Type Of Anion Research Articles

Anion and Substituents Effect on Spectral‐Kinetic and Biological Characteristics of Spiropyran Salts

Spiropyran salts containing a cationic vinyl‐3H‐indolium moiety are characterized by NIR absorption and fluorescence of their merocyanine forms. This feature makes them promising fluorescent probes and markers for bioimaging. The article focuses on the synthesis and study of the spectral, kinetic and toxic characteristics of such compounds with respect to various substituents in different moieties and the type of anion. A detailed analysis of the acquired data made it possible to draw some important conclusions regarding the influence of structural factors, which will be very useful for the further rational design of such derivatives. In particular, it was shown that the counterion has minimal effect on the spectral and kinetic characteristics of the dyes but dramatically affects the toxicity of the compounds. Following selection of the most appropriate compounds, bioimaging experiments were carried out to visualize planktonic bacteria and bacterial biofilms of E. coli and A. calcoaceticus. The ability to visualize biofilms is critical for the diagnosis of chronic diseases. By the results of molecular docking a theoretical interaction pattern between spiropyran molecules and DNA was proposed.

Enhancing flocculation and dewatering performance of fine phosphate tailings: A sustainable approach for water resources management

The sustainable recovery of water from fine phosphate tailings (FPTs) is essential for reducing water consumption and mitigating the environmental risks associated with phosphate beneficiation operations, particularly during tailings storage. Dewatering through enhanced flocculation techniques is among the most sustainable management practices in the mining industry. However, the interactions between phosphate tailings and polymers remain insufficiently explored, particularly in the context of the flocculation process. To address this, the present study investigates the improvement of dewatering performance through optimized flocculation techniques. Fourteen flocculants, including anionic, nonionic, and cationic types, were assessed for their effectiveness in enhancing water recovery, sedimentation rates, and turbidity reduction. Among the tested flocculants, polyethylene oxide (PEO 4 M) and anionic polyacrylamide (AN923) exhibited superior performance, achieving water recovery rates exceeding 84 %, solid contents above 38 %, and settling rates over 13.9 cm/min, along with significant turbidity reductions to below 4.40 NTU. Insights into the adsorption mechanisms, derived from zeta potential measurements and Fourier-transform infrared spectroscopy, revealed that anionic polyacrylamide (APAM) induces flocculation primarily through hydrogen bonding and polymer bridging, whereas polyethylene oxide (PEO) operates via hydrophobic interactions and charge neutralization. These findings lay the groundwork for more sustainable water management strategies in phosphate mining, enhancing both resource efficiency and environmental protection.

Research on a synergistic formula of anionic and betaine type surfactants for natural gas fields

Abstract To further improve the foaming properties, foam stability, salt and temperature resistance, betaine surfactants were combined with sodium dodecyl sulphate-derived multifunctional surfactants synthesized in laboratory. Sodium dodecyl sulphate-derived multifunctional surfactants (HSDS) was synthesized and the changes in performance before and after the addition of hexadecyl betaine (HB) to hydroxymethylated sodium dodecyl sulfate were comprehensively compared by carrying out experiments such as such as measuring foam volume and surface tension. The foaming volume of hexadecyl betaine (HB) compounded with HSDS-4 is found to reach 475 mL with a half-life of 7.72 min. The temperature resistance test shows that the foam volume of HS-4 at 70 °C is 22.9 mL. At a salt content of 200 g L−1, the foam volume of HS-4 is still 355 mL with a half-life of 6.13 min. Finally, the microstructure of the foams produced by the different compounds was measured. The foam produced by HS-4 had the lowest defoaming rate compared to the other compounds. The effectiveness of the compounded product in improving the recovery rate is shown, providing support for the further innovation and utility of this technology.

A small-molecule carrier for the intracellular delivery of a membrane-impermeable protein with retained bioactivity.

Intracellular protein delivery has the potential to revolutionize cell-biological research and medicinal therapy, with broad applications in bioimaging, disease treatment, and genome editing. Herein, we demonstrate successful delivery of a functional protein, cytochrome c (CYC), by using a boron cluster anion as molecular carrier of the superchaotropic anion type (B12Br11OPr2-). CYC was delivered into lipid bilayer vesicles as well as living cells, with a cellular uptake ratio approaching 90%. Mechanistic studies showed that CYC was internalized into cells through a permeation pathway directly into the cytoplasm, bypassing endosomal entrapment. Upon carrier-assisted internalization, CYC retained its bioactivity, as reflected by an induced cell apoptosis rate of 25% at low dose (1 µM). This study furbishes a direct protein delivery method by a molecular carrier with high efficiency, confirming the potential of inorganic cluster ions as protein transport vehicles with an extensive range of future cell-biological or biomedical applications.

(C10N2H10)(HI2O6)(HIO3)(IO3): A Birefringent Material Featuring Large π-Conjugated Organic Cation and Two Types of Iodate Anions.

Birefringent crystals, which can modulate and polarize light, play a vital role in the development of optical sensors and optoelectronic devices. Herein, we synthesized a new birefringent crystal [(C10N2H10)(HI2O6)(HIO3)(IO3)] with large birefringence by integrating the large π-conjugated 4,4'-bipyridine group with two types of iodates anions ([IO3]- and [HI2O6]-) characterized by high polarizability anisotropy and strong stereochemically active lone pairs (SCALP). The crystal exhibits a large measured birefringence of 0.171 at 550 nm, surpassing most organic-inorganic hybrid iodate birefringent materials reported in the literature. Theoretical analyses reveal that the optical properties of the crystal arise primarily from the synergistic interactions between the π-conjugated 4,4'-bipyridine group and I-O groups. This research presents an effective method for the strategic integration of large π-conjugated organic cations into iodates, facilitating the design of novel birefringent materials and encouraging further exploration of superior birefringent substances.

Lone Pair Induced 1D Character and Weak Cation-Anion Interactions: Two Ingredients for Low Thermal Conductivity in Mixed-Anion Metal Chalcohalide CuBiSCl2.

Mixed-anion compounds, which incorporate multiple types of anions into materials, display tailored crystal structures and physical/chemical properties, garnering immense interest in various applications such as batteries, catalysis, photovoltaics, and thermoelectrics. However, detailed studies regarding correlations among crystal structure, chemical bonding, and thermal/vibrational properties are rare for these compounds, which limits the exploration of mixed-anion compounds for associated thermal applications. In this work, we investigate the lattice dynamics and thermal transport properties of the metal chalcohalide, CuBiSCl2. A high-purity polycrystalline CuBiSCl2 sample exhibits a low lattice thermal conductivity (κL) of 0.9-0.6 W/(m·K) from 300 to 573 K. By combining various experimental techniques, including three-dimensional (3D) electron diffraction, with theoretical calculations, we elucidate the origin of low κL in CuBiSCl2. The stereochemical activity of the 6s2 lone pair of Bi3+ favors an asymmetric environment with neighboring anions involving both short and long bond lengths. This particularity often implies weak bonding, low structure dimensionality, and strong anharmonicity, leading to a low κL. In addition, the strong 2-fold linear S-Cu-S coordination with weak Cu···Cl interactions induces a large anisotropic vibration of Cu, which enables strong phonon-phonon scattering and decreases κL. The investigations into lattice dynamics and thermal transport properties of CuBiSCl2 broaden the scope of the existing mixed-anion compounds suitable for the associated thermal applications, offering a new avenue for the search for low thermal conductivity materials in low-cost mixed-anion compounds.

Wetting and interfacial behavior of imidazolium-based ionic liquids and water: A comprehensive review

Ionic liquids (ILs) have garnered considerable attention for their diverse applications, notably in controlling wettability on specific solid substrates, which holds ramifications for various processes reliant on interfacial behaviour encompassing adhesion and wetting. This review encompasses key advancements in IL wetting behavior and its implications. Factors such as drop size, temperature, alkyl chain structure, anion type, water concentration, and external electric fields influence the contact angle of ILs and their aqueous solutions. Despite challenges arising from IL property susceptibility to water content and wettability measurement sensitivity to solid surface, this review navigates the extent of IL wetting research, addressing line tension, surface tension measurement, and hydrogen bonding. The study aspires to furnish profound insights into IL wetting dynamics, informing IL-based fluidic technology design and elucidating intricate static and dynamic wetting attributes in analogous complex fluids.

Phonon-Lithium Ion Interactions: A Case Study of LiM(SeO3)2 (M = Al, Ga, In, Sc, Y, and La).

Li ion diffusion is fundamentally a thermally activated ion hopping process. Recently, soft lattice, anharmonic phonon, and paddlewheel mechanism have been proposed to potentially benefit the ion transport, while the understanding of vibrational couplings of mobile ions and anions is still very limited but essential. Herein, we accessed the ionic conductivity, stability, and especially, lattice dynamics in LiM(SeO3)2 (M = Al, Ga, In, Sc, Y, and La) with two different types of oxygen anions within a LiO4 polyhedron, namely, edge-shared and corner-shared with MO6 polyhedra, the prototype of which, LiGa(SeO3)2, has been theoretically reported before with the similar structural features to NASICON and later experimentally synthesized with the room temperature conductivity ∼0.11 mS cm-1. It is interesting to note that LiM(SeO3)2 with a higher Li phonon band center shows higher Li conductivity, which is in contradiction to the conventional understanding of the importance for soft lattice to superionic conductors. The anharmonic and harmonic phonon interactions as well as the couplings between the vibration of the edge-bonded or corner-bonded anion in Li polyanions and the Li ion diffusion have been studied in detail. With transition metal M changing from La, Y, In, Ga, Al, and Sc, anharmonic phonons increase with reduced activation energy for Li diffusion. The phonon modes dominated by the edge-bonded oxygen anions contribute more to the migration of the Li ion than those dominated by the corner-bonded oxygen anions because of the greater atomic interaction between the Li ion and the edge-bonded anions. Thus, rather than the overall lattice softness, attention shall be given to reduce the frequency of the critical phonons contributing to Li ion diffusion as well as to increase the anharmonicity, i.e., through asymmetric Li polyhedra, for the design of Li ion superionic conductors for all-solid-state batteries.

Generation of superoxide ions in the electrochemical reduction of molecular oxygen in concentrated lithium bis(trifluoromethanesulfonyl)imide aqueous solutions

Electrolytic generation of superoxide ions (O2•-) from the reduction of molecular oxygen (O2) was previously successful only by the formation of a hydrophobic reaction field on an electrode surface. However, in our study, O2•- was generated in concentrated lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) aqueous solutions that can be confirmed electrochemically or spectroscopically. In the concentrated LiTFSI aqueous solution, O2•- was more stable than it is in normal aqueous solutions, but it was not as stable as it is in organic solvents. When other related-concentrated electrolyte solutions are used, the electrolysis of O2•- greatly varies depending on the types of cations and anions used as electrolytes. Thus, a synergistic effect of reducing free water with cations and creating a hydrophobic atmosphere with anions was achieved.

Designing of new functionalized imidazolium based ionic liquids attached to the antracene derivatives and investigation on the influence of intramolecular hydrogen bondings in anions on their intermolecular hydrogen bondings and some of the other properties: A DFT M06-2X-GD3 study

To promote the development of new functionalized ionic liquids, it is necessary to get a deeper insight into their features of physicochemical and electronic and molecular structure. In this study, the interaction energies and structural and vibrational frequencies parameters in accompanied with some of the physiochemical, electronic and optic attributes of ionic liquids designed by the covalently attachement of imidazolium to anthracene derivatives ([X-AnMIM][A2] and [X-AnMIM][A3], X: NH2, OH, OMe, H, Cl, CHO, CN and NO2) ILs have been evaluated. Two conjugate bases of acids 1,3,5-pentanetriol (A2) and 3-(2-hydroxyethyl)-1,3,5-pentanetriol (A3) are used as anions which have two and three intramolecular hydrogen bonds, respectively. Based on the results of calculations at M06-2X-GD3/6-311++(d,p) level of theory, the differences in these properties in addition to the structural type of anions and cations can be attributed to the cation- anion , intra and intermolecular hydrogen bonding, interactions in ionic liquids. The results depict that the ILs based on A2 anions form stronger hydrogen bonds with [X-AnMIM]+ cations. The potency of interaction between cations and anion reduces with the increasement in the number of intramolecular hydrogen bonds and also decreasement in the basic strength in the anionic part. A clear red shift is observed between [X-AnMIM][A2] and [X-AnMIM][A3] ILs and isolated anthracene, which is a clear manifestation of the effect of the imidazolium cation on the electronic energy levels of anthracene. It can be expected that the studied ILs are not electrochemically stable during the electrochemistry applications.

Heterometallic Uranyl Squarate Compounds with Transition Metal‐Bipyridine Bulky Cations as Structure Directing Components

AbstractHeterometallic actinide compounds with tailored components functions have attracted much attention, but their controllable synthesis is still challenging. In this work, using bulky transition metal‐bipyridine cations as structure directing components, we have successfully synthesized six novel heterometallic uranyl squarate compounds, 1–6 with different metal‐bipyridine units. A time‐dependent crystal transformation from 1 with triple interwoven structure to 2 with parallel stacked structure is observed within the observation period of one month and further characterized via single‐crystal X‐ray diffraction (SCXRD) and powder X‐ray diffraction (PXRD). Further evidences from a combination of several techniques including thermal analysis, variable‐temperature PXRD and variable‐temperature SCXRD demonstrate dehydration‐related lattice evolution of 1 on the basis of structural flexibility of 1, which could be the origin of above‐mentioned crystal transformation from 1 to 2. Furthermore, the effect of types of anions (NO3−, Cl−, and SO42−) on structural diversity of 1–6 is also discussed in detail, where the Cl− or NO3− ion coordinate to Cu2+ center in isostructural 3 and 4, while SO42− bonds to uranyl nodes in isostructural 5 and 6. This work provides a feasible method for the tailored synthesis of multicomponent actinide complexes by the involvement of bulky charge balance components.

Superparamagnetic composites of lignin regenerated from ionic liquid solutions for the efficient and selective removal of cationic dyes

Magnetic lignin nanoparticles (MLNs) were prepared by inducing their self-assembly through lignin regeneration in the [N-methyl-2-pyrrolidone][C1–C4 carboxylic acid] ionic liquids ([NMP]ILs), which are low-cost protic ionic liquid. [NMP]ILs are self-assembling solvent that can enhance the adsorption capacity of MLNs to a greater degree than tetrahydrofuran or H2O. Additionally, the anion types of [NMP]IL greatly influence the physiochemical properties of MLNs. The MLNs prepared through self-assembly with [NMP][formate] (MLN/[NMP][For]) exhibited a higher maximum adsorption capacity (134.53 mg/g) than the [NMP]ILs of C2–C4 carboxylate anions. MLN/[NMP][For] demonstrated stable adsorption within a pH range of 6–10 or at high salt concentrations (0.01–0.5 mol/L), retaining over 80 % of its regeneration efficiency after 5 cycles. In addition, MLN/[NMP][For] selectively removed cationic dyes in mixed binary anionic–cationic dye solutions. This work demonstrated the feasibility of preparing magnetic biosorbents with good selectivity and stability though regeneration and by adjusting the anions of ionic liquids.

Poly(dimethyldiallylammonium chloride)-modified magnetic bentonite for removal of polystyrene nanoplastics

Nanoplastics (NPs) can contaminate water sources and living organisms, posing significant challenges for removal due to their small size and complex surface properties. There is a need to develop efficient technologies for the removal of NPs. In this study, bentonite was magnetically modified and loaded with Poly(dimethyldiallylammonium chloride) (PDMDAC) to enhance the adsorption for NPs, and improve separation and recovery efficiency. The synthesized PDMDAC-modified magnetic bentonite (PDMMB) had a high specific surface area of 49.386 m2/g and a maximum adsorption capacity of 250.50 mg/g for polystyrene nanoplastics (PS-NPs). The incorporation of PDMDAC increased the surface charge of magnetic bentonite from −39.50 mV to +37.7 mV, generating strong electrostatic attraction to the negatively charged PS-NPs (-64.3 mV). The PDMMB exhibited a saturation magnetization of 17.619 emu/g and an S-type hysteresis curve, indicating strong superparamagnetism that facilitating magnetic separation and recovery. Characterization analysis revealed that the adsorption was driven by electrostatic attraction and the Fe-O functional group. Kinetics and adsorption model analyses indicated that the adsorption mechanism involved electrostatic attraction, complexation, and single/multilayer adsorption, the adsorption process was exothermic and thermodynamically favorable. The adsorption rate remained at 86.41 % after 5 adsorption-desorption cycles. PDMMB exhibited high removal efficiency over a wide range of pH (3−10), ionic strength (0.01–0.5 mol/L), and in the presence of various anion types, indicating its potential for flexible application. The high efficiency, easy operation and excellent regeneration of PDMMB demonstrate its potential for effective removal of NPs from wastewater.

Synthesis, Spectroscopic Characterization, DFT, Molecular Docking, Catechol Oxidase Activity, and Anti-SARS-CoV-2 of Acylhydrazone Derivatives

In the present work, five pyrazole-hydrazone biomolecule ligands (L1–L5) were synthesized by condensation between 1H-pyrazole-3-carbohydrazide (2) and aromatic benzaldehydes. Their corresponding structures were elucidated employing NMR and FT-IR spectra and ESI-MS data. Li-Cu(II) complexes (i = 1–5) were evaluated for catecholase activity in situ at standard conditions. The findings disclose that the catecholase oxidation rate varies with the substituted functional groups in ligand and the anion type in the copper (II) salt. Catecholase activity results showed that the L(i = 1–5) -Cu(II)SO4 complexes exhibited efficient catalytic activity, and a maximum activity of 105 ± 42 µM.min−1 is obtained with L5-Cu(II)SO4. DFT and NBO calculations have been carried out to identify the global reactivity and the strength of interaction bonds between the donors and acceptors in L1–L5. The optimized structure of L1–L3 and L5 were found planar, while that of L4 is out of the molecular plan and forms a torsion angle of 18 degrees due to the presence of methoxy and hydroxyl group at meta and para. In L4, the 5-methyl-1H-pyrazole moiety. NBO findings show that the strongest interactions in L1–L5 are those involved in the electronic transition from π-bonding → π*-antibonding and LP → π*- antibonding molecular orbitals. Further, the anti-SARS-CoV-2 of L1–L5 are investigated by estimating their binding affinities into its binding. The docking results reveal that L1–L5 may act as SARS-CoV-2 main protease inhibitors with estimated binding energies in the −6.00 to −8.0 kcal.mol−1 range.

Impact of Hofmeister anion type on the structural and mechanical properties of composite whey protein hydrogels

Biopolymer hydrogels are widely employed in food products to provide desirable functional attributes, especially texture and mouthfeel. Hydrogels can be created from whey proteins, but they are too soft and brittle for certain applications. Previously, it was shown that the mechanical properties of whey protein hydrogels could be enhanced by embedding whey protein nanofibers in them. In the current study, the impact of soaking these nanofiber-filled composite hydrogels in salt solutions containing anions in different positions within the Hofmeister series was studied. In addition, the impact of hydrogel pH (1, 3, 7, or 9) on the properties of the hydrogels was investigated. The hardness and shear modulus of the hydrogels increased appreciably after they were soaked in the salt solutions. For example, at pH 7 and pH 9, the hardness of the composite hydrogels soaked in K2SO4, KCl, and KBr solutions were around 5.8-, 4.8-, and 2.3-fold higher and 7.3-, 6.0-, and 3.3-fold higher than that of the original hydrogels, respectively. The magnitude of increase in gel strength was consistent with the position of the anions in the Hofmeister series: SO42− > Cl− > Br−. Fourier transform infrared showed that the presence of Hofmeister ions increased the number density and strength of protein-protein bonds in the gel network by strengthening hydrogen bonding and hydrophobic interactions. Therefore, composite whey protein hydrogels with different structural and textural characteristics could be produced by controlling their pH values and/or by soaking them in salt solutions containing anions in different positions within the Hofmeister series.

Efficient photocatalytic degradation of 24 imidazolium ionic liquids in an N-ZnO/simulated sunlight irradiation system and its mechanism

An efficient nitrogen (N)-ZnO photocatalytic composite was synthesized and well characterized to demonstrate its superior photocatalytic performance as well as the degradation kinetics of 24 ILs in an N-ZnO/Xe lamp irradiation system, as well as the pathways and mechanisms of the photocatalytic degradation (PCD) of typical ionic liquids [OMIm]Br was systematically studied. To investigate the catalytic effect, nitrogen was synthesized from various inorganic and organic nitrogen compounds to ZnO. The NH4NO3-ZnO composite calcined at 300 °C with a molar ratio of NH4NO3 to Zn(NO3)2·6H2O of 10:1 exhibited superior catalytic performance as assessed by SEM, TEM, FT-IR, UVDRS, BET surface area, XPS, and XRD characterizations. After 24 h of exposure to Xe lamp irradiation, all 24 ILs were significantly degraded by the introduction of 0.125 g/L of catalyst, whereas simulated sunlight alone resulted in minimal degradation. The pseudo-first-order rate coefficients (k) for PCD were closely related to the carbon chain length of the alkyl substituents and the type of anion. Multiple linear regression analysis indicated no linear correlation between the parameters E, H°, Eth, and Cv° from the Gaussian calculation and k. Conversely, a positive correlation was observed for EHOMO (B=0.742, β = 1.282, P = 0.011), qH+ (B=1.040, β = 3.284, P = 0.006), and G° (B=0.001, β = 5.400, P = 0.007) with k. Mass spectrometry analysis revealed that the primary PCD pathway for [OMIm]Br involved C-N and/or C-C bond breaking, mono-, di-, and tri-hydroxylation, single and double oxygen transfer, and bromo-substitution reactions.

Electrochemical Oxidation of Single-Walled Carbon Nanotubes in Aqueous Electrolytes Containing Various Types of Anions

Electrochemical Oxidation of Single-Walled Carbon Nanotubes in Aqueous Electrolytes Containing Various Types of Anions

Comprehensive evaluation of physical properties and carbon dioxide capacities of new 2-(butylamino)ethanol-based deep eutectic solvents

Abstract The aim of this research was to assess the impact of the components of alkanolamine deep eutectic solvents (DESs) on the physical properties of those DESs and their carbon dioxide capacity. To achieve this goal, novel deep eutectic solvents were synthesized by using 2-(butylamino)ethanol (BAE) as the hydrogen bond donor (HBD), along with tetrabutylammonium bromide TBAB), tetrabutylammonium chloride (TBAC), or tetraethylammonium chloride (TEAC) as the hydrogen bond acceptors (HBA) at various molar ratios (1:6, 1:8, and 1:10). To confirm the presence of hydrogen bond interactions between the components Fourier Transform Infrared Spectroscopy measurements were conducted. Furthermore, thermal properties, including melting points and thermal stability, of these deep eutectic solvents as well as key physical properties, such as density, viscosity, refractive index, and sound velocity, within the temperature range of 293.15–333.15 K and at a pressure of 0.1 MPa were examined. The effect of the molar ratio of HBA to HBD, the type of anion, and the length of the alkyl chain were studied and analysed in regard to physicochemical properties. In this work, the solubility of carbon dioxide in DESs derived from 2-(butylamino)ethanol, 3-aminopropan-1-ol (AP), and 2-(methylamino)ethanol (MAE) was measured. The highest CO2 capacity was found for TEAC:MAE 1:10 DES characterized by the shortest alkyl chain length in both HBA and HBD molecules, the highest amine content, and the lowest viscosity. Additionally, the effect of water addition on carbon dioxide solubility was explored. The results showed that the influence of water on CO2 solubility varies with the type of DES. In general, this work highlighted that DESs can serve as effective media for carbon dioxide capture, and their performance can be tailored by changing the type of hydrogen bond acceptor or donor, their molar ratio and by the addition of water.

Combined deep-learning optimization predictive models for determining carbon dioxide solubility in ionic liquids

This study explores the development of predictive models for carbon dioxide (CO2) solubility in ionic liquids based on a compiled dataset of 10,116 experimentally measured data points involving four input variables: pressure (P), temperature (T), cation type, and anion type. The deep-learning (DL) predictive models evaluated are standalone and hybrid versions of convolutional neural network (CNN) and long short-term memory (LSTM) algorithms with cuckoo optimization algorithm (COA) and gradient-based optimization (GBO). The laboratory-measured data was separated into training and test categories, and each category was normalized separately to improve the performance of the deep learning algorithms. The Mahalanobis distance-based quantile method was utilized to identify any outliers in the training data. Once identified, the outlier data points were eliminated from the training dataset. The control parameters of the deep learning algorithms were optimized using COA to enhance their efficiency, and the algorithms were hybridized with optimization algorithms to further improve their performance. The resulting models were analyzed to assess their accuracy, degree of overfitting, and the importance of input features. The study found that using 80% of the data for training and 20% for testing results in more accurate and generalizable models. Using the outlier detection method on the training data led to 307 data points being eliminated as outliers. Developing CO2-solubility predictive model showed that, the CNNCOA model had the lowest RMSE and highest R2 among the developed models, indicating high generalizability for data unseen by the trained model. The analysis revealed that using optimization algorithms increased the CO2-solubility prediction performance of DL algorithms and reduced overfitting. T and cation type were the most and least important input features, respectively. Simultaneous changes in cation and anion type on CO2-solubility predictions displayed no systematic pattern. For increases in T, CO2 solubility typically decreased, whereas for increases in P CO2 solubility always increased but at variable rates. The results of this study can be used to develop accurate and generalizable CO2-solubility predictive models for various applications.

A Step towards CO2 Sequestration through Mineral Carbonation: Using Ammonium-Based Lixiviants for the Dissolution of Calcium from Iron-Making Blast Furnace Slag

In recent years, technical processes for the sequestration of CO2 through industrial waste mineral carbonation have been explored and developed. There is a large portfolio of carbon capture, utilisation, and storage (CCUS) techniques that have been employed in laboratories and at pilot scale. These include geological storage, ocean storage, and mineralisation by carbonate ores. In view of this, the main purpose of this research was to investigate and explore chemical variables, particularly ammonium salts as lixiviants for calcium mineral extraction from iron-making slag. The slag in use was acquired from a steel mill in the Vaal Triangle Region in Gauteng, South Africa. The experimental test work was conducted using different ammonium lixiviants, namely, NH4NO3, NH4Cl, and CH3COONH4, to understand the influence of anion type as well as possible differences in mechanisms of interactions. Lixiviant concentration as well as reaction time were varied in this research study. The three selected ammonium-based lixiviants showed different extents of calcium extraction owing to differences in the anion groups. NH4NO3, NH4Cl, and CH3COONH4 were found to be capable of dissolving 50% to 80% of the calcium from the selected slag for different molar concentrations. Anion type and leaching time also had significant influences on the leaching of calcium from the slag. Rapid pH degradation resulted in better calcium extraction capabilities. This work has shown that the selected ammonium salts have the potential to be lixiviants for calcium dissolution from iron-making blast furnace slags. These lixiviants would, therefore, be important to consider during calcium mineral carbonation for CO2 sequestration.