Hydroxide Hydrate Research Articles

Superior charge storage performance of optimized nickel cobalt carbonate hydroxide hydrate nanostructures for supercapacitor application

In our work, we report superior electrochemical performance of optimized 3D nanostructured, nickel-cobalt carbonate hydroxide hydrate (Ni3 − xCox-CHH (1 ≤ x ≤ 2)) materials with flower like morphology synthesised via one-step hydrothermal methods. A Ni rich sample (x = 1) demonstrate better specific capacitance and the improvement is attributed to more oxygen deficient neighbourhood of Ni compared to that of Co. The structural, morphological and electronic properties of the samples were investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), High resolution transmission electron microscopy (HRTEM), field emission electron microscopy (FESEM), Energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). A comprehensive characterization was used for physicochemical properties-electrochemical performance correlation. Cyclic voltammetry (CV), Galvanostatic charging and discharging (GCD) shows the supercapacitor feature of the samples for the composition containing the highest nickel concentration achieving a specific capacitance of 1649.51 F g− 1 at a current density of 1 A g− 1 and excellent rate capability of 1610.30 F g− 1 at a high current density of 5 A g− 1. The sample shows high cyclic stability of 80.86% after 3000 cycles. Improved specific capacitance is attributed to the synergy effect of bimetallic transition metals as well as improved surface area of flower like morphology. These findings show that Ni2Co-CHH electrode material demonstrates great potential as electrode material for supercapacitor device fabrication.

Ready-to-Use Flowable Hydraulic Tricalcium Silicate-Based Dental Cement Paste with Antibiotic Releasing Capacity

Calcium silicate-based cements have been investigated recently for various medical applications. One notable application is using calcium silicate cement in dental root canal treatments. This work aimed to develop a novel flowable dual-paste calcium silicate sealer with an extended capacity for releasing antibiotic drugs. This study prepared a composite dental cement incorporating tri- and dicalcium silicate (C2S and C3S) and nano-hydroxyapatite (nHA). International standards are followed by the sealers' film thickness, flowability values, working time, and setting time. The formation of calcium hydroxide and calcium silicate hydrate was proved in the XRD patterns, which attributed to the hydration of C2S and C3S. The in vitro release of Amoxicillin (AMX) loaded in the composite cement was conducted in deionized (DI) water and phosphate-buffered saline (PBS) and investigated using Higuchi and Weibull models. Upon immersion in PBS, the sedimentation of hydroxyapatite layer on the cement surface, led to a comparatively slower AMX release rate than that in water. The results of the agar diffusion test showed that the presence of the antibiotic drug improved antibacterial properties in such a way that by adding AMX in the cement formulation, the diameter of the inhibition zone increased from 31.61 mm in TCS to 40.17 mm in TCS- 30 mM sample after 72 hours. These results imply that the drug-loaded cement pastes hold potential for application as a bioactive dental root canal sealer, offering antibiotic-loading properties with long-term release capabilities.

Influence of CaO/Al2O3 molar ratio of synthetic calcium aluminate hydrates on the engineering properties of metakaolin-based alkali-activated materials

This study evaluates the influence of the CaO/Al2O3 molar ratio of synthetic calcium aluminate hydrates on the properties of alkali-activated materials based on metakaolin. Calcium aluminate hydrates with CaO/Al2O3 molar ratios of 0.4, 0.6, 0.8, 1.0 and 1.2 were synthesised from bauxite and eggshells. Alkali-activated materials were prepared in which metakaolin was replaced by 0 and 10 wt.% calcium hydroxide and calcium aluminate hydrate with different CaO/Al2O3 molar ratios. Rice husk ash with a SiO2/Na2O molar ratio of 1.6 was used for the preparation of the hardener. The 28-day compressive strengths of alkali-activated materials containing 0 and 10 wt.% calcium aluminate hydrate with different CaO/Al2O3 molar ratios of 0, 0.4, 0.6, 0.8, 1.0 and 1.2 are 48.86, 63.59, 47.36, 47.89, 34.66 and 32.76 MPa, respectively. 22.08 MPa for that containing 10% by weight of calcium hydroxide. The apparent densities are 1.87, 1.79, 1.99 and 2.10 g/cm3, respectively. It has been found that the best molar ratio of CaO to Al2O3 in the structure of the 10% by weight of calcium aluminate hydrate used to replace metakaolin, which is required to produce alkali-activated materials with higher mechanical and physical properties, is about 0.4.HighlightsCalcium aluminate hydrates (CAHs) with molar ratio CaO/Al2O3 of 0.4, 0.6, 0.8, 1.0 and 1.2 were prepared using calcined bauxite, calcined eggshell and distillated water.Calcium hydroxide (CH) was prepared using calcined eggshell and distillated water.Metakaolin was substituted by 0 and 10 wt.% of CH and the different CAHs.The highest strength was archived at 63.59 MPa for alkali-activated material using CAH with molar ratio CaO/Al2O3 of 0.4 as additive.

Oxygen Evolution Behavior of Ni-Containing Alloy Electrodes in NaOH–KOH Hydrate Melt

Hydrogen is expected to be the next-generation energy carrier with zero CO2 emissions. Alkaline water electrolysis (AWE) is one of the methods for hydrogen production; however, improving its energy efficiency is a challenge. We are currently developing a highly efficient water electrolysis using hydroxide hydrate melts at 150–200°C [1,2]. Recently, we reported that the overpotential for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) at a Ni electrode in a NaOH–KOH hydrate melt at 200°C under atmospheric pressure was significantly reduced compared to a 30 wt% KOH aqueous solution at 80°C, which is a typical electrolyte for conventional commercial AWE [2]. In addition, the OER overpotential was found to be larger than the HER overpotential at the Ni electrode in the NaOH–KOH hydrate melt [2]. In the present study, we investigated the OER behavior of Ni-containing alloys in the NaOH–KOH hydrate melt.Linear sweep voltammetry was performed in the NaOH–KOH hydrate melt (NaOH:KOH:H2O = 9:61:30 mol%) at 150 and 200°C using a three-electrode cell. Several types of commercially available Ni-containing alloy plates with a flag-shaped and 3 mm diameter were used as the working electrode. A Ni rod was used as the counter electrode. A palladium hydride (Pd–H) electrode was used as the reference electrode and the potential was calibrated with respect to the reversible hydrogen electrode (RHE). All measured potentials were IR compensated. All measurements were performed in stationary electrolytes under Ar gas flow at atmospheric pressure.Figure 1 shows anodic polarization curves at Ni–Fe and Ni–Cu alloy electrodes in the NaOH–KOH hydrate melt at 150°C. The polarization of Ni–Fe and Ni–Cu alloy electrodes is lower than that of the Ni electrode. In this paper, we will also present the results for other Ni-containing alloys.A part of this study was supported by Adaptable and Seamless Technology transfer Program through Target-driven R&D (A-STEP) from Japan Science and Technology Agency (JST) Grant Number JPMJTR23TB.[1] K. Kawaguchi, K. Goto, A. Konno, and T. Nohira, J. Electrochem. Soc., 170, 084507 (2023).[2] K. Goto, K. Kawaguchi, and T. Nohira, Electrochemistry, 92, 043021 (2024). Figure 1

Durability of a Metakaolin-Incorporated Cement-Based Grouting Material in High Geothermal Tunnels.

To improve the durability of cement-based grout in high geothermal tunnel grouting projects, metakaolin was incorporated to replace 8% of the cement. The permeability, chloride penetration, and sulfate and carbonate erosion tests were carried out on the grout cured at varying temperatures (20, 30, 40, 50, and 60 °C). It was shown that with the increase in curing temperature, the impermeability and resistance to chloride penetration initially increased and then decreased, reaching the highest values at 40 °C. Furthermore, the incorporation of metakaolin into grout enhanced the impermeability by 11.11-38.91% and resistance to chloride penetration by 12.23-12.77%. As attacked by sulfate, the surface spalling of the specimen was more obvious with the increase in the curing temperature and immersion time. Conversely, the appearance remained almost unchanged under carbonate erosion. As immersion time increased, both the antisulfate and anticarbonate erosion coefficients declined. The effect of curing temperature on erosion resistance was assessed via the relative antierosion coefficient. When immersed in sulfate, the coefficient achieved the highest value of 1.08 as cured at 30 °C, and in carbonate, the coefficient reached a maximum of 0.99 as cured at 40 °C. Through scanning electron microscopy and binarized images, it was verified that gypsum and ettringite were formed during sulfate attack, leading to volume expansion and cracking, consequently reducing the strength. Meanwhile, in the case of carbonate erosion, calcium hydroxide (CH) and calcium silicate hydrate gel (C-S-H) were dissolved and degraded, resulting in a large number and size of pores in the grout. The research results have certain theoretical significances and reference values for the application of cement-based grouting materials in high geothermal environments.

Bi doping induces the quantum dots to improve the supercapacitor performance of cobalt carbonate hydroxide hydrate

Cobalt carbonate hydroxide has been widely used in supercapacitor electrodes because of its excellent theoretical electrochemical properties and easy synthesis. However, in actual synthesis, its excellent electrochemical properties are often weakened due to its oxide-like properties, which restricts its further development. Herein, the Bi heteroatoms are introduced into the Co(CO3)0.5(OH)·0.11H2O, which not only modifies the microstructure, but also induces the formation of quantum dots, thus improving the performance of supercapacitors. By regulating the doping amount of Bi, the optimized Co/Bi-3:1 exhibits a specific capacitance of 680 F g−1 at 1 A g−1, which is 5.74 times than the pristine Co(CO3)0.5(OH)·0.11H2O. Furthermore, the assembled Co/Bi-3:1//activated carbon soft-pack asymmetric supercapacitor has a relatively superior power density (10547.58 W kg−1, relative to 14.06 Wh kg−1 energy density) and energy density (17.83 Wh kg−1, relative to 2146.76 W kg−1 power density). The present study demonstrates that Bi doping not only facilitates the formation of quantum dots and enhances electron conduction ability, but also regulates the microscopic morphology, thereby enhancing the electrochemical energy storage capacity of cobalt carbonate hydroxide hydrate electrode materials.

Effect of PVDF binder on the performance of Zn-Ni carbonate hydroxide hydrate battery electrode in supercapattery

In the midst of enhancing the energy density of energy storage devices, a novel approach has emerged involving the hybridisation of supercapacitors and batteries to fabricate energy storage systems with superior energy density, power density, and longevity. A critical aspect in boosting the energy density of these devices lies in the performance enhancement of the active materials utilised. Therefore, this work developed a densely packed zinc-nickel carbonate hydroxide composite resembling marigold flowers (Zn/NCHH) to facilitate rapid redox reactions. Together, this work highlights the impact of the direct deposition technique over conventional binder-based technique in terms of electrochemical performance. It was revealed that the direct growth of Zn/NCHH led to a four-fold increase in specific capacity (1215.30 C g−1 at 3 A g−1) compared to binder-based electrodes. This enhancement was attributed to the uniform and robust network formed between the active materials and the substrate through direct deposition, resulting in improved mechanical adhesion, electrolyte ion percolation, increased exposed active sites, reduced charge transfer resistance, and exceptional reproducibility. Conversely, the introduction of binders hindered the network formation, leading to elevated resistance, material degradation over charge/discharge cycles, severe agglomeration limiting active site exposure, resulting in compromised electrochemical performance. The assembled supercapattery utilising Zn/NCHH/NF//AC/NF demonstrated remarkable maximum energy density and power density of 31.00 Wh kg−1 and 6243.67 W kg−1, respectively, with excellent cyclic stability (96 %) over 9000 charge-discharge cycles. Additionally, it exhibited an enhanced coulombic efficiency of 112 % over the 9000 cycles.

Surficial Reconstruction of Pt-Ni/NiS and Its Effect on Electrocatalytic Hydrogen Evolution in Alkaline Medium.

Cyclic voltammetry pretreatment of Pt-based electrocatalysts has been proven to be a normal activation process on achieving the optimal alkaline hydrogen evolution performance. Until now, the congruent relationship between the microstructural evolution and performance improvement during this process has rarely been reported. Herein, when the in situ transmission electron microscopy and in situ Raman analyses are employed, a self-reconstruction process from crystalline NiS into amorphous nickel hydroxide hydrate [Ni(OH)2-x·H2O, where x ≈ 0.3] on the surface of platinum-nickel nanowires has first been captured, which is the critical water dissociation active site to offer a sufficient proton supply. Furthermore, such a surficial reconstruction triggers an increase in the current density from -2.3 to -38.8 mA/cm2 (at -70 mV), which is nearly 17 times. These observations point to the fact that it is essential to consider the fundamental mechanisms of hydrogen evolution on the active sites when the process is scaled up.

In Situ Hydrophobization of Lithium Aluminate Particles for Flotations by Dry Grinding in the Presence of Punicines

The engineered artificial mineral (EnAM) lithium aluminate (LiAlO2) is a promising candidate for the recycling of lithium from slags, which can originate from the reprocessing of batteries, for example. Derivatives of the natural product Punicine (1-(2′,5′-dihydroxyphenyl)-pyridinium) from Punica granatum have been proven to be effective switchable collectors for the flotation of this mineral as they react to light. In the present study, three Punicines were added to a planetary ball mill before grinding LiAlO2 to particle sizes suitable for flotation. We investigated the influence of Punicine and two derivatives with C10 and C17 side chains on the grinding results at different grinding times and conditions as well as on the yields in flotations. SEM images of the particles, IR and ICP–OES measurements provided insights into the Punicine–particle interactions. They showed that Punicines not only prevent the formation of hydrophilic and thus undesirable lithium aluminate hydroxide hydrate (LiAl2(OH)7 ▪ x H2O) surfaces in this process, as is unavoidable in aqueous flotation without this pretreatment, they also prevent the undesired release of lithium cations into the aqueous phase. Due to considerable hydrophobization of the particle surface of LiAlO2, nearly quantitative recovery rates of this engineered artificial mineral are achieved using the process described here.

Co-doped NiFe carbonate hydroxide hydrate nanosheets with edge effect constructed from spent lithium-ion battery ternary cathodes for oxygen evolution reaction

The recycling of spent lithium-ion batteries (LIBs) has received increasing attention for environment and resource reclamation. Converting LIBs wastes into high-efficiency catalysts is a win-win strategy for realizing resource reclamation and addressing sustainable energy challenges. Herein, we developed a simple method to upcycle spent-LIBs cathode powder into Co-doped NiFe carbonate hydroxide hydrate (Co/NFCH-FF) as a low-cost and efficient oxygen evolution reaction (OER) electrocatalyst. The optimized Co/NFCH-FF electrode appears very competitive OER performances with low overpotentials of 201 and 249 mV at 10 and 100 mA cm−2, respectively, a small Tafel slope of 48.4 mV dec−1, and a high long-term stability. Moreover, we reveal that the existence of Co atoms leads to the formation of a crystalline/amorphous (c/a) interface at the Co/NFCH nanosheet edge, inducing the nanosheets possess a unique edge effect to enhance electric fields and accumulate hydroxide ions (OH–) at the edge during the OER process. Benefiting from edge effect, Co/NFCH-FF shows outstanding intrinsic activity. Furthermore, Co atoms as dopants stabilize the electronic structure of Co/NFCH-FF, enabling Co/NFCH-FF to exhibit excellent catalytic stability. This work provides an effective strategy for converting the end-life LIBs to high-performance multicomponent OER electrocatalysts and proposes new insights into the mechanism of enhanced catalytic activity of Co/NFCH.

Whole-life carbon emissions of concrete mixtures considering maximum CO2 sequestration via carbonation

A comparison of cradle-to-gate embodied carbon emissions and carbon dioxide (CO2) sequestration potential due to carbonation of portland cement (PC), portland limestone cement (PLC), and limestone calcined clay cement (LC3) concrete mixtures is presented in this work. First, the cradle-to-gate embodied carbon emissions of the concrete mixtures were calculated using life cycle assessment (LCA). Then, the CO2 sequestration potential of each mixture was computed using a theoretical model for CO2 sequestration that was derived using principles of cement chemistry to account for the carbonation of both calcium hydroxide (CH) and calcium silicate hydrate (C-S-H). The results indicate that a theoretical maximum of 33 % of the cradle-to-gate embodied carbon emissions of the concrete mixtures analyzed herein can be realistically sequestered via carbonation. Data also substantiate that concrete mixtures with higher cradle-to-gate embodied carbon emissions sequester the most CO2. However, concrete mixtures with lower cradle-to-gate embodied carbon emissions, namely PLC and Type I, II, III, IV, and V mixtures with high-SCM replacements, typically yield the lowest whole-life carbon emissions. The results indicate that concrete mixtures with high SCM replacement should be prioritized—regardless of which cement is used to produce the concrete—from a whole-life carbon emissions perspective.

Emerging Vanadium-Doped Cobalt Chloride Carbonate Hydroxide for Flexible Electrochromic Micro-Supercapacitor: Charged-State Prediction from RGB Input by ANN Model.

Multifunctional devices integrated with electrochromic and supercapacitance properties are fascinating because of their extensive usage in modern electronic applications. In this work, vanadium-doped cobalt chloride carbonate hydroxide hydrate nanostructures (V-C3H NSs) are successfully synthesized and show unique electrochromic and supercapacitor properties. The V-C3H NSs material exhibits a high specific capacitance of 1219.9Fg-1 at 1mVs-1 with a capacitance retention of 100% over 30000 CV cycles. The electrochromic performance of the V-C3H NSs material is confirmed through in situ spectroelectrochemical measurements, where the switching time, coloration efficiency (CE), and optical modulation (∆T) are found to be 15.7 and 18.8s, 65.85cm2C-1 and 69%, respectively. A coupled multilayer artificial neural network (ANN) model is framed to predict potential and current from red (R), green (G), and blue (B) color values. The optimized V-C3H NSs are used as the active materials in the fabrication of flexible/wearable electrochromic micro-supercapacitor devices (FEMSDs) through a cost-effective mask-assisted vacuum filtration method. The fabricated FEMSD exhibits an areal capacitance of 47.15mFcm-2 at 1mVs-1 and offers a maximum areal energy and power density of 104.78Whcm-2 and 0.04mWcm-2, respectively. This material's interesting energy storage and electrochromic properties are promising in multifunctional electrochromic energy storage applications.

Safety and Effect of Fly Ash Content on Mechanical Properties and Microstructure of Green Low-Carbon Concrete

Based on the promotion and application of green and low-carbon technology, this study aims to develop a high-safety performance cement concrete incorporating a large dosage of fly ash (FA). The safety and effect of FA content on the mechanical properties of FA composited cement were studied through compressive strength, flexural strength, and microscopic tests. The results show that when the FA replaced 20% cement, the properties of concrete were the best in this study. The flexural strengths and compressive strengths of the standard cured concrete for 28 days with 20% FA content are 0.82 MPa and 4.32 MPa larger than that of the pure cement concrete. The XRD and SEM analysis suggested that the mechanical properties of the composite cement FA system are improved significantly since the replacement of cement by FA promotes secondary hydration of calcium hydroxide in the concrete, leading to a more compact and safe interface between cement and FA.

Nuclear Quantum Effects in Hydroxide Hydrate Along the H-Bond Bifurcation Pathway.

Path integral (PI) simulations are used to explore nuclear quantum effects (NQEs) in hydroxide hydrate and its perdeuterated isotopomer along the H-bond bifurcation pathway. Toward this, a new potential energy surface using the symmetric gradient domain machine learning method with ab initio data at the CCSD(T)/aug-cc-pVTZ level is built. From PI umbrella sampling (US) simulations, free energy profiles along the bifurcation coordinate are explored as a function of temperature. At ambient temperature, the bifurcation barrier is increased upon inclusion of NQEs. At low temperatures in the deep tunneling regime, the barrier is strongly decreased and flattened. These trends are examined, and the role of the O-O distance is also investigated through two-dimensional US simulations.

Occurrence Mechanism of the Abnormal Gelation Phenomenon of High Temperature Cementing Slurry Induced by a Polycarboxylic Retarder.

The class G oil well cement is a type of special cement that can be subjected to a high temperature formation environment. It was found that the class G cement tail slurry with a low polycarboxylic retarder dosage (usually ≤1% by weight of cement) was more prone to cause the abnormal gelation phenomenon (AGP) than the lead slurry with a high retarder dosage at a high temperature (usually when T ≥ 120 °C). This study aimed at the occurrence mechanism of this unfavorable phenomenon that seriously endangers the cementing security. Results showed that the abnormal gelatinous region underwent premature hydration; namely, the calcium hydroxide and calcium silicate hydrate (C-S-H) content were all higher than the nongelatinous region, while the copolymer content was the opposite. Correspondingly, the theory of "premature hydration and crystal nucleation" was proposed to explain the abnormal gelation mechanism of a cementing tail slurry with an insufficient retarder dosage. Furthermore, a novel functionalized copolymer retarder "PAIANS" was synthesized to alleviate the AGP.

A Cost‐Effective Production Route of Li4Ti5O12 Resisting Unsettled Market and Subsequent Application in the Li‐Ion Capacitor

Outstanding materials and novel device structures are key factors in satisfying the increasing demand for energy storage. Li‐ion capacitors, as one typical model of asymmetric supercapacitors, benefit from the battery's ultrahigh specific energy and supercapacitor's superlarge specific power to meet the balanced electrochemical energy storage requirements. The inherent and irreplaceable advantages make spinel lithium titanate an optimal candidate for power batteries and Li‐ion capacitors. However, upstream market volatility, including price spikes and supply shortages, tremendously threatens spinel lithium titanate's production, sale, and application. Lithium hydroxide hydrate is an alternative raw material to synthesize spinel lithium titanate synthesis, which can help address these concerns. The indirect production path generates high‐quality lithium carbonate as an intermediate product. Spinel lithium titanate is synthesized preferably via another economically and technically more efficient method that skips the isolation step after carboxylation. The electrochemical performance of the resulting spinel lithium titanate is evaluated to be better than that of commercial competitors. The spinel lithium titanate negative electrode‐based lithium‐ion capacitor achieves a specific energy of 89.5 Wh kg−1. These results demonstrate the success of efforts to find a feasible and affordable synthesis route to mitigate market risks.

ZnO Additive Boosts Charging Speed and Cycling Stability of Electrolytic Zn–Mn Batteries

HighlightsLow pH value of electrolyte suppresses the charge capabilities of electrolytic Zn–Mn batteries.Unique solid phase alkaline properties of zinc sulfate hydroxide hydrate endow the electrolytic Zn–Mn batteries with greatly enhanced charge capabilities.The highly active Zn2Mn3O8·H2O nanorods array deposited during the charge process improve the discharge efficiency and stability of electrolytic Zn–Mn batteries.

An iron phosphate hydroxide hydrate electrocatalyst: synergistic effects of Fe2+ and Fe3+ for enhanced hydrogen evolution reaction stability

Synthesized via unique electrodeposition, Fe3(PO4)(OH)6·3H2O HER catalyst, with varied ratios, boasts enriched Fe3+/Fe2+ sites. In 1 M KOH, it excels with a low 130 mV overpotential, 87 mV dec−1 Tafel value, and 80 hour durability at 100 mA cm−2.

Solubility of neodymium and dysprosium sulfates at different pH and temperature and the effect of yttrium sulfate, sodium sulfate, and ammonium sulfate mixtures: Strengthening the predictive capacities of the OLI software

This study focuses on investigating the solubilities of two rare earth element (REE) sulfate salts, Nd2(SO4)3 (representing light REEs) and Dy2(SO4)3 (representing heavy REEs), under various conditions. Four different systems are studied: 1) binary REE2(SO4)3–H2O system at natural pH and temperatures of 25, 46, 65, and 80 °C, 2) ternary REE2(SO4)3–NaOH–H2O system, covering a pH range from 7 down to neutral, at temperatures of 25, 46, 65, and 80 °C, 3) ternary REE2(SO4)3–Y2(SO4)3–H2O system, involving Y2(SO4)3 concentrations ranging from 0 to 20 g/L, pH values of 3 and 7, all at 25 °C, and 4) quaternary REE2(SO4)3–Na2SO4–(NH4)2SO4–H2O system, encompassing Na2SO4 and (NH4)2SO4 concentrations varying from 0 to 20 g/L, pH values of 3 and 7, and at 25 °C. Solubilities of Nd2(SO4)3 and Dy2(SO4)3 decrease as temperature rises, attributed to the exothermic dissolution reactions. Within pH 2 to 5, solubilities remain relatively constant, but at higher pH, they decrease due to the formation of REE2(SO4)(OH)4(H2O)2 (rare earth sulfate hydroxide hydrate). Addition of Y2(SO4)3 does not significantly affect solubilities because of the relatively low Y2(SO4)3 concentration range (below 0.03 mol/kg of water), but solubilities are lower at pH 7 due to REE2SO4OH4H2O2 formation. For Nd2(SO4)3, solubility decreases with increasing Na2SO4 and (NH4)2SO4 concentrations, especially at pH 3 due to the formation of NaNd(SO4)2(H2O) (sodium neodymium bis(sulfate) hydrate) which is also confirmed by the decrease in Na2SO4 concentration compared with the target value. However, at pH 7, the concentration of Na2SO4 is much closer to the target range. This suggests that the formation of NaNd(SO4)2(H2O) is less significant at pH 7 and most of Nd precipitates as Nd2SO4OH4H2O2. For Dy2(SO4)3, solubility increases with increasing sulfate concentrations again due to the to the formation of REESO4+ and REE(SO4)2− complexes but the solubility is lower at pH 7 due to Dy2SO4OH4H2O2 and DySO4OH formation. The outcomes of this investigation represent a notable augmentation to the existing repository of solubility data for Nd2(SO4)3 and Dy2(SO4)3. These particular systems were deliberately chosen to emulate the process of extracting rare earth elements (REEs) from ion-adsorbed clays. Nonetheless, the implications of this research extend beyond this context and hold relevance for various procedures that involve the handling of REEs in sulfate-based environments. One prominent application of these findings lies in the augmentation of thermodynamic models, notably the MSE model integrated into the OLI software. Through the incorporation of this new dataset, the OLI software is poised to become a more potent tool for forecasting and simulating the chemistry of rare earth sulfate systems. This advancement bears significant promise for forthcoming research endeavors and industrial applications where precise modeling of REE behavior is of paramount importance.

Nanometer lanthanum hydroxide modified anionic polymer for deep fluoride removal: Adsorption properties and mechanism study

The development of chemical industry has brought about serious fluoride pollution, and there is an urgent need to develop an adsorbent with high efficiency and stability for fluoride removal. Despite the remarkable adsorption capacity of lanthanum hydroxide hydrate for fluoride ions, its industrial application is limited by powder leaching and strict pH requirements.In this study, lanthanum-containing anionic resin (HLO-D201) was synthesized by the method of precursor introduction and in-situ deposition, mainly by introducing La3+ into the resin, adding sodium hydroxide to precipitate it in the resin pore, forming hydrated lanthanum oxide.The characterization analysis showed that hydrated lanthanum oxide (HLO) was successfully introduced into the porous matrix of the resin and existed in the form of crystalline hydrated oxide.Static adsorption experiments demonstrated that HLO-D201 could effectively adsorb fluoride ions in a wide pH range (2–10). Since nano La (OH) 3 was encapsulated in the resin pore, the loss of La (OH) 3 was greatly reduced, and under the condition of competitive adsorption of several coexisting ions, Only phosphoric acid group interferes obviously with the adsorption of F-. The synthesized HLO-D201 still showed good adsorption capacity after regenerated by NaOH–NaCl composite solution for six times. The removal mechanism of fluoride by HLO-D201 is mainly electrostatic attraction and ligand exchange.Overall, HLO-D201 is a kind of fluorine removal adsorbent with excellent performance and wide application prospects.