Photocatalytic degradation of dyes and organic contaminants in water using nanocrystalline anatase and rutile TiO2

Nanocrystalline TiO₂ was synthesized by controlled hydrolysis of titanium tetraisopropoxide. The anatase phase was converted to rutile phase by thermal treatment at 1023 K for 11 h. The catalysts were characterized by X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), Fourier-transform infrared absorption spectrophotometry (FT-IR) and N₂ adsorption (BET) at 77 K. This study compare the photocatalytic activity of the anatase and rutile phases of nanocrystalline TiO₂ for the degradation of acetophenone, nitrobenzene, methylene blue and malachite green present in aqueous solutions. The initial rate of degradation was calculated to compare the photocatalytic activity of anatase and rutile nanocrystalline TiO₂ for the degradation of different substances under ultraviolet light irradiation. The higher photocatalytic activity was obtained in anatase phase TiO₂ for the degradation of all substances as compared with rutile phase. It is concluded that the higher photocatalytic activity in anatase TiO₂ is due to parameters like band-gap, number of hydroxyl groups, surface area and porosity of the catalyst.     

Controlled Synthesis of Various Hollow Cu Nano/MicroStructures via a Novel Reduction Route

Hollow Cu nano/microstructures are prepared by reduction of CuSO₄ · 5 H₂O with glucose by using a mild hydrothermal process. The X‐ray powder diffraction and energy‐dispersive X‐ray analysis indicate that the products are pure Cu and of cubic phase. The morphology of the products can be controlled between nanotubes and microspheres assembled from hollow nanoparticles by adjusting the concentration of sodium dodecyl sulfate. A series of experiments confirm that the concentration of the glucose and NaOH also play important roles in the formation of the hollow Cu nano/microstructures.     

水热法制备锰锌铁氧体纳米晶

以水热法制备了粒径为20－40nm的锰锌铁氧体纳米晶，以XRD、SEM、磁强计等对产物做了表征，分析了影响锰锌铁氧体纳米晶的因素。结果表明，在T≥150℃,t≥5h条件下，均能得到阵锌铁氧体纳米晶粉末。T＝450℃时制备的纳米晶的磁强度最高；添加剂能改善水热体系的均匀性，使产物分布均匀、晶相单一、团聚少。     

Hydrothermal conversion of FAU zeolite into aluminous MTN zeolite

The hydrothermal conversion of FAU zeolite into aluminous MTN zeolite is described here. In the presence of both benzyltrimethylammonium hydroxide (BTMAOH) and sodium chloride (NaCl) the highly crystalline and pure MTN zeolites with Si/Al ratios of 21-23 could be obtained from the hydrothermal conversion of FAU zeolite. Based on powder XRD refinement and ¹³C CP/MAS NMR spectra, BTMA⁺ ions were not present in cages of the obtained zeolites, but TMA⁺ ions existed instead. It means that BTMAOH underwent degradation during the conversion. Moreover, the effects of Si/Al ratio of starting FAU zeolite, synthesis parameters (BTMAOH/SiO₂ and H₂O/SiO₂ ratios) and the addition of alkali metal chlorides on the hydrothermal conversion of FAU zeolite into MTN zeolite are discussed. As compared to amorphous SiO₂/γ-Al₂O₃, which produced impurity, the hydrothermal conversion of FAU zeolite showed a fast crystallization rate and a high selectivity to MTN zeolite formation. These phenomena indicate that the assembly of locally ordered aluminosilicate species coming from the decomposition or dissolution of FAU zeolite should be taking part in the conversion process.     

Hydrothermal synthesis of hexagonal ZnO clusters

Hydrothermal process was applied to synthesize zinc oxide nanocrystals. X-ray powder diffraction and scanning electron microscopy were used to analyze the crystal structure and surface morphology. XRD pattern analysis showed that the ZnO clusters are single hexagonal phase of wurtzite structure (space group P63 mc) with no impurity of Zn and Zn(OH)₂. Also, SEM images revealed that the size of a single ZnO crystal is between 200-500 nm in diameter and 2-5 μm in length. The influence of potassium iodide (KI) as a surfactant on the crystallinity of ZnO has been investigated.     

水热法合成(Mn,Zn)Fe_2O_4磁性晶体粉末

采用水热加工技术研究（Ｍｎ，Ｚｎ）Ｆｅ２Ｏ４晶体粉末的合成条件，对水热体系的碱度、温度、时间进行了系统实验．结果表明在ｐＨ＝７～１２．５范围内可有效合成（Ｍｎ，Ｚｎ）Ｆｅ２Ｏ４．当温度在１９０～２２０℃时，完成合成所需的时间为１～２ｈ，提高碱度有利于合成反应．本文还初步探讨了（Ｍｎ，Ｚｎ）Ｆｅ２Ｏ４的合成机理，为扩大实验提供依据．     

Phase studies of pozzolanic stabilized calcium silicate hydrates at 180 °C

Phase studies of calcium silicate hydrates formed at elevated temperature and pressure have been well documented. At 180 °C, the initially formed amorphous calcium silicate gel [C-S-H] transforms into well-defined crystalline phases, the stability of which is primarily dependent on the C/S ratio in the CaO-SiO₂-H₂O system and the hydrothermal conditions. Hillebrandite [C₂SH], α-dicalcium silicate hydrate [α-C₂SH] and β-tricalcium silicate [β-C₆S₂H₃] are predominantly the stable phases in the lime-rich part of the CaO-SiO₂-H₂O system and are typically associated with high permeability and compressive strength retrogression. Gyrolite [C₂S₃H_~2], tobermorite [C₅S₆H₅], truscottite [C₇S₁₂H_~3] and xonotlite [C₆S₆H] have all been reported to coexist stably in aqueous solution with silica in the silica-rich part of the CaO-SiO₂-H₂O system.The addition of excess silica to the CaO-SiO₂-H₂O system is usually in the form of silicon dioxide [SiO₂], either as microsilica or quartz flour, which, in theory, should not affect the equilibrium chemistry. This has not been found to be the case, and metastable phases formed in the early stages of reaction modify the long-term stability and phase equilibrium. Pozzolanic materials that are predominantly alumino-silicates have also been investigated as a source of excess silica. Partial replacement of aluminum for silicon occurred, but had no apparent influence on the stability of the calcium silicate hydrates formed.     

用山东某电厂脱硫石膏制备α-半水石膏

山东某电厂产生的脱硫石膏目前仅作为水泥及其制品的常规掺和料和普通石膏制品的生产原料直接出售,售价低廉。为提高该脱硫石膏的综合利用附加值,对其进行了常压NaCl盐溶液水热法制备α-半水石膏的试验研究。试验以制品结晶水含量和制品中结晶体的微观形貌为判据,对工艺条件进行了优化,最终确定的盐溶液浓度为20%,料浆浓度为20%,料浆pH为自然状态,反应温度为100℃,反应时间为3 h。在此条件下,所得制品的结晶水含量为8.74%,结晶为平均长径比=4∶1的柱状体。X射线衍射分析结果证明,制品中的主要物相确实为α-半水石膏。     

Continuous synthesis of Zn2SiO4:Mn fine particles in supercritical water at temperatures of 400-500 °C and pressures of 30-35 MPa

Sub-micron sized Zn₂SiO₄:Mn²⁺ phosphors particles were continuously synthesized in supercritical water with a flow reactor. Colloidal silica or sodium silicate was used as the Si source. Zn and Mn sources were chosen from their nitrates, sulfates, and acetates. The syntheses were carried out at temperatures from 400 to 500 °C, at pressures from 30 to 35 MPa, at NaOH concentrations from 0.014 to 0.025 M, and for residence times from 0.025 to 0.18 s. Sodium silicate formed α- and β-Zn₂SiO₄:Mn²⁺ phases regardless of the Zn and Mn sources, while colloidal silica formed phases dependent on the type of Zn and Mn sources used in addition to the use of alkali. As the reaction temperature increased, the crystallinity of α-Zn₂SiO₄:Mn²⁺ phase increased and the Mn substitution into the Zn sites of the α-Zn₂SiO₄ phase decreased. Of the conditions studied, the most highly crystalline α-Zn₂SiO₄:Mn²⁺ was produced at a temperature of 400 °C, a pressure of 30 MPa, a NaOH concentration of 0.14 M, and a residence time of 0.13 s with Zn and Mn sulfates and colloidal silica as starting materials. The α-Zn₂SiO₄:Mn²⁺ fine particles synthesized were round in shape, had an average diameter of 268 nm, and exhibited a green-emission with a peak wavelength of 524 nm.     

水热法一步合成磷酸铁锂及其性能研究

为优化液相法一步制备磷酸铁锂（LiFePO₄）技术,以七水合硫酸亚铁、磷酸二氢铵、一水合氢氧化锂为原料,通过添加十二烷基苯磺酸钠（SDBS）作为表面活性剂,采用液相水热法合成技术,一步合成了LiFePO₄正极材料。研究了水热法一步合成技术对LiFePO₄材料的组成、结构、形貌、粒度等的影响,通过电感耦合等离子体发射光谱仪（ICP-OES）、X射线衍射仪（XRD）、扫描电镜（SEM）、粒度分析仪等对材料进行了表征分析,并测试了材料的电化学性能。研究结果表明,合成得到的LiFePO₄材料为微米级球形颗粒形貌的正交晶系非化学计量比的Li_1.02Fe_0.994PO₄材料。电化学性能测试结果表明,在0.1C倍率下首次充、放电比容量分别为162.0、159.9 mA·h/g,库伦效率达到98.7%、倍率性能（以1C/0.1C保持率计）为92.3%,0.1C倍率循环100次容量保持率为96.4%,展现出良好的电化学性能。