Photocatalytic degradation of aqueous 4-chlorophenol by silica-immobilized polyoxometalates

The degradation of 4-chlorophenol with near-UV light by silica-immobilized polyoxometalate (POM-in-SiO2) catalysts has been studied. The silica-immobilized Na6W7O24 (SW7), H4W1032 (SW10), H3PW12O40 (SPW12), and H6P2W18O62 (SP2W18) were prepared by means of the sol-gel hydrothermal technique through the hydrolysis of tetraethoxysilane in aqueous solution of the corresponding polyoxometalate, respectively. The degradation of 4-chlorophenol was monitored by measuring Cl- and CO2 concentrations and analyzing reaction intermediates by GC/MS analysis. During irradiation, 4-chlorophenol first dechlorinated to form hydroquinone and p-benzoquinone, and then these intermediates further mineralized to form CO2 and H2O. The degree to which 4-chlorophenol was mineralized by photocatalytic oxidation was investigated. Results indicate less than 15% for SW7 but nearly complete mineralization for SW10 after 60 min of photoirradiation. The present studies suggest that POM-in-SiO2 catalysts may be a novel type of photocatalyts for the purification of the environmentally chlorophenol-contaminated water.     

Synthesis of indium borate and its application in photodegradation of 4-chlorophenol

Indium borate has been prepared by a sol-gel method. The structure, morphology, and photophysics of the resultant photocatalysts have been studied via the techniques of X-ray diffraction (XRD), transmission electron microscopy (TEM), and diffuse reflectance UV-visible light spectroscopy. These photocatalysts have been used to photodegrade 4-chlorophenol. The photocatalytic activity depends on the annealing temperature during preparation. It is found that borates can exhibit a high photodegradation activity under UV-light irradiation, for which the efficiency can be higher than that of as-prepared TiO(2). This is explained according to the results of fluorescence spectra and valence band X-ray photoelectron spectroscopy (XPS). It is confirmed by the results of time-resolved photoluminescence decay spectra; i.e., the lifetime of electrons and holes involved in the radiative process can be longer for the borates than that for TiO(2). This implies that indium borate can be a promising photocatalyst for future applications in treatment of environment contaminants.     

Kinetics and mechanism of photoactivated periodate reaction with 4-chlorophenol in acidic solution

The application of photoactivated periodate (UV/IO4-) to the degradation of 4-chlorophenol (4-CP) was explored in this study. Under low irradiation intensities (23 microW/cm2), wavelength of 266 nm, and pH 3, 4-CP was observed to degrade by pseudo-first-order reaction kinetics. The small reduction in 4-CP degradation in the presence of tert-butyl alcohol (t-BuOH) suggests that degradation of 4-CP by UV/IO4- was not dominated by an OH* pathway. O3 production was suppressed in the presence of t-BuOH under O2-limited environments and in the presence of 4-CP. Faster degradation of 4-CP in the presence of an OH* scavenger under nitrogen purging as compared to air-saturated conditions indicates that O(3P) is an important reactive species with 4-CP in this system. When 4-CP is added to the system, IO3- production is enhanced. On the basis of the elimination of potential reaction pathways, O(3P) and IO3* are suspected reactive species with 4-CP in this system.     

4-Ethylphenol and 4-ethylguaiacol depletion in wine using esterified cellulose

The ability of cellulose acetate, cellulose acetate propionate (CAP), cellulose acetate butyrate and cellulose propionate (CP) fibres to reduce 4-ethylphenol and 4-ethylguaiacol, causing the off-flavour named “Brett character”, was studied. CAP and CP performed best in a preliminary comparative test. The former was chosen because of its more favourable FDA classification for food contact substances. CAP effectiveness was studied in relation to the reduction in volatile phenols with doses of up to 20 g/l and wine contact times of up to 60 min. Using 4 g/l, reduction of both phenols was, on average, 31–32% in defective red wines. Wine treatment affected neither colour nor total proanthocyanidins and catechins, and wines were judged to be better than the corresponding spoiled controls. CAP fibre can be regenerated by washing with ethanol or aqueous solution (pH 12), without notable changes in depletion efficiency. The technological characteristics of CAP and, to a lesser extent, CP offer interesting prospects for producing filtration beds, pads and membranes for the treatment of wines and beverages affected by “Brett character”.     

Highly active and stable Ni-Fe bimetal prepared by ball milling for catalytic hydrodechlorination of 4-chlorophenol

A novel Ni-Fe bimetal with high dechlorination activity for 4-chlorophenol (4-CP) was prepared by ball milling (BM) in this study. Increasing Ni content and milling time greatly enhanced the dechlorination activity, which was mainly attributed to the homogeneous distribution of Ni nanoparticles (50-100 nm) in bulk Fe visualized by scanning electron microscopy/energy dispersive X-ray spectrometry (SEM/EDS) with image mapping. In comparison with the Ni-Fe bimetal prepared by a chemical solution deposition (CSD) process, the ball milled Ni-Fe bimetal possessed high dechlorination activity and stability before being used up. Dechlorination kinetics indicated that the dechlorination rates of 4-CP increased with increasing Ni-Fe dose but decreased with increasing solution pH. Solution pH had a significant effect on the dechlorination of 4-CP and the passivation of the Ni-Fe bimetal. The enhanced pH during the dechlorination process significantly accelerated the formation of passivating film on the bimetallic surface. The Ni-Fe bimetal at the dose of 60 g/L was reused 10 times without losing dechlorination activity for 4-CP at initial pH less than 6.0, but the gradual passivation was observed at initial pH above 7.0.     

An infrared and X-ray spectroscopic study of the reactions of 2-chlorophenol, 1,2-dichlorobenzene, and chlorobenzene with model cuO/silica fly ash surfaces

The surface-mediated reactions of 2-chlorophenol, 1,2-dichlorobenzene, and chlorobenzene were studied using CuO/ SiO2 as a fly ash surrogate. These compounds served as model precursors that have been implicated in the formation of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs). With FTIR, we determined that reactions of the model precursors with a substrate composed of CuO dispersed on silica result in the formation of a mixture of surface-bound phenolate and carboxylate partial oxidation products from 200 to 500 degrees C. Chemisorption of 2-chlorophenol and 1,2-dichlorobenzene resulted in the formation of identical surface-bound species. Using X-ray absorption near-edge structure spectroscopy, we measured the time- and temperature-dependent reduction of Cu(II) in a fly ash surrogate during reaction with each precursor. It was demonstrated that CuI2O is the major reduction product in each case. The rate of Cu(II) reduction could be described using pseudo-first-order reaction kinetics with Arrhenius activation energies for reduction of Cu(II) of 112, 101, and 88 kJ mol(-1) for 2-chlorophenol, 1,2-dichlorobenzene, and chlorobenzene, respectively. We demonstrate that chlorinated phenol and chlorinated benzene both chemisorb to form chlorophenolate. Although chlorinated phenols chemisorb at a faster rate, chlorinated benzenes are found at much higher concentrations in incinerator effluents. The implication is that chlorinated benzenes may form 10 times more chlorophenolate precursors to PCDD/Fs than chlorinated phenols in combustion systems.     

Identification of 4-bromo-2-chlorophenol as a contaminant responsible for organoleptic taint in melons.

An off-odour, described by the growers as similar to profenofos, occurred in melons in which this pesticide had been used in crop treatment. However, profenofos, O-(4-bromo-2-chlorophenyl) O-ethyl S-propyl phosphorothioate, could not be detected in the melons using GC/MS although a component with a shorter retention time was found. Concentration of melon volatiles by steam distillation yielded a product identical to that obtained by hydrolysis of profenofos, identified as 4-bromo-2-chlorophenol. A solution of this compound in water had similar organoleptic properties to that of the contaminated fruits. It was concluded that 4-bromo-2-chlorophenol was responsible for the taint detected in melons.     

TiO2-based photocatalytic degradation of 2-chlorophenol adsorbed on hydrophobic clay

The combination of adsorption and heterogeneous photocatalysis has been investigated as a promising technology for the removal of organic water pollutants. A laboratory study of the removal and decomposition of 2-chlorophenol (2-CP) as a toxic organic pollutant was carried out under various conditions with an organophilized clay mineral (hexadecylpyridinium chloride-modified montmorillonite; HDPM) as adsorbent and Degussa P25 TiO2 as photocatalyst. Three different oxidation processes leading to the degradation of 2-CP were compared: direct photolysis, heterogeneous photocatalysis in a TiO2 suspension, and the decomposition of substrate adsorbed on HDPM in the presence of TiO2. Both the degradation of 2-CP and the formation of intermediates were analyzed by HPLC, the total organic carbon content and the total organic and inorganic chloride contents were measured to monitor the mineralization process, and X-ray diffraction and thermoanalytical measurements were made to characterize the hydrophobic clay adsorbent. The heterogeneous photocatalytic degradation of dissolved (2-CP/UV/TiO2) and desorbed 2-CP (2-CP/HDPM/UV/TiO2) appeared to be equally efficient, whereas direct photolysis of 2-CP was far less efficient in the oxidative destruction. HDPM proved to be a suitable adsorbent, capable of adsorbing toxic organics from water. It was demonstrated that the adsorbent (at relatively high concentration) did not decrease the rate of mineralization of 2-CP. The results confirmed that the adsorbent retains its structure and composition during the mineralization process, and thus it can be reused without regeneration. The combination of adsorption and heterogeneous photocatalysis studied may be an efficient and economical means of accumulating, removing, and oxidizing organic water contaminants, and its application is in accordance with the growing environmental demands.     

锰盐引发丙烯腈在维纶上接枝共聚制备螯合纤维

以聚乙烯醇缩甲醛纤维（维纶纤维PVF）为基体，制备螯合纤维，采用四价锰盐引发丙烯腈（AN）在PVF上接枝共聚，经胺肟化反应使接枝在PVF基体上的聚丙烯腈的腈基转化为偕胺肟基，制备了偕胺肟功能基含量较高，对重金属离子和铀酰离子有较好的选择吸附性的螯合纤维，研究了高锰酸钾预处理条件及接枝共聚各条件对接枝反应的影响。并以接枝率和接枝效率为参数确定了最佳实验条件，分析腈基转化为胺肟基的胺肟化反应的各种影响因素，以转化率为参数确定实验条件，结果表明，在选定的实验条件下进行预处理，接枝共聚反应，胺肟化反应。则螯合纤维接枝共聚效果较好。     

细菌纤维素发酵条件的优化及结构分析

以木葡糖酸醋杆菌Gyll为目标菌株,采用单因素法对液体发酵生产细菌纤维素的发酵条件(氮源、碳源、初始pH值、种龄、接种量和静态发酵周期)进行了优化,并对其代谢生产的细菌纤维素的微观结构进行了观察。结果表明,最优发酵条件为蔗糖5%,玉米浆干粉5%;初始培养基pH 6.2,发酵液中接种量10%;采用动静三步结合发酵时,一级种子的种龄24h,二级种子扩大化培养时种龄为20h,静态培养周期为8d。菌株最高产量为11.49g/L,约是优化前的5倍。通过红外光谱(FT-IR)、扫描电镜(SEM)、X射线衍射对细菌纤维素的表征,确定制得的细菌纤维素属于Ⅰ型纤维素,具有典型的网状结构,纤维束尺寸为纳米级且结晶度很高。     

添加羧甲基纤维素钠对动态细菌纤维素生产的影响

考察添加不同浓度羧甲基纤维素钠(CMC-Na)对Acetobacter xylinum NUST4.1在摇瓶和机械搅拌发酵罐中产细菌纤维素(BC)的影响。结果发现:添加0.06% CMC-Na能有效解决发酵罐中严重结团和菌株逐级放大后生产稳定性差的2大难题,而且能显著提高纤维素产量,优化发酵罐基本工艺后能获得3.35g/L干纤维素,是基础培养的3.1倍。     

纤维素酶及其应用

介绍了纤维素酶的来源、组成功能、作用机理及其在食品等各个领域的应用研究,并展望其发展前景。     

直接大红4BS杂化硅溶胶的染色性能

以正硅酸乙酯、3-缩水甘油醚氧丙基三甲氧基硅烷（GPTMS）、乙醇、水和盐酸为原料制备硅溶胶,将直接大红4BS杂化其中,制备直接染料杂化硅溶胶。探讨该杂化硅溶胶的染色性能,并与直接大红4BS染色后固色剂固色工艺对比。结果表明,相对于染色后固色剂固色工艺,硅溶胶含量40%,氯化钠用量10g/L,焙烘温度150℃,焙烘时间5 min工艺下,染色K/S提高了11.1%,干湿摩擦牢度各提高了1级,原样变色牢度和沾色牢度各提高了0.5级。杂化硅溶胶染色织物的拉伸断裂强力与未处理样相比略有增加,其中径向拉伸断裂伸长率增加11.6%。经杂化硅溶胶处理后织物弯曲刚度和弯曲滞后矩略增加,织物手感略减小。通过SEM照片可以看出杂化硅溶胶染色的纤维表面形成一层溶胶薄膜。     

Mechanisms of dioxin formation from the high-temperature oxidation of 2-chlorophenol

The homogeneous, gas-phase oxidative thermal degradation of 2-chlorophenol was studied in a 1 cm i.d., fused silica flow reactor at a concentration of 88 ppm, reaction time of 2.0 s, over a temperature range of 300 to 1000 degrees C. Observed products in order of yield were as follows: 4,6-dichlorodibenzofuran (4,6-DCDF) > dibenzo-p-dioxin (DD) > 1-monochlorodibenzo-p-dioxin (1-MCDD), 4-chlorodibenzofuran (4-MCDF), dibenzofuran (DF), naphthalene, chloronaphthalene, 2,4-dichlorophenol, 2,6-dichlorophenol, phenol, chlorobenzene, and benzene. In contrast to pyrolysis, 4,6-DCDF is the major product rather than DD, and 1-MCDD and naphthalene are formed at temperatures as low as 400 degrees C. Under oxidative conditions, .OH and Cl. are the major carriers, which favors 4,6-DCDF formation over DD or 1-MCDD through abstraction of H. through diketo- and ether- intermediates. It is proposed that below 500 degrees C, unimolecular tautomerization/HCI elimination and CO elimination/isomerization reactions result in the formation of 1-MCDD and naphthalene, respectively.     

纤维素酒精发酵的研究进展

本文介绍了纤维素的结构、特征和纤维素酒精发酵的途径,并综述了目前国内外纤维素酒精发酵的研究进展,特别是基因工程、固定化等现代生物工程技术在这一领域的应用。     

细菌纤维素生物合成的研究

研究了以玉米浆作为氮源的细菌纤维素生产的主要影响因素.通过优化培养基的方法,提高纤维素的产量,最终确定了木醋杆菌产纤维素的最优发酵液培养基为4%葡萄糖、10%玉米浆、pH6、产膜后的pH值为3.5～4.5,培养温度30℃,纤维素产量可达7.22g/L.     

Effects of microcrystalline cellulose on functional properties of hydroxy propyl methyl cellulose microcomposite films

ABSTRACT:  Edible films and coatings in foods can be used to increase shelf-life and improve organoleptic characteristics of foods by avoiding deterioration of food components and therefore promoting preservation of the final product. This study is the first to investigate the use of different size fillers for the purpose of preparing edible composite films with fillers < 1.0 μm in size. For this purpose, water vapor permeability and mechanical properties of HPMC (hydroxy propyl methyl cellulose) based films with the inclusion of different size MCC (microcrystalline cellulose) fillers were studied. The water vapor permeability of the control HPMC film was 1.2 ± 0.2 g-mm/kPa-h-m² and did not show a significant change with the addition of fillers. A comparison of mechanical properties of the films with a tensile test showed that tensile strength of the control film, which was prepared using a 3 wt% HPMC solution, increased from 29.7 ± 1.6 MPa to 70.1 ± 7.9 MPa with the addition of 500-nm size particles, while it increased only to 37.4 ± 5.5 MPa with the addition of 3-μm size particles. Also important is that the elongation percentage of the control film did not decrease significantly with the addition of submicron size fillers to the HPMC films. This study showed that the increased surface area per weight of smaller size MCC fillers compared to their larger size counterparts was highly beneficial in terms of film mechanical property improvement.