Characterization of cross-linked poly(N-isopropylmethacrylamide) microgel latexes

 This article reports the colloidal and physicochemical characterization of crosslinked poly (N-isopropylmethacrylamide) (poly[NIPMAM]) latexes. The latex particles were first characterized by determining the lowest critical solubility temperature by measuring the optical density variation as a function of temperature. In addition, the electrophoretic mobility behaviors of all latexes were examined as a function of pH and temperature. Finally, the colloidal stability was investigated by determining the critical coagulation concentration and the critical flocculation temperature, and the corresponding results were discussed by taking into account both the effect of salinity and temperature on the solvency of poly[NIPMAM]. Received: 25 March 1999 Accepted: 5 May 1999     

钻井污水处理的实验研究

钻井污水是油田开发中的主要环境污染物之一。其成分复杂,使得CODCr值高而处理难度大。以渤深6井为研究对象,采用混凝与微电解相结合处理废水。试验结果表明,原水的CODCr从35 155 mg/L降到186 mg/L,达到二级排放标准。     

混凝吸附法联合处理小麦麸膳食纤维废水

用聚合硫酸铝铁为混凝剂,阳离子型聚丙烯酰胺为助凝剂,活性炭为吸附剂,采用混凝吸附的方法,处理了小麦麸膳食纤维废水.结果表明当聚合硫酸铝铁(PAFS)的质量浓度为500 mg/L,聚丙烯酰胺(PAM)的质量浓度为10 mg/L,pH为4.21时,混凝处理后的废水COD去除率最大.絮凝后水样经活性炭吸附后COD去除率可达85.82%,色度去除率为100%,浊度去除率为93.03%.     

Experimental and Numerical Study of Aerosol Coagulation by Gravitation

The behaviors of aerosols having particle diameters of 1–5 μm were studied experimentally and the results were compared with numerical calculations. For the experimental study, a specially designed coagulation cylinder was developed and the moment method was used in the numerical predictions. The experimental results were characterized by the size parameters including the geometric mean diameter (GMD), the geometric standard deviation (GSD) and the particle number concentration (N). Particle distributions in the cylinder were measured at certain time intervals. In a closed cylinder, the mechanism governing aerosol behavior appeared to be gravitational coagulation. Separately, the numerical calculations were carried out using the moment method. The experimental results and the numerical predictions were in reasonable agreement. It is believed that the present work represents the first experimental study on gravitational coagulation.     

Dynamic buckling mode of an elastic bar

The conception of buckling relative initial imperfection is presented in this paper. According to Boulli-Euler beam equation, the dynamic buckling mode of an elastic bar under the homogeneous boundary conditions can be derived by applying the preferred mode analytical method. As an example, the dynamic buckling mode of an elastic bar clamped at both ends is discussed.     

Acrylonitrile–maleic anhydride copolymer membrane (I): effects of casting conditions

The effects of casting conditions, including casting solution (composition and temperature) and coagulation conditions (pre‐evaporation time, temperature and concentration of coagulation bath) on the structure and performance of acrylonitrile–maleic anhydride copolymer membrane have been investigated. The results showed that the water flux decreased gradually while the rejection of bovine serum albumin (BSA) decreased as the concentration of copolymer increased. When the total solid concentration was kept unchanged, the water flux increased with additive polyvinylpyrrolidone (PVP), the rejection did not decrease until the ratio of PVP/copolymer was 60%. When the content of copolymer in the casting solution was kept constant, the water flux decreased rapidly while the rejection increased a little (compared with the case of no additive) as the ratio of PVP/copolymer increased. As to the temperature of casting solution, the water flux had a maximum at 45 °C and the rejection had a maximum and a minimum at 45 and 55 °C, respectively. The water flux had a maximum value when the pre‐evaporation time was 40 sec. The rejection of BSA was almost unchanged when the pre‐evaporation time was less than 40 sec. and then decreased and reached a minimum value at 60 sec. As the temperature of coagulation bath increased, the water flux reached a maximum at 35 °C while the rejection increased uniformly. With increasing the concentration of DMSO in the coagulation bath, the water flux decreased gradually and got to a minimum at 50 wt% as the concentration of dimethylsulfoxide in the coagulation bath increased, but no apparent effect on the rejection was observed. Copyright © 2000 John Wiley & Sons, Ltd.     

牛奶蛋白质含量的SSA-SVM高光谱预测模型

牛奶中包含着很多人体需要的营养元素,如脂肪、蛋白质、钙等;对牛奶营养元素进行分析是牛奶安全检测关键的一部分.高光谱技术可以有效地结合图像和光谱数据识别牛奶种营养元素.为了实现对牛奶中蛋白质含量快速、精确的预测,采用竞争性自适应重加权(CARS)算法选取特征波长,并提出一种基于麻雀搜索算法(SSA)优化支持向量机(SVM...     

Ultrasound stabilization of raw milk: Microbial and enzymatic inactivation,physicochemical properties and kinetic stability

The aim of this study was to evaluate the effects of non-thermal and thermal high-intensity ultrasound (HIUS) treatment on the microbial and enzymatic inactivation, physicochemical properties, and kinetic stability of the raw milk by applying different energy densities (1, 3, 5, and 7 kJ/mL). Two HIUS treatments were evaluated based on different nominal powers, named HIUS-A and HIUS-B, using 100 W and 475 W, respectively. HIUS-A treatment was non-thermal processing while HIUS-B was a thermal treatment only for the energy densities of 5 and 7 kJ/mL since the final temperature was above 70 °C. The HIUS-B treatment showed to be more efficient. Log reductions up to 3.9 cycles of aerobic mesophilic heterotrophic bacteria (AMHB) were achieved. Significant reductions of the fat globule size, with diameters lower than 1 µm, better color parameters, and kinetic stability during the storage were observed. Also, HIUS-B treatment inactivated the alkaline phosphatase and lactoperoxidase. The HIUS-B treatment at 3 kJ/mL worked below 57 °C being considered a border temperature since it did not cause unwanted physicochemical effects. Furthermore, a microbial inactivation of 1.8 ± 0.1 log cycles of AMHB was observed. A proper inactivation of only the Alkaline phosphatase and a significant reduction of the fat globules sizes, which kept the milk kinetically stable during storage was achieved.     

Coagulation Behavior of Antimony Oxyanions in Water: Influence of pH,Inorganic and Organic Matter on the Physicochemical Characteristics of Iron Precipitates

The presence of inorganic and organic substances may alter the physicochemical properties of iron (Fe) salt precipitates, thereby stabilizing the antimony (Sb) oxyanions in potable water during the chemical treatment process. Therefore, the present study aimed to examine the surface characteristics, size of Fe flocs and coagulation performance of Sb oxyanions under different aqueous matrices. The results showed that surface properties of Fe flocs significantly varies with pH in both Sb(III, V) suspensions, thereby increasing the mobility of Sb(V) ions in alkaline conditions. The negligible change in surface characteristics of Fe flocs was observed in pure water and Sb(III, V) suspension at pH 7. The key role of Van der Waals forces of attraction as well as hydration force in the aggregation of early formed flocs were found, with greater agglomeration capability at higher more ferric chloride dosage. The higher Sb(V) loading decreased the size of Fe flocs and reversed the surface charge of precipitates, resulting in a significant reduction in Sb(V) removal efficiency. The competitive inhibition effect on Sb(III, V) removal was noticed in the presence of phosphate anions, owing to lowering of ζ-potential values towards more negative trajectory. The presence of hydrophobic organic matter (humic acid) significantly altered the surface characteristics of Fe flocs, thereby affecting the coagulation behavior of Sb in water as compared to the hydrophilic (salicylic acid). Overall, the findings of this research may provide a new insight into the variation in physicochemical characteristics of Fe flocs and Sb removal behavior in the presence of inorganic and organic compounds during the drinking water treatment process.     

离子色谱-质谱联用测定牛奶中的高氯酸盐、溴酸盐和碘离子

以离子色谱-质谱联用同时测定了不同品牌牛奶中的高氯酸盐、溴酸盐和碘离子。以高容量、强亲水性IonPac AS20(2 mm)为分析柱,EGC在线产生KOH为淋洗液,串联质谱检测。ESIMS/MS以多元反应监测(MRM)模式分别监控高氯酸盐的m/z100.8/84.9、98.8/82.9离子对,溴酸盐的m/z126.8/110.9、126.8/95.0离子对和碘离子的m/z126.8/127.0离子对,并分别对高氯酸盐、溴酸盐和碘离子以m/z98.8/82.9、126.8/110.9和126.8/127.0离子对的峰面积进行定量。该方法对高氯酸盐、溴酸盐和碘离子的检出限(S/N=3)分别为0.02、0.1和0.5μg/L,线性相关系数分别是0.999(0.05~50μg/L)、0.999(0.5~100μg/L)、0.998(1~1 000μg/L)。高氯酸盐和碘离子的样品加标回收率分别在102%~108%之间和86%~114%之间。