인공고관절의 세라믹 볼 헤드의 기계적 안정성 평가를 위한 3 차원 유한요소 해석

Considering the previous work on layered double hydroxides (LDHs) as novel photocatalysts, research on this group of materials has become one of the most exciting subjects of today. LDH has become an important class of layered materials having prospects in photocatalysis, wherein great attention has been paid to the exhaustive aerobic degradation of pollutants, photocatalytic water splitting, and CO2 photo-reduction. The unique structure, uniform distribution of different metal cations in the brucite layer, surface hydroxyl groups, flexible tunability, intercalated anions with interlayer spaces, swelling properties, oxo-bridged linkage, and high chemical stability are some of the important advantages of this group of materials. This article provides an up-to-date review on significant progress in the fabrication of LDH photocatalytic systems aiming at environmental clean-up and energy production, such as degradation of pollutants, photocatalytic H2 generation and photocatalytic CO2-reduction. This article, after discussing the recent significant progress in the synthesis of different photoactive LDH materials and photocatalytic applications through their structural and electronic properties, considers many typical examples. In particular, recent progress on the emerging strategies of LDH to improve their photocatalytic activity is also presented. Eventually, the future challenges and outlooks for this group of materials are also discussed.

A review on the recent progress, challenges and perspective of layered double hydroxides as promising photocatalysts

The unavailability of clean drinking water is one of the significant health issues in modern times. Industrial dyes are one of the dominant chemicals that make water unfit for drinking. Among these dyes, methylene blue (MB) is toxic, carcinogenic, and non-biodegradable and can cause a severe threat to human health and environmental safety. It is usually released in natural water sources, which becomes a health threat to human beings and living organisms. Hence, there is a need to develop an environmentally friendly, efficient technology for removing MB from wastewater. Photodegradation is an advanced oxidation process widely used for MB removal. It has the advantages of complete mineralization of dye into simple and nontoxic species with the potential to decrease the processing cost. This review provides a tutorial basis for the readers working in the dye degradation research area. We not only covered the basic principles of the process but also provided a wide range of previously published work on advanced photocatalytic systems (single-component and multi-component photocatalysts). Our study has focused on critical parameters that can affect the photodegradation rate of MB, such as photocatalyst type and loading, irradiation reaction time, pH of reaction media, initial concentration of dye, radical scavengers and oxidising agents. The photodegradation mechanism, reaction pathways, intermediate products, and final products of MB are also summarized. An overview of the future perspectives to utilize MB at an industrial scale is also provided. This paper identifies strategies for the development of effective MB photodegradation systems.

https://www.mdpi.com/2073-4441/14/2/242/pdf?version=1642404093

Review on Methylene Blue: Its Properties, Uses, Toxicity and Photodegradation

Removal of safranin dye from water using polypyrrole nanofiber/Zn-Fe layered double hydroxide nanocomposite (Ppy NF/Zn-Fe LDH) of enhanced adsorption and photocatalytic properties

Defect-mediated Z-scheme BiO2-x/Bi2O2.75 heterojunction photocatalysts without electron mediator was prepared via a simple low-temperature hydrothermal method. DFT proved that the existence of oxygen vacancies would affect the geometric and electronic structure of BiO2-x and Bi2O2.75, which played an indispensable role in promoting exciton dissociation. BiO2-x/Bi2O2.75 exhibited a higher redox ability compared with the pure BiO2-x due to the Z-scheme photocatalytic mechanism, which could be ascribed to the formation of the build-in electric field induced by Bi and O defects. The as-synthesized photocatalysts exhibited excellent photocatalytic activity over the full solar spectrum from UV to NIR light due to the LSPR effect of oxygen vacancies, indicating its effective utilization of solar energy. The degradation rates of RhB over the optimal BiO2-x/Bi2O2.75 were 8.49, 10.22 and 3.24 times higher than that of the pure BiO2-x under visible light, simulated sunlight and NIR light irradiation, respectively. The excellent photocatalytic activity was ascribed to the synergistic effects of the LSPR effect of oxygen vacancies and the Z-scheme interfacial heterojunction. It was believed that this work provided a new idea to design high active and full solar spectrum-driven photocatalysts for energy conversion and environmental remediation.

Defect-mediated Z-scheme BiO2-x/Bi2O2.75 photocatalyst for full spectrum solar-driven organic dyes degradation

Visible light responsive 2 : 1 Ni/Ti layered double hydroxide (LDH) was synthesized by a single step hydrothermal route using commercially available Ni(NO3)2·6H2O, TiCl4 and urea. The material exhibited significant absorption in the visible range with a very narrow band gap (2.68 eV). This could be attributed to structural defects as confirmed by diffuse reflectance spectroscopy (DRS), photoluminescence (PL), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements. FT-IR, TGA, DTA, DSC, HR-TEM and SEM-EDX measurements yielded information about structural aspects, thermal stability and surface morphology. Surface and pore characteristics of the material were obtained from the BET isotherm for N2 adsorption at 77 K. Zeta potential measurements were used to characterize the electrical properties of the surface while XPS revealed changes in surface states and oxygen deficiencies. The material was found to be an excellent photocatalyst for the degradation of aqueous methylene blue in visible light. The photocatalytic properties of the material were explained on the basis of the narrow band gap, the high surface area and the presence of surface defects. The photocatalytic activity improved in alkaline media [pH 11.0, catalyst load 15 mg in 200 ml dye solution, dye concentration 1 × 10−6 M (= 0.3198 mg L−1)] due to the electrostatic attractions between the dye cations and the negative charges on the Ni/Ti LDH surface. The catalytic activity was found to be higher than the common commercial catalysts like ZnO, ZnS, NiO, TiO2 and Degussa P25. The catalytic activity was retained even after five methylene blue degradation cycles, demonstrating that the LDH could be an important addition to the field of wastewater treatment.

/pdf/ni-ti-layered-double-hydroxide-synthesis-characterization-3ksywkfh1q.pdf

Ni/Ti layered double hydroxide: synthesis, characterization and application as a photocatalyst for visible light degradation of aqueous methylene blue

2 : 1 Co/Ti layered double hydroxide (LDH) was synthesized hydrothermally using commercially available Co(NO3)2·6H2O and TiCl4, on a urea template. The high surface area material (~180 m2 g-1) had a narrow band gap (2.67 eV) and shallow and deep trap defect sites. The layered nanomaterial exhibited remarkable semiconductor properties and demonstrated excellent visible light decolourisation efficiency for the anionic dye Congo Red in aqueous medium. The photocatalytic efficiency of the LDH was better than common commercial materials in use such as ZnO, ZnS, NiO, CoO, TiO2 and Degussa P25. The presence of different surface states of defect sites in the LDH was confirmed by PL, EIS and XPS measurements. XRD, DRS, FT-IR, AFM, TEM, SEM/EDX and TG/DTG analyses yielded information about the structural, morphological properties and thermal stability of the LDH. BET N2 adsorption-desorption measurements at 77 K gave surface area and porosity data for the LDH. The surface charge characteristics of the LDH were evaluated with ξ-potential measurements over a wide pH-range in aqueous medium. The photocatalytic behaviour towards decolourisation of the dye was evaluated depending on the reaction variables of pH, LDH amount, initial dye concentration and effects of quenchers, and variation of molar ratios of Co/Ti LDH. The pseudo-first order model satisfactorily described the degradation kinetics of the anionic dye. The photocatalytic mechanistic pathways of the LDH were explained on the basis of an electron-hole (e--h+) hopping conduction model and also photosensitization of the dye. The maximum catalytic efficiency was observed with 15.0 mg of LDH at pH 4 for the anionic Congo Red dye at a concentration 1 × 10-5 M. The LDH was stable even after the fifth catalytic cycle, indicating its remarkable efficiency in potential decolourisation treatments. The dye degradation products were analysed with GC-MS and a reaction mechanism was proposed for the breakdown of the dye to simple and less toxic components.

/pdf/synthesis-and-characterization-of-co-ti-layered-double-1dsuxxukyp.pdf

Synthesis and characterization of Co/Ti layered double hydroxide and its application as a photocatalyst for degradation of aqueous Congo Red.

Optically responsive, luminescent Ni/Co/Ti layered double hydroxide (LDH), synthesized by a single step hydrothermal route, exhibits highly efficient photodegradation of cationic and anionic dyes, Rhodamine B (∼99.8%) and Acid Red G (∼99.6%) respectively, better than that of commercial catalysts like NiO, CoO and TiO2. The LDH has been characterized by using XRD, XPS, PL, TRES, EIS, TEM, SEM-EDX, AFM, UV-visible DRS, N2-sorption desorption, ξ-potential, FT-IR and TG techniques. The characterized results indicate that the LDH possesses hexagonal morphology, a high surface area, a narrow band gap, defect states and oxygen vacancies within its layered framework. The degradations follow the e--h+ hopping pattern and dye-photosensitized mechanistic pathways. The active species generated during photocatalysis have been evaluated using ESR, terephthalic acid fluorescence probe and indirect radical-hole trapping experiments. The colourless end products were investigated by GC-MS and reaction mechanisms have been established for the degradation of the dyes to less toxic and more eco-friendly molecules than their parent analogues. Dye mineralization studies (performed using a TOC analyser) and closure of carbon mass balance experiments quantified the amount of carbon entering and leaving the reaction systems. Reaction mechanisms have been proposed on the basis of the asymmetric cleavage of the dyes. The LDH demonstrated its remarkable efficiency in the field of waste water treatment.

/pdf/ni-co-ti-layered-double-hydroxide-for-highly-efficient-33pz45r5d9.pdf

Ni/Co/Ti layered double hydroxide for highly efficient photocatalytic degradation of Rhodamine B and Acid Red G: a comparative study

Copper is an essential micronutrient; however, as a result of its increasing demand, subsequent mining followed by its direct discharge into the environment has led to the contamination of our ecosystem. Thevetia peruviana (TP) is an ornamental herb of medicinal interest and is extensively used as an antipyretic and anticancer agent due to the presence of cardiac glycosides. In this work, we have explored the TP leaf powder as a biosorbent for Cu(II) removal from aqueous media and observed that it yields better results in comparison to other reported biosorbents for the removal of Cu(II). This work also emphasizes on the biosorption kinetics along with its plausible mechanism of interactions. The leaf powder characterized by FT-IR spectroscopy confirmed the diverse surface functionalities including hydroxyl, carbonyl, glycosides, etc. The morphology and elemental composition of the plant material have been investigated using SEM-EDAX analysis that confirms the heterogeneity and porosity of the biosorbent surface. The encouraging results revealed that the TP leaf powder could be used as a cost-effective biosorbent with an adsorption capacity of 187.51 mg g-1 for Cu(II) in aqueous media at pH ∼ 5 and a temperature of 303 K. The complex functionality of the TP surface most likely played a significant role in attaining fast equilibrium within 60 min by following pseudo-second-order kinetics, having a rate constant of 2 × 103 mg g-1 min-1 that has been confirmed with statistical tools such as regression coefficient, chi-squared, and sum of error square tests. The adsorption mechanism is controlled by diffusion of Cu(II) from the liquid phase to the solid phase of the TP biosorbent followed by the chemical interaction between the biosorbent and the adsorbate with slow intraparticle diffusion on the biosorbent surface. The adsorption of Cu(II) on TP has been observed to rise from 59.29 to 197.63 mg g-1 with the rise in the pH of the medium from 2 to 7. The adsorption of Cu(II) has been found to increase from 176.80 to 191.33 mg g-1 with increasing temperature from 293-308 K, confirming the endothermic nature of the adsorption process. The thermodynamic study revealed the adsorption process to be spontaneous with negative ΔG (-10.43 to -13.74 kJ mol-1) and that it has an endothermic nature with positive ΔH (54.24 kJ mol-1). The isotherm study for Cu(II) on TP followed the Langmuir adsorption isotherm model with the maximum monolayer adsorption capacity of 303.03 mg g-1 rather than Freundlich and Temkin isotherm models, which confirmed the chemical interaction between the sorbent and sorbate. FT-IR and SEM-EDAX analyses have also been used to confirm the adsorption of Cu(II) onto the TP surface. The present study revealed 99.7% Cu(II) desorption using 0.8 N HCl as the desorbent accompanied by a 69.71% regeneration efficiency of the TP biosorbent. After desorption of Cu(II), the regenerated TP could be disposed of in soil. The encouraging results revealed that TP could be used as an alternative and low-cost biosorbent for the removal of heavy metals from aqueous solutions.

https://pubs.acs.org/doi/pdf/10.1021/acsomega.9b04032

Kinetics of Aqueous Cu(II) Biosorption onto Thevetia peruviana Leaf Powder.

Luminescent Mn/Co/Ti LDH, synthesized by a single step hydrothermal route, has been found to be optically responsive for utilization as a highly efficient photocatalyst in destruction of the cationic dye Rhodamine B, in aqueous solution under visible light irradiation. The material has been found to be better than the commercial catalysts like MnO, CoO, TiO2 and Degussa P25. Multiple techniques like XRD, XPS, FT-IR, EIS, TG, UV-visible DRS, PL, TRES, N2-sorption–desorption, dynamic light scattering, TEM-EDS and AFM analyses were used to characterize the LDH. The results indicated Mn/Co/Ti LDH to have a multilayered crystalline structure with hexagonal morphology that carries metal ions in mixed valences, oxygen vacancies, defect states, thermal stability, narrow band gap, high surface area, and electrostatic surface charge variation with pH. The photocatalytic activity of the LDH could be co-related with the structural aspects such as oxidation states, narrow band gap, high surface area and existence of defects. The active species responsible for photocatalysis have been evaluated with EPR, terephthalic acid fluorescence probe and indirect radical-hole trapping experiments. The photodegradation mechanism involves electron and hole hopping across the material and also photosensitization of the dye. Ex situ 1H-NMR and GC-MS analyses of the colorless end products of Rhodamine B destruction provide further insight into the reaction mechanism. The complete mineralization of the decolorized end product of degradation was evaluated with TOC analysis. The results indicate the potential for using multi metal incorporated LDH in destroying dyes and their degradation products in industrial wastewater.

Priyadarshi Roy Chowdhury

Papers

Ni/Ti layered double hydroxide: synthesis, characterization and application as a photocatalyst for visible light degradation of aqueous methylene blue

Synthesis and characterization of Co/Ti layered double hydroxide and its application as a photocatalyst for degradation of aqueous Congo Red.

Ni/Co/Ti layered double hydroxide for highly efficient photocatalytic degradation of Rhodamine B and Acid Red G: a comparative study

Kinetics of Aqueous Cu(II) Biosorption onto Thevetia peruviana Leaf Powder.

Synthesis and characterization of Mn/Co/Ti LDH and its utilization as a photocatalyst in visible light assisted degradation of aqueous Rhodamine B.