0.07 to 0.88 mg P L−1 solution. Taking into account amounts of phosphate ions which balance CP by diffusion using (Pr=v×CPw×tp) equations, a single response curve is observed for the 9 LTFEs when the replenishment time is 1500 minutes (i.e. about one day). The critical CP thresholds closely correlated to the ability of the soil solid phase to buffer phosphate ions in solution. ConclusionsFor the 9 studied LTFEs on P fertilization, the [Pr vs. (CP, t)] relationships were more able to account for maize response curves than P extracted by Olsen method, improving the precision and reliability of the multisite diagnosis of maize yield response. Implications or significanceAs a result, P fertilization recommendations are more reliable regardless of soil type. Further progress could be gained by taking into account for the role of the soil layer beneath the plough layer.

Binary aqueous solutions of choline salts: Determination and modelling of liquid density (298.15 or 313.15 K) and Vapour Pressure Osmometry (313.15 K)

Salts composed of the cholinium cation (such as choline hydroxide and choline chloride) have become one of the main reactants for the synthesis of greener ionic liquids, but, for a proper description of the aqueous solutions of these strong electrolytes by thermodynamic modelling, reliable data on liquid density (ρ) and vapour pressure (p) are needed, which are often unavailable. So, in this work, the liquid density (ρ) of binary aqueous solutions of choline bicarbonate ([Ch][Bic]), choline (2R,3R)-bitartrate ([Ch][Bit]), choline chloride ([Ch]Cl), choline dihydrogen citrate ([Ch][H2Cit]) and choline hydroxide ([Ch]OH) were measured at 298.15 or 313.15 K and 0.1 MPa and correlated using second-degree polynomials with salt molality (m), obtaining determination coefficients (R2) higher than 0.9974. Furthermore, the osmotic coefficients (ϕ) of these binaries were determined using vapour pressure osmometry (VPO), at 313.15 K and 0.1 MPa, being satisfactorily described by the Extended Pitzer Model of Archer, which yielded low values of standard deviation (3.58<σϕ·103<12.86). Then, the mean molal activity coefficients (γ±) and excess Gibbs free energies (GE/RT) were calculated, following the order [Ch][H2Cit] > [Ch][Bit] > [Ch][Bic] > [Ch]OH > [Ch]Cl, which corresponds to the decreasing polarity of the choline salts and agrees with the empirical law of matching water affinities (LMWA).

Leaching phosphorous from the lime mud of kraft pulp mills: Towards sustainability

AbstractThe optimum conditions needed to separate phosphorus from the lime mud generated in kraft pulp mills were identified using different leaching solutions including carbonate, bicarbonate, and green liquor under variety of conditions. Carbonate ions seemed to be the active ion in the phosphorus leaching process. Bicarbonate solution seems to be the most effective leaching agent by removing 84% of phosphorus under the optimum operating conditions of 95°C, 2.92 m, and solution‐to‐ mud mass ratio of 3.6. The shrinking core model was used to determine the leaching mechanism and it showed that the leaching process is controlled by a mix of chemical reaction and diffusion through the particle. Two empirical models were developed to predict the leaching efficiency as a function of carbonate concentration and temperature. Counter‐current leaching was shown to be beneficial in increasing the leaching efficiency with the carbonate solutions.

Optimization of Hydrochemical Leaching Process of Kaolinite Fraction of Bauxite with Response Surface Methodology

A technology for the hydrochemical processing of the kaolinite fraction of bauxite has been developed, and it involves preliminary chemical activation in a sodium bicarbonate solution and alkaline leaching in a recycled high-modulus solution with the addition of an active form of calcium oxide. Chemical activation allows for the transformation of the difficult-to-explore kaolinite phase to form easily soluble phases of dawsonite, sodium hydroaluminosilicate and bemite. An active, finely dispersed form of calcium oxide was obtained as a result of CaO quenching in Na2SO4 solution at elevated temperature and pressure. Using a central composite design (CCD) via response surface methodology (RSM), the technological leaching mode was achieved. The influence on the leaching process was studied by adjusting the CaO/SiO2 ratio, temperature, alkaline solution concentration and duration. It was found that the determining factors are the concentration of the leaching solution and the temperature. At a stable CaO/SiO2 ratio, a combination of these two factors determines the duration of the process to achieve the predicted degree of recovery. The results of experiments carried out using the developed model of the leaching process confirmed the validity of the calculated indicators, with an error of 2.01%. In an optimal technological mode at a Na2O leaching solution concentration of 260 g/L, a temperature of 260 °C, a CaO/SiO2 ratio of 1.5 and a leaching time of 5 h, the extraction of Al2O3 into the solution was 89.7%, which is close to the value of 87.9% predicted by the model.