硫脲的热分析研究

在非等温条件下,改变升温速率对硫脲进行了热分解动力学方面的研究,并用微分Kissinger法和Ozawa法对硫脲的热重和热流曲线进行了动力学分析,得出硫脲热分解过程的动力学参数,硫脲异构化活化能为80 kJ/mol,硫氰酸胍生成反应的活化能为205 kJ/mol,实验结果与文献吻合。     

EDTA减量滴定法快速测定废水中汞

研究了采用EDTA减量滴定法快速测定废水中的汞含量.水样消解后,在pH值为5～6时,以二甲酚橙为指示剂,先用EDTA标准溶液滴定废水中金属离子的总量;然后在另一份试液中,加入硫脲掩蔽Hg2 离子后,再用EDTA滴定除Hg2 离子外的其它金属离子.两者之差即相当于汞的量.结果表明,改进后的方法,操作简单、测定快速、准确度高、干扰小、颜色变化敏锐、终点易于判断.其测定结果的相对标准偏差(RSD)＜1.0%,加标回收率R在98.3%～100.8%之间.     

微胶囊技术在缓蚀剂中的应用及产品性能评价（Ⅰ）

利用微胶囊制备技术将缓蚀剂亚硝酸钠和硫脲制备成微胶囊,并用紫外分光光度法、极化曲线法和电化学阻抗法对微胶囊缓蚀剂进行评价.研究发现,微胶囊技术能有效地抑制缓蚀剂的释放速度,释放出来的缓蚀剂能有效地抑制金属的腐蚀速度.     

Effective and Selective Recovery of Precious Metals by Thiourea Modified Magnetic Nanoparticles

Adsorption of precious metals in acidic aqueous solutions using thiourea modified magnetic magnetite nanoparticle (MNP-Tu) was examined. The MNP-Tu was synthesized, characterized and examined as a reusable adsorbent for the recovery of precious metals. The adsorption kinetics were well fitted with pseudo second-order equation while the adsorption isotherms were fitted with both Langmuir and Freundlich equations. The maximum adsorption capacity of precious metals for MNP-Tu determined by Langmuir model was 43.34, 118.46 and 111.58 mg/g for Pt(IV), Au(III) and Pd(II), respectively at pH 2 and 25 °C. MNP-Tu has high adsorption selectivity towards precious metals even in the presence of competing ions (Cu(II)) at high concentrations. In addition, the MNP-Tu can be regenerated using an aqueous solution containing 0.7 M thiourea and 2% HCl where precious metals can be recovered in a concentrated form. It was found that the MNP-Tu undergoing seven consecutive adsorption-desorption cycles still retained the original adsorption capacity of precious metals. A reductive adsorption resulting in the formation of elemental gold and palladium at the surface of MNP-Tu was observed.     

二[N-p-氯苯甲酰基-N’,N’-二乙基硫脲-kS]合镍的合成及其结构的研究

硝酸镍与相应的硫脲衍生物反应合成了一种结构新颖的标题化合物。该化合物通过元素分析、红外光谱、核磁共振氢谱和粉末X射线衍射(PXRD)分析进行了表征,并通过X射线衍射法对其晶体结构进行了测定。该化合物属于单斜晶系,P21/c空间群,a=12.796 5(11),b=15.391 8(13),c=14.091 5(12),β=92.869(1)。该化合物采用1∶2的平面几何结构进行配位,两个硫原子和两个氧原子围绕在镍(Ⅱ)离子周围。配体中二乙基的无序致使相邻的两个镍原子的距离较长。     

Oxidative conversion of thiourea and N-substituted thioureas into formamidine disulfides with acidified chloramine-T: a kinetic and mechanistic approach

The kinetics of oxidation of thiourea and N-substituted thioureas namely: N-methylthiourea, N-allylthiourea N-phenylthiourea and N-tolylthiourea to the corresponding formamidine disulfides by sodium N-chloro-p-toluenesulfonamide or chloramine-T (CAT) in the presence of HClO₄ has been investigated at 278 K. The reactions follow identical kinetics for all thioureas, being first order each with respect to [CAT]_o, [Thiourea]_o and [H⁺]. Ionic strength of the medium and addition of p-toluenesulfonamide or halide ions have negligible influence on the rate. The solvent isotope effect has been studied using D₂O in the case of the oxidation of thiourea. Decrease in the dielectric constant of the medium by adding methanol decreases the rate. The reactions were studied at different temperatures, and the composite activation parameters have been computed. An isokinetic relationship was observed with β=314 K, indicating that enthalpy factors control the reaction rate. Under comparable experimental conditions, the rate of oxidation of thioureas increases in the order: N-allylthiourea>N-phenylthiourea>N-methylthiourea>thiourea>N-tolylthiourea. A mechanism involving the interaction of conjugate acid (CH₃C₆H₄SO₂NHCl) and substrate giving an intermediate complex, in a slow step, has been suggested. The derived rate law is in agreement with the observed kinetics.     

Synthesis of Soluble,Curable, and Thermally Stable Aromatic Polyamides Bearing Thiourea and Pendent 4-Pyridylformylimino Groups

A new aromatic dicarboxylic acid monomer 4-pyridylformylimino-N-(phenyl,2′,5′ – dicarboxylic acid) (PPDC) containing pyridine and azomethine units was synthesized through a simple one-step condensation reaction between 2-aminoterephthalic acid and 4-pyridinecarboxaldehyde. A series of new polyamides was prepared through the direct one-pot phosphorylation polycondensation of PPDC with simple aromatic commercial diamines and diamines bearing phenylthiourea groups. The polyamides were characterized by FT-IR, ¹H-NMR, and ¹³C-NMR spectroscopy. Thermal stability of the polymers was evaluated using thermogravimetric analysis. The polyamides with inherent viscosities in the range of 0.30–0.51 dL/g showed an outstanding solubility in various solvents such as 1-methyl-2-pyrrolidone (NMP), dimethly sulfoxide (DMSO), N,N-dimethylformamide (DMF), N,N-dimetylacetamide (DMAc), and pyridine. The cured polyamides displayed significantly higher thermal stability than the uncured polyamides. The conductivity of the polyamides, when blended with 20% by weight of doped polyanilines, was in the range 3.09–4.21 × 10^?3 S cm^?1.     

还原染料的还原体系探讨

本文详细介绍了还原染料还原工艺中保险粉及其他传统还原体系的利弊,阐述了当前还原染料新型还原技术的特点及需要解决的问题。     

硫脲浸金技术研究现状

针对氰化浸金存在环境不友好、生产周期长的不足,诸多非氰浸金方法得以研究和应用。综合阐述了硫脲浸金技术的研究现状,主要有酸性硫脲浸金体系、碱性硫脲浸金体系、硫脲浸出贵液回收等,展望了今后的研究重点。     

一锅法合成6-甲基-2-硫脲嘧啶的工艺研究

采用了一锅法合成工艺,以乙酰乙酸乙酯和硫脲为起始原料,经过脱水、脱醇缩合成环得到6-甲基-2-硫脲嘧啶,其结构经1H NMR、IR和MS表征。最佳反应条件为:硫脲90 mmol,n(硫脲):n(乙酰乙酸乙酯):n(氢氧化钾)=1:2.30:2.32时,产物收率为96.64%。