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.

Molecular Design of Viologens to Exhibit Low-Order Liquid-Crystalline Phases

Viologens that are useful as stimulus-responsive compounds and exhibit a low-order liquid-crystalline (LC) phase at relatively low temperatures (approximately 20 °C), can be developed into materials that combine the redox...

Photocatalytic Performance of Carbon-Containing CuMo-Based Catalysts under Sunlight Illumination

Carbon-doped nanostructured CuMo-based photocatalysts were prepared by solvothermal synthesis. Two thermal treatments—oxidative and inert atmosphere—were used for the synthesis of the catalysts, and the influence of spherical carbon structures upon the crystalline phases on the photocatalytic activity and stability was studied. XRD showed the catalysts are nanostructured and composed by a mixture of copper (Cu, Cu2O, and CuO) and molybdenum (MoO2 and MoO3) crystalline phases. The catalysts were used for the degradation of yellow 5 under solar light. A remarkable leaching of Mo both in dark and under solar irradiation was observed and quantified. This phenomenon was responsible for the loss of photocatalytic activity for the degradation of the dye on the Mo-containing series. Conversely, the Cu-based photocatalysts were stable, with no leaching observed after 6 h irradiation and with a higher conversion of yellow 5 compared with the Mo- and CuMo series. The stability of Cu-based catalysts was attributed to a protective effect of spherical carbon structures formed during the solvothermal synthesis. Regarding the catalysts’ composition, sample Cu4-800-N2 prepared by pyrolysis exhibited up to 4.4 times higher photoactivity than that of the pristine material, which is attributed to a combined effect of an enhanced surface area and micropore volume generated during the pyrolytic treatment due to the presence of the carbon component in the catalyst. Scavenger tests have revealed that the mechanism for tartrazine degradation on irradiated Cu-based catalysts involves successive attacks of •OH radicals.

Organised Functional Liquids for Photon Upconversion

<p>Photon upconversion is a process by which lower energy photons are converted to higher energy photons, which can be achieved by the interaction of two triplet excited states. This process holds potential for wavelength shifting solid films in photovoltaic cells. Not all wavelengths emitted by the sun have sufficient energy to be utilized by such devices. Typical solar cells have a band gap of around 1 µm, however there is a significant amount of energy output by the sun that falls below this threshold. Upconversion could lead to more efficient use of energy by converting these lower energy wavelengths to wavelengths that could be directly absorbed by the solar panel. Upconversion has thus far been harnessed in solution, where diffusion is the limiting factor for the efficiency of the process. However, for technological applications it would be better to create thin solid films. In these films, molecules would have to be brought within the distance on which upconversion occurs, as the process would no longer be defined by diffusion. One way to achieve this would be to create liquid crystalline derivatives of upconversion emitter molecules. This would provide ordering in the system, which would enhance electronic coupling and bring molecules within the scale on which upconversion occurs. The work of this thesis has focused on the synthesis of these organised functional liquids: liquid crystals of common upconversion emitter molecules. 9,10-diphenylanthracene (DPA) and 9,10-bis(phenylethynyl)anthracene (BPEA) are popular emitter molecules, and derivatives of these molecules were synthesized. A variety of alkyl chains were attached with or without phenyl linkers. The alkyl chains would provide entropy to the system in order to induce the formation of liquid crystalline phases. The resulting phase behaviour of these derivatives was studied using differential scanning calorimetry (DSC) and polarised optical microscopy (POM). Eight novel derivatives of DPA and BPEA were synthesized. New information was gained as to the requirements of inducing liquid crystallinity in these dye molecules. Direct addition of chains symmetrically to the central dye molecules did not result in the formation of liquid crystalline phases. Through extension of the central core by an extra phenyl ring a liquid crystalline behaviour was observed. A synthesized derivative of DPA exhibited extreme supercooling, which is one of a few derivatives of 9,10-diphenylanthracene to exhibit a liquid state at room temperature. A derivative of BPEA was synthesized that exhibited formation of a mesophase (liquid crystal phase). These two derivatives were investigated for potential use as a material for upconversion.</p>

Organised Functional Liquids for Photon Upconversion

<p>Photon upconversion is a process by which lower energy photons are converted to higher energy photons, which can be achieved by the interaction of two triplet excited states. This process holds potential for wavelength shifting solid films in photovoltaic cells. Not all wavelengths emitted by the sun have sufficient energy to be utilized by such devices. Typical solar cells have a band gap of around 1 µm, however there is a significant amount of energy output by the sun that falls below this threshold. Upconversion could lead to more efficient use of energy by converting these lower energy wavelengths to wavelengths that could be directly absorbed by the solar panel. Upconversion has thus far been harnessed in solution, where diffusion is the limiting factor for the efficiency of the process. However, for technological applications it would be better to create thin solid films. In these films, molecules would have to be brought within the distance on which upconversion occurs, as the process would no longer be defined by diffusion. One way to achieve this would be to create liquid crystalline derivatives of upconversion emitter molecules. This would provide ordering in the system, which would enhance electronic coupling and bring molecules within the scale on which upconversion occurs. The work of this thesis has focused on the synthesis of these organised functional liquids: liquid crystals of common upconversion emitter molecules. 9,10-diphenylanthracene (DPA) and 9,10-bis(phenylethynyl)anthracene (BPEA) are popular emitter molecules, and derivatives of these molecules were synthesized. A variety of alkyl chains were attached with or without phenyl linkers. The alkyl chains would provide entropy to the system in order to induce the formation of liquid crystalline phases. The resulting phase behaviour of these derivatives was studied using differential scanning calorimetry (DSC) and polarised optical microscopy (POM). Eight novel derivatives of DPA and BPEA were synthesized. New information was gained as to the requirements of inducing liquid crystallinity in these dye molecules. Direct addition of chains symmetrically to the central dye molecules did not result in the formation of liquid crystalline phases. Through extension of the central core by an extra phenyl ring a liquid crystalline behaviour was observed. A synthesized derivative of DPA exhibited extreme supercooling, which is one of a few derivatives of 9,10-diphenylanthracene to exhibit a liquid state at room temperature. A derivative of BPEA was synthesized that exhibited formation of a mesophase (liquid crystal phase). These two derivatives were investigated for potential use as a material for upconversion.</p>