CONVECTION PROMOTION AND GEL FORMATION IN AN ULTRAFILTRATION PROCESS

Convection promotion within a tubular ceramic membrane by using the kenics static mixer is studied. The experiments were carried out with aqueous solutions of pectin and sodium carboxymethylcellulose (CMC), for Reynolds number in the range of 60-5000. From the results of these experiments it can be concluded that the presence of convection promotor decreasing the concentration of the gel layer. The experimental data are correlated satisfactorily by the equation of the general form Sh=A Re^aSc^b.     

MEASUREMENT OF WATER DIFFUSIVITY IN AQUEOUS LITHIUM BROMIDE AND LITHIUM CHLORIDE SOLUTIONS

A relatively simple method was employed for measurement of water diffusivity in aqueous lithium bromide and lithium chloride solutions. The twin bulb apparatus used for these measurements was developed using an analogy between this apparatus and the conventional diaphragm cell apparatus. Tritiated water (TOH) was used as a tracer for these experiments because of its chemical similarity and proximity to the molecular weight of water. High tracer activity used at the beginning of the experiments allowed the use of relatively shorter time duration for each experiment (s;≈ 20 h) and a quasi-steady state equation to calculate the diffusivity from the observed tracer activity data

Initially, the water diffusivity in lithium bromide solutions for concentrations varying from 0.5 M to 3 M (22.1 weight percent) was measured to obtain a comparison with published values. The lithium bromide concentration was further varied from 3 M to 11 M (57.4 weight percent) to obtain data in the concentration range usually employed in absorption cooling applications, which is near the solubility limit. The water diffusivity was found to vary with lithium bromide concentration, and to have a maximum of 16.7 × 10^-10m²/s at 4 M. These diffusivity values were also compared with those obtained using an equation proposed by Rosevaere etal. (1941) for nonideal solutions. The water diffusivity in lithium chloride solutions was measured at concentrations of 7 M (25.7 weight percent) and 8 M (28.87 weight percent) to obtain a comparison with published values. The lithium choride concentration was further varied from 8 M to 13 M (43.24) weight percent) to gather data beyond those of other researchers. Similar to the trend of water diffusivity in lithium bromide solutions, water diffusivity in lithium chloride solutions was also found to vary with concentration with a minimum of 6.2 × 10^-10m²/s near the solubility limit.     

Enzyme-assisted aqueous extraction of shea fat: A rural approach

The use of enzyme-assisted partial hydrolysis as a preextraction treatment in a rural shea fat extraction process to improve upon the extraction rates of the process was explored following an observed possibility in a preliminary investigation. Finely ground shea kernel meal samples were mixed with water in predetermined ratios and heated to inactivate any enzymes present. A crude protease and an enzyme with both hemicellulase and cellulase activities were added and mixed, also in predetermined concentrations. The suspensions were incubated in a waterbath shaker at temperatures ranging from 30 to 45°C for specified periods of time. The treated meal samples were then extracted using an adapted traditional aqueous extraction process. At optimum meal-to-water ratio of 1:2, enzyme concentration of 1%, the natural pH of the meal (about 5.3), and incubation time of 4 h, the enzyme treatment increased the extraction rate from about 40% in the typical traditional system (control) to about 75%, of the total fat content (estimated by the Soxhlet method). The enzyme-treated meal samples were very easy to extract as there was no need to cream or whip out the fat, as is laboriously done in the traditional process. The extracted fat samples had apparently less unsaponifiable matter content and slightly less free fatty acid content and peroxide value, compared to samples from the typical traditional process and, in some cases, the Soxhlet extracted samples. The observations confirmed the results of the preliminary investigations and suggest that the enzyme-assisted preextraction treatment could significantly improve upon the aqueous shea fat extraction process.     

水基防锈剂的研究进展

金属因生锈每年造成巨大经济损失.目前的金属防锈技术存在很多缺点,相比之下,环保型水基防锈剂在金属材料保护方面有许多优点.综述了国内外近年来水基防锈剂的研究状况,重点介绍了几种新型水基防锈剂的防锈机理和性能,并简要概述了美国水基防锈剂的研究进展,最后提出了水基防锈剂的发展趋势,即利用丰富的自然资源或农副产品提取防锈剂的有效成分,经改性后制成高效低毒的复合水基防锈剂.     

Modified Indigo Method For Gaseous And Aqueous Ozone Analyses

The indigo method developed by Bader and Hoigné for aqueous ozone analysis was modified to allow for both gaseous and aqueous ozone determination. Gas or water samples were extracted with a gas-tight syringe containing a known volume of indigo reagent. The modified procedure provided a more consistent basis for gaseous and aqueous ozone determination allowing for more accurate ozone mass balance calculations. Direct gaseous ozone UV absorbance with molar absorptivity of 3,000 M^?1cm^?1 at 258 nm was used as primary standard to determine the molar absorptivity of the indigo reagent. The molar absorptivity of indigo reagent, assuming a 1:1 stoichiometric ratio for the reaction between indigo and ozone, was determined to be 23,150 ± 80 M^?1cm^?1, or approximately 16 percent higher than that of 20,000 M^?1cm^?1 suggested by Bader and Hoigné. An independently calibrated membrane-electrode ozone monitor showed good correlation with indigo method results using the molar absorptivity value determined in this study. The apparent molar absorptivity of aqueous ozone at the wavelength of 258 nm measured by the modified indigo method increased from 2,400 to 3,600 M^?1cm^?1 in the investigated ozone concentration range of 0.4 to 11.0 mg/L. This variation might have been caused by the inherent interference of unidentified ozone byproducts, which presence was supported with scanning spectra in the wavelength range of 200 to 300 nm.     

NaCl水溶液中AZ91与A3钢的接触腐蚀

研究了NaCl水溶液中AZ9l镁合金与A3钢的接触腐蚀特性。试验结果表明，NaCl水溶液中，镁合金与A3钢接触时发生严重的接触腐蚀，腐蚀主要集中在镁合金与A3钢接触部附近；点蚀的平均孔深和腐蚀质量损失随NaCl浓度的增加和浸泡时间的延长而增加；镁合金接触腐蚀的主要腐蚀产物为Mg(OH)2，MgCO3和MgAl2O4，产物中还检测到因基体腐蚀而脱落的第二相Mgl7Al12。     

浇筑式钢桥面铺装层推挤变形病害机理分析

以贵州省北盘江大桥钢桥面铺装层推挤变形病害为研究背景,采用凝胶渗透色谱法(GPC)和傅里叶变换红外光谱法(FTIR),从沥青分子尺度分析钢桥面铺装产生推挤变形的原因。分析结果表明:沥青老化并不是造成钢桥面铺装层推挤变形的主要原因;从现场调查可知,第2层粘层粘结能力的降低是造成钢桥面铺装层推挤变形病害的次要原因;通过级配分析发现,造成钢桥面铺装层推挤变形的主要原因是浇筑式沥青混合料(GA)级配偏细以及GA中集料颗粒的棱角性较差所致。     

Kinetic study of photocatalytic degradation of carbamazepine, clofibric acid, iomeprol and iopromide assisted by different TiO2 materials--determination of intermediates and reaction pathways

The light-induced degradation of clofibric acid, carbamazepine, iomeprol and iopromide under simulated solar irradiation has been investigated in aqueous solutions suspended with different TiO2 materials (P25 and Hombikat UV100). Kinetic studies showed that P25 had a better photocatalytic activity for clofibric acid and carbamazepine than Hombikat UV100. For photocatalytic degradation of iomeprol Hombikat UV100 was more suitable than P25. The results can be explained by the higher adsorption capacity of Hombikat UV100 for iomeprol. The study also focuses on the identification and quantification of possible degradation products. The degradation process was monitored by determination of sum parameters and inorganic ions. In case of clofibric acid various aromatic and aliphatic degradation products have been identified and quantified. A possible multi-step degradation scheme for clofibric acid is proposed. This study proves the high potential of the photocatalytic oxidation process to transform and mineralize environmentally relevant pharmaceuticals and contrast media in water.     

Tribological Properties and Film Formation Behavior of Thermoreversible Gel Lubricants

The tribological properties of a new and unique thermoreversible gel lubricant (TR gel lube) were investigated. TR gel lube, which includes 10–40% of amide-type gelling agent in base fluid, is able to repeatedly alter or convert phase from gel state to liquid state at the melting point of the gelling agent. High-pressure rheological tests were performed in order to characterize the behavior of base oil and TR gel lube as a function of pressure and temperature. The effect of TR gel lube on ball bearing fatigue life was carried out by systematic tests using thrust ball bearings. The results of L ₁₀ life tests of TR gel lube showed a longer life than the conventional greases. This result was investigated from the oil film formation. It was found that the gelling agent played a key role in the lubricating properties. Some mechanisms such as adsorbed film formation and solid-like formation are proposed.     

凝胶注模成形技术的研究与发展

凝胶注模成形是一种近净尺寸成形工艺，是制备形状复杂、成分均匀和可靠性高的陶瓷材料的理想成形工艺。笔者阐述了凝胶注模成形工艺过程和成形原理，以及国内外的研究现状，指出了凝胶注模成形技术的未来发展方向。