Search Results (69)

Weathering steel (WS) is widely used in bridge construction due to its high corrosion resistance, durability, and low maintenance requirements. This paper reviews the performance of WS bridges in Canadian climates, focusing on the formation of protective patina, influencing factors, and long-term maintenance strategies. The protective patina, composed of stable iron oxyhydroxides, develops over time under favorable wet–dry cycles but can be disrupted by environmental aggressors such as chlorides, sulfur dioxide, and prolonged moisture exposure. Key alloying elements like Cu, Cr, Ni, and Nb enhance corrosion resistance, while design considerations—such as drainage optimization and avoidance of crevices—are critical for performance. The study highlights the vulnerability of WS bridges to microenvironments, including de-icing salt exposure, coastal humidity, and debris accumulation. Regular inspections and maintenance, such as debris removal, drainage system upkeep, and targeted cleaning, are essential to mitigate corrosion risks. Climate change exacerbates challenges, with rising temperatures, altered precipitation patterns, and ocean acidification accelerating corrosion in coastal regions. Future research directions include optimizing WS compositions with advanced alloys (e.g., rare earth elements) and integrating climate-resilient design practices. This review highlights the need for a holistic approach combining material science, proactive maintenance, and adaptive design to ensure the longevity of WS bridges in evolving environmental conditions. Full article

Improper emissions from industrial activities pose toxicological risks to groundwater safety. Based on an environmental forensic identification case involving livestock (sheep) damage caused by groundwater pollution in a pastoral area, we comprehensively evaluated groundwater quality risks, toxicological risks, and pollution sources using multivariate statistical methods, the Nemerow index method, and a non-carcinogenic health risk model. The potential specific pollutants in the region mainly included calcium, potassium, sodium, magnesium, manganese, fluoride, chloride, sulfate, ammonia nitrogen, total dissolved solids, and nitrate. An evaluation of the groundwater health risk factors showed that fluoride, nitrate, and manganese pose higher health risks (HQ > 1), as fluoride > nitrate > manganese. This suggests that these three pollutants were the primary causes of livestock damage. Identification of pollution sources using multivariate statistical analysis revealed that the main pollutants in the groundwater originate from two rare earth enterprises in the surrounding industrial park, followed by the emissions from animal husbandry. This study provides guidelines into comprehensive regional toxicological risk assessment and source tracing, offering an identification method for similar forensic environmental damage cases. Full article

The precipitation process of rare earth from a rare earth chloride solution using magnesium bicarbonate yields a dilute magnesium chloride (MgCl₂) solution. The dilute MgCl₂ solution can only be concentrated to a maximum concentration of about 70 g/L by conventional reverse osmosis (RO), which is insufficient for recycling. Low-salt-rejection reverse osmosis (LSRRO) allows for a higher concentration of brine while operating at moderate pressures. However, research on LSRRO for the concentration of MgCl₂ solution is still at an initial stage. In this study, polyamide RO membranes were treated with sodium hypochlorite (NaClO) to prepare low-salt-rejection membranes. The effects of NaClO concentration, pH, and chlorination time on the membrane properties were investigated. Under alkaline chlorination conditions, the membrane’s salt rejection decreased, and water flux increased with increasing NaClO concentration and chlorination time. This can be explained by the hydrolysis of polyamide in the alkaline solution to form carboxylic acids and amines, resulting in a decrease in the crosslinking degree of polyamide. The low-salt-rejection membrane was prepared by exposing it to a NaClO solution at a concentration of 15 g/L and a pH of 11 for 3 h, and the salt rejection of MgCl₂ was 50.7%. The MgCl₂ solution with a concentration of 20 g/L was concentrated using multi-stage LSRRO at the pressure of 5 MPa. The concentration of the concentrated brine reached 120 g/L, which is 87% higher than the theoretical maximum concentration of 64 g/L for conventional RO at the pressure of 5 MPa. The specific energy consumption (SEC) was 4.17 kWh/m³, which decreased by about 80% compared to that of mechanical vapor recompression (MVR). This provides an alternative route for the efficient concentration of a diluted MgCl₂ solution with lower energy consumption. Full article

Organometallic rare-earth complexes have attracted considerable attention in recent years due to their unique structures and exceptional magnetic properties. In this study, we report the synthesis and magnetic characteristics of a family of monopentamethylcyclopentadienyl-coordinated trinuclear rare-earth hepta-chloride clusters [(Li(THF)(Et₂O))(Cp^*RE)₃(μ-Cl)₄(μ₃-Cl)₂(μ₄-Cl)] (RE₃: RE =Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu; Cp* = pentamethylcyclopentadienide). These clusters were synthesized by reacting LiCp* with RECl₃ in a 1:1 molar ratio within a mixed solvent system (THF: Et₂O = 1:9), resulting in high solubility in common organic solvents such as DCM, THF, and Et₂O. Magnetic studies conducted on these paramagnetic clusters reveal the coexistence of ferromagnetic and antiferromagnetic superexchange interactions in Gd₃. Additionally, Dy₃ exhibits both ferromagnetic and antiferromagnetic intramolecular dipolar interactions. Notably, slow magnetic relaxation was observed in Dy₃ below 23 K under a zero DC applied field with an energy barrier of 125(6) cm⁻¹. Full article

LaOCl-mediated ethane chlorination into 1,2-dichloroethane offers a promising pathway for low-temperature, large-scale ethane upgrading. However, under Cl₂-rich conditions, LaOCl undergoes detrimental chlorination into lanthanum chloride (LaCl₃), accompanied by extensive surface hydroxylation. Such severe structural evolution limits the practical application of La-based catalysts under industrially relevant conditions. In this study, an alumina-stabilized La catalyst was prepared via a coprecipitation method. We demonstrated that strong La-O-Al interactions effectively resist structural degradation of La species under reaction conditions, enabling the modified catalyst to maintain exceptional stability under high Cl₂ concentrations. At a C₂H₆/Cl₂ ratio of 4:9, the optimized catalyst achieves an ethane conversion of 61%, with 1,2-dichloroethane selectivity sustained above 74% for 12 h without noticeable deactivation. In contrast, the bulk LaOCl counterpart suffers from rapid over-chlorination, shifting product dominance to trichloroethane within 10 h. Advanced spectroscopy characterization reveals that selectivity loss in LaOCl originates from phase collapse into LaCl₃, whereas Al₂O₃ stabilization preserves the metastable LaOCl_x phase in a highly dispersed state, ensuring selective C–Cl bond formation. These results highlight the critical role of stabilizing metastable oxychloride phases through robust metal oxide interactions, establishing a design framework for rare-earth catalysts in high-concentration chlorine environments. Full article

Furnas volcano, one of the three active central volcanoes of São Miguel (the Azores archipelago), hosts mineral waters with significant special variations, divided into hyperthermal (89.4–95.4 °C), thermal (29.9–70.0 °C), and cold (14.2–21.4 °C) waters. Groundwaters are classified as Na-HCO₃, with a neutral to slightly acidic pH, except one SO₄-Na acidic sample. The major elements are primarily influenced by rock leaching and volcanic input, patterns also reflected in the trace elements, including the rare earth elements. The major cations, along with lithium, iron, aluminum, rubidium, and strontium, indicate the influence of water–rock interactions. Some samples depict a higher influence in this input, shown by the similar REE behavior between them and the local rock behavior. The volcanic input is distinguished into two environments: an acid sulfate boiling pool, formed by steam heating, and neutral HCO₃-Cl waters, where bicarbonate-rich waters mix with a neutral chloride fluid from a deep reservoir. The deeper reservoir also provides boron, arsenic, antimony, and tungsten, also seemingly associated with a positive spike in europium due to rock dissolution at temperatures above 250 °C or a reducing environment. This interpretation is corroborated by the stability of the strontium isotopes between samples. Full article

This work presents a comparative study of five rare earth compounds—Erbium nitrate pentahydrate lll (Er), Neodymium nitrate pentahydrate (Nd), Samarium III Nitrate Hexahydrate (Sm), Yterbium III Chloride Hexahydrate (Yb) and Praseodymium nitrate hexahydrate lll (Pr)—protecting API 5L X70 steel from corrosion in saline medium that uses electrochemical impedance spectroscopy (EIS) and polarization curves (CPs) at different concentrations and in static mode. The results show that Erbium is the best corrosion inhibitor, containing 50 ppm and reaching an inhibition efficiency of about 89%, and similar result was shown by Sm with an IE~87.9%, while the other rare earths (Nd, Yb and Pr) showed a decrease in corrosion protection at the same concentration, since they were below an IE~80%. On the other hand, with the Langmuir model it was possible to describe that the adsorption process of the three rare earths follows a combined physisorption–chemisorption process to protect the metal’s surface. The observed adsorption free energy, ΔG°ads, reaches −38.7 kJ/mol for Er, −34.4 kJ/mol for Nd, and −33.6 kJ/mol for Pr; whereas Sm and Yb have adsorption free energies of −33.9 and −35.0 kJ/mol, respectively. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) further confirmed the formation of a protective film. Their characterization using density functional theory showed the transference of charge from the iron cluster towards the rare earth metal compounds. The adsorption process produced a slightly polarized region of interaction with the metal surface. Also, it was found that the adsorption of the rare earths affected the magnetic properties of the surface of the iron cluster. Quantum chemical descriptors, such as Pearson’s HSAB (Hard and Soft Acids and Bases) descriptors, were useful in predicting the behavior of the flow of electrons between the metal surface and the interacting rare earth ions. Full article

This systematic study was conducted on the separation of yttrium (Y) and erbium (Er) from a chloride medium using a mixed extractant system composed of [N1444][P507] and TRPO (trialkylphosphine oxide) in kerosene. This investigation focused on the effects of various extractants, extraction systems, the initial acidity of the aqueous phase, and the phase contact time on the extraction efficiencies of Y and Er. This study showed that using the combination of [N1444][P507] and TRPO notably increased the extraction performance and enhanced the separation factor between Y and Er, outperforming the individual use of P507 or [N1444][P507] under identical conditions. The extraction efficiencies for Y and Er reached 88.4% and 93.3%, respectively, with a separation factor (Er/Y) of 1.84, highlighting the system’s effectiveness in selectively isolating rare earth elements. Optimal stripping conditions were obtained using 0.1 mol/L of HCl, resulting in a successful recovery of 93.1% of Y³⁺ and 78.9% of Er³⁺ from the organic phase. The extraction mechanism involved both ion exchange and ion association. The enthalpy changes (ΔH) associated with the extraction of Y³⁺ (−2.5 kJ·mol⁻¹) and Er³⁺ (4.6 KJ·mol⁻¹) demonstrate that the extraction processes are exothermic, reflecting the thermodynamic differences between the two ions. Full article

At present, the use of conventional reactive dyes on banana-fiber fabric leads to the problem of excessive salt consumption, which is not conducive to environmental protection. In this experimental study, rare-earth-pretreated banana-fiber fabric was dyed with the reactive dye Argazol Navy Blue. The rare-earth pretreatment was carried out to reduce the level of salt consumption, improve dyeing and fixation rates, and reduce the treatment burden of printing and dyeing wastewater. Dye uptake and fixation rates were used as indicators. Single-change factors were assessed by analyzing different amounts of rare earth, sodium carbonate, and sodium chloride, as well as different fixation times and temperatures, so that the effects of the dye additive on the dyed banana-fiber fabric could be investigated. After appropriate ranges were determined for single-change factors, an orthogonal experiment was carried out to establish optimal parameters for the process of dyeing rare-earth-pretreated banana-fiber fabric with Argazol Navy Blue. These parameters were as follows: the required amount of rare earth was 0.40% (o.w.f.); the amount of dye was 2% (o.w.f.); the amount of sodium chloride was 15 g/L; the amount of sodium carbonate was 9 g/L; the fixing temperature was 75 °C; and the fixing time was 45 min. These optimized process parameters were then used to dye the banana-fiber fabric as a whole. Our results showed that the dye uptake and fixation rates for rare-earth-pretreated banana-fiber fabric dyed with navy-blue dye reached 56.85% and 45.32%, respectively. Finally, the effect of rare-earth pretreatment on dyeing performance was analyzed using FT-IR, SEM, and EDS. Full article

Solvent extraction of metals from Ti ore was investigated with a view of enhancing extraction yields by changing the concentration of the ligands, the rate of mixing, the pH, and the temperature of the solution. Norwegian Ti ore was leached with 5M HNO₃ alongside 10% ascorbic acid to obtain a pregnant solution containing transition metals and some rare earth elements (REEs). Part Two of the study will address the recovery of the REEs in the ore. The elemental analysis of solid and aqueous samples was done by two models of total reflection X-ray fluorescence spectrometers (S2 PICOFOX, Bruker Corporation, Berlin, Germany; and T-STAR, Bruker Corporation, Berlin, Germany). The same analysis was repeated using an inductively coupled plasma-mass spectrometer (Perkin Elmer Sciex ELAN DRC II, Perkin Elmer, Waltham, MA, USA). The extraction process and parameters were examined by ICP-MS. The extraction efficiencies were studied under different conditions through the use of various concentrations of ligands at different pHs, temperatures, and mixing rates of the solution. At pH 1.0, 22.5 °C, and a mixing rate of 1400 rpm, the selectivity of 150 g/L trioctyl methyl ammonium chloride (Aliquat 336) was 99% Ti⁴⁺, 94% V⁴⁺, and 82% Hf⁴⁺, while 99% of Co²⁺ was recovered at pH 0.8. The extraction efficiency of triethyl phosphate (10% TEP) was 58% Cu²⁺, 68% Mn²⁺, and 63% V⁴⁺ at 55 °C, 1400 rpm, and without a pH change. Tributyl phosphate (10% TBP) was able to retrieve 87% Cu²⁺ and 78% Zn²⁺ at pH 1.3, 1400 rpm, and 22.5 °C, and 80% Ti⁴⁺ at pH 1.2. A 10% solution of 2,4,6-tris (allyloxy)-1,3,5-triazine (TAOT) demonstrated 61% Mn²⁺ and 56% Hf⁴⁺ extraction at pH 1.3, 22.5 °C, and 1400 rpm. Under the same conditions, 10% methyl salicylate (MS) was able to recover 56% Hf⁴⁺ at pH 1.3. Using 1400 rpm, di (2-ethylhexyl) phosphoric acid (10% D2EHPA) was found to selectively extract 87% Hf⁴⁺ at 22.5 °C without a pH change, and around 99% Co²⁺, Ti⁴⁺, and Fe²⁺ at pH 1.3. This study provides valuable insights into optimizing solvent extraction conditions for transition metals’ recovery and serves as a precursor to future research on the extraction of REEs from Ti ores. This process is relevant from the environmental and economic perspectives since it provides the best approach to recycling metals to reduce the rate of raw ore mining. Full article

In this study, an ionic liquid-based polymer inclusion membrane (IL-PIM) made of (50% polymer-50% CyphosIL104) was used to extract and separate the rare earth elements (REEs) Y, La, Nd, and Sm in chloride solutions. The effect of extraction time and pH was studied to optimize the extraction and separation conditions. The four REEs were effectively extracted at pH 4–5 from both single and mixed metals solutions. However, at pH 2, only Y was extracted. The recovery of the extracted REEs from the loaded PIM was achieved using HNO₃ and H₂SO₄. In the case of La, it was quantitatively back-extracted with H₂SO₄ after a contact time of 1 h, while up to 4 h was necessary to recover 70% of the extracted Y, Sm, and Nd. Extraction isotherms were studied, and the Freundlich isotherm model was the most adequate to describe the interaction between the PIM and the REEs. Finally, the developed PIM was investigated for the extraction of REEs from mixtures containing other metals, which showed great selectivity for the REEs. Full article

A large amount of ammonium salt leaching agent will remain in the leaching site of weathered crust elution-deposited rare earth ore (WREOs). The release of residual ammonium (RA) will seriously affect the water system ecology of the mining area, and it is urgent to control it. In this paper, column eluting was used to simulate the eluting process of RA in rare earth (RE) ore tailings, and the effects of calcium chloride concentration, eluting temperature, liquid-solid ratio, eluent pH and eluent flow rate on the eluting process of RA in rare earth ore tailings were discussed. It was found that calcium chloride could effectively elute the RA from ore tailings. Eluting agent pH almost had no effect on the eluting process of RA in the pH range of 4–6, and a greater impact on it at pH 8. The flow rate could effectively enhance the elution efficiency. The optimum conditions were calcium ion concentration of 0.1 mol/L, liquid-solid ratio of 2:1, pH 4–6, flow rate of 0.6 mL/min and elution at room temperature. At this time, the elution efficiency of RA was 91.85%. The eluting process of RA in ore tailings was controlled by the inner particle diffusing according to the kinetic analysis. The reaction order was 0.368, and the activation energy of the reaction is 12.450 kJ/mol. This will provide a theoretical basis and technical support for the efficient eluting process of residual ammonium in the leaching site of WREOs. Full article

Due to the coexistence of Al³⁺ and RE³⁺ and their similar properties, the separation of aluminum from rare earths is difficult. In this study, selective precipitation was used to separate aluminum from rare earth chloride solution via electrochemical regulated hydrolysis. By controlling the current density and electrolytic time, the rate of hydroxyl ion production was regulated, and the selective separation of rare earth and aluminum was realized according to the different precipitation sequences. By altering the temperature, current density, pH value, and other parameters, the separation performance of aluminum from rare earth in mixed rare earth chloride systems was systematically investigated. The removal rate of aluminum reached 88.35%, and the loss rate of rare earth was only 5.99% under optimized conditions. Compared with traditional neutralization hydrolysis, the new process showed higher efficiency and lower rare earth loss rate. Furthermore, a kinetic analysis of aluminum precipitation revealed that the reaction adhered to pseudo-first order kinetics. Additionally, the precipitate obtained via separation and filtration was amorphous alumina hydroxide with a small amount of rare earth attached. No reagent was consumed for the new process, which was more efficient and cleaner, providing a new idea for removing aluminum impurities from rare earth solutions. Full article

Self-healing polydimethylsiloxane (PDMS) has garnered significant attention due to its potential applications across various fields. In this study, a functionalized modification of PDMS containing di-aminos was initially conducted using 2,6-pyridinedicarbonyl chloride to synthesize pyridine-PDMS (Py-PDMS). Subsequently, rare earth metal europium ions (Eu³⁺) were incorporated into Py-PDMS. Due to the coordination interaction between Eu³⁺ and organic ligands, a coordination cross-linking network was created within the Py-PDMS matrix, resulting in the fabrication of Eu³⁺-Py-PDMS elastomer. At a molar ratio of Eu³⁺ to ligands of 1:1, the tensile strength of Eu³⁺-Py-PDMS reached 1.4 MPa, with a fracture elongation of 824%. Due to the dynamic reversibility of coordination bonds, Eu³⁺-Py-PDMS with a metal-to-ligand molar ratio of 1:2 exhibited varying self-healing efficiencies at different temperatures. Notably, after 4 h of repair at 60 °C, its self-healing efficiency reached nearly 100%. Furthermore, the gas barrier properties of Eu³⁺-Py-PDMS with a molar ratio of 1:1 was improved compared with that of Eu³⁺-Py-PDMS with a molar ratio of 1:1. This study provides an effective strategy for the design and fabrication of PDMS with high mechanical strength, high gas barrier properties, and exceptional self-healing efficiency. Full article

In this study, the extraction of rare earth elements (REEs) from chloride solutions after leaching REE carbonate concentrate with solutions of the mixtures of P507 (2-ethylhexylphosphonic acid mono-2-ethylhexyl ester) and Cyanex 272 (bis(2,4,4-trimethylpentyl)phosphinic acid) (1:1) at various concentrations was experimentally studied. It was shown that the distribution ratios of all REEs decrease with the increasing concentration of these metals in the initial solution, which is associated with the loading of the organic phase. The most significant improvement in the extraction is observed for the heavy group of rare earth elements. The extractability of REEs increases with the increasing atomic number of the element, as is typical for the extraction of these metals with acidic organophosphorus extractants. The data obtained show that the separation factors of adjacent rare earth elements decrease slightly with the increasing concentration of metals in the initial aqueous solution. Increasing the concentration of the extractant mixture does not have a significant effect on the values of the adjacent REE separation factors. The data obtained on the distribution ratios and separation factors made it possible to propose a flow sheet for the separation of rare earth elements with the production of Y, Ho, Tb and Dy. Full article