RESUMO
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-1) than HPMH (1431 mg g-1), 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)2 deposits in situ. Concurrently, Mg(ii) ions diffuse into the solution, substituting Pb(ii) ions in the MH lattice. Second, the resultant Pb(OH)2, which is unstable, reacts with CO2 dissolved in water to yield Pb3(CO3)2(OH)2. Therefore, owing to its outstanding Pb(ii) adsorption performance and simple preparation method, FGMH is a promising solution for Pb(ii) pollution.
RESUMO
In this study, we fabricated magnetic Fe3O4@Mg(OH)2 composites through the seed deposition technique to achieve Cu(ii) ion removal from aqueous solutions. As indicated by the characterization results, three-dimensional flower-like spheres composed of external Mg(OH)2 were formed, with nano-Fe3O4 particles uniformly embedded in the "flower petals" of the spheres. The efficacy of Fe3O4@Mg(OH)2-3 in Cu(ii) ion removal was examined through batch experiments. The impact of solution pH on removal efficiency was examined, and the pseudo-second-order model and the Langmuir model provided good fits to the adsorption kinetics and isotherm data, respectively. Remarkably, Fe3O4@Mg(OH)2-3 exhibited a significant removal capacity of 1051.65 mg g-1 for Cu(ii) ions. Additionally, the composite displayed a notable saturation magnetization value of 17.3 emu g-1, facilitating isolation from sample solutions through external magnetic fields after Cu(ii) ion absorption. At the solid-liquid interface, a mechanism involving ion exchange between Mg(ii) and Cu(ii) cations was realized as the mode of Cu(ii) ion removal. The composites' effective adsorption properties and rapid magnetic separation highlighted their suitability for use in treating copper-contaminated water.
RESUMO
To alleviate the safety hazards associated with the use of epoxy resin (EP), a multifunctional filler was designed. This study firstly combines the superior mechanical properties of magnesium borate rods (MBR) with the excellent smoke suppression and flame-retardant characteristics of layered double hydroxide (LDH). H2PO4- intercalated LDH (LDHP) was coated on the MBR surface to obtain inorganic composite particles MBR@LDHP. Subsequently, MBR@LDHP was modified with 3-aminopropyltriethoxysilane (APES) to obtain organic-inorganic composite particles MBR@LDHP-APES. Eventually, the hybrid particles were added to EP to prepare the composite materials. Thereafter, the morphology, composition, and structure of MBR@LDHP-APES were characterized utilizing scanning electron microscopy (SEM), Fourier transform infrared (FTIR), and X-ray diffraction (XRD). The results indicated the successful preparation of MBR@LDHP-APES, after which we investigated the effects of MBR@LDHP-APES on the smoke suppression, flame retardancy, and mechanical characteristics of EP. As observed, the EP composites containing 7.5 wt% MBR@LDHP-APES exhibited superior smoke suppression and flame retardancy abilities. The limiting oxygen index reached 33.5%, which is 36.73% greater than pure EP, and the lowest values of total heat and smoke release were observed for the composite materials. In addition, the mechanical properties test revealed that MBR@LDHP-APES considerably enhanced the tensile strength as well as the flexural strength of the composites. Furthermore, mechanistic studies suggested that the barrier effect of MBR, endothermic decomposition of LDHP, and the synergistic effect of LDHP and APES contributed essentially to the smoke suppression and flame-retardant properties of the material. The findings of this research point to a potential method for enhancing the EP's ability to suppress smoke and flames while enhancing its mechanical properties.
RESUMO
A composite particle with hydrated alumina deposited on the surface of magnesium borate whisker (MBW@HA) was prepared following a chemical liquid deposition method. Subsequently, dodecyl dihydrogen phosphate (DDP) was grafted onto the surface of the composite particles to synthesize an inorganic-organic hybrid (MBW@HA-DDP). The structure, morphology, and composition of MBW@HA-DDP were well characterized. The results revealed the hybrid of MBW@HA-DDP was successfully synthesized characterized by a hydrophobic surface. Subsequently, the obtained MBW@HA-DDP was incorporated into epoxy resin (EP) to fabricate flame retardant composites. The results revealed that the incorporation of MBW@HA-DDP significantly improved the fire safety of EP, for instance, the total heat release (THR) and peak heat release rate (PHRR) of the EP composite with 10-phr MBW@HA-DDP added were reduced by 28.1% and 32.0%, respectively, accompanied with lower total smoke production (TSP) and smoke production rate (SPR). The improved fire safety was due to the barrier function of MBW and HA, and the dilution effect of water vapor generated from HA. Meanwhile, the phosphorus oxoacids generated from DDP could function as catalysts and increase the degree of graphitization of the char residues, thus protecting the matrix effectively. In relation to mechanical properties, the incorporation of MBW@HA-DDP did not deteriorate the mechanical properties of EP but improved them to some extent. The results presented herein help develop a novel strategy for developing flame retardants characterized by good flame-retardant behavior and improved mechanical properties.
RESUMO
Genetic divergence for nitrogen utilization in germplasms is important in wheat breeding programs, especially for low nitrogen input management. In this study, a nested association mapping (NAM) population, derived from "Yanzhan 1" (a Chinese domesticated cultivar) crossed with "Hussar" (a British domesticated cultivar) and another three semi-wild wheat varieties, namely, "Cayazheda 29" (Triticum aestivum ssp. tibetanum Shao), "Yunnan" (T. aestivum ssp. yunnanense King), and "Yutian" (T. aestivum petropavloski Udats et Migusch), was used to detect quantitative trait loci (QTLs) for nitrogen utilization at the seedling stage. An integrated genetic map was constructed using 2,059 single nucleotide polymorphism (SNP) markers from a 90 K SNP chip, with a total coverage of 2,355.75 cM and an average marker spacing of 1.13 cM. A total of 67 QTLs for RDW (root dry weight), SDW (shoot dry weight), TDW (total dry weight), and RSDW (root to shoot ratio) were identified under normal nitrogen conditions (N+) and nitrogen deficient conditions (N-). Twenty-three of these QTLs were only detected under N- conditions. Moreover, 23 favorable QTLs were identified in the domesticated cultivar Yanzhan 1, 15 of which were detected under N+ conditions, while only four were detected under N- conditions. In contrast, the semi-wild cultivars contributed more favorable N--specific QTLs (eight from Cayazheda 29; nine from Yunnan), which could be further explored for breeding cultivars adapted to nitrogen-deficient conditions. In particular, QRSDW-5A.1 from YN should be further evaluated using high-resolution mapping.