Preparation of modified MFI-type/PDMS composite membranes for the separation of dichlorobenzene isomers via pervaporation.

Zeolite-polymer composite membranes have become promising and effective materials for the pervaporative separation of liquids, especially for isomeric mixtures. In this paper, silicalite-1/PDMS composite membranes have been used to investigate the separation of dichlorobenzene (DCB) isomers via pervaporation for the first time. Silicalite-1 zeolites modified by the silane coupling agent, NH3-C3H6-Si(OC2H5)3, have been incorporated into polydimethylsiloxane (PDMS). Then, the silicalite-1/PDMS composite membranes have been successfully prepared on porous polyvinylidene fluoride (PVDF) supports. The morphology and structure of the silicalite-1 zeolites and silicalite-1/PDMS composite membranes have been characterized by XRD, FTIR, SEM and BET techniques. The results show that the modified silicalite-1 zeolite particles have smaller pore sizes dispersed more uniformly in the active layers of the silicalite-1/PDMS composite membranes and present fewer aggregation and pinholes formed by the accumulation of zeolite particles. The silicalite-1/PDMS composite membranes are all dense and continuous with good homogeneity. To evaluate the pervaporative separation performance of the DCB isomers, the unmodified and modified silicalite-1/PDMS composite membranes have been further tested in single-isomer and binary-isomer systems at 60 °C. The modified silicalite-1/PDMS composite membranes present higher DCB isomer separation factors. The separation factors of the modified silicalite-1/PDMS composite membranes in the binary-isomer systems for p-/o-DCB and p-/m-DCB are 3.53 and 5.63, respectively. The permeate flux of p-DCB through the modified silicalite-1/PDMS composite membranes in the p-/o-DCB binary-isomer system is 116.7 g m-2 h-1 and in the p-/m-DCB binary-isomer system, it is 93.5 g m-2 h-1. The result provides a new approach towards the pervaporative separation of DCB isomers from their mixture for future industrialization applications.

Synthesis of silicalite-1 zeolite membranes for vapor-permeation separation of dichlorobenzene Isomers.

Silicalite-1 zeolitic membranes have been successfully fabricated on the porousα-Al2O3support by templated and template-free protocol, respectively, for vapor permeation separation of dichlorobenzene (DCB) isomers. After proving the high quality of the membranes by single gas permeation (He and SF6) performance, the vapor-permeation of DCB isomers over two types of the silicalite-1 membrane was then investigated. The separation results clearly indicated that under the lower partial pressure and higher temperature, the effect of DCB isomer adsorption on the permeance could be kept at a sufficiently low level and sharp selectivity become more important. Thus, highp-DCB selectivity could be achieved. Comparatively, the template-free silicalite-1 zeolite has a much higher p-DCB selectivity due to the relatively fewer inter-crystalline gaps. Under certain separation conditions, the highest selectivity ofp-DCB forp-/m-DCB andp-/o-DCB binary systems could reach 165 and 113, respectively.

MFI-Type Zeolite Membranes for Pervaporation Separation of Dichlorobenzene Isomers.

MFI-type zeolitic membranes were prepared on the porous α-A2O3 support to investigate the separation properties of dichlorobenzene isomers. The pervaporation tests were performed with unary and binary isomer mixtures at 333 K. The results indicate that the silicalite membranes, irrespective of being synthesized by the templated or template-free method, are permeable for all dichlorobenzene isomers. The pervaporation fluxes of the pure dichlorobenzene isomers decrease in the order p-DCB > o-DCB > m-DCB. For the binary pervaporation system, the dichlorobenzene fluxes are all less than those with a single component due to the binary interactions between DCB isomers and between the DCB isomer and the zeolite membrane. Comparatively, the template-free MFI-type zeolite exhibits higher selectivity for dichlorobenzene isomers due to less inter-crystalline gaps. The separation factors for p-/o-DCB and p-/m-DCB can reach 16.7 and 22.0, respectively.

[Development of high speed UV-Vis spectrophotometer].

A high speed spectrophotometer based on a linear CCD was developed. The function and structure of the hardware and the software for the instrument were discussed. The elementary performance was tested as follows: wavelength range 200-820 nm, full spectrum scan time < 0.1 s, spectral bandwidth 0.7 nm, wavelength accuracy +/-1 nm, photometric accuracy +/- 0.005 AU, baseline flatness < 0.001 AU (rms), and stray light < 0.1%. Results showed that this instrument is easy to use, fast and with high analytical performance. In addition, it has internet function of remote control and remote access. With the powerful data processing and spectrum analyzing software, it will provide a strong tool for routine analysis and the research on dynamic reaction in chemistry and biology fields.

[The simultaneous measurements of time-dependent laser-induced fluorescence intensity of hematoporphyrin monomethyl ether in animal tissues with rheumatoid arthritis].

Since the selectivity of photodynamic therapy (PDT) depends on the distribution of a photosensitizer in a tissue during the treatment, an investigation of drug distribution is a key step for performing PDT effectively. The distribution of photosensitizer absorbed in tissues is adjusted by the animal body system, so an apparatus that can measure the fluorescence intensity of photosensitizer in different tissues of the same body simultaneously is in demand. To achieve precise estimate of tissue selectivity of the photosensitizer, a spatially separated three-channel laser-induced fluorescence (LIF) detection system was set up and employed in the present study to measure the fluorescence intensity of Hematoporphyrin Monomethyl Ether (HMME) in different tissues of the same body simultaneously. The time-dependent variations in the concentrations of HMME within the skin,cartilage, normal synovium and inflammatory synovium of rabbit were monitored in vivo. The results obtained showed that the synovium has higher absorptivity of HMME thanthe skin and cartilage. The difference is distinct from the very beginning of injection. Although the quantity of HMME absorbed in the inflammatory synovium is not very high in the first 20 min, it is still 6 times higher than that in the skin and cartilage. In addition, the absorptivity of HMME is much stronger for the inflammatory synovium than that for the normal synovium. If thelaser beam irradiates outside the joint for the rheumatoid arthritis, tissues around the inflammatory synovium have less HMME, thereby causing weak PDT effect. This would help reduce the side effect of PDT. Thus we suggest that for PDT treated rheumatoid arthritis, taking the first 20 min after the injection for outside-the-joint excitation employing HMME maybe a good choice.

[Near-infrared spectral studies of hydrogen-bond in water-methanol mixtures].

Investigations of hydrogen bond in a water-alcohol mixture were carried out with the near-infrared (NIR) spectra of water-methanol solutions over a concentration range of 0-100 wt% with an interval of 5 wt% by analyzing the concentration-dependent variations of OH bands due to combination and overtone modes. Since the OH bands strongly overlapped in the NIR region, various spectral analysis methods, such as second derivatives, principal component analysis (PCA), and two-dimensional (2D) correlation analysis, were employed to improve the spectral resolutions and obtain the effective information from the NIR spectra of water-methanol mixtures. The possible combined modes between water and alcohol in the system of water-alcohol mixture were qualitatively described. The present study provides a new possibility for investigating the hydrogen bond in water-alcohol mixtures.