多位电动搅拌交换-全自动凯氏定氮法测定土壤中阳离子交换量

测定土壤阳离子交换量（CEC）的行业标准方法中,以玻璃棒手动搅拌进行离子交换和铵离子的清洗,使用传统方式进行蒸馏,手动滴定测定土壤样品中的阳离子交换量。但是这些方法搅拌操作劳动强度大、蒸馏过程较为繁琐,耗时长、效率低、不利于大批量样品的快速检测。以自制的多位电动搅拌装置代替玻璃棒搅拌,选择乙酸铵加入量、乙酸铵交换次数和交换搅拌时间3个因素,进行3因素3水平正交试验,结合实际操作需要选择加入50 mL乙酸铵溶液,交换1次,搅拌5 min,用乙醇清洗3次,运用全自动凯氏定氮仪进行蒸馏和测定土壤样品中的阳离子交换量。当搅拌时间为5 min时,搅拌速度大于100 r/min时,增加搅拌速度对分析结果无影响。使用本方法对不同酸碱性的国家标准物质和实际样品进行测定,测定结果的相对标准偏差为1.51%～2.38%,且国家标准物质的测定结果均在认定值的不确定范围内,表明本方法有较好的精密度和准确度。与标准方法相比,本方法以多位电动搅拌装置代替玻璃棒搅拌,用全自动凯氏定氮仪代替传统的蒸馏方式和手动滴定,自动化程度较高,蒸馏过程操作简单,解放了分析测试人员的双手,降低了劳动强度,自动滴定,节约了试剂成本,整个分析效率提高一倍以上,可实现批量化快速检测土壤中的阳离子交换量。     

Development of a high pressure stirring cell up to 2 GPa: a new window for chemical reactions and material synthesis

ABSTRACT

A new method for stirring under high pressure conditions has been developed and tested. The key component is a Teflon cell assembly equipped with magnetic stirring function, which is capable to operate across a wide pressure range, up to at least 2?GPa, in a large volume press. The setup enables adjustable stirrer rotation rate and detection of stirring in a sample, e.g. to observe liquid–solid phase transitions at high pressure. The viscosity limit of stirring is ca. 500 times that of water at room temperature (i.e. ～500?mPas). Moreover, we show that zinc oxide nanoparticles hydrothermally synthesized at 0.5?GPa and 100°C under stirring conditions show an order of magnitude smaller size (100?nm) compared to those synthesized under non-stirring conditions (1?μm). The wide pressure range for stirring of viscous media opens interesting possibilities to produce novel materials via hydrothermal synthesis and chemical reactions.     

高速搅拌对淀粉/聚乙烯醇共混物溶液成膜性能的影响

淀粉与聚乙烯醇（ＰＶＡ）溶液在高速搅拌下共混,可大大改善淀粉／ＰＶＡ共混薄膜的力学性能、透明性与耐水性,对其生物降解性有明显的影响．淀粉／ＰＶＡ共混体系在高速搅拌前后的光谱分析、显微观察、分子量及流变性能的测定表明,这些变化起因于高速搅拌增加了淀粉中直链淀粉的含量,同时提高了淀粉与ＰＶＡ共混溶液的稳定性,改善了淀粉／ＰＶＡ共混物薄膜的使用性能．     

Feasibility of treating swine manure in an anaerobic sequencing batch biofilm reactor with mechanical stirring

Anaerobic sequencing batch reactors containing granular or flocculent biomass have been employed successfully in the treatment of piggery wastewater. However, the studies in which these reactors were employed did not focus specifically on accelerating the hydrolysis step, even though the degradation of this chemical oxygen demand (COD) fraction is likely to be the limiting step in many investigations of this type of wastewater. The mechanically stirred anaerobic sequencing batch biofilm reactor offers an alternative for hastening the hydrolysis step, because mechanical agitation can help to speed up the reduction of particle sizes in the fraction of particulate organic matter. In the present study, a 4.5-L reactor was operated at 30°C, with biomass immobilized on cubic polyurethane foam matrices (1 cm of side) and mechanical stirring provided by three flat-blade turbines (6 cm) at agitation rates varying from 0 to 500 rpm. The reactor was operated to treat diluted swine waste, and mechanical stirring efficiently improved degradation of the suspended COD. The operational data indicate that the reactor remained stable during the testing period. After 2 h of operation at 500 rpm, the suspended COD decreased by about 65% (from 1500 to 380 mg/L). Apparent kinetic constants were also calculated by modified first-order expressions.     

磁力搅拌和激光辐照处理水溶液对ICP辐射的增强作用

在电感耦合等离子体原子发射光谱法中,仍然是以溶液方式把样品引入到光源。为了提高对水溶液的处理效果,改变其物理性质,采用磁力搅拌与激光辐照相结合的手段,测量了不同实验条件下水溶液的表面张力和粘度。将处理后的溶液引入到电感耦合等离子体(ICP)中,测量了样品元素的谱线强度和信背比以及等离子体的激发温度和电子密度。实验结果表明：在磁力搅拌器的转速为1 197 r·min-1、激光输出功率密度为0.227 6 W·cm-2和样品处理时间为15 min的优化条件下,溶液的表面张力和粘度比未经处理时的分别减小了27.85%和8.66%;样品元素谱线As 188.980 nm,Cd 214.439 nm,Cr 267.716 nm,Cu 324.754 nm,Hg 253.652 nm和Pb 220.353 nm的强度分别提高了32.07%,65.36%,18.27%,32.29%,19.38%和54.28%,信背比分别增大了25.13%,60.97%,18.18%,27.69%,21.11%和48.93%。通过测量等离子体的激发温度和电子密度两个主要参数,在一定程度上解释了水溶液被处理以后等离子体辐射增强的原因。这种预处理水溶液的方法能够明显提高ICP发射光谱强度,而且与单独利用激光辐照水溶液的方法比较,明显缩短了处理样品的时间,有利于提高工作效率。此方法操作简便,在处理样品溶液过程中不存在二次污染问题,便于推广使用。     

连续搅拌反应器中自催化化学反应的同步与控制

讨论了由两个连续搅拌反应器组成的化学反应体系的同步问题. 基于Lyapunov稳定性理论,提出了设计控制函数的方法,分别探讨了入料溶液的流速恒定和存在周期微扰两种情况下使反应实现同步的耦合强度范围. 用数值模拟验证了方法的有效性. 结果表明该方法不仅适用于自治系统,同时也适用于具有周期扰动的非自治系统. 关键词： 同步与控制 化学反应 连续搅拌反应器 周期扰动     

温度及搅拌速度对纳米氢氧化镍性能的影响

采用化学沉淀法制备出片状和棒状混合的纳米β-Ni(OH)2.将纳米粉体以8;比例掺入到球镍中制成复合电极,研究了反应温度和搅拌速度对纳米粉体结构、形貌及其复合电极电化学性能的影响.结果表明:反应温度升高,纳米颗粒粒径增大;搅拌速度提高,粒径减小;复合电极的放电比容量随反应温度和搅拌速度提高先增大后减小,当反应温度为50 ℃、搅拌速度为500 r/min时,相应的复合电极放电比容量最大,达到了263.3 mAh/g,比纯球镍电极放电比容量(239.4 mAh/g)提高了约10;.研究还显示,复合电极的放电比容量与其粉体的压实密度有直接关系,其放电比容量和放电平台均高于纯球镍电极.     

Eco-friendly synthesis of 2-azetidinone analogs of isonicotinic acid hydrazide

Abstract

2-Azetidinones possess broad and potent activity due to presence of β-lactam ring and has been established as one of the biologically important scaffolds. The synthesis of N-(4-aryl-2-oxoazetidinone)-isonicotinamide by novel methods of stirring and sonication are described. The conventional method for synthesis of 2-azetidinones involves use of Dean–Stark water separator for the removal of water from the reaction with long reaction time (12–16 h reflux) at a very low temperature (?70 to ?90°C). The microwave method reported requires inert atmosphere of nitrogen gas for the synthesis of 2-azetidinones. We report herein the synthesis of 2-azetidinone analogs of isonicotinic acid hydrazide by novel green route methods of sonication and stirring using molecular sieves. Results indicate that higher yields and shorter reaction times can be achieved by employing novel green route methods of synthesis.