Search Results (38)

Titanium and its alloy scaffolds are widely utilized in clinical settings; however, their biologically inert surfaces and inherent mechanical characteristics impede osteogenesis and soft tissue integration, thereby limiting their application. Selective laser melting (SLM) was employed to fabricate scaffolds with matched cortical bone mechanical properties, achieving a composite coating of hydroxyapatite complexed with trace elements of silicon, strontium, and fluoride (mHA), along with type I collagen (Col I) and fibrinogen (Fg), thus activating the scaffold surface. Initially, we utilized the excellent adhesive properties of dopamine to co-deposit mHA and polydopamine (PDA) onto porous Ti-6Al-4V scaffolds, which was followed by immobilization of type I collagen and fibrinogen onto PDA. This bioinorganic/bioprotein composite coating, formed via PDA bonding, exhibits excellent stability. Moreover, in vitro cell experiments demonstrate excellent biocompatibility of the porous Ti-6Al-4V scaffold with composite bioactive coatings on its surface. Preosteoblasts (MC3T3-E1) and human keratinocytes (HaCaT) exhibit enhanced adhesion and proliferation activity, and the osteogenic performance of the scaffold is significantly improved. The PDA-mHA-Col I-Fg composite-coated porous titanium alloy scaffold holds significant promise in enhancing the efficacy of percutaneous bone transplantation and requires further investigation. Full article

Red mud (RM) is a strongly alkaline waste residue produced during alumina production, and its high alkali and fine particle characteristics are prone to cause soil, water, and air pollution. Phosphogypsum (PG), as a by-product of the wet process phosphoric acid industry, poses a significant risk of fluorine leaching and threatens the ecological environment and human health due to its high fluorine content and strong acidic properties. In this study, RM-based cemented paste backfill (RCPB) based on the synergistic curing of PG and ordinary Portland cement (OPC) was proposed, aiming to achieve a synergistic enhancement of the material’s mechanical properties and fluorine fixation efficacy by optimizing the slurry concentration (63–69%). Experimental results demonstrated that increasing slurry concentration significantly improved unconfined compressive strength (UCS). The 67% concentration group achieved a UCS of 3.60 MPa after 28 days, while the 63%, 65%, and 69% groups reached 2.50 MPa, 3.20 MPa, and 3.40 MPa, respectively. Fluoride leaching concentrations for all groups were below the Class I groundwater standard (≤1.0 mg/L), with the 67% concentration exhibiting the lowest leaching value (0.6076 mg/L). The dual immobilization mechanism of fluoride ions was revealed by XRD, TGA, and SEM-EDS characterization: (1) Ca²⁺ and F⁻ to generate CaF₂ precipitation; (2) hydration products (C-S-H gel and calixarenes) immobilized F⁻ by physical adsorption and chemical bonding, where the alkaline component of the RM (Na₂O) further promotes the formation of sodium hexafluoroaluminate (Na₃AlF₆) precipitation. The system pH stabilized at 9.0 ± 0.3 after 28 days, mitigating alkalinity risks. High slurry concentrations (67–69%) reduced material porosity by 40–60%, enhancing mechanical performance. It was confirmed that the synergistic effect of RM and PG in the RCPB system could effectively neutralize the alkaline environment and optimize the hydration environment, and, at the same time, form CaF₂ as well as complexes encapsulating and adsorbing fluoride ions, thus significantly reducing the risk of fluorine migration. The aim is to improve the mechanical properties of materials and the fluorine-fixing efficiency by optimizing the slurry concentration (63–69%). The results provide a theoretical basis for the efficient resource utilization of PG and RM and open up a new way for the development of environmentally friendly building materials. Full article

In order to effectively recover Li from cathode active materials of lithium-ion batteries, model samples of LiCoO₂ mixed with polyvinylidene fluoride (PVDF) were calcined at temperatures of 350–700 °C under an Ar or air atmosphere. Complete Li recovery was achieved by calcining the model sample at 400 °C under an Ar atmosphere, followed by water leaching. Additionally, to immobilize PVDF-derived F, an impurity in Li purification, we explored the use of calcium compounds (Ca(OH)₂ and CaCO₃) and a layered double hydroxide in both dry and wet processing methods. In the wet process, F was fixed by adding Ca(OH)₂ to an aqueous LiF solution containing 1000 ppm of F. We confirmed that 98.6% of F was successfully removed from the solution after repeated fixation procedures. Furthermore, the unreacted Ca in the solution was separated and removed as CaCO₃ by concentrating the solution. Full article

Long-time exposure to volatile organic compounds (VOCs) in the atmosphere can have negative health effects on humans and other living organisms. In order to purify ambient air, these VOCs can be degraded using photocatalysis. In this research, commercially available TiO₂ nanoparticles were immobilized in a porous poly(vinylidene fluoride-co-hexa-fluoropropylene) (PVDF) polymer matrix, synthesized using the phase inversion method. The most used solvent for PVDF is N-methyl-2-pyrrolidone (NMP). However, this solvent is known to be harmful to humans and the environment, and there is a need to replace NMP with a more ecological ‘green’ solvent. Here, triethyl phosphate (TEP), methyl-5-(dimethylamino)-2-methyl-5-oxopentanoate (Rhodiasolv^® PolarClean) and propylene carbonate (PC) were used to dissolve PVDF for the phase inversion synthesis of porous photocatalytically active PVDF/TiO₂ hybrid layers onto aluminium slides. The photocatalytic degradation under UV (365 nm) of gaseous ethanol in an argon/oxygen (Ar/O₂) atmosphere shows that these solvents are suitable replacements for NMP, but optimization is required to improve the performance of the layers. Apart from changing the solvent for PVDF, the UV and photocatalysis stability of PVDF has been determined, as well as the repeatability of the photocatalytic reaction, to prove that PVDF is a suitable polymer for this application. Full article

The increasing generation of industrial solid wastes, such as red mud and phosphogypsum, poses significant environmental challenges due to their complex chemical compositions and low utilization rates. This study aims to develop an innovative composite material by combining RM and PG, modified with ferric chloride (FeCl₃) and sodium silicate (Na₂SiO₃), to address their environmental risks and enhance their potential for soil and ecological remediation. The modification mechanisms and immobilization of toxic ions were investigated through leaching behavior analysis and advanced microscopic techniques, including BET and XRD. Under the optimal ratio (RM:PG = 7:3), the composite material exhibited excellent performance, with stable pH (8.03), low electrical conductivity (4.89 mS/cm), and significantly reduced concentrations of phosphate (PO₄³⁻: 0.36 mg/L) and fluoride ions (F⁻: 1.34 mg/L), achieving an upgrade from industrial Class II to Class I slag. The modification process increased the specific surface area, optimized pore structure, and enhanced surface activity and structural stability. Pot experiments demonstrated that the modified composite supported normal plant growth, with leachate meeting Grade I wastewater discharge standards. This study not only provides a sustainable approach for the utilization of RM and PG, but also offers valuable insights into the development of eco-friendly materials for soil remediation and ecological restoration, benefiting both the scientific community and environmental management practices. Full article

Phosphogypsum (PG), a by-product of phosphoric acid production, contains high levels of fluorine and phosphorus impurities, which negatively impact the strength and setting time of PG-based cement materials and pose environmental risks. This study explores a dual approach combining physical adsorption using zeolite powder and chemical modification with quicklime (CaO) to immobilize these impurities. The composition of 90 wt.% PG, 5 wt.% zeolite powder, and 5 wt.% quicklime reduces the soluble phosphorus to below the detection limits and significantly lowers the free water content in the PG. Through SEM, XRD, and FT-IR analyses, it was found that zeolite powder adsorbs fluorine and phosphorus through encapsulation, while quicklime chemically reacts to form insoluble calcium phosphate and calcium fluoride. This transformation decreases the solubility, mitigating potential environmental contamination. The combination of physical adsorption and chemical conversion provides a sustainable strategy to reduce environmental hazards and enhance PG’s suitability for cement-based materials. The findings from this research offer a promising pathway for the sustainable utilization of PG, providing a mechanism for its safe incorporation into building materials, while addressing both environmental and material performance concerns. Full article

Phosphogypsum (PG)-based cemented paste backfill (PCPB) is a widely used method for the large-scale disposal of phosphoric acid waste. However, fluoride contaminants in PG pose a significant risk of groundwater pollution. Effective pretreatment methods have been developed to mitigate this issue, but there is limited research on the specific pretreatment standards needed to control fluoride leaching. This study investigates the impact of initial fluoride content (IFC) in PG samples on the strength and leaching behavior of PCPB to establish appropriate pretreatment standards. Pure CaSO₄·2H₂O and NaF were used to simulate PG samples with varying IFC levels. The findings indicate that lower IFC leads to stronger PCPBs after 28 days of curing. To ensure compliance with Chinese national standards, the initial fluoride concentration must be below 0.0093 wt% to prevent excessive leaching. Microlevel analyses reveal that fluoride influences the hydration reactions of C₂S and C₃S in cement, affecting the formation of C-S-H and Ca(OH)₂. Fluoride is primarily immobilized in PCPB as CaF₂, which can either form gypsum crystals within the complex structure or be adsorbed onto hydration products. This research provides crucial insights into the pretreatment standards required for controlling fluoride leaching, offering a foundation for the industrial application of PG. Full article

Immobilizing different enzymes on membranes can result in biocatalytic active membranes with a self-cleaning capacity toward a complex mixture of foulants. The membrane modification can reduce fouling and enhance filtration performance. Protease, lipase, and amylase were immobilized on poly(vinylidene fluoride) (PVDF) microfiltration membranes using a polydopamine coating in a one-step method. The concentrations of polydopamine precursor and enzymes were optimized during the immobilization. The higher hydrolytic activities were obtained using 0.2 mg/mL of dopamine hydrochloride and 4 mg/mL of enzymes: 0.90 mg_starch/min·cm² for amylase, 10.16 nmol_tyrosine/min·cm² for protease, and 20.48 µmol_{p-nitrophenol}/min·cm² for lipase. Filtration tests using a protein, lipid, and carbohydrate mixture showed that the modified membrane retained 41%, 29%, and 28% of its initial water permeance (1808 ± 39 L/m²·h·bar) after three consecutive filtration cycles, respectively. In contrast, the pristine membrane (initial water permeance of 2016 ± 40 L/m²·h·bar) retained only 23%, 12%, and 8%. Filtrations of milk powder solution were also performed to simulate dairy industry wastewater: the modified membrane maintained 28%, 26%, and 26% of its initial water permeance after three consecutive filtration cycles, respectively, and the pristine membrane retained 34%, 21%, and 7%. The modified membrane showed increased fouling resistance against a mixture of foulants and presented a similar water permeance after three cycles of simulated dairy wastewater filtration. Membrane fouling is reduced by the immobilized enzymes through two mechanisms: increased membrane hydrophilicity (evidenced by the reduced water contact angle after modification) and the enzymatic hydrolysis of foulants as they accumulate on the membrane surface. Full article

It has been observed that the immobilization of a phosphotriesterase enzyme (PTE) onto polyvinylidene fluoride (PVDF) membranes significantly decreased the enzyme activity, and this negative effect was attributed to the hydrophobic character of the membrane. The indirect indication of this reason was that the same enzyme immobilized on other membrane materials bearing hydrophilic character showed better performance. In this work, we provide direct evidence of the mechanism by immobilizing a PTE on a PVDF membrane hydrophilized by blending it with alkali lignin (AL). The PTE was immobilized on PVDF membrane by a covalent bond with the same procedure used in earlier studies to attribute changes in enzyme activity solely to the wettability properties (and not to the material chemistry). The activity of the PTE immobilized on the PVDF membrane hydrophilized with AL was 50% higher than that of the enzyme immobilized on the PVDF hydrophobic membrane. Further improvements of the membrane structure tailored for the development of a biocatalytic membrane reactor (BMR) were also promoted. In particular, the performance of the BMR was studied as a function of the thickness of the membrane, which allowed us to modulate the residence time into the enzyme-loaded membrane pores while maintaining the flow rate through the pores at a constant. Full article

The present study investigates the influence of photosensitizer selection and the polymer electrolyte composition on the performance of quasi-solid-state dye-sensitized solar cells (QsDSSCs). Two benchmark ruthenium dyes, N719 and Z907, alongside a novel photoactive phenothiazine dye were used. Each dye was incorporated into a QsDSSC architecture employing poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) as the gel electrolyte matrix, with varying molecular weights, to investigate their impacts on the overall device performance and long-term stability. Our results demonstrated that the N719 dye exhibited the highest power conversion efficiency (PCE), attributed to its strong absorption in the visible spectrum and efficient electron injection into the TiO₂ photoanode. Z907, on the other hand, showed moderate PCE due to its broader absorption profile but slower electron injection kinetics. The phenothiazine dye revealed promising PCE, with tunable absorption properties and efficient charge transfer. Furthermore, the impact of PVDF-HFP polymer gel electrolytes with varying molecular weights on cell stability was explored. The QsDSSC incorporating the PVH80 polymer with the phenothiazine dye exhibited reduced dye desorption, due to the effective dye molecules’ immobilization by the gel matrix, and consequently enhanced long-term stability over 600 h. This comparative study sheds light on the interplay between dye selection, the polymer gel’s properties, and QsDSSCs’ performance. These insights are crucial in designing robust and efficient QsDSSCs for practical applications. Full article

Prosthetic infections are associated with high morbidity, mortality, and relapse rates, making them still a serious problem for implantology. Staphylococcus aureus is one of the most common bacterial pathogens causing prosthetic infections. In response to the increasing rate of bacterial resistance to commonly used antibiotics, this work proposes a method for combating pathogenic microorganisms by modifying the surfaces of synthetic polymeric biomaterials using proteolytic enzyme inhibitors (serine protease inhibitors—4-(2-aminoethyl)benzenesulfonyl fluoride hydrochloride and puromycin). While using techniques based on the immobilization of biologically active molecules, it is important to monitor the changes occurring on the surface of the modified biomaterial, where spectroscopic techniques (e.g., FTIR) are ideal. ATR-FTIR measurements demonstrated that the immobilization of both inhibitors caused large structural changes on the surface of the tested vascular prostheses (polyester or polytetrafluoroethylene) and showed that they were covalently bonded to the surfaces of the biomaterials. Next, the bactericidal and antibiofilm activities of the tested serine protease inhibitors were determined using the CLSM microscopic technique with fluorescent staining. During LIVE/DEAD analyses, a significant decrease in the formation of Staphylococcus aureus biofilm after exposure to selected concentrations of native inhibitors (0.02–0.06 mg/mL for puromycin and 0.2–1 mg/mL for 4-(2-aminoethyl)benzenesulfonyl fluoride hydrochloride) was demonstrated. Full article

Coating layers consisting of a crystalline apatite matrix with immobilized basic fibroblast growth factor (bFGF) can release bFGF, thereby enhancing bone regeneration depending on their bFGF content. We hypothesized that the incorporation of fluoride ions into apatite crystals would enable the tailored release of bFGF from the coating layer depending on the layer’s fluoride content. In the present study, coating layers consisting of fluoride-incorporated apatite (FAp) crystals with immobilized bFGF were coated on a porous collagen sponge by a precursor-assisted biomimetic process using supersaturated calcium phosphate solutions with various fluoride concentrations. The fluoride content in the coating layer increased with the increasing fluoride concentration of the supersaturated solution. The increased fluoride content in the coating layer reduced its solubility and suppressed the burst release of bFGF from the coated sponge into a physiological salt solution. The bFGF release was caused by the partial dissolution of the coating layer and, thus, accompanied by the fluoride release. The concentrations of released bFGF and fluoride were controlled within the estimated effective ranges in enhancing bone regeneration. These findings provide useful design guidelines for the construction of a mineralized, bFGF-releasing collagen scaffold that would be beneficial for bone tissue engineering, although further in vitro and in vivo studies are warranted. Full article

The present study investigated the effects of protocols for slurry preparation on the release of pollutants into bleeding water from cemented phosphogypsum (PG) backfill. Backfill slurry was prepared using four different protocols in which different parameters varied, including binder/PG ratio, solid concentration, binder type and mixing procedure. The concentrations of phosphate, fluoride and sulfate and the pH values of the obtained bleeding water were measured. The results demonstrated that the slurry preparation protocols affected the quantities of pollutants through the concentrations of pollutants in bleeding water and the bleeding rate. On the one hand, the binder/PG ratio was the key factor influencing the concentrations of all pollutants in bleeding water. Comparatively speaking, the binder type and mixing procedure had an obvious influence on the fluoride concentration but had little influence on the phosphate and sulfate concentrations in the bleeding water. On the other hand, the protocols for slurry preparation affected the bleeding rate by determining the water retention and water content of the backfill slurry. The most effective protocol for slurry preparation for cemented PG backfill could reduce the bleeding rate and enhance the immobilization of pollutants, minimizing the phosphate concentration in bleeding water to below 0.2 mg/L. However, it appeared that the fluoride concentration was still tens of milligrams per liter (over the limit of 10 ten milligrams per liter), to which attention should be paid. Full article

A database of 479 glass formulations used to immobilize radioactive wastes for facilities in a safe and resilient infrastructure was analyzed, searching for underlying statistical patterns and associated glass performance features. The analyzed data cover many oxides, including SiO₂, B₂O₃, Na₂O, Fe₂O₃, and some fluorides. Borosilicates were the most common glasses (60.1%), while silicates were only 11.9%. In addition to these two families, five radioactive waste vitrification matrices were identified: Boroaluminosilicates, iron phosphates, aluminosilicates, sodium iron phosphates, and boroaluminates, totaling seven glass families. Almost all compositions (97.7%) contained sodium oxide, followed by silica (91.4%), iron (82.7%), boron (73.7%), phosphorus (54.9%), and cesium oxides (26.1%). Multivariate exploratory methods were applied to analyze and classify glass compositions using hierarchical and non-hierarchical (K-means) clusters and principal component analysis. Four main clusters were observed, the largest comprising 417 formulations containing mainly silicates, borosilicates, aluminosilicates, and boroaluminosilicates; two principal components, representing 73.75% of all compositions, emerge from these four clusters derived from a covariance analysis. The principal components and four clusters may be associated with the following glass features in terms of glass compositions: liquidus temperature, glass transition temperature, density, resistivity, microhardness, and viscosity. Some general underlying properties emerged from our classification and are discussed. Full article

In this study, four polycarbazole derivatives (PCMB-Ds) with different alkyl side chains were designed and synthesized via Wittig–Horner reaction. A novel solid-phase electrochemiluminescence (ECL) system was prepared by immobilizing PCMB-D on an indium tin oxide (ITO) electrode with polyvinylidene fluoride (PVDF) in the presence of tripropylamine (TPrA). It could be found that the increase in alkyl side chain length had little effect on the ECL signal of PCMB-D, while the increase in the degree of polymerization (DP) greatly enhanced the ECL signal. Furthermore, the P-3/ITO ECL sensor based on the polyoctylcarbazole derivative (P-3) with the best ECL performance was successfully constructed and detected Fe³⁺ under the optimal experimental conditions. The ECL signal steadily diminished with the increased concentration of Fe³⁺ because of the competition and complexation between Fe³⁺ and P-3 under the condition of pH 7.4. This P-3/ITO platform could realize a highly sensitive and selective detection of Fe³⁺ with a wide detection range (from 6 × 10⁻⁸ mol/L to 1 × 10⁻⁵ mol/L) and low detection limit of 2 × 10⁻⁸ mol/L, which could allow the detection of Fe³⁺ in multiple scenarios, and would have a great application prospect. Full article