Acid Dissolution Research Articles

Comparing MICADAS Gas Source, Direct Carbonate, and Standard Graphite 14C Determinations of Biogenic Carbonate

AbstractNorthern Arizona University, Flagstaff, Arizona, USA, recently installed a MIni CArbon DAting System (MICADAS) with a gas interface system (GIS) for determining the 14C content of CO2 gas released by the acid dissolution of biogenic carbonates. We compare 48 paired graphite, GIS, and direct carbonate 14C determinations of individual mollusk shells and echinoid tests. GIS sample sizes ranged between 0.5 and 1.5 mg and span 0.1 to 45.1 ka BP (n = 42). A reduced major axis regression shows a strong relationship between GIS and graphite percent Modern Carbon (pMC) values (m = 1.011; 95% CI [0.997–1.023], R2 = 0.999) that is superior to the relationship between the direct carbonate and graphite values (m = 0.978; 95% CI [0.959-0.999], R2 = 0.997). Sixty percent of GIS pMC values are within ±0.5 pMC of their graphite counterparts, compared to 26% of direct carbonate pMC values. The precision of GIS analyses is approximately ±70 14C yrs to 6.5 ka BP and decreases to approximately ±130 14C yrs at 12.5 ka BP. This precision is on par with direct carbonate and is approximately five times larger than for graphite. Six Plio-Pleistocene mollusk and echinoid samples yield finite ages when analyzed as direct carbonate but yield non-finite ages when analyzed as graphite or as GIS. Our results show that GIS 14C dating of biogenic carbonates is preferable to direct carbonate 14C dating and is an efficient alternative to standard graphite 14C dating when the precision of graphite 14C dating is not required.

Effects of microbially induced calcite precipitation on static liquefaction behavior of a gold tailings sand

Loose tailings are susceptible to static liquefaction during which they lose a substantial amount of their strength. This study examines a sustainable technique known as Microbially-Induced Calcite Precipitation (MICP) to improve the static liquefaction resistance of gold mine silty sand tailings. These materials were enriched with Sporosarcina pasteurii, consolidated in a direct simple shearing apparatus, and subjected to several injections of a cementation solution. Calcified tailings were then sheared under constant-volume and constant vertical stress conditions to evaluate their undrained and drained shearing behaviors. Results showed that bio-mineralization can prevent the occurrence of static liquefaction in tailings by reducing their contraction tendency. This is demonstrated by the strong strain-hardening behaviors of the treated tailings specimens compared to the strain-softening and undrained strength loss in specimens of the untreated tailings. Substantial increases in the tailings undrained and drained shear strengths (by up to 30 - 50 kPa), improvements (by up to 5 MPa) in their tangent moduli, and more than 5° rise in their friction angles are observed in the direct simple shear tests following MICP-treatment. The critical state line of tailings is also found to be steeper and shifted to denser void ratios following MICP treatment. These changes reduce liquefaction susceptibility of tailings and enhance their resistance against static liquefaction. Post-treatment acid dissolution further indicates that CaCO3 contents of about 4% to 11% precipitated in the treated specimens. This amount decreases with increasing specimens void ratio. Changes in the microstructural fabric of the cemented tailings particles are also characterized using scanning electron microscopic (SEM) images and X-ray diffraction (XRD) analyses.

In situ detection of spatial distribution information of temperature-pH-strain of sandstone cultural relics

To monitor in situ the temperature, pH, and micro-strain change information of sandstone artifacts in the process of oxalic acid corrosion, the temperature, pH, and micro-strain fiber Bragg grating (FBG) sensors are developed. A theoretical model of the sensors is established. The surface morphology, material composition, pore structure, temperature, pH, and micro-strain of sandstone corroded by oxalic acid solutions of different concentrations are investigated. The experimental results show that the higher the concentration of oxalic acid, the stronger the corrosiveness of the sandstone. Ferrous oxalate and calcium oxalate produced by corrosion continuously precipitate from the inside of the rock, and the dual reaction of crystallization and dissolution occurs, reducing the proportion of fine pores in the rock pore suction and gravity. The oxalic acid solution is transported to the middle of the sandstone (3 cm) and undergoes the strongest chemical reaction with ore particles and debris, resulting in the maximum wavelength drift of the temperature, pH, and micro-strain sensors. The results of this study provide important support for analyzing the acid dissolution mechanism of stone cultural relics and the preventive protection of cultural relics.

Kinetics of Estonian Phosphate Rock Dissolution in Hydrochloric Acid

The kinetics of the dissolution of Estonian phosphate rock and the governing reaction mechanisms in hydrochloric acid in technological processes were investigated. The influences of particle size and acid concentrations of 0.5–1.5 M on the reaction rate and the pH variation during the process were studied at a dosage of 2.1 moles of HCl per mole of calcium for 60 min. The results indicated that the solubility of phosphorus reached 94%–100% for the fine samples and 82%–99% for the coarse samples. The time required to achieve an apparent steady-state pH reduced with the increasing acid concentrations and decreasing particle sizes. It was determined that the CaF2 precipitation in solutions starting at 1 M was faster at higher concentrations. The SEM surface analysis of the insoluble particles proved the existence of etch pit formation. The XPS and EDX analyses affirmed that the dissolution was incongruent. The surface composition of the unreacted particles gave a stoichiometry of CaF1.8, showing the formation of CaF2 on the surface. The dissolution kinetics were analyzed using the shrinking core model and showed a combination of chemical reaction, diffusion or interfacial transfer, and diffusion, sequentially for coarse particles or simultaneously for fine fractions.

Determination of triazole fungicides in soybeans with cobalt-enhanced lanthanide metal chloride anion magnetic deep eutectic solvents in-situ dispersion extraction

In this work, we synthesized a series of magnetic deep eutectic solvents (MDESs) with lanthanide metal chlorides as paramagnetic metal centers and developed a reversed-phase dispersive liquid–liquid microextraction method (DLLME) based on the in-situ dispersion of MDESs for the extraction and preconcentration of triazole fungicides (TFs) from bean samples. Different MDESs were synthesized by combining quaternary ammonium salts, short-chain carboxylic acids, and lanthanide metal chlorides. The dissolution of short-chain carboxylic acids in n-hexane led to the in-situ dispersion of MDESs to replace the toxic dispersant of traditional DLLME species and shorten extraction time. Cobalt powder was added to encapsulate MDESs to enhance the magnetic properties after the extraction and achieve the purpose of easy phase separation. Notably, the highest extraction efficiency of TFs was observed in the MDES formed by tetrabutylammonium bromide, propionic acid, and gadolinium chloride in a ratio of 1:10:0.06. We optimized various parameters that affected the extraction efficiency of the method, including volume of MDES, extraction time, amount of cobalt powder, and volume of elution solvent. Under the optimal conditions, the detection limits (LODs) and quantification limits (LOQs) of the technique varied between 0.097–0.13 ng·g−1 and 0.32–0.43 ng·g−1, respectively. To assess the accuracy, the method was tested with samples spiking at three concentration levels, and the obtained results revealed that the recovery rates varied from 88.97–113.7%. To summarize, this study represents the initial application of in-situ dispersed lanthanide metal chloride anion-MDESs for analyzing bean samples and the proposed DLLME technique is rapid, straightforward, and efficient.

Remediation of multifarious metal ions and molecular docking assessment for pathogenic microbe disinfection in aqueous solution by waste-derived Ca-MOF.

The present study demonstrates an eco-friendly and cost-effective synthesis of calcium terephthalate metal-organic frameworks (Ca-MOF). The Ca-MOF were composed of metal ions (Ca2+) and organic ligands (terephthalic acid; TPA); the former was obtained from egg shells, and the latter was obtained from processing waste plastic bottles. Detailed characterization using standard techniques confirmed the synthesis of Ca-MOF with an average particle size of 461.9 ± 15nm. The synthesized Ca-MOF was screened for its ability to remove multiple metal ions from an aqueous solution. Based on the maximum sorption capacity, Pb2+, Cd2+, and Cu2+ ions were selected for individual parametric batch studies. The obtained results were interpreted using standard isotherms and kinetic models. The maximum sorption capacity (qm) obtained from the Langmuir model was found to be 644.07 ± 47, 391.4 ± 26, and 260.5 ± 14mgg-1 for Pb2+, Cd2+, and Cu2+, respectively. Moreover, Ca-MOF also showed an excellent ability to remove all three metal ions simultaneously from a mixed solution. The metal nodes and bonded TPA from Ca-MOF were dissociated by the acid dissolution method, which protonated and isolated TPA for reuse. Further, the crystal structure of Ca-MOF was prepared and docked with protein targets of selected pathogenic water-borne microbes, which showed its disinfection potential. Overall, multiple metal sorption capability, regeneration studies, and broad-spectrum antimicrobial activity confirmed the versatility of synthesized Ca-MOF for industrial wastewater treatment.

Combined Remediation Effects of Sewage Sludge and Phosphate Fertilizer on Pb-Polluted Soil from a Pb-Acid Battery Plant.

Pb soil pollution poses a serious health risk to both the environment and humans. Immobilization is the most common strategy for remediation of heavy metal polluted soil. In this study, municipal sewage sludge was used as an amendment for rehabilitation of Pb-contaminated soils, for agricultural use, near a lead-acid battery factory. The passivation effect was further improved by the addition of phosphate fertilizer. It was found that the leachable Pb content in soils was decreased from 49.6 mg kg-1 to 16.1-36.6 mg kg-1 after remediation of sludge for 45 d at applied dosage of municipal sewage sludge of 4-16 wt%, and further decreased to 14.3-34.3 mg kg-1 upon extension of the remediation period to 180 d. The addition of phosphate fertilizer greatly enhanced the Pb immobilization, with leachable Pb content decreased to 2.0-23.6 mg kg-1 with increasing dosage of phosphate fertilizer in range of 0.8-16 wt% after 180 d remediation. Plant assays showed that the bioavailability of Pb was significantly reduced by the soil remediation, with the content of absorbed Pb in mung bean roots decreased by as much as 87.0%. The decrease in mobility and biotoxicity of the soil Pb is mainly attributed to the speciation transformation of carbonate, Fe-Mn oxides and organic matter bound Pb to residue Pb under the synergism of reduction effect of sludge and acid dissolution and precipitation effect of phosphate fertilizer. This study suggests a new method for remediation of Pb-contaminated soil and utilization of municipal sewage sludge resources.

Coprecipitation as a One-Step Se Separation for Determination of Isotope Ratios Completed with Revised Uncertainty Evaluation.

This study introduces a simplified purification method for analyzing 82Se/78Se isotope ratios in diverse natural samples using hydride generation MC-ICP-MS. Unlike the thiol resin method, which is time-consuming and sensitive to the concentrations of reagents used at individual stages, our proposed alternative is quicker, simpler, and robust. The procedure involves coprecipitation of selenium with iron hydroxide and dissolution in hydrochloric acid. Combining hydride generation and a second cleanup stage achieves sufficient purification for Se isotope ratio measurements. The method is efficient, taking 3-4 h after sample decomposition, utilizing common reagents [HCl, Fe(NO3)3, NH4Cl] without evaporation or clean lab conditions. Results on 82Se/78Se isotope ratios in various matrices are presented, comparing them with literature data. All isotopic results have been subjected to a newly proposed state-of-the-art approach to uncertainty estimation dedicated to isotope ratio measurements. The approach is based on applying Monte Carlo simulations with consideration of different samples' results normalized by the expected value. By doing that, we obtained estimated uncertainty for any Se sample with the influence of particular measurements on the final estimation included. We employ a Monte Carlo simulation-based uncertainty estimation approach for isotope ratio measurements, providing estimated uncertainty for each selenium sample.

Production of low-carbon amorphous SiO2 for use as a supplementary cementitious material and nesquehonite from olivine

Amorphous silica and hydrated magnesium carbonate (nesquehonite, MgCO3·3H2O) have been produced by acid dissolution of olivine ((Mg,Fe)2·SiO4). The amorphous silica is a viable supplementary cementitious material, and the formation of nesquehonite by carbonation, results in a carbon negative process. Using the amorphous silica as a supplementary cementitious material produces low-carbon cement. The global reserve of olivine makes this a viable route to producing low-carbon concrete.

In-situ iron oxide particle size and shape evolution during the dissolution in oxalic acid

In this study, the influence of temperature (40, 60 and 80∘C) and light exposure on the dissolution of ▪ particles in aqueous, oxalic acid (0.45 mol/l) is experimentally investigated. A novel experimental setup, consisting of a vessel with undistorted optical access, allows the recording of dissolving particles using a video system. During post-processing, particles are automatically identified and their size and morphology are determined. Binning particles into discrete time-steps during the reaction yields heavy-tailed distributions characterized by a single parameter estimated through a maximum-likelihood estimation of a doubly truncated power-law fit. For the first time, up to three consecutive phases could be identified during the dissolution process of iron oxide particles. The contribution of each phase to the overall dissolution process is determined by a complex interplay between particle fragmentation, different reaction mechanisms and solid product formation. The initial phase is characterized by the fragmentation of larger particles with a more complex morphology, resulting in greater surface area available for reaction. In the second phase, fragmentation is less apparent and the available particle surface area is reduced. The transition to the third phase relies primarily on the supply of short wavelength light, which leads to the formation of a solid product that can increase the tracked particle diameter.

Investigation of Nonlinear Flow Behavior Along a Rough-Walled Limestone Fracture With Acid Dissolution

Investigation of Nonlinear Flow Behavior Along a Rough-Walled Limestone Fracture With Acid Dissolution

Cleaner production of 3.5 valent vanadium electrolyte from ammonium metavanadate by ammonia reduction-sulfuric acid dissolution method

Cleaner production of 3.5 valent vanadium electrolyte from ammonium metavanadate by ammonia reduction-sulfuric acid dissolution method

CO2–Water–Rock Interaction and Its Influence on the Physical Properties of Continental Shale Oil Reservoirs

Shale oil resources are abundant, but reservoirs exhibit strong heterogeneity with extremely low porosity and permeability, and their development is challenging. Carbon dioxide (CO2) injection technology is crucial for efficient shale oil development. When CO2 is dissolved in reservoir formation water, it undergoes a series of physical and chemical reactions with various rock minerals present in the reservoir. These reactions not only modify the reservoir environment but also lead to precipitation that impacts the development of the oil reservoir. In this paper, the effects of water–rock interaction on core porosity and permeability during CO2 displacement are investigated by combining static and dynamic tests. The results reveal that the injection of CO2 into the core leads to reactions between CO2 and rock minerals upon dissolution in formation water. These reactions result in the formation of new minerals and the obstruction of clastic particles, thereby reducing core permeability. However, the generation of fine fractures through carbonic acid corrosion yields an increase in core permeability. The CO2–water–rock reaction is significantly influenced by the PV number, pressure, and temperature. As the injected PV number increases, the degree of pore throat plugging gradually increases. As the pressure increases, the volume of larger pore spaces gradually decreases, resulting in an increase in the degree of pore blockage. However, when the pressure exceeds 20 MPa, the degree of carbonic acid dissolution will be enhanced, resulting in the formation of small cracks and an increase in the volume of small pores. As the temperature reaches the critical point, the degree of blockage of macropores gradually increases, and the blockage of small pores also occurs, which eventually leads to a decrease in core porosity.

Silver diamine fluoride – ‘The silver bullet’ in pediatric dentistry: An overview of past, present and prospects

Various fluoride-containing topical agents like sodium fluoride, acidulated phosphate fluoride, Silver fluoride, and Silver diamine fluoride (SDF) have also been developed to prevent and intercept dental caries, particularly in children. SDF in 38% concentration for preventing and arresting dental caries in children. SDF is applied exclusively to carious lesions, both cavitated and non-cavitated, forming a protective layer on demineralized enamel and dentin. This layer enhances resistance to acid dissolution and enzymatic digestion of collagen, promoting mineralization and the formation of hydroxyapatite and fluorapatite SDF is a versatile treatment option for caries management, offering benefits in various clinical scenarios, including difficult access cases, high caries risk patients, and prevention of pit and fissure caries. The present article discusses the utility of SDF in dentistry, with an emphasis on pediatric dentistry

Atomic surface of cobalt-chromium-molybdenum alloy induced by novel green chemical mechanical polishing through controlling pH values and oxidation processes

Cobalt-chromium-molybdenum (CoCrMo) alloy has superior wear resistance, high corrosion resistance and excellent biocompatibility. However, these properties make CoCrMo alloy become a difficult-to-machine material. Nevertheless, high-performance CoCrMo devices strictly require the surface roughness Ra less than 1 nm, arising a challenge for ultraprecision machining. To overcome the challenge, a novel green chemical mechanical polishing (CMP) is developed, including silicon oxide, hydrogen peroxide, tartaric acid and deionized water. After CMP, surface roughness Ra of 0.16 nm is achieved for CoCrMo alloy. Compared with those published on CoCrMo alloys previously, the surface roughness is the lowest. X-ray photoelectron and infrared spectroscopies reveal that hydrogen peroxide dominated the oxidation processes in CMP. Co oxides were softened and dissolved by hydrogen ions. Relatively, Cr and Mo oxides showed better stability and less dissolution in tartaric acid, avoiding excessive corrosion. The remaining oxides are removed by silicon oxide. The metal ions released are chelated by tartaric acid during the polishing process. The chelation formulas of metal ions and tartaric acid are further proposed. The developed novel green CMP provide new insights to manufacture atomic surface on an alloy with high corrosion and wear resistances, which is beneficial for the potential applications on medical devices.

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

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

Reassembly of wood to plastic- and paper-like films via ultra-mild dissolution in formic acid

Lignocellulosic biomass was converted into plastic- and paper-like films via solubilization in formic acid without using ball milling and added catalysts. The formylated cell wall components were reassembled after casting.

A SIMPLE RP-HPLC METHOD DEVELOPMENT AND VERIFICATION OF THE DISSOLUTION OF BROMELAIN-A COMPLEX MIXTURE OF PROTEOLYTIC ENZYMES, IN DELAYED-RELEASE TABLETS

Objective: To develop a simple, accurate, precise and linear Reverse Phase High-Performance Liquid Chromatographic (RP-HPLC) method and verify for the quantitative estimation (Dissolution) of Bromelain in delayed-release tablets. Methods: The optimized RP-HPLC method for both acid and buffer stage dissolutions of delayed-release tablets uses Zorbax 300 SB-C8 column (150 mm X 4.6 mm; 3.5μ), a mobile phase-A of 0.1% trifluoroacetic acid in water and a mobile phase-B of 0.1% Trifluoroacetic acid in Acetonitrile in the gradient proportion, flow rate of 1.0 ml/min, injection volume of 25 µl, detection wavelength of 280 nm using a UV/PDA detector, column temperature of 40 °C, sample tray/compartment temperature of 5 °C and a run time of 20 min. Results: The developed method gave Bromelain eluting at about 6 min. Bromelain exhibited linearity in the range 53.4-800.6 μg/ml (r2=0.99992). The precision is exemplified by relative standard deviation of 1.3 and 2.3% for acid and buffer stages, respectively. Percentage recovery of the drug was found to be between 90.0 and 110.0 during accuracy studies. Conclusion: A simple, accurate, precise, and linear RP-HPLC method was developed and verified for the quantitative estimation (Dissolution) of Bromelain in tablets and hence this method can be explored for the analysis of Bromelain in tablets in various pharmaceutical industries.

Development of eco-friendly pretreatment processes for high-purity silicon recovery from end-of-life photovoltaic modules.

This study examines the efficacy of photovoltaic (PV) recycling processes and technologies for the recovery of high-purity silicon powder from waste solar modules. In order to facilitate the simplification of complex processes, such as the conventional nitric acid dissolution, solvent and ultrasonic irradiation, and solvent dissolution, a variety of mechanical separation processes have been established. These processes are designed to enhance the efficiency and effectiveness of the aforementioned processes. And a novel method for separating EVA from recycled Si powder was devised, which studied the WGS process using aqueous solutions of H2O, HNO3, and NaCl with different specific gravities. The WGS process using NaCl solution demonstrated superior performance, removing over 94% of the EVA, requiring less energy input and producing 73% less CO2 emissions compared to the thermal process. These technologies facilitate the transition towards a circular economy and bolster the implementation of carbon-neutral initiatives.

Energy saving Chemical Beneficiation Method of Improving Low Grade Nigeria Chromite Ore for Use in Steel Industries

This study detailed how direct acid leaching can be used to extract high grade chromite from low grade chromite ore for utilization in the steel industry. The suggested method, which makes use of nitric acid, avoids using traditional pyrometallurgical processes because they use a lot of energy. The leaching procedure is adjusted in accordance with the circumstances that will maximize chromium recovery. In this context, the independent variables are the nitric acid concentration (0.5–4 M), temperature (28–80°C), liquid to solid ratio (L/S) (3–10 mL g–1), and leaching period (10–120 min). The three parameters that affect the leaching process most effectively are, in order, acid concentrations, temperature, and particle sizes. By doing this, 86.7% of the chromite in the lean chromite ore was recovered. Shirking core model examination of the kinetics of leaching reveals that internal diffusion reaction controls the rate of leaching, and the apparent activation energy calculated is 24.8 kJ.mol-1. This approach is successful and relatively inexpensive for chromite beneficiation. The gap is thus filled by the use of all-known inefficient acid dissolution procedures, which are less expensive and could serve as an alternate way of chromite beneficiation for use in iron and steel.