Search Results (3,575)

In this work, a method for leaching black mass from spent Li batteries using oxalic acid was developed and experimentally verified with the objective of selectively separating lithium and cobalt. Oxalic acid proved to be an efficient and selective leaching agent. Under 1 M C₂H₂O₄, 120 min, L:S = 20, 80 °C and 300 rpm, a lithium yield of 90% was achieved, while cobalt dissolution remained low at 1.57%. Subsequently, cobalt spontaneously precipitated from the leachate within several hours, and the solid phase was fully separated after 24 h. The leachate contained minor amounts of accompanying metals, with dissolution yields of 0.5% Mn, 8% Fe and 1.4% Cu. These impurities were removed from the leachate by controlled pH adjustment using NaOH at ambient temperature and 450 rpm, with complete precipitation at pH 12. This procedure generated a purified lithium-rich leachate, which was converted into lithium oxalate by crystallisation at 105 °C. Subsequent calcination of the resulting solid at 450 °C for 30 min produced Li₂CO₃ with a purity of 91%. Based on the experimental findings, a conceptual technological process for selective lithium leaching using oxalic acid was proposed, demonstrating the potential of this method for sustainable lithium recovery. Full article

The new mineral polyarsite, ideally Na₇CaMgCu₂(AsO₄)₄F₂Cl, was discovered in high-temperature incrustations of the active Arsenatnaya fumarole at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. It is associated with aegirine, sanidine, ferrisanidine, hematite, halite, sylvite, cassiterite, evseevite, axelite, badalovite, johillerite, arsmirandite, aphthitalite, tridymite, potassic-magnesio-fluoro-arfvedsonite and litidionite. Polyarsite forms short-prismatic, equant or tabular crystals up to 0.15 mm across, their clusters up to 0.3 mm in size or crusts up to 0.5 mm across and up to 0.03 mm thick. Polyarsite is transparent, sky-blue to light blue, with vitreous lustre. It is brittle, no cleavage is observed and the fracture is uneven. D_calc. = 3.592 g cm⁻³. Polyarsite is optically biaxial (+), α = 1.624 (4), β = 1.645 (4), γ = 1.682 (4) (589 nm), 2V_meas. = 70 (10)°. The empirical chemical formula calculated based on 19 O+F+Cl apfu is Na_7.04Ca_1.00Mg_0.92Cu_2.06Fe³⁺_0.06(As_3.96S_0.05)_Σ4.01O_16.28F_1.66Cl_1.06. Polyarsite is monoclinic, space group I2/m, a = 8.4323(4), b = 10.0974(4), c = 10.7099(6) Å, β = 90.822(4)°, V = 911.79(8) ų and Z = 2. The crystal structure was determined based on SCXRD data, R = 0.0391. Polyarsite demonstrates a novel structure type. The structure is based on the (1 0 1) heteropolyhedral layers formed by Cu₂O₈Cl dimers built by CuO₄Cl tetragonal pyramids sharing common Cl vertex, AsO₄ tetrahedra and MgO₄F₂ octahedra. Adjacent layers are linked via CaO₈ cubes to form a pseudo-framework which hosts octahedrally coordinated Na cations. Polyarsite was named based on the Greek words πολύς, poly, “many” and due to belonging to arsenates: this arsenate contains many chemical components ordered between different positions in crystal structure. Full article

This work investigates the corrosion behavior of 18%Ni high-strength steel (00Ni18Co-8Mo5TiAl, solution-treated at 820 °C for 3 h and aged at 480 °C for 3 h) in NaCl solutions with 1%, 3.5%, and 6% chloride ions, as well as chloride ions’ effect on passive film properties. The corrosion process was systematically studied via chemical immersion tests (GB/T 17897-1999, 144 h, solution-to-sample contact area ratio 20:1) and electrochemical methods, including EIS (frequency range: 100 kHz–0.01 Hz) and Tafel polarization curves (scan rate: 10 mV/min). Passive film evolution was analyzed via Mott–Schottky curves (fixed frequency: 1000 Hz, scanning potential: −1 V to 1 V vs. SCE). Microstructural observations show the steel exhibits pitting corrosion in chloride environments, with corrosion products transforming from loose outer α-FeOOH/γ-FeOOH to dense inner Fe₃O₄/β-FeOOH. These dense products inhibit anodic reactions. Electrochemical results reveal polarization resistance decreases and corrosion current density rises with increasing chloride concentration. Mott–Schottky curves indicate that flat band potential increases from −0.2177 V to −0.1258 V with rising chloride concentration, increasing point defects in the passive film and weakening its self-healing ability. Full article

Lead-free transparent ferroelectric ceramics with integrated opto-electro-mechanical functionalities are pivotal for next-generation multifunctional devices. In this study, K_0.48Na_0.52NbO₃-xLa₂O₃ (KNN-xLa, x = 0.005 − 0.04) ceramics were fabricated via a conventional solid-state route to investigate the La³⁺-induced multiscale structural evolution and its modulation of optical and electrical properties. La³⁺ substitution drives a critical structural transition from an anisotropic orthorhombic phase (Amm2) to a high-symmetry pseudocubic-like tetragonal phase (P4mm) for x ≥ 0.025, characterized by minimal lattice distortion (c/a = 1.0052). This enhanced structural isotropy, coupled with submicron grain refinement (<1 μm) driven by -mediated solute drag, effectively suppresses light scattering. Consequently, a high-transparency plateau (T₇₈₀ ≈ 53–58%, T₁₇₀₀ ≈ 70–72%) is achieved for 0.025 ≤ x ≤ 0.035. Simultaneously, the system undergoes a crossover from normal ferroelectric (FE) to relaxor (RF) state, governed by an FE–RF boundary at x = 0.015. While x = 0.005 exhibits robust piezoelectricity (d₃₃ ≈ 92 pC/N), the x = 0.015 composition facilitates a transitional polar state with large strain (0.179%) and high polarization (P_m ≈ 33.3 μC/cm², P_r ≈ 15.8 μC/cm²). Piezoresponse force microscopy (PFM) confirms the domain evolution from lamellar macro-domains to speckle-like polar nanoregions (PNRs), elucidating the intrinsic trade-off between optical transparency and piezoelectricity. This work underscores La³⁺ as a potent structural modifier for tailoring phase boundaries and defect chemistry, providing a cost-effective framework for developing high-performance transparent electromechanical materials. Full article

The South Sakhalin mud volcano (Sakhalin Island, Russia) emits HCO₃-Cl/Na-Mg water, emanates CO₂ prevailing over CH₄ in the gas phase, and extrudes mud bearing five carbonate mineral species. The study focuses on the distribution, diversity, and origin of the carbonate minerals from the mud volcano (MV) ejecta, in terms of carbon cycle processes. The data presented include a synthesis of field observations, compositions of MV gases and waters, chemistry of carbonate minerals, as well as stable isotope geochemistry of MV waters (δ¹³С, δD, and δ¹⁸O) and carbonates (δ¹³С and δ¹⁸O). The sampled MV waters are isotopically heavy, with δ¹⁸O = +5.7 to +7.5 ‰ VSMOW, δD = −18.0 to −11.0 ‰ VSMOW, and ¹³С (δ¹³С_DIC = +6.9 to +8.1 ‰ VPDB). This composition may be due to the dilution of basinal water with dehydration water released during the diagenetic illitization of smectite. Carbonates in the sampled mud masses belong to three genetically different groups. Mg-rich siderite, (Fe_0.54–0.81Mg_0.04–0.30Ca_0.05–0.23Mn_0.00–0.08)CO₃, disseminated in abundance throughout the mud masses, coexists with common calcite and sporadic ankerite. The trace-element chemistry of Mg-siderite, as well as the oxygen (δ¹⁸O = +34.4 to +36.8 ‰ VSMOW) and carbon (δ¹³C = −1.3 to +0.6 ‰ VPDB) isotopic signatures, confirms its authigenic origin. Siderite formed during early diagenesis of the Upper Cretaceous sandy and clayey marine sediments mobilized by mud volcanism in the area. Another assemblage, composed of dawsonite, siderite, and vein calcite (±kaolinite), represents altered arkose sandstones found as few fragments in the mud. This assemblage may be a marker of later CO₂ flooding into the sandstone aquifer in the geological past. The trace-element chemistry, particular morphology, and heavy C (δ¹³С = +5.5 to +7.0 ‰ VPDB) and O (δ¹⁸О = +39.1 to +39.5 ‰ VSMOW) isotope compositions indicate that aragonite is the only carbonate species that is related to the current MV activity. It crystallized in a shallow reservoir and was maintained by СО₂ released from rapidly ascending liquefied mud and HCO₃-Cl/Na-Mg-type of MV waters. Full article

The phaeozem in Northeast China is rich in soil organic carbon (SOC). However, the excessive and inefficient application of chemical fertilizers, particularly nitrogen fertilizers, has primarily led to a decrease in soil pH in this region. Currently, the relationship between soil pH and the stability of soil organic carbon (SOC) remains ambiguous. This study, conducted over 13 years of field experiments, focused on soils exhibiting varying degrees of pH resulting from different nitrogen application rates. The research employed aggregate classification, ¹³C nuclear magnetic resonance spectroscopy, and analysis of microbial community composition to investigate the alterations in the SOC stabilization mechanisms under varying nitrogen application levels. Our results demonstrated that the decline in soil pH led to reductions in macroaggregates (>2 mm) and the soil aggregate destruction rate (PAD) by 4.8–14.6%, and in soil aggregate unstable agglomerate index (E_LT) by 9.7–13.4%. The mean weight diameter (MWD) and geometric mean diameter (GMD) exhibited significant declines (p < 0.05) with decreasing pH levels. According to the ¹³C NMR analysis, the SOC was predominantly composed of O-alkyl carbon and aromatic carbon. At a pH of 5.32, the Alip/Arom values decreased, while the molecular structure of SOC became more complex under different levels of pH. In addition, the increase in [Fe(Al)-OC] (31.4–71.9%) complex indicates a shift in the stability of organic carbon from physical protection to organic mineral binding. Declining soil pH significantly reduced the diversity of soil microbial communities and promoted a shift toward copiotrophic microbial groups. Overall, declining soil pH resulted in a decline in soil aggregate stability and an increase in SOC aromaticity. This drove the shift in the stabilization mechanism of SOC in the black soil ecosystem of meadows in Northeast China from physical protection to chemical stability. Full article

Arsenic (As) contamination threatens ecosystems and human health, and iron (hydr)oxides-mediated formation of Fe-As composites is a key strategy for arsenic immobilization, while the long-term stability of these composites under complex environmental conditions remains a critical concern. This study systematically investigated the interactive effects of environmental factors (temperature: 5–35 °C, pH: 4–8, competing ions: phosphate and citrate) and material intrinsic properties (ferrihydrite aging: 0–60 days, Fe/As molar ratio: 1.875 and 5.66, adsorption time) on Fe-As composite stability using multiscale characterization techniques and theoretical modeling. Results showed that temperature was the dominant controlling factor, with arsenic release increasing by 4.25% per 1 °C rise (178% higher at 35 °C vs. 20 °C) and an exponential relationship model established (R² = 0.96). Ferrihydrite aging enhanced stability, as 60-day aged composites (Fh_60d-As) exhibited minimal arsenic release (18.83%) at pH 4/20 °C, attributed to increase As(V)-O-Fe binding energy (1.2 eV) and -OH group enhancement (12.5%). Phosphate induced 2.4-fold higher arsenic release than citrate, and lower pH (4–6) reduced release via enhanced protonation. A stability prediction model was developed (R² = 0.91), and practical remediation strategies were proposed: maintaining temperatures below 25 °C in arsenic-containing waste repositories and using pre-aged iron-based materials. This work provides quantitative benchmarks and mechanistic insights for contaminated site rehabilitation. Full article

The six platinum group elements (PGE) are among the rarest elements in the upper continental crust of the earth. Higher values of PGE have been detected in the upper mantle and in chondrite meteorites. The PGE are siderophile and chalcophile elements and are divided into the following: (1) the Ir subgroup (IPGE) = Os, Ir, and Ru and (2) the Pd subgroup (PPGE) = Rh, Pt, and Pd. The IPGE are more refractory and less chalcophile than the PPGE. High concentrations of PGE led, in rare cases, to the formation of mineral deposits. The PGE are carried in discrete phases, the platinum group minerals (PGM), and are included as trace elements into the structure of base metal sulphides (BM), such as pentlandite, chalcopyrite, pyrite, and pyrrhotite. Similarly to PGE, the PGM are also divided into two main groups, i.e., IPGM composed of Os, Ir, and Ru and PPGM containing Rh, Pt, and Pd. The PGM occur both in mafic and ultramafic rocks and are mainly hosted in stratiform reefs, sulphide-rich lenses, and placer deposits. Presently, there are only 169 valid PGM that represent about 2.7% of all 6176 minerals discovered so far. However, 496 PGM are listed among the valid species that have not yet been officially accepted, while a further 641 are considered as invalid or discredited species. The main reason for the incomplete characterization of PGM resides in their mode of occurrence, i.e., as grains in composite aggregates of a few microns in size, which makes it difficult to determine their crystallography. Among the PGM officially accepted by the IMA, only 13 (8%) were discovered before 1958, the year when the IMA was established. The highest number of PGM was discovered between 1970 and 1979, and 99 PGM have been accepted from 1980 until now. Of the 169 PGM accepted by the IMA, 44% are named in honour of a person, typically a scientist or geologist, and 31% are named after their discovery localities. The nomenclature of 25% of the PGM is based on their chemical composition and/or their physical properties. PGM have been discovered in 25 countries throughout the world, with 64 from Russia, 17 from Canada and South Africa (each), 15 from China, 12 from the USA, 8 from Brazil, 6 from Japan, 5 from Congo, 3 from Finland and Germany (each), 2 from the Dominican Republic, Greenland, Malaysia, and Papua New Guinea each, and only 1 from Argentine, Australia, Bulgaria, Colombia, Czech Republic, England, Ethiopia, Guyana, Mexico, Serbia, and Tanzania each. Most PGM phases contain Pd (82 phases, 48% of all accepted PGM), followed, in decreasing order of abundances, by those of Pt 35 phases (21%), Rh 23 phases (14%), Ir 18 phases (11%), Ru 7 phases (4%), and Os 4 phases (2%). The six PGE forming the PGM are bonded to other elements such as Fe, Ni, Cu, S, As, Te, Bi, Sb, Se, Sn, Hg, Ag, Zn, Si, Pb, Ge, In, Mo, and O. Thirty-two percent of the 169 valid PGM crystallize in the cubic system, 17% are orthorhombic, 16% hexagonal, 14% tetragonal, 11% trigonal, 3% monoclinic, and only 1% triclinic. Some PGM are members of a solid-solution series, which may be complete or contain a miscibility gap, providing information concerning the chemical and physical environment in which the mineral was formed. The refractory IPGM precipitate principally in primitive, high-temperature, mantle-hosted rocks such as podiform and layered chromitites. Being more chalcophile, PPGE are preferentially collected and concentrated in an immiscible sulphide liquid, and, under appropriate conditions, the PPGM can precipitate in a thermal range of about 900–300 °C in the presence of fluids and a progressive increase of oxygen fugacity (fO₂). Thus, a great number of Pt and Pd minerals have been described in Ni-Cu sulphide deposits. Two main genetic models have been proposed for the formation of PGM nuggets: (1) Detrital PGM represent magmatic grains that were mechanically liberated from their primary source by weathering and erosion with or without minor alteration processes, and (2) PGM reprecipitated in the supergene environment through a complex process that comprises solubility, the leaching of PGE from the primary PGM, and variation in Eh-pH and microbial activity. These two models do not exclude each other, and alluvial deposits may contain contributions from both processes. Full article

The design of ladle furnace (LF) refining pathways for weathering steels requires precise control of multi-component steel/slag reactions governed simultaneously by thermodynamics and interfacial mass transfer kinetics. An EERZ-based kinetic modeling strategy was employed using the Thermo-Calc^® (version 2022a) Process Metallurgy Module and the CALPHAD TCOX11 database to develop LF refining schedules capable of upgrading conventional S355J2R steel to weathering steel grades: S355J2W and S355J2WP. First, the sensitivity of predicted compositions to key kinetic inputs was quantified. The validated model was then used to simulate deoxidation and desulfurization sequences, predicting the evolution of liquid–steel and slag compositions, slag basicity, and FeO activity throughout the LF cycle. Subsequently, Cr- and P-ferroalloys were introduced to design tap-to-tap schedules that meet the EN 10025-5 chemical specifications for S355J2W and S355J2WP. To correlate simulation outcomes with material performance, plates produced following the modeled schedules were evaluated through a 1000 h accelerated salt spray test. Steel density and steel phase mass transfer coefficients were found to produce the highest prediction sensitivity (up to 7.5 wt.% variation in C and S), whereas slag phase parameters exhibited a lower impact. The predicted steel compositions showed strong agreement with industrial values obtained during plant trials. SEM-EDS analyses confirmed the development of a Cr-enriched protective patina and validated model-based alloying strategies. Full article

Topaz is one of the most economically important fluorine-rich nesosilicates, which are predominantly colorless in natural crystals. Hence, the trade relies almost entirely on irradiated blue topaz with an unstable color center, which has been shown to fade over time. The cobalt (Co) diffusion treatment is a stable alternative process for converting colorless topaz to blue by a solid-state diffusion mechanism. To investigate the potential role of Co²⁺ substitution in the formation of the blue layer and the coupled behavior of F/OH dehydroxylation in facilitating this process, systematic diffusion treatments have been successfully conducted and compared. In this study, gem-quality topazes were annealed in air at 1000 °C for 20–40 h (hr) along with CoO, Fe₂O₃, Cr₂O₃, and CuO powders. The diffused products were characterized using Scanning Electron Microscope (SEM), Ultraviolet-Visible absorption spectroscopy (UV-Vis), Near-Mid Infrared spectroscopy (NMIR), and X-ray photoelectron spectroscopy (XPS). Parallel runs with CuO, Fe₂O₃, or Cr₂O₃ alone confirmed that none of these oxides produces a stable blue layer, underscoring the unique role of Co. The Co-diffused sample displays an intense blue layer characterized by a Co²⁺ octahedral isomorphism triplet at 540, 580, and 630 nm, which are absent from both untreated and heat-only controls. XPS analysis reveals the emergence of Co²⁺ (binding energy: 780.63 eV) and a concomitant depletion in F⁻, along with the disappearance of the OH overtone absorption at 7123 cm⁻¹. These observations confirm that defluorination generates octahedral vacancies accommodated by the coupled substitution: CoF₂ (solid reactant) + (AlO₂)⁻ (fragment of topaz structure) → AlOF (solid product) + (CoOF)⁻ (fragment of topaz structure). Prolonged annealing leads to decreased relative atomic percentages of K⁺ and F⁻ ions, consistent with volatilization losses during the high-temperature process, thereby directly correlating color intensity with cobalt valence state, which transfers from Co²⁺ to Co³⁺. These findings establish a Co-incorporation chronometer for F–rich aluminosilicate systems, with an optimal annealing time of approximately 20 hr at 1000 °C. Furthermore, the above results demonstrate that the color mechanism in nesosilicate gems is simultaneously governed by volatile release and cation availability. Full article

The dimensions and the reduction capacity of Fe₃O₄ nanoparticles are considered to be the key parameters in achieving the successful, efficient removal of hexavalent chromium, aiming for drinking water purification. This research study focuses on the optimization of reaction parameters during the oxidative precipitation of FeSO₄ carried out in a microwave-heated plug-flow reactor, to realize the preparation of Fe₃O₄ nanoparticles with an increased reduction potential as reflected in the Fe²⁺/Fe³⁺ ratio by approximating the ideal value of 0.5. In particular, the coupling of synthesis with features that allow for control of the oxidation extent, and include the addition of a reducing agent, an increase in ageing temperature, and inhibition of aggregation, were tested as potential approaches to tune the reducing potential and overcome reported Cr(VI) capture efficiencies provided by Fe₃O₄ nanoparticles. The evaluation results showed that adding a reductant after nanoparticle formation inhibits spontaneoussurface oxidation, bringing an improvement in the Cr(VI) uptake capacity for a residual concentration equal to the new EU regulation limit, by around 40%, reaching a value of 2.15 mg/g. However, working at an ageing temperature of around 100 °C resulted in an even better performance with an uptake increase of 120% and a capacity value of 3.45 mg/g. Finally, adding nanoparticles in the form of a dispersion instead of a dried powder provides an extra 10% improvement as a consequence of limited aggregation. Full article

Both organic matter and iron oxide (FeO) dynamics pose key roles in soil cadmium (Cd) bioavailability. However, the microbially driven transformation of soil organic matter and FeO and their linkages to Cd fractions remain unclear under reductive soil disinfestation (RSD) with different organic sources, which limits our mechanistic understanding of Cd immobilization by RSD. To address this gap, we conducted a 45 day microcosm experiment using a paddy soil contaminated with 22.8 mg/kg Cd. Six treatments were established: untreated control (CK), waterlogged (WF), and RSD-amended soils with 0.7% or 2.1% wheat straw (LWD, HWD) or soybean meal (LSD, HSD). We systematically assessed soil Cd fractionation, organic carbon and FeO concentrations, and bacterial community structure, aiming to clarify differences in Cd immobilization efficiency and the underlying mechanisms between wheat straw and soybean meal. For strongly extractable Cd, wheat straw RSD reduced the soil Cd concentrations from 6.02 mg/kg to 4.32 mg/kg (28.2%), whereas soybean meal RSD achieved a maximum reduction to 2.26 mg/kg (62.5%). Additionally, the soil mobility factor of Cd decreased from 44.6% (CK) to 39.2% (HWD) and 32.5% (HSD), while the distribution index increased from 58.5% (CK) to 62.2% (HWD) and 66.8% (HSD). Notably, the HWD treatment increased soil total organic carbon, humus, and humic acid concentrations by 34.8%, 24.6%, and 28.3%, respectively. Regarding amorphous FeO, their concentrations increased by 19.1% and 33.3% relative to CK. RSD treatments significantly altered soil C/N ratios (5.91–12.5). The higher C/N ratios associated with wheat straw stimulated r-strategist bacteria (e.g., Firmicutes, Bacteroidetes), which promoted carbohydrate degradation and fermentation, thereby enhancing the accumulation of humic substances. In contrast, the lower C/N ratios of soybean meal increased dissolved organic carbon and activated iron-reducing bacteria (FeRB; e.g., Anaeromyxobacter, Clostridium), driving iron reduction and amorphous iron oxide formation. PLS-PM analysis confirmed that wheat straw RSD immobilized Cd primarily through humification, whereas soybean meal RSD relied on FeRB-mediated FeO amorphization. These findings suggest that Cd immobilization in soil under RSD may be regulated by microbially mediated organic matter transformation and iron oxide dynamics, which was affected by organic materials of different C/N ratios. Full article

In this work, the characteristic temperatures (solidus and liquidus) of selected lead blast furnace slags were investigated using in situ high-temperature optical microscopy. The effects of the basicity of the slag (CaO/SiO₂), the Fe/SiO₂ ratio, and the Zn content were investigated. The deformation temperature associated with the rounding of the sample edges and the temperature at which 75% of the sample height decreases were experimentally considered as the solidus and liquidus temperatures, respectively. The pseudoternary phase diagrams CaO-SiO₂-Fe_0.63Zn_0.37O and FeO-Ca_0.54Si_0.46O_1.46-ZnO were calculated, along with the crystallization curves, using the thermodynamic software FactSage to estimate the characteristic temperatures and phase evolution during the cooling of the slag. The difference between the calculated and experimental solidus and liquidus temperatures was about 70 °C. The results of XRD, SEM, and DSC analysis at high temperatures showed that spinel (ZnFe₂O₄), melilite (Ca₂ZnSi₂O₇), and andradite (Ca₃Fe₂Si₃O₁₂) were the base crystals for all slag samples. The liquidus temperature increases with decreasing slag basicity (CaO/SiO₂), while the liquidus temperature increases with increasing Fe/SiO₂ ratio or Zn content. Full article

This work investigates the feasibility of synthesis hybrid x Gd₂O₃ + (100 − x) Fe₃O₄ nanoparticles using the scalable method of high-energy ball milling for dual-contrast magnetic resonance imaging applications. Comprehensive studies of the structure, magnetic and functional properties of the hybrid nanoparticles were conducted. It was found that the milling process initiates the transformation of the cubic phase c-Gd₂O₃ ($\mathrm{I}\mathrm{a}\overline{3}$) into the monoclinic m-Gd₂O₃ (C2/m). Measurements of the magnetic properties showed that the specific saturation magnetization of the Fe₃O₄ phase is substantially reduced, which is a characteristic feature of nanoparticles due to phenomena such as surface spin disorder and spin-canting effects. The transmission electron microscopy results confirm the formation of hybrid Fe₃O₄-Gd₂O₃ nanostructures and the measured particle sizes show good correlation with the X-ray diffraction results. A comprehensive structure–property relationship study revealed that the obtained hybrid nanoparticles exhibit high r₂ values, reaching 160 mM⁻¹s⁻¹ and low r₁ values, a characteristic that is determined primarily by the presence of a large fraction of Gd₂O₃ particles with sizes of ≈30 nm and Fe₃O₄ crystallites of ≈10 nm. Full article

Sulfamethoxazole (SMX), a widely used antibiotic, poses potential threats to ecosystems and human health due to its persistence and residues in aquatic environments. This study developed a novel intelligent water treatment system, namely Intelligent Pulsed Electrochemical Activation of NaClO₂ (IPEA_NaClO2), which integrates a FeCuC-Ti₄O₇ composite electrode with machine learning (ML) to achieve efficient SMX removal and energy consumption optimization. Six key operational parameters—initial SMX concentration, NaClO₂ dosage, reaction temperature, reaction time, pulsed potential, and pulsed frequency—were systematically investigated to evaluate their effects on removal efficiency and electrical specific energy consumption (E-SEC). Under optimized conditions (SMX 10 mg L⁻¹, NaClO₂ 60~90 mM, pulsed frequency 10 Hz, temperature 313 K) for 60 min, the IPEA_NaClO2 system achieved an SMX removal efficiency of 89.9% with a low E-SEC of 0.66 kWh m⁻³. Among the ML models compared (back-propagation neural network, BPNN; gradient boosting decision tree, GBDT; random forest, RF), BPNN exhibited the best predictive performance for both SMX removal efficiency and E-SEC, with a coefficient of determination (R²) approaching 1 on the test set. Practical application tests demonstrated that the system maintained excellent stability across different water matrices, achieved a bacterial inactivation rate of 98.99%, and significantly reduced SMX residues in a simulated agricultural irrigation system. This study provides a novel strategy for the intelligent control and efficient removal of refractory organic pollutants in complex water bodies. Full article