Influence of particle size on the aggregation behavior of nanoparticles: Role of structural hydration layer

More and more attention has been paid to the aggregation behavior of nanoparticles, but little research has been done on the effect of particle size. Therefore, this study systematically evaluated the aggregation behavior of nano-silica particles with diameter 130–480 nm at different initial particle concentration, pH, ionic strength, and ionic valence of electrolytes. The modified Smoluchowski theory failed to describe the aggregation kinetics for nano-silica particles with diameters less than 190 nm. Besides, ionic strength, cation species and pH all affected fast aggregation rate coefficients of 130 nm nanoparticles. Through incorporating structural hydration force into the modified Smoluchowski theory, it is found that the reason for all the anomalous aggregation behavior was the different structural hydration layer thickness of nanoparticles with various sizes. The thickness decreased with increasing of particle size, and remained basically unchanged for particles larger than 190 nm. Only when the distance at primary minimum was twice the thickness of structural hydration layer, the structural hydration force dominated, leading to the higher stability of nanoparticles. This study clearly clarified the unique aggregation mechanism of nanoparticles with smaller size, which provided reference for predicting transport and fate of nanoparticles and could help facilitate the evaluation of their environment risks.     

Photo-degradation organic dyes by Sb-based organic-inorganic hybrid ferroelectrics

The organic-inorganic hybrid halide compounds have emerged as one of the most promising photoelectric material for their superior optoelectronic properties and hold great prospects for renewable energy substitutes and environmental protection as photocatalysis. Here, we report the optical properties of the Sb-based organic-inorganic hybrid ferroelectric materials: pyridine-4-aminium tetrachloroantimonate ((C₅H₇N₂)SbCl₄, sample 1), piperidin-1-aminium tetrachloroantimonate ((C₅H₁₃N₂)SbCl₄, sample 2) and tris(trimethylammonium) nonachlorodiantimonate (((CH₃)₃NH)₃Sb₂Cl₉, sample 3), which are a kind of exploited efficient photocatalysts. Samples 2 and 3 exhibit distinct photoelectric respond, which are mainly ascribed to their minor narrow band-gap compared with sample 1. For the ferroelectrics, the intrinsic of spontaneous polarization of sample 3 at room temperature is favourable for the separation of photogenerated electrons and holes within the photorespond process. Moreover, sample 3 shows the highest efficiency of photo-decomposed Rhodamine B (90.2% within 80 min) and Methyl Orange (MO) (97.4% within 50 min), thanks to the photo-excited electrons and holes promoting the formation of oxidative radical species during the photo-redox progress. These findings prove that the development of a novel Sb-based organic-inorganic hybrid halide compounds with good stability in the degradation of organic dyes paves a way to designing new photocatalyst.     

有机钙孔隙结构与脱硫性能研究

在定碳炉上对有机钙进行煅烧试验,利用氮吸附仪测定样品的微观孔隙结构,采用智能定硫仪对有机钙进行了脱硫实验研究.结果表明.900℃下煅烧.醋酸钙镁的比表面积高达46.6 m2/g,大约为普通石灰石比表面积的4倍.醋酸钙比表面积主要分布在孔径小于5 nm的微孔和中孔,醋酸钙镁比表面积主要集中在孔径为5 nm左右的中孔.醋酸钙的烧结主要发生在微孔和中孔,醋酸钙镁的烧结发生在整个孔径分布区域,有机钙表现出良好的抗烧结特性.1 000℃下按钙硫比为1添加钙基,有机钙的脱硫效率为68.28%-75.55%.比普通石灰石高1倍以上.煅烧形成的良好孔隙结构使得有机钙具有较高的脱硫效果.     

电动力学技术修复苯酚污染土壤的研究

用电动力学技术对苯酚污染砂土的修复进行了实验研究.探讨了苯酚污染砂土电动力学修复的可行性及在不同电场强度下苯酚的迁移特征和机制.研究了采用添加阴离子表面活性剂十二烷基苯磺酸钠(LAS)和控制液(柠檬酸和NaOH)等对迁移效果的影响,以及苯酚在砂土中的迁移和分布规律.实验结果表明,在电场作用下苯酚在砂土中发生富集.在电场强度为2.0V/cm时的苯酚富集效果明显,比在电场强度为0.5 V/cm时苯酚多增加30%,且向阳极的迁移距离增大了12 cm;在阴极添加不同浓度的LAS,苯酚在砂土中的富集效果不同,LAS浓度越大向阳极迁移得越快富集效果越明显,当LAS为0.046 0 mol/L时苯酚最高增加了143%;向阳极添加NaOH,苯酚在阳极区增加了136%,比向阴极添加柠檬酸的效果明显.     

乳酸和复合脂肪酸抑制奶牛对环境污染的效果分析

将20头荷斯坦产奶奶牛随机分为对照组和试验Ⅰ～Ⅲ组,对照组饲喂全混日粮(TMR),试验Ⅰ组每头奶牛每天饲喂TMR加150.0 g复合脂肪酸,试验Ⅱ组每头奶牛每天饲喂TMR加150.0 g乳酸,试验Ⅲ组每头奶牛每天饲喂TMR加150.0 g复合脂肪酸/乳酸(质量比为1∶1),分析探讨了复合脂肪酸和乳酸对奶牛粪尿、氮、总磷排泄量和CH4释放量的影响.结果表明,相比对照组,试验Ⅲ组1头奶牛1年CH4释放量减少30.64 kg,粪尿、氮、总磷排泄量分别减少1.43 t、28.32 kg和2.36 kg,标准乳(FCM)提高3.28%.在奶牛饲料中添加乳酸和复合脂肪酸的混合酸,能有效抑制奶牛对土壤、水体及空气的污染,显著提高奶牛的生态效益和经济效益.     

基于BP神经网络的垃圾焚烧过程故障诊断

应用BP神经网络方法,建立了垃圾焚烧过程故障诊断的模型.该方法采用梯度下降法训练网络权值,利用最优停止法对网络进行了优化,避免了过拟合现象.提高了BP神经网络的训练速度和泛化能力.并以实际焚烧过程工况数据进行性能检验,检验结果表明了该BP网络具有较高的诊断精度.     

由粉煤灰合成单一的沸石及其对Cr(Ⅵ)的吸附研究

以粉煤厌为原料采用两步法合成了2种单一沸石矿物种的NaA和NaX型沸石,并对产物的结构和性能进行了详细表征.2种沸石产物的吸附性能比较结果表明,NaA型沸石优于NaX型沸石.在静态吸附条件下,研究了NaA型沸石吸附水溶液中Cr(Ⅵ)的相关参数(溶液pH值、吸附温度和吸附时间),并用Langmuir和Freundlich等温吸附线对吸附结果进行拟和.结果表明:Cr(Ⅵ)的吸附行为符合Langmuir方程;饱和吸附量为47.78 mg/g.NaA型沸石对Cr(Ⅵ)的吸附是物理和化学吸附两种行为共同作用的结果.     

示波极谱滴定法测定工业废水中的氰化物

在ｐＨ为１０３的氯化铵氨水底液中,使氰化物与Ｎｉ２＋离子形成稳定物〔Ｎｉ（ＣＮ）４〕２－络离子,过量的Ｎｉ２＋离子用标准ＥＤＴＡ溶液返滴,以Ｎｉ２＋离子在交流示波极谱图上的切口消失指示滴定终点,废水的色度、浊度等对测定不产生干扰,无须进行预蒸馏处理,操作简便,快速。方法的相对偏差小于１０％,变异系数小于０７％,水样的加标收率为９６～１０７％。     

粪秆混合厌氧发酵渗滤床工艺的消化性能

以玉米秸秆-牛粪为原料,利用自行设计的渗滤床反应器（Leach bed reactors）,对比研究了渗透液回流喷淋时间、喷淋量、发酵温度及粪秆比4因素对原料物能转化率的影响。结果表明：发酵结束后罐内物料的TS浓度在13%~15%之间,属于高浓度发酵范畴;9样品产气峰值出现在发酵后的10~14 d,物能转化率排序为L6 > L2 > L9 > L7 > L1 > L8 > L4 > L5 > L3;TS产气率相对较高的共同特点主要为35 ℃中温、较高的渗滤液回流量以及较高的粪秆比。通过TS产气率的直观分析,4因素对实验结果影响大小排序分别为发酵温度> 粪秆比 > 喷淋量 > 喷淋时间间隔,得到的最佳工况参数为喷淋时间间隔2 h、喷淋量4 L、发酵温度35 ℃、粪秆比1∶1,此条件下得到的平均TS产气率为（98.4±3.5）mL·g-1。方差分析结果表明,发酵温度、粪秆比及喷淋量对产气结果影响极显著,为控制渗滤床发酵工艺的主要参数。     

MnO2/Al2O3吸附草甘膦及微波紫外耦合降解再生工艺

以掺混煅烧法制备MnO2/Al2O3,并对草甘膦进行吸附,将吸附态草甘膦置于微波紫外耦合系统中进行降解和再生。研究并给出了MnO2/Al2O3的最佳制备条件、最佳吸附条件和微波紫外耦合降解再生的最佳工艺参数。MnO2/Al2O3最佳制备条件为MnO2质量分数15%,煅烧温度500℃,煅烧时间2 h。在常温下,MnO2/Al2O3对草甘膦的最大吸附量为75 mg/g。微波紫外耦合系统最佳工艺参数为功率500 W,时间25 min,空气量0.06 m3/h。在此操作条件下,MnO2/Al2O3的再生率达到85%,并且可以多次再生利用,草甘膦最终降解产物为二氧化碳、氮氧化物、磷酸和水,矿化率为65%。