氧化石墨烯杂化分子印迹复合膜制备及性能研究

采用改进的Hummers法，通过冷冻干燥制备了氧化石墨烯(GO)。以辛弗林盐酸盐为模板分子，水溶性的丙烯酰胺为功能单体，离子液体(溴代1-丁基-3-甲基咪唑)为致孔剂，把GO加入聚合液中，制备了GO杂化的分子印迹复合膜(GO-MIM)。利用透射电镜、扫描电镜、X射线衍射和红外光谱等方法对GO及GO-MIM进行了表征。通过将分子印迹膜技术与GO相结合，明显提高了分子印迹膜的力学性能。吸附及渗透实验表明，GO-MIM可在纯水溶剂体系，对辛弗林盐酸盐具有很好的选择性吸附能力和优先透过能力，体现了明显的分子印迹效果。     

溶胀嵌入脂肪酸分子制备高脱硼反渗透膜

采用“溶胀-嵌入-收缩”方法改性聚酰胺反渗透膜，制备了一种高脱硼反渗透膜。通过甲醇溶胀增加了高分子链之间的距离，为疏水性癸酸分子的嵌入提供了场所，然后在压力和浓差极化共同作用下，改性分子选择性嵌入聚酰胺膜的孔内；当甲醇分子离开后，聚酰胺膜收缩将癸酸分子固定在高分子网络中。实验借助溶胀和分子嵌入以及溶胀后的收缩调节聚酰胺膜的孔径大小；利用脂肪酸的疏水性降低聚酰胺膜的极性，从而实现增加空间位阻和减少氢键结合位点数量的目的。实验结果显示，改性膜的脱硼率和截盐率均明显升高，截盐率从90.36%增加到96.46%，脱硼率从未改性膜的47.85%增加到77.32%，渗透液的硼含量达到WTO的使用标准。虽然水和硼的渗透性均下降，但是水和硼的渗透选择性增加，证明该方法有利于提高水硼选择性。     

Co-based zeolitic imidazolate framework ZIF-9 membranes prepared on α-Al2O3 tubes through covalent modification for hydrogen separation

Hydrogen has been regarded as the most promising clean and renewable energy. Beside the production of the hydrogen, the separation of hydrogen is also an import issue before it can be used in fuel cells. Membrane-based separation technologies have gained considerable attentions due to its high efficiency and low energy consumption. Zeolite imidazolate framework (ZIF) membranes have drawn intense interest due to their zeolite-like properties such as permanent porosity, uniform pore size and exceptional thermal and chemical stability. It is rather challenged to prepare well-intergrown Co-based zeolitic imidazolate frameworks (ZIFs) membranes on porous α-Al₂O₃ tubes since Co-based ZIFs prefer to form crystals in the synthesis solution rather than grow as membrane layer on the support surface. In this work, we report the preparation of high-quality ZIF-9 membrane with high H₂/CO₂ selectivity and excellent thermal stability by using 3-aminopropyltriethoxysilane (APTES) as a covalent linker to modify the α-Al₂O₃ tube. Due to the formation of covalent bonds between APTES and ZIF-9, ZIF-9 nutrients are bound to the support surface, thus promoting the growth of dense and phase-pure ZIF-9 membrane with a thin thickness of about 4.0 μm. The gas separation performances of the ZIF-9 membrane were evaluated by single gas permeation and mixture gas separation of H₂/CO₂, H₂/N₂ and H₂/CH₄, respectively. The mixture separation factors of H₂/CO₂, H₂/CH₄, and H₂/N₂ of the ZIF-9 membrane are 21.5, 8.2 and 14.7, respectively, which by far exceeds corresponding Knudsen coefficients. Moreover, the as-prepared ZIF-9 membrane exhibits excellent stability at a relatively broad range of operating temperature, which is beneficial for the industrial application of hydrogen separation or further membrane reactor.     

Investigation of OSN properties of PDMS membrane for the retention of dilute solutes with potential industrial applications

Few commercially available membranes can be used for organic solvent nanofiltration (OSN). Applying OSN in chemical industries is nevertheless of high interest to cut with energy consumption linked to solvent recycling and soluble catalysts recovery. A commercial membrane, PERVAP4060, was used to investigate the retention of dilute solutes in toluene feeds and to mimic metathesis medium. The studied solutes were R-BINAP a neutral polyaromatic molecule used in metathesis chemistry, tetraoctylammonium bromide (ToABr), a charged molecule used as a homogeneous catalyst and n-hexadecane. Retention of polar ToABr (95%) was higher than that of neutral R-BINAP (80%). The transfer mechanism, either pore flow or solution-diffusion, was discussed. All the results obtained suggested that the transport is governed by the solution-diffusion mechanism. The measured retentions could be explained in terms of solubility affinities and diffusion coefficients. The stability and performances of PERVAP4060 were well established, showing the strong potential for industrial applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48359.     

Bootstrap procedures for detecting multiple persistence shifts in heteroskedastic time series

This article proposes new bootstrap procedures for detecting multiple persistence shifts in a time series driven by non-stationary volatility. The assumed volatility process can accommodate discrete breaks, smooth transition variation as well as trending volatility. We develop wild bootstrap sup-Wald tests of the null hypothesis that the process is either stationary [I(0)] or has a unit root [I(1)] throughout the sample. We also propose a sequential procedure to estimate the number of persistence breaks based on ordering the regime-specific bootstrap p-values. The asymptotic validity of the advocated procedures is established both under the null of stability and a variety of persistence change alternatives. A comparison with existing tests that assume homoskedasticity illustrates the finite sample improvements offered by our methods. An application to OECD inflation rates highlights the empirical relevance of the proposed approach and weakens the case for persistence change relative to existing procedures.     

Reduction of chlorophenols and sludge management from paper industry wastewater using electrocoagulation process

ABSTRACT

In this study, electrocoagulation (EC) was used to determine the optimum conditions on the basis of maximum chemical oxygen demand (COD) and color removal. At the optimum conditions chlorophenols (CPs), biological oxygen demand and total organic carbon (TOC) were determined. The biodegradability of wastewater was increased significantly with 63% COD, 98% color, 61% TOC and overall 65.51% reductions in CPs. Further, the electro-coagulated sludge was characterized by using different analytical techniques to assist the physicochemical and elemental phases, to find-out better management option, reusability for plant growth and safe disposal. Additionally, aluminum content (70.62%) was successfully recovered from sludge.     

Fabrication of magnetically recoverable Fe3O4/CdS/g-C3N4 photocatalysts for effective degradation of ciprofloxacin under visible light

Photocatalytic technology is an environmentally safe method of eliminating organic pollutants and antibiotics in wastewater. In this research, the performance of Fe₃O₄/CdS/g-C₃N₄ (FCN) photocatalyst for degradation of antibiotics was studied. The composite photocatalysts with different concentrations of g-C₃N₄ were prepared. FCN has better photocatalytic activity than degradation dyes in removal of antibiotics under visible light. This indicates that FCN could effectively hinder the recombination of carriers, and the addition of g-C₃N₄ increases the optical response range of CdS. At the same time, the introduction of Fe₃O₄ magnetic nanoparticles overcomes the problem of difficulty in recovery of the powder photocatalyst. The photocatalytic activity is not reduced to any significant after three cycles of use.