Defluoridation performance comparison of aluminum hydroxides with different crystalline phases

Aluminum hydroxide is an eye catching and extensively researched adsorbent for fluoride removal and its defluoridation performance is closely related to the preparation method and crystalline phase. In this research, the defluoridation performances of aluminum hydroxides with different crystalline phases are compared and evaluated in terms of fluoride removal capacity, sensitivity to pH values and residual Al contents after defluoridation. It is found that the defluoridation performance of different aluminum hydroxides follows the order of boehmite > bayerite > gibbsite. The fluoride adsorption on aluminum hydroxides follows pseudo-second-order kinetic model and Langmuir isotherm model, and the maximum defluoridation capacities of boehmite, bayerite and gibbsite are 42.08, 2.97 and 2.74 mg m−2, respectively. The pH values and FTIR analyses reveal that the ligand exchange between fluoride and surface hydroxyl groups is the fluoride removal mechanism. Different aluminum hydroxides have different surface hydroxyl group densities, which results in the different defluoridation capacities. This work provides a new idea to prepare aluminum hydroxide with outstanding defluoridation performance.

Features of Functionalization of the Surface of Alumina Nanofibers by Hydrolysis of Organosilanes on Surface Hydroxyl Groups

Small additions of nanofiber materials make it possible to change the properties of polymers. However, the uniformity of the additive distribution and the strength of its bond with the polymer matrix are determined by the surface of the nanofibers. Silanes, in particular, allow you to customize the surface for better interaction with the matrix. The aim of our work is to study an approach to silanization of nanofibers of aluminum oxide to obtain a perfect interface between the additive and the matrix. The presence of target silanes on the surface of nanofibers was shown by XPS methods. The presence of functional groups on the surface of nanofibers was also shown by the methods of simultaneous thermal analysis, and the stoichiometry of functional groups with respect to the initial hydroxyl groups was studied. The number of functional groups precipitated from silanes is close to the number of the initial hydroxyl groups, which indicates a high uniformity of the coating in the proposed method of silanization. The presented technology for silanizing alumina nanofibers is an important approach to the subsequent use of this additive in various polymer matrices.

Plasma-catalytic NOx production in a three-level coupled rotating electrodes air plasma combined with nano-sized TiO2

A novel three-level coupled rotating electrodes air plasma with nano-sized TiO2 photocatalysts is developed for plasma-catalytic NOx production. The effects of plasma catalysis on NOx production with different air flow rates, different N2 fractions and different humidity levels are evaluated. Final results show that the exceptionally synergistic effect between TiO2 and three-level coupled rotating electrodes air plasma significantly increases the NOx concentration by 68.32% (from 4952 to 8335 ppm) and reduces the energy cost by 40.55% (from 2.91 to 1.73 MJ mol-1) at an air flow rate of 12 l min-1 and relative humidity level of 12%, which beats the ideal thermodynamic energy limit ~2.5MJ/mol for the thermal gas-phase process. A possible mechanism for enhanced NOx production with TiO2 is discussed: Highly energetic electrons in plasma contribute to the formations of the electron–hole pairs and oxygen vacancy (Vo) on the TiO2 catalyst surface, it may facilitate the dissociative adsorption of O2 molecules to form superoxide radical groups (like O2.-), and H2O molecules to form surface hydroxyl groups (like OH.), and thus, improving energy efficiency.

Porphyrin Molecules Decorated on Metal–Organic Frameworks for Multi-Functional Biomedical Applications

Metal–organic frameworks (MOFs) have been widely used as porous nanomaterials for different applications ranging from industrial to biomedicals. An unpredictable one-pot method is introduced to synthesize NH2-MIL-53 assisted by high-gravity in a greener media for the first time. Then, porphyrins were deployed to adorn the surface of MOF to increase the sensitivity of the prepared nanocomposite to the genetic materials and in-situ cellular protein structures. The hydrogen bond formation between genetic domains and the porphyrin’ nitrogen as well as the surface hydroxyl groups is equally probable and could be considered a milestone in chemical physics and physical chemistry for biomedical applications. In this context, the role of incorporating different forms of porphyrins, their relationship with the final surface morphology, and their drug/gene loading efficiency were investigated to provide a predictable pattern in regard to the previous works. The conceptual phenomenon was optimized to increase the interactions between the biomolecules and the substrate by reaching the limit of detection to 10 pM for the Anti-cas9 protein, 20 pM for the single-stranded DNA (ssDNA), below 10 pM for the single guide RNA (sgRNA) and also around 10 nM for recombinant SARS-CoV-2 spike antigen. Also, the MTT assay showed acceptable relative cell viability of more than 85% in most cases, even by increasing the dose of the prepared nanostructures.

Novel Hybrid Materials And Their Applications

<p>The development of novel hybrid materials of cellulose fibres and substrates with nanoparticles, conducting polymers and quantum dots, opens up novel application for new packaging materials and paper based products for the ‘smart packaging’ and ‘functional products’ areas that are emerging in the paper and packaging industries. Examples of these materials which have been developed here include cellulose fibres and substrates functionalised with magnetic nanoparticles, electrically conducting polypyrrole, and photoluminescent zinc sulfide quantum dots. Such materials were synthesised and then characterised using Alternating Gradient Magnetometry (AGM), Atomic Absorption Spectroscopy (AA), Cotec Profilometer Measurements, DC Conductivity Measurements, Photoluminescence Spectroscopy (PL), Scanning Electron Microscopy (SEM), SQUID Magnetometry, Transmission Electron Microscopy (TEM), Vibrational Sample Magnetometry (VSM), X-ray Diffraction (XRD), X-ray Fluorescence (XRF) and X-ray Photoelectron Spectroscopy (XPS). Ferrimagnetic magnetite nanoparticles (particle size 12-26 nm) were synthesised by a simple aqueous precipitation method and had a magnetic saturation of approximately 60 emu g⁻¹, a coercive field of approximately 12-120 Oe, and a remnant magnetisation of approximately 11 emu g⁻¹. Magnetite coated Kraft fibres (1.2 – 3.15 wt. % Fe) were synthesised by adding a colloidal suspension of magnetite nanoparticles to a suspension of Kraft fibres. The fibres retained their inherent properties, such as tensile strength and flexibility, but inherited the magnetic properties of the magnetic nanoparticles. The nanoparticles remained unchanged on bonding - presumably through hydrogen bonding between the surface hydroxyl groups of the cellulose and the oxygen present in the magnetite. Newsprint, Kraft Board and Cotton fabric were coated with polypyrrole using a chemical polymerisation method. SEM shows a complete coating, whereby the fibres are completely encapsulated by the polymer, including individual fibrils. Again, bonding is facilitated through hydrogen bonding between the surface hydroxyl groups of the cellulose and the lone pairs of the nitrogen in the polypyrrole backbone. Samples were doped with p-toluenesulfonic acid to increase conductivity, of which up to 4 S cm⁻¹ was achieved. The samples were coated with magnetite nanoparticles using a starch binder, and tested for their application in EMI shielding. A maximum shielding effectiveness of 43 % in the 1-18 GHz range and 47 % in the 16-40 GHz range was obtained using cotton fabrics coated with both polypyrrole and magnetite. A synergistic effect is observed on using a polypyrrole and magnetite coating. Photoluminescent ZnS quantum dots, synthesised using an aqueous precipitation method, were doped with Mn²⁺ and Cu²⁺ to achieve emissions at approximately 600 nm (Mn²⁺) and 530 nm (Cu²⁺) on irradiation with UV light. The quantum dots had a particle size of approximately 2 nm, and were present in the zinc blende phase. Doped ZnS-coated Kraft fibres (5 – 30 wt. % Zn) were synthesised by a number of methods, the most successful being the ‘in-situ’ method, in which a uniform and complete coating was afforded. The fibres retained their inherent properties, such as tensile strength and flexibility, but inherited the photoluminescent properties of the ZnS quantum dots. The quantum dots remained unchanged on bonding - presumably through hydrogen bonding between the surface hydroxyl groups of the cellulose and the sulfur present in the ZnS quantum dots. ZnS quantum dots doped with Mn² and Cu²⁺ were successfully formulated for inkjet printing by capping with mercaptosuccinic acid. Upon irradiation with UV light, emissions at approximately 600 nm (Mn²⁺-doped) and 530 nm (Cu²⁺-doped) were observed. These were successfully inkjet printed in intricate patterns onto a number of substrates, including photographic quality inkjet paper, cotton, and wool.</p>

Novel Hybrid Materials And Their Applications

<p>The development of novel hybrid materials of cellulose fibres and substrates with nanoparticles, conducting polymers and quantum dots, opens up novel application for new packaging materials and paper based products for the ‘smart packaging’ and ‘functional products’ areas that are emerging in the paper and packaging industries. Examples of these materials which have been developed here include cellulose fibres and substrates functionalised with magnetic nanoparticles, electrically conducting polypyrrole, and photoluminescent zinc sulfide quantum dots. Such materials were synthesised and then characterised using Alternating Gradient Magnetometry (AGM), Atomic Absorption Spectroscopy (AA), Cotec Profilometer Measurements, DC Conductivity Measurements, Photoluminescence Spectroscopy (PL), Scanning Electron Microscopy (SEM), SQUID Magnetometry, Transmission Electron Microscopy (TEM), Vibrational Sample Magnetometry (VSM), X-ray Diffraction (XRD), X-ray Fluorescence (XRF) and X-ray Photoelectron Spectroscopy (XPS). Ferrimagnetic magnetite nanoparticles (particle size 12-26 nm) were synthesised by a simple aqueous precipitation method and had a magnetic saturation of approximately 60 emu g⁻¹, a coercive field of approximately 12-120 Oe, and a remnant magnetisation of approximately 11 emu g⁻¹. Magnetite coated Kraft fibres (1.2 – 3.15 wt. % Fe) were synthesised by adding a colloidal suspension of magnetite nanoparticles to a suspension of Kraft fibres. The fibres retained their inherent properties, such as tensile strength and flexibility, but inherited the magnetic properties of the magnetic nanoparticles. The nanoparticles remained unchanged on bonding - presumably through hydrogen bonding between the surface hydroxyl groups of the cellulose and the oxygen present in the magnetite. Newsprint, Kraft Board and Cotton fabric were coated with polypyrrole using a chemical polymerisation method. SEM shows a complete coating, whereby the fibres are completely encapsulated by the polymer, including individual fibrils. Again, bonding is facilitated through hydrogen bonding between the surface hydroxyl groups of the cellulose and the lone pairs of the nitrogen in the polypyrrole backbone. Samples were doped with p-toluenesulfonic acid to increase conductivity, of which up to 4 S cm⁻¹ was achieved. The samples were coated with magnetite nanoparticles using a starch binder, and tested for their application in EMI shielding. A maximum shielding effectiveness of 43 % in the 1-18 GHz range and 47 % in the 16-40 GHz range was obtained using cotton fabrics coated with both polypyrrole and magnetite. A synergistic effect is observed on using a polypyrrole and magnetite coating. Photoluminescent ZnS quantum dots, synthesised using an aqueous precipitation method, were doped with Mn²⁺ and Cu²⁺ to achieve emissions at approximately 600 nm (Mn²⁺) and 530 nm (Cu²⁺) on irradiation with UV light. The quantum dots had a particle size of approximately 2 nm, and were present in the zinc blende phase. Doped ZnS-coated Kraft fibres (5 – 30 wt. % Zn) were synthesised by a number of methods, the most successful being the ‘in-situ’ method, in which a uniform and complete coating was afforded. The fibres retained their inherent properties, such as tensile strength and flexibility, but inherited the photoluminescent properties of the ZnS quantum dots. The quantum dots remained unchanged on bonding - presumably through hydrogen bonding between the surface hydroxyl groups of the cellulose and the sulfur present in the ZnS quantum dots. ZnS quantum dots doped with Mn² and Cu²⁺ were successfully formulated for inkjet printing by capping with mercaptosuccinic acid. Upon irradiation with UV light, emissions at approximately 600 nm (Mn²⁺-doped) and 530 nm (Cu²⁺-doped) were observed. These were successfully inkjet printed in intricate patterns onto a number of substrates, including photographic quality inkjet paper, cotton, and wool.</p>

Hydrophobicity and Charge Distribution Effects in the Formation of Bioorganoclays

Interactions of bioorganic moieties with clay minerals have attracted attention not only from the perspective of novel bioclay materials but also because they play a crucial role in our understanding of physical and chemical processes in soils. The aim of the present article is to explore the interactions responsible for the formation of a phosphatidylcholine-kaolinite bioclay by employing a series of classical molecular dynamic simulations. Detailed analysis of the structure and energies of the resulting bioclays reveals that the phosphatidylcholine molecules bind to the kaolinite surface either via their zwitterionic heads or hydrophobic aliphatic tails, depending on the kaolinite surface characteristics and the density of organic coating. The phosphatidylcholine molecules have a tendency to form irregular layers with a preferred parallel orientation of molecules with respect to the kaolinite surface. The tails exhibit varying degrees of flexibility and disorder depending on their distance from the surface and the density of surface coating. Significant differences in the binding can be spotted with respect to the two types of kaolinite basal surfaces, i.e., the hydrophobic siloxane surface, which possesses a considerable dispersion character, and the hydrophilic alumina surface, polarized by the surface hydroxyl groups.