Preparation and characterization of polyvinylidene fluoride hollow fiber membranes for ultrafiltration

Polyvinylidene fluoride (PVDF) hollow fiber membranes were prepared using the solvent spinning method. N,N-dimethylacetamide was the solvent and ethylene glycol was employed as non-solvent additive. The effect of the concentration of ethylene glycol in the PVDF spinning solution as well as the effect of ethanol either in the internal or the external coagulant on the morphology of the hollow fibers was investigated. The prepared membranes were characterized in terms of the liquid entry pressure of water measurements, the gas permeation tests, the scanning electron microscopy, the atomic force microscopy, and the solute transport experiments. Ultrafiltration experiments were conducted using polyethylene glycol and polyethylene oxides of different molecular weights cut-off as solutes. A comparative analysis was made between the membrane characteristic parameters obtained from the different characterization techniques.     

利用含锌工业固废制备高纯氧化锌的工艺研究

针对氧化锌尾矿和废弃水渣等工业固废中有价锌难以回收的问题,以当地工业含锌固废为原料,利用碳热还原氧化法,制备了高纯氧化锌微粉。通过HSC Chemistry进行热力学计算和试验研究结合的方式,分析了含锌废渣中硅酸锌与碳还原反应的热力学过程。讨论了配碳量、焙烧温度、焙烧时间以及CaF₂对硅酸锌还原过程锌产率的影响。结果表明,在以CaF₂为催化剂时,1 000～1 100℃催化效果最显著。得出最佳工艺条件：在温度为1 100℃、保温时间40 min、碳含量20 wt%、CaF₂添加5 wt%的条件下锌产率(氧化锌回收率)为97.44%。对挥发产物进行结构和成分分析,其物相为六方纤锌矿结构的氧化锌晶体,粒度大小2～4μm,纯度达到了99.47%。     

铝电解废旧阴极酸浸液除氟回收锂工艺研究

铝电解废旧阴极经过硫酸浸出得到了含有Na、Li、Al、F等有价元素的浸出液,具有回收价值的同时伴随着严重的二次污染。采用冰晶石结晶法两次除氟,除氟后回收锂。实验结果表明：当反应pH=9、n(Al):n(F)=1∶6、反应温度为50℃、反应时间为90 min、晶种添加量为0.8 g/L时,溶液中残氟浓度为48 mg/L,一次除氟率为98.15%,锂除去率为1.38%;经过二次除氟后,溶液中氟的浓度为49 mg/L,二次除氟率为85.12%,锂除去率为2.13%;经过两次除氟后,氟总除去率为99.38%,锂总除去率为1.31%;制备出的Li₂CO₃纯度大于99.5%。     

Calculation of Symmetric Stretching Frequency in Molten BeF2 by Molecular Dynamics Method

The molecular dynamics method was applied to molten BeF₂, in which the pair potentials of the Born-Mayer-Huggins type were employed. The Fourier transform of the distances between a Be²⁺ ion and its nearest neighboring F^? ions averaged over total 12 Be²⁺ ions gave the frequency of about 175 cm^?1 as the symmetric stretching frequency which is in satisfactory agreement with 282 cm^?1 obtained with Raman spectroscopy.

The self-diffusion coefficients of Be²⁺ and F^? ions were estimated to be 2×l0^?10m²/sec and the internal energy was ?2,559 kJ/mol at 973 K.     

Gd2O3-NH4HF2系制备氟化钆机制及工艺研究

以氧化钆和氟化氢铵为原料，通过X射线衍射、化学分析和实际观察，确定了反应过程中的产物，研究了该体系在不同条件下的反应规律，制定了新的GdF3制备工艺。常压下，粉状Gd2O3与NH4HF2在100℃开始反应，生成GdNH4F4，NH4F，NH3和H2O。224℃时GdNH4F4分解为GdF3和NH4F，NH4F在156—430℃间挥发和分解。反应过程包括合成、分解和脱铵3个反应环节。真空可以降低每一步反应的起、止温度，特别有利于脱铵反应进行。用氟化氢铵制备氟化钆应采用“常压低温合成-真空中温分解．真空高温脱铵”工艺：即压力为101kPa，温度为185℃合成GdNH4F4；压力小于10．1kPa，温度为210℃分解GdNH4F4；压力小于10．1kPa，温度为385℃脱除NH4F。     

氟化改性D751螯合树脂的制备及应用

通过直接对亚胺基二乙酸型螯合树脂(D751)进行表面氟化改性,使氟原子在树脂骨架上分布,在树脂表层形成橡胶弹性体。改性螯合树脂用于离子膜法烧碱盐水的二次精制,吸附性能和力学性能均得到提高。     

BaF2/BaO替代对钡镓锗酸盐玻璃结构的影响

用Raman光谱技术研究了Ga2O3/GaF3GeO2二元玻璃的结构,并用XRD技术和Raman光谱技术研究了BaF2/BaOGa2O3GeO2系统玻璃的结构。讨论了BaF2替代BaO对玻璃结构的影响。结果表明:摩尔组成为20BaO15Ga2O365GeO2玻璃的主要亚稳相是BaGa2·Ge2O8,而以BaF2替代玻璃中的全部BaO后,玻璃的主要亚稳相转变为BaGe2O5。玻璃中引入氟化物后,其中频段强Raman散射峰宽化,主峰值向高频方向移动,表明在玻璃中形成一些较大的四面体环。同时玻璃高频段最强的振动峰同样移向高频,高频带低频侧的肩明显减弱。这些变化可解释为玻璃中Q2振动模的减少和Ga,Ge四面体的对称性降低,使Raman光谱中的高频成分增加。     

含盐乙醇-水-异辛醇体系液液平衡

用自制的液液平衡釜测定了乙醇-水-异辛醇体系和乙醇-水-异辛醇-氟化钾/氯化钠体系的液液平衡数据。比较了上述3种体系的乙醇在有机相和水相中的分配系数,其中含盐体系高于无盐体系,含氟化钾体系高于氯化钠体系。对所测液液平衡数据用hand方程进行关联,结果良好。     

PEG/GO/TiO2纳米复合材料改性PVDF膜的制备及其抗污性能

为改善聚偏氟乙烯(PVDF)膜的抗污性能,以聚乙二醇2000接枝的GO/TiO₂(PEG/GO/TiO₂)纳米复合材料为添加剂,通过非溶剂诱导沉淀相分离法制备了一系列PEG/GO/TiO₂/PVDF复合超滤膜。采用FTIR、SEM和接触角测试仪对其结构和形貌进行了表征,采用超滤法评价其纯水通量和抗污性能。结果表明,当PEG/GO/TiO₂纳米复合材料质量分数为0.60%时,制备的PEG/GO/TiO₂/PVDF复合超滤膜(记为0.60%PEG/GO/TiO₂/PVDF)表现出最佳的亲水性和抗污性能,其接触角比PVDF膜下降8.2°,总孔隙率增加13.40%,PEG/GO/TiO₂纳米复合材料在PVDF膜中分散较均匀。在0.08 MPa的工作压力下,0.60%PEG/GO/TiO₂/PVDF的纯水通量高达282.44 L/(m²·h),对腐植酸溶液的过滤通量为131.96 L/(m^2...     

Herausforderungen in der Membranentwicklung für die Fruchtsaftklarfiltration – vom Labor in die Produktion

For fining/clarification of apple juices, an ultrafiltration polyethersulfone tubular membrane has been used successfully for many years. However, this membrane is not suitable for filtration of dark fruit juices, as some natural dyes are also rejected. In order to be able to open up a new market, a tubular membrane based on polyvinylidene fluoride has to be developed that does not discolor dark juices but retains turbidity. The steps from the general understanding of fruit juice clarification, through laboratory tests, to field-testing's of finished membrane modules are briefly described.