Search Results (452)

This study presents a starch-modified calcined-ZnAl layered double-hydroxide (S-C-ZnAl-LDH) nanocomposite as a multifunctional nanofiller for poly(vinylidene fluoride) (PVDF) efficiently performing, simultaneously, ultrafiltration membrane filtration and efficient adsorbent for the recovery of Acid Blue dye-contaminated water. The synergistic effects of starch modification and thermal activation on nanofiller structure, interfacial compatibility, and membrane performance were systematically investigated through a comparison with pristine ZnAl-LDH, calcined ZnAl-LDH, starch-modified ZnAl-LDH, and calcined starch-modified ZnAl-LDH. SEM, TEM, and XRD analyses confirmed the formation of hierarchical layered nanosheet architectures with a uniform dispersion of crystalline ZnAl domains within a partially amorphous starch matrix, promoting enhanced polymer–nanofiller interfacial interactions Adsorption performance was influenced by solution pH, initial dye concentration, and temperature. Nonlinear kinetic analysis showed that the PFO model described the kinetic data better. However, the overall kinetic modeling findings suggest that Acid Blue 92 adsorption is governed by a combination of physicochemical interactions, suggesting a complex adsorption mechanism was involved. The starch-modified nanocomposite exhibited excellent regeneration stability, retaining approximately 88–90% of its adsorption capacity after five adsorption–desorption cycles. More importantly, the incorporation of S-C-ZnAl-LDH into PVDF membranes significantly enhanced membrane functionality, increasing water flux and permeance by 42.9% and 25%, respectively, while improving Acid Blue rejection by 35.7% to approximately 98%. These improvements are attributed to enhanced membrane hydrophilicity, optimized nanofiller dispersion, and favorable polymer–filler interfacial interactions that facilitate water transport while maintaining high separation efficiency. This work demonstrates an effective strategy for integrating renewable bio-based modifiers with layered nanomaterials to engineer advanced polymeric films exhibiting enhanced permeability, selectivity, durability, and reusability, providing a sustainable platform for multifunctional membrane technologies in water purification and environmental protection. Full article

Driven by the urgent need for large-scale disposal and resource valorization of bauxite residue (red mud), this review adopts a narrative review perspective, grounded in the Earth’s Macro-Cycle concept, and employs a structured yet non-systematic literature survey across multiple databases (Web of Science, ScienceDirect, etc.) to compare the physicochemical property differences of red mud derived from different production processes and to establish a classification–evaluation system integrating calcium content gradient with reaction type. Building upon this framework, three distinct cementitious systems are elucidated: three-dimensional network formation via low-calcium geopolymerization, the symbiotic coexistence of C-(A)-S-H and N-A-S-H dual gels in medium- and high-calcium systems, and the integration of clinker hydration with alkali activation in high-calcium systems. Furthermore, by evaluating alkalization, heavy metal stabilization, and fluoride immobilization behaviors, we propose optimal, scenario-specific application pathways: Low-calcium geopolymer systems are ideal for the ecological or structural remediation of acid-contaminated sites, medium-to-high-calcium systems for backfilling large-scale mining voids, and high-calcium systems for the structural repair of expressways. This work bridges the gap between fundamental solid waste mineralogy and practical engineering applications, offering robust strategies for the high-value, environmentally safe, and large-scale recycling of industrial solid wastes. Full article

Efficient and reusable photo-Fenton catalysts require the rational integration of photocatalytic platforms, effective H₂O₂ activation sites, and practical immobilization strategies. Herein, nitrogen-vacancy-rich tubular g-C₃N₄ (HCNT) was prepared as the photocatalytic platform. Iron (II) phthalocyanine (FePc) was then loaded onto HCNT to form the FePc/HCNT composite for antibiotic degradation. The FePc/HCNT composite was further immobilized in a poly (vinylidene fluoride) (PVDF) membrane, denoted as FePc/HCNT-PVDF, to facilitate catalyst recovery and reuse. Benefiting from the micrometer-scale tubular morphology, the FePc/HCNT remained exposed on the membrane surface, preserving accessible catalytic interfaces and reducing encapsulation within the polymer matrix. The tubular architecture facilitated reactant transport, while surface nitrogen vacancies enhanced photogenerated-carrier separation and utilization. Component-dependent experiments revealed that FePc served as the primary center for H₂O₂ activation, whereas HCNT functioned as a defect-engineered tubular photocatalytic platform that promoted photogenerated-carrier separation and reactive oxygen species formation. The optimized FePc/HCNT achieved 94% oxytetracycline degradation within 60 min, with an apparent rate constant of 0.04462 min⁻¹, approximately 11 times higher than bulk g-C₃N₄, and exhibited broad-spectrum degradation capability toward various organic pollutants, including rhodamine B, tetracycline, amoxicillin, and ciprofloxacin. The FePc/HCNT-PVDF membrane removed 90% of oxytetracycline within 60 min and maintained stable performance over ten cycles. This work provides insights into the integrated roles of nitrogen vacancy regulation, FePc-mediated H₂O₂ activation, and morphology-assisted membrane immobilization in the development of reusable g-C₃N₄-based photo-Fenton catalysts. Full article

In this study, a method for introducing titanium dioxide nanoparticles (TiO₂NPs) into the polymer matrix of a ferroelectric copolymer of vinylidene fluoride with tetrafluoroethylene P(VDF-TFE) is proposed and optimized. A comprehensive analysis showed that TiO₂NPs content has a significant effect on the structure formation processes in the polymer matrix, the degree of crystallinity, phase composition, and surface morphology of the composites. By optimizing the amount of doped nanoparticles, it is possible to increase the electrical strength and permittivity of the material, as well as enhance the piezoelectric response compared to a film without TiO₂NPs. The introduction of TiO₂NPs into the P(VDF/TFE) polymer matrix promotes efficient polarization of the composite film without preliminary high-temperature orientational drawing. The approaches presented in this study can simplify process operations in the manufacture of flexible sensors, wearable electronics, and other devices that require a combination of piezoelectric activity and high electrical strength. Full article

This work is devoted to the investigation of rare-metal granites associated with anorthosite–rapakivi granite rock complexes. This article evaluates the physicochemical conditions that governed the formation of a rare-metal granite dike. It also explores assumptions regarding the geological characteristics of the magmatic chamber, describes evidence for liquid immiscibility, and addresses the post-entrapment evolution of hydrosilicate liquids. In addition, new mineralogical data are presented. The methods employed include optical and electron microscopy, Raman spectroscopy, secondary ion mass spectrometry, laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS), melt inclusion homogenisation experiments, and fluid inclusion study. The investigated granitic dike formed under low pressure (60–110 MPa) and temperatures of about 580–600 °C, from a specific volatile-saturated magma rich in H₂O (up to 16.76 wt% in quenched hydrosilicate liquid products) and in F (up to 4.16 wt%) and Li (up to 3804 ppm), as indicated by homogenised melt inclusions. At the time of emplacement, a silicate melt, a probable Ca-fluoride melt, an Mg-Fe Al-Si-rich hydrosilicate liquid (either mutually soluble with or mixed with the inferred Ca-fluoride melt), and an essentially aqueous fluid coexisted. Depolymerisation of the silicate melt and the presence of complex ions probably promoted the dissolution and transport of high field strength elements (HFSE) and large ion lithophile elements (LILE) elements by the Mg-Fe Al-Si-rich hydrosilicate liquid. During the final stage of evolution of the granitic magmatic system, Mg behaved incompatibly because of its negligible partitioning into mica; rather than accumulating in the silicate melt, it entered the hydrosilicate liquid as a major component. The residual silicate melt consequently attained even lower Zr/Hf, Nb/Ta, and Y/Ho ratios than the studied rock. Full article

Groundwater is the principal source of drinking water in northern Ghana, where fluoride and nitrate are the major groundwater-quality concerns. Naturally elevated fluoride concentrations (>1.5 mg/L) have resulted in the closure of wells, while nitrate pollution regularly occurs in shallow aquifers due to lack of sanitation infrastructure and agricultural activities. Distinguishing natural from human-induced groundwater contamination is therefore essential for effective groundwater management. This study assessed groundwater quality with regard to fluoride enrichment and established lithology-specific natural background levels (NBLs) for major ions and selected trace elements using groundwater samples from 110 wells across three different lithologies in the Vea Catchment, northern Ghana. The results reveal high fluoride NBLs in a K-feldspar-rich granitoid formation (3.84 mg/L) and near-guideline concentrations in a hornblende–biotite tonalite (1.41 mg/L). Silicate weathering, lithology-dependent dissolution of fluorine-bearing minerals, and cation exchange were identified as the principal processes controlling groundwater chemistry and fluoride enrichment. Elevated NBLs of Sr, Li, Ba and SiO₂ in the K-feldspar-rich granitoids indicate enhanced water–rock interaction whereas relationships between nitrate and Cl⁻, Br⁻, and SO₄²⁻ suggest localized anthropogenic impacts. These findings demonstrate the value of lithology-specific NBLs for improving groundwater quality assessment and supporting groundwater resource management in crystalline basement aquifers. Full article

High-purity quartz processing currently faces three critical factors: depleting reserves of high-grade natural ore, inadequate impurity removal efficiency, and heavy environmental pollution driven by traditional refining methods. Therefore, this article first introduces the reasons for the formation of different types of impurities in quartz, as well as the methods and difficulties in removing different types of impurities. Then, a comprehensive summary was made of the current research progress and purification mechanism of quartz purification technology. The study of acid leaching kinetics in quartz purification can accurately determine the optimal operating parameters and support process scaling up. Calcination treatment has been verified to achieve efficient impurity removal. Specifically, the phase transformation and vacuum calcination behaviors during thermal treatment dominate the impurity elimination mechanism. Correspondingly, targeted and efficient purification strategies are proposed to remove different categories of impurities. The future quartz purification holds strong potential in several key areas. These include optical sorting, microwave-assisted calcination furnaces, biological surfactants, and fluoride-free acid leaching. Additional high-potential directions involve rapid macroscopic identification methods for quartz ore and the extraction of quartz from solid waste. Full article

Titanium dioxide nanotubes (TiO₂ NTs) fabricated by electrochemical anodization have attracted attention because their morphology can be regulated by processing parameters. Although the anodic fabrication of TiO₂ NTs has been widely studied, the morphology evolution of nanotubes on Ti6Al4V during secondary anodization after ultrasonic removal of the first nanotube layer still requires further clarification. In this study, anodic nanotubular oxide structures were fabricated on Ti6Al4V substrates by primary anodization and secondary anodization. The effects of anodization voltage, fluoride ion concentration, oxidation time, and secondary anodization on nanotube morphology were investigated. The results show that increasing anodization voltage promotes nanotube formation and increases tube diameter, whereas excessive oxidation time and high fluoride concentration lead to nanograss formation, tube collapse, and surface damage. Compared with primary anodization, secondary anodization produced smaller nanotube diameters and distinct morphology evolution, which may be associated with changes in the initial surface state after ultrasonic removal of the first nanotube layer. Among the investigated conditions, primary anodization at 40 V in 0.5 wt.% NH₄F electrolyte followed by secondary anodization at 50 V produced relatively regular nanotubular regions, although nanograss was also present on the surface. This work provides a process-oriented understanding of TiO₂ nanotube morphology regulation on Ti6Al4V substrates during primary and secondary anodization. Full article

Enhancing the performance of titanium biomaterials remains a critical challenge in the development of durable implant materials, particularly under complex physiological conditions where corrosion processes are influenced by interactions with biological species. Electrochemical oxidation has emerged as a promising approach for generating nanostructured titanium dioxide layers, which can improve corrosion resistance. In this study, nanostructured oxide layers were synthesized on additively manufactured 3D titanium scaffolds via anodization in a fluoride-containing ethylene glycol and water electrolyte. Corrosion resistance was systematically evaluated using open-circuit potential measurements, Tafel analysis, and electrochemical impedance spectroscopy, considering the effects of biological medium composition and prolonged exposure to corrosive conditions. The main scientific contribution of this work is the elucidation of the time-dependent corrosion behavior and electrochemical stability of anodized additively manufactured titanium scaffolds under physiological exposure conditions. The results demonstrated that the medium composition significantly influenced the properties of the anodized materials, primarily due to the adsorption of medium species on the nanostructured surface. Prolonged exposure tests further confirmed the superior durability of the coatings, which is attributed to the formation of a protective protein layer that enhances corrosion resistance in aggressive environments. These findings advance the understanding of time-dependent corrosion behavior in complex biological environments and highlight the effectiveness of nanostructured oxide layers in maintaining the electrochemical stability of titanium biomaterials during prolonged exposure. Combined with additive manufacturing, this approach represents a promising route toward the development of patient-specific implants with enhanced durability and long-term functionality for bone regeneration applications. Full article

Germanium is a critical rare-dispersed metal with irreplaceable applications in infrared optics, fiber-optic communications, and semiconductor industries, making its efficient recovery from secondary resources of great strategic importance. This study investigates the selective recovery of germanium from complex zinc smelting leachates using a novel hydroxamic acid extractant, BGYW, in synergistic combination with P204. The feed solution contained approximately 360 mg/L Ge, 10,790 mg/L Fe²⁺, and 98,530 mg/L Zn, representing a highly complex matrix. Continuous counter-current extraction was performed in a 30-stage miniature mixer-settler. Under optimized conditions of 10% BGYW + 5% P204 in white oil, an O/A ratio of 1:1, and 8 mol/L NH₄F as strippant, the single-stage germanium extraction efficiency reached 99.4%. Over 16 consecutive cycles, the extraction system maintained stable performance with average germanium extraction above 99%. A 3-stage scrubbing section using 50 g/L H₂SO₄ effectively removed co-extracted Zn, Cu, and Al impurities. Iron co-extraction, a major challenge, was successfully mitigated through a 2–3 stage iron scrubbing step using a chloride-containing scrubbing solution, which reduced the iron concentration in the strip liquor from approximately 600 mg/L to below 4 mg/L, and decreased the Fe/Ge mass ratio from 0.197 to below 0.01. The overall germanium recovery across the entire 30-stage continuous process reached 98.82%, and the dissolution loss of BGYW in the aqueous phase was reduced by over 85% compared to the conventional YW100 extractant. Third-phase formation caused by residual organic flocculants from the leaching step was eliminated through enhanced pre-treatment, while ferric fluoride precipitation in the stripping section was resolved by incorporating the iron scrubbing stage. This study demonstrates that the BGYW-P204 extraction system with the integrated iron scrubbing step offers an efficient, stable, and industrially viable approach for germanium recovery from zinc smelting leachates, providing a practical solution to the long-standing challenge of germanium–iron separation and contributing to the sustainable supply of this critical metal. Full article

Flexible wearable piezoelectric sensors have attracted increasing attention in human motion monitoring and motion classification applications due to their self-powered sensing capability and rapid response. In this work, poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) flexible piezoelectric films were fabricated using a phase separation method with different loading masses of PVDF-HFP to regulate the crystal structure and output signal characteristics of the films. X-ray diffraction and Fourier-transform infrared spectroscopy analyses demonstrated that an appropriate mass of PVDF-HFP promoted the formation of polar β-phase crystals, and the optimized film exhibited a β-phase content of 86.81%. The prepared films generated stable and distinguishable response signals under different gait conditions, indicating high potential for flexible motion sensing. Furthermore, machine learning-assisted motion classification was preliminarily performed based on the acquired sensing signals, achieving an accuracy above 90%. This work demonstrates the potential of phase-separated PVDF-HFP films for flexible gait sensing and wearable motion recognition applications. Full article

This study aimed to systematically evaluate the effects of the Zein/poly(vinylidene fluoride) (PVDF) blend ratio on the formation, structure, and performance of electrospun nanofiber membranes and to further assess the feasibility of incorporating bromothymol blue (BTB) into the optimized matrix as a pH-responsive functional component for intelligent food-packaging applications. Increasing PVDF content reduced the conductivity but increased the viscosity of the spinning solutions, and all formulations exhibited shear-thinning behavior. Pure Zein failed to form continuous fibers, whereas PVDF incorporation promoted uniform fibrous networks, with average fiber diameters increasing from 113.02 ± 27.06 nm to 530.68 ± 113.33 nm. FTIR and TGA/DTG analyses confirmed the coexistence of Zein and PVDF and the improved thermal stability associated with increasing PVDF content. Surface hydrophobicity and water resistance increased with PVDF content, whereas water vapor permeability (WVP) and water solubility (WS) increased with the Zein proportion. Considering spinnability, morphology, mechanical behavior, barrier performance, and water stability, the Zein/PVDF = 5:5 formulation provided a comparatively balanced performance and was selected as the functional carrier matrix. Incorporation of BTB into this matrix produced a distinct pH-responsive color change, and the color difference (ΔE) showed a strong correlation with shrimp pH during storage (R² = 0.997), demonstrating the feasibility of the optimized membrane as a freshness-responsive functional carrier. Full article

Electrospun poly(vinylidene fluoride) (PVDF) nanofiber filters are attractive for particulate air filtration because they combine high filtration efficiency with low airflow resistance. Here, three inorganic additives, namely aluminum chloride (AlCl₃), potassium nitrate (KNO₃), and silicon nitride (Si₃N₄), were investigated using formulation-specific electrospinning conditions selected to achieve stable fiber formation. Although all filters exhibited high initial filtration efficiencies above 96%, clear differences were observed in fiber morphology, pressure drop, electrostatic potential decay, and long-term filtration stability. Among the tested samples, the Si₃N₄-containing filter showed the best long-term performance, retaining approximately 94% filtration efficiency after 30 days, whereas neat PVDF decreased to about 85%. These results suggest that differences in long-term filtration stability are closely associated with charge-retention behavior, and that the incorporation of inorganic additives can influence the durability of PVDF-based electrospun nanofiber air filters. Full article

Sulfur(VI) fluoride exchange (SuFEx) chemistry is a powerful click reaction for modular synthesis, distinguished by high chemoselectivity, broad functional-group tolerance and the formation of robust sulfur(VI)-based linkages. These attributes are particularly valuable for polymer functionalization, as S(VI)–F handles on either the polymer or the modifier enable covalent coupling under controlled conditions. This review spans SuFEx-mediated post-polymerization modification and architectural control of synthetic polymers, surface, interfacial and porous-material functionalization, and SuFEx-based conjugation and covalent capture in natural and sequence-defined biopolymers. Across these contexts, we compare the advantages, supporting mechanistic and analytical evidence, current limitations and future opportunities of SuFEx-enabled polymer functionalization. Full article

Poly(vinylidene fluoride) (PVDF) exhibits excellent piezoelectric properties governed by the content and orientation of its polar phases. Herein, a synergistic regulation strategy integrating a flow field induced by a designed solid-phase extrusion die and ion–dipole interactions introduced by CTAB is established to achieve highly oriented β phase in PVDF. The incorporation of CTAB promotes the formation of the γ phase before extrusion, providing a structurally favorable precursor for the subsequent flow-induced γ-β phase transformation. During solid-phase extrusion, the converging flow field drives extensive molecular chain alignment, promoting the γ-β phase transformation and substantially enhancing both β phase content and orientation. The synergistic effects of CTAB-induced ion–dipole interactions and the converging flow field further regulate the melting behavior and crystal perfection of PVDF, driving the transformation of the lamellar structure into highly oriented lamellar bundles along the extrusion direction. Among all compositions studied, the blends containing 5 wt% CTAB exhibit the optimal polar phase content and orientation characteristics, along with the highest dielectric constant. This work elucidates the synergistic regulation of PVDF hierarchical structures by ion–dipole interactions and flow fields, offering an effective strategy for fabricating high-performance piezoelectric PVDF materials. Full article