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RSC Advances May 2024Magnesium hydroxide (Mg(OH)), as a green halogen-free flame retardant, has attracted significant attention in the field of flame retardant composite materials. In...
Magnesium hydroxide (Mg(OH)), as a green halogen-free flame retardant, has attracted significant attention in the field of flame retardant composite materials. In addition to conventional indicators such as purity and whiteness, Mg(OH) is required to take the form of regular hexagonal sheets to ensure the dispersion of composite materials. We use irregular large particles of Mg(OH) prepared by the magnesium factory in western Qinghai as raw materials to study the influence of alkali metal ions K and Na mainly present in salt lakes on the physicochemical properties of Mg(OH). The products were characterized X-ray diffraction, scanning electron microscopy, automatic nitrogen physical adsorption apparatus, and other modern characterization techniques. Results show that alkali metal ions K and Na considerably influence the crystal surface polarity, particle size, and morphology of the prepared Mg(OH). The mechanism analysis shows that the presence of K and Na alters the dissolution, recrystallization, and growth characteristics of Mg(OH). This study provides theoretical support for the realization of high-performance Mg(OH) using salt lake resources and demonstrates the value for promoting the large-scale industrial application of the salt lake industry.
PubMed: 38708105
DOI: 10.1039/d4ra00305e -
RSC Advances Apr 2024The reasonable construction of one-dimensional (1D)/two-dimensional (2D) hybrid dimensional porous carbon materials with complementary advantages and disadvantages is an...
The reasonable construction of one-dimensional (1D)/two-dimensional (2D) hybrid dimensional porous carbon materials with complementary advantages and disadvantages is an important approach to addressing the structural and performance deficiencies of single carbon materials, while also significantly improving the electrochemical performance of super-capacitors. In this study, 1D hollow tubular/2D nanosheet hybrid dimensional porous carbon was synthesized through one-step carbonization using 1D fibrous brucite and 2D layered magnesium carbonate hydroxide as templates. By adjusting the feed ratio of 1D fibrous and 2D layered templates, the morphology, pore structure and specific surface area (SSA) of the prepared 1D hollow tubular/2D nanosheet hybrid dimensional porous carbon were controlled. The prepared hybrid dimensional porous carbons were characterized using scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and nitrogen adsorption-desorption. And their electrochemical performance was also studied by cyclic voltammograms (CV), galvanostatic charge/discharge (GCD) and electrochemical impedance spectroscopy (EIS). The results show that the use of templates with different dimensions significantly influences the morphology, pore structure, SSA and electrochemical performance of the synthesized hybrid dimensional porous carbon. The hybrid dimensional porous carbon (3F) exhibits a high specific capacitance and excellent cycling stability. 3F demonstrates the specific capacitance of 245.3 F g at 1 A g. Furthermore, the capacity retention rate remains as high as 93.4% after 8000 cycles at 10 A g. This work reveals that hybrid dimensional porous carbon composed of 1D hollow carbon tubes and 2D carbon nanosheets has great potential for use in supercapacitor electrode materials.
PubMed: 38655464
DOI: 10.1039/d4ra01873g -
Polymers Mar 2024Using alkali pretreatment can effectively remove residual variable-valence metals from non-metallic powder (WPCBP) in waste printed circuit boards. However, substantial...
Using alkali pretreatment can effectively remove residual variable-valence metals from non-metallic powder (WPCBP) in waste printed circuit boards. However, substantial amounts of waste lye are generated, which causes secondary pollution. On this basis, this study innovatively utilized waste alkali lye to prepare nano-magnesium hydroxide. When the dispersant polyethylene glycol 6000 was used at a dosage of 3 wt.% of the theoretical yield of magnesium hydroxide, the synthesized nano-magnesium hydroxide exhibited well-defined crystallinity, good thermal stability and uniform particle size distribution, with a median diameter of 197 nm. Furthermore, the in situ method was selected to prepare WPCBP/Mg(OH) hybrid filler (MW) and the combustion behavior, thermal and mechanical properties of PP blends filled with MW were evaluated. The combustion behavior of the PP/MW blends increased with the increasing hybrid ratio of Mg(OH), and the MW hybrid filler reinforced PP blends showed better thermal and mechanical properties compared to the PP/WPCBP blends. Furthermore, the dynamic mechanical properties of the PP/MW blends were also increased due to the improved interfacial adhesion between the MW fillers and PP matrix. This method demonstrated high economic and environmental value, providing a new direction for the high value-added utilization of WPCBP.
PubMed: 38543427
DOI: 10.3390/polym16060822 -
Polymers Feb 2024Thermally conductive and flame-retardant polyolefin composites are facing great challenges in meeting the increasing demands for fire safety and thermal management....
Thermally conductive and flame-retardant polyolefin composites are facing great challenges in meeting the increasing demands for fire safety and thermal management. Aiming at simultaneously enhancing thermal conductivity and flame retardancy, hexagonal boron nitride (hBN) and magnesium hydroxide (MH) were adopted in ethylene-vinyl acetate copolymer/polyolefin elastomer (EVA/POE) blends to design composites with selective filler distributions and co-continuous networks via different processing schemes. The thermal conductivity and flame retardancy show strong dependence on the distributed structure of hBN and MH. The composites with hBN-rich centers and MH-rich edges in the filled POE phase show a thermal conductivity of 0.70 W/(m·K) and an LOI of 27.7%, which are very close to the thermal conductivity of EVA/POE/hBN and the LOI of EVA/POE/MH at the same total filler content. The composites with MH-rich centers and hBN-rich edges show pHRR, THR and TSP values of 169 kW/m, 49.8 MJ/m and 1.8 m, which are decreased by 40%, 33% and 62% in comparison with EVA/POE/MH, respectively. Modulating the filler structure distribution provides a strategy to co-enhance thermal conductivity and flame retardancy.
PubMed: 38475329
DOI: 10.3390/polym16050646 -
The Science of the Total Environment May 2024This study proposed and examined a new process flowsheet for treating neutral mine drainage (NMD) from an open-pit gold mine. The process consisted of three sequential...
This study proposed and examined a new process flowsheet for treating neutral mine drainage (NMD) from an open-pit gold mine. The process consisted of three sequential stages: (1) in situ hydrotalcite (HT) precipitation; (2) low-cost carbon substrate driven microbial sulfate reduction; and (3) ferrosol reactive barrier for removing biogenic dissolved hydrogen sulfide (HS). For concept validation, laboratory-scale columns were established and operated for a 140-days period with key process performance parameters regularly measured. At the end, solids recovered from various depths of the ferrosol column were analysed for elemental composition and mineral phases. Prokaryotic microbial communities in various process locations were characterised using 16S rRNA gene sequencing. Results showed that the Stage 1 HT-treatment substantially removed a range of elements (As, B, Ba, Ca, F, Zn, Si, and U) in the NMD, but not nitrate or sulfate. The Stage 2 sulfate reducing bioreactor (SRB) packed with 70 % (v/v) Eucalyptus woodchip, 1 % (w/v) ground (<1 mm) dried Typha biomass, and 10 % (w/v) NMD-pond sediment facilitated complete nitrate removal and stable sulfate removal of ca. 50 % (50 g-SO m d), with an average HS generation rate of 10 g-HS md. The HS-removal performance of the Stage 3 ferrosol column was compared with a synthetic amorphous Fe-oxyhydroxide-amended sand control column. Although both columns facilitated excellent (95-100 %) HS removal, the control column only enabled a further ca. 10 % sulfate reduction, giving an overall sulfate removal of 56 %. In contrast, the ferrosol enabled an extra 99.9 % sulfate reduction in the SRB effluent, leading to a near complete sulfate removal. Overall, the process successfully eliminated a range of metal/metalloid contaminants, nitrate, sulfate (2500 mg-SO L in the NMD to <10 mg-SO L in the final effluent) and HS (>95 % removal). Further optimisation is required to minimise release of ferrous iron from the ferrosol barrier into the final effluent.
Topics: Hydrogen Sulfide; RNA, Ribosomal, 16S; Nitrates; Sulfates; Bioreactors; Aluminum Hydroxide; Magnesium Hydroxide
PubMed: 38460684
DOI: 10.1016/j.scitotenv.2024.171537 -
Heliyon Feb 2024Magnesium and its alloys are considered excellent materials for biodegradable implants because of their good biocompatibility and biodegradability as well as their... (Review)
Review
Magnesium and its alloys are considered excellent materials for biodegradable implants because of their good biocompatibility and biodegradability as well as their mechanical properties. However, the rapid degradation rate severely limits their clinical applications. Plasma electrolytic oxidation (PEO), also known as micro-arc oxidation (MAO), is an effective surface modification technique. However, there are many pores and cracks on the coating surface under conventional PEO process. The corrosive products tend to penetrate deeply into the substrate, reducing its corrosion resistance and the biocompatibility, which makes PEO-coated Mg difficult to meet the long-term needs of implants. Hence, it is necessary to modify the PEO coating. This review discusses the formation mechanism and the influential parameters of PEO coatings on Mg. This is followed by a review of the latest research of the pretreatment and typical amelioration of PEO coating on biodegradable Mg alloys in the past 5 years, including calcium phosphate (Ca-P) coating, layered double hydroxide (LDH)-PEO coating, ZrO incorporated-PEO coating, antibacterial ingredients-PEO coating, drug-PEO coating, polymer-PEO composite coating, Plasma electrolytic fluorination (PEF) coating and self-healing coating. Meanwhile, the improvements of morphology, corrosion resistance, wear resistance, biocompatibility, antibacterial abilities, and drug loading abilities and the preparation methods of the modified PEO coatings are deeply discussed as well. Finally, the challenges and prospects of PEO coatings are discussed in detail for the purpose of promoting the clinical application of biodegradable Mg alloys.
PubMed: 38434039
DOI: 10.1016/j.heliyon.2024.e24348 -
RSC Advances Feb 2024In this study, magnesium hydroxide (MH) particles with distinct morphologies were obtained through direct precipitation and subsequent hydrothermal treatment with...
In this study, magnesium hydroxide (MH) particles with distinct morphologies were obtained through direct precipitation and subsequent hydrothermal treatment with various magnesium salts. The synthesized products were systematically characterized and utilized for the removal of Pb(ii) ions from aqueous solutions. The adsorption process of Pb(ii) by two different MH structures, namely flower globular magnesium hydroxide (FGMH) and hexagonal plate magnesium hydroxide (HPMH), adhered to the Langmuir isotherm and pseudo-second-order model. FGMH exhibited higher Pb(ii) removal capacity (2612 mg g) than HPMH (1431 mg g), attributable to the unique three-dimensional layered structures of FGMH that provide a larger surface area and abundant active sites. Additionally, metallic Pb was obtained by recycling the adsorbed Pb(ii) through acid dissolution-electrolysis. Furthermore, Pb(ii) removal mechanisms were investigated by analyzing adsorption kinetics and isotherms, and the adsorbed products were characterized. Based on the findings, the removal process occurs in two key stages. First, Pb(ii) ions bind with OH ions on the surface upon diffusing to the MH surface, resulting in Pb(OH) deposits . Concurrently, Mg(ii) ions diffuse into the solution, substituting Pb(ii) ions in the MH lattice. Second, the resultant Pb(OH), which is unstable, reacts with CO dissolved in water to yield Pb(CO)(OH). Therefore, owing to its outstanding Pb(ii) adsorption performance and simple preparation method, FGMH is a promising solution for Pb(ii) pollution.
PubMed: 38433932
DOI: 10.1039/d3ra08040d -
Toxics Jan 2024The recovery and recycling of metals that generate toxic ions in the environment is of particular importance, especially when these are tungsten and, in particular,...
The recovery and recycling of metals that generate toxic ions in the environment is of particular importance, especially when these are tungsten and, in particular, thorium. The radioactive element thorium has unexpectedly accessible domestic applications (filaments of light bulbs and electronic tubes, welding electrodes, and working alloys containing aluminum and magnesium), which lead to its appearance in electrical and electronic waste from municipal waste management platforms. The current paper proposes the simultaneous recovery of waste containing tungsten and thorium from welding electrodes. Simultaneous recovery is achieved by applying a hybrid membrane electrolysis technology coupled with nanofiltration. An electrolysis cell with sulphonated polyether-ether-ketone membranes (sPEEK) and a nanofiltration module with chitosan-polypropylene membranes (C-PHF-M) are used to carry out the hybrid process. The analysis of welding electrodes led to a composition of W (tungsten) 89.4%; Th 7.1%; O 2.5%; and Al 1.1%. Thus, the parameters of the electrolysis process were chosen according to the speciation of the three metals suggested by the superimposed Pourbaix diagrams. At a constant potential of 20.0 V and an electrolysis current of 1.0 A, the pH is varied and the possible composition of the solution in the anodic workspace is analyzed. Favorable conditions for both electrolysis and nanofiltration were obtained at pH from 6 to 9, when the soluble tungstate ion, the aluminum hydroxide, and solid thorium dioxide were formed. Through the first nanofiltration, the tungstate ion is obtained in the permeate, and thorium dioxide and aluminum hydroxide in the concentrate. By adding a pH 13 solution over the two precipitates, the aluminum is solubilized as sodium aluminate, which will be found after the second nanofiltration in the permeate, with the thorium dioxide remaining integrally (within an error of ±0.1 ppm) on the C-PHF-M membrane.
PubMed: 38393198
DOI: 10.3390/toxics12020103 -
Heliyon Feb 2024In this study, a simple in-situ preparation method for coating on Mg-Zn alloy in a carbonic acid solution was investigated. The formation of a precursor carbonate layer...
In this study, a simple in-situ preparation method for coating on Mg-Zn alloy in a carbonic acid solution was investigated. The formation of a precursor carbonate layer on the alloy surface was observed. As the soaking time increased, the solution gradually turned alkaline, leading to the transformation of the precursor into a basic carbonate coating with a layered hydroxide structure. The corrosion potential () of the coated samples initially decreased and then increased with increasing the soaking time. After 2 h of soaking, the lowest corrosion potential observed was approximately -1.5105 V. At 12 h, the corrosion potential reached around -1.4645 V, which was comparable to that of the ZK61M magnesium alloy. After 48 h, the corrosion potential was measured to be approximately -1.3507 V.
PubMed: 38371983
DOI: 10.1016/j.heliyon.2024.e25587