Electrochemically instantaneous reduction of conducting polyaniline-coated latex particles dispersed in acidic solution

A cathodic voltammetric wave was observed in an aqueous suspension of mono-dispersed, spherical polyaniline-coated polystyrene particles, whereas no anodic wave was detected. This irreversibility was common to particles with eight different diameters ranging from 0.2 to 7.5 μm. Such irreversibility cannot be found at polyaniline-coated electrodes, and thus is a property of the dispersion of polyaniline latex. The reduction current was controlled by diffusion of dispersed particles. The reduction, being the conversion from the electrical conducting state to the resistive one, should begin at a point of contact between the conducting particle and the electrode in order to be propagated to the whole particle rapidly. In contrast, the oxidation proceeds slowly with the propagation of conducting zone, during which Brownian motion lets the particle detach from the electrode. The number of loaded aniline units per particle, determined by weight analysis, ranged from 6 × 10⁶ (Ø 0.2 μm) to 3 × 10¹¹ (Ø 7.5 μm) and was proportional to 2.9 powers of the particle diameter. The diffusion-controlled current of the cathodic wave was proportional to 2.4 powers of the diameter. The difference in these powers, 0.5, agreed with a theoretical estimation of the diffusion-controlled current, the diffusion coefficient for which was given by the Stokes-Einstein equation.     

Raman spectroscopy studies of concentrated vanadium redox battery positive electrolytes

Spectroscopic changes in highly concentrated vanadium(V)-sulfate solutions to be used in the vanadium redox battery are consistent with the presence of more than one V(V)-sulfate species. The results of Raman spectroscopy indicate that the major species in highly acidic conditions are VO₂SO₄ ^–, VO₂(SO₄)₂ ^3–, VO₂(HSO₄)₂ ^–, VO₃ ^–, V(V) dimers with V₂O₃ ⁴⁺ and V₂O₄ ²⁺ central units. The nature and amount of these species depends upon the V(V) and total sulfate concentrations as well as on S to V and H⁺ to V ratios in the positive half-cell electrolyte. V(V) forms V₂O₃ ⁴⁺, VO₂(SO₄)₂ ^3– and their copolymer species at higher total sulfate concentrations, which tends to stabilize the vanadium (V) positive electrolyte in the vanadium redox battery. The V(V) and V(IV) species show the least interaction with each other. Ageing of concentrated V(V) solutions at elevated temperature (50 °C) produces decomposition of species causing formation of V₂O₅ precipitates with a decrease in the amount of vanadium polymer.     

磷肥工业高氟废水的处理方法

介绍湿法磷酸高氟废水的处理方法.传统的废水处理工艺或因除氟效果差,或因成本高,不能满足高氟废水的处理要求.提出采用二级石灰乳过量-硫酸反滴法处理高氟废水的新工艺,控制第一级中和反应pH4-6,第二级中和反应pH9～11,通过硫酸调控pH至6～9,可达到氟离子质量浓度小于10mg/L的排放最高标准.此方法工艺简单,运行成本低.     

Electro‐induced polymerization of acrylamide initiated by the potassium permanganate–titriplex VI redox system

The polymerization of acrylamide (AAm) was carried out with a potassium permanganate–Titriplex VI redox initiator system with and without electrolysis. Because of the high metal‐ion concentration in general, low‐molecular‐weight polymers were obtained (weight‐average molecular weight = 2600–4000). The effect of potassium permanganate and AAm concentrations and temperature on the polymerization yield was studied and compared with results obtained under the same experimental conditions used for electrolysis. The results of Fourier transform infrared spectroscopy, atomic absorption spectrometry, and scanning electron microscopy (SEM) results are given. SEM micrographs of the polymer obtained by electrochemical methods exhibited smoother surfaces than those obtained by nonelectrolytic methods. In the absence of potassium permanganate, there was no polymerization under experimental conditions. A possible reaction mechanism is suggested. The electro‐induced system resulted in about a 50% increase in the yield. Manganese content in the electro‐induced and chemical polymerization systems were 2.7 and 8.2%, respectively, supporting the yield increase in the electro‐induced system. A graphite electrode was used and resulted in a high yield and a fibrous polymeric structure. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1526–1534, 2001     

重铬酸钾滴定法测定硼铁合金中全铁

采用氢氧化钠和过氧化钠混合熔剂熔融分解试样, 分解后的熔融物以热水浸取, 30 mL HNO₃(1+1)酸化、硫磷混酸冒烟除去氮氧化物及过氧化氢、盐酸提取后, 用二氯化锡先将大量的三价铁还原为二价铁, 然后以钨酸钠为指示剂指示还原的终点, 逐滴加7滴15 g/L三氯化钛溶液至试液呈蓝色, 进一步将剩余的三价铁全部还原为二价铁, 同时采用重铬酸钾氧化至“钨蓝”褪去的方法消除了过量三氯化钛的影响。最后, 以二苯胺磺酸钠为指示剂, 用重铬酸钾标准滴定溶液对样品溶液中全铁进行滴定, 实现了对硼铁合金中全铁量的测定。实验表明, 硼铁合金中共存元素不干扰全铁的测定。方法已用于硼铁合金标准样品中全铁的测定, 测定结果与认定值相符, 相对标准偏差(n=7)均小于0.5%。     

碱熔-硼氢化钾还原重铬酸钾滴定法测定铁矿石中全铁

样品用过氧化钠熔融,试液经酸化后,以硫酸铜作为还原指示剂和催化剂,氟化铵作为络合剂,在硫酸介质中利用硼氢化钾强烈水解产生的氢化物还原Fe³⁺为Fe²⁺,然后用重铬酸钾滴定法测定了铁矿石中全铁。铁矿石中共存大量铜对测定没有影响,钒和钛被氟化铵掩蔽也不干扰测定。方法用于铁矿石国家标准物质中全铁的测定,测定值与认定值相符,相对标准偏差均小于2%。     

碘-乙醇分离—重铬酸钾滴定法间接测定脱硫渣中金属铁

脱硫渣中金属铁的含量对其再利用具有重要的指导意义,因此测定脱硫渣中金属铁的方法受到关注。在采用碘-乙醇浸取—重铬酸钾滴定法直接测定脱硫渣中金属铁时,因碘-乙醇的存在会干扰后续重铬酸钾滴定法对金属铁的测定,故在过滤分离沉淀后,需在高温下除尽滤液中的碘-乙醇后再进行测定,不仅操作较繁琐,且存在一定的安全隐患。据此,提出了碘-乙醇分离—重铬酸钾法间接测定脱硫渣中金属铁的方法,并对测定条件进行了优化。称取两份相同质量的试样,一份试样采用重铬酸钾滴定法测定其中的全铁量;另一份试样用碘-乙醇浸取其中的金属铁,过滤分离,弃去滤液,采用相同方法测定沉淀中的全铁量;两者之差即为一份试样中的金属铁量,以此间接计算出试样中金属铁的含量。采用实验方法测定金属铁质量分数在0.63%～2.63%之间的脱硫渣生产试样,测定结果与碘-乙醇浸取—重铬酸钾滴定直接测定法相符,相对标准偏差(RSD,n=6)在3.1%～15.9%之间。选择2个脱硫渣生产试样,分别加入不同质量的纯铁进行加标回收试验,金属铁的加标回收率在96%～108%之间。     

活性炭的孔隙结构和表面酸性对其香料吸附性的影响

本文主要研究两种活性炭吸附材料SY-1和SY-11对薄荷醇,呋喃酮和2-环戊烯酮三种香料的吸附性能。使用ASAP2010M测定了活性炭SY-1和SY-11的孔隙结构,用Boehm滴定测定了活性炭表面化学性质的含氧基团的浓度,用静态吸附法测试了三种香料在两种活性炭上的吸附动力学,采用程序升温脱附技术测定了三种香料在两种活性炭上的脱附活化能。结果表明,两种活性炭SY-1和SY-11的比表面积分别为928 m2/g、1065 m2/g,平均孔径分别为2.3和2.6 nm,表面酸性基团总含量分别为0.5498 mmol/g,0.5289 mmol/g。SY-1对三种香料的平衡吸附量均大于SY-11,这主要由于SY-1的平均孔径小于于SY-11,SY-1表面的酸性基团含量高于SY-11。较小的孔径则有利于孔壁表面对香料分子形成较强的吸附作用,较丰富的表面基团含量,有助于形成更多吸附位,从而提高吸附量。三种香料在两种活性炭上的脱附活化能大小顺序均为:薄荷醇呋喃酮2-环戊烯酮,这主要是由于三种香料分子的分子直径大小的顺序也是:薄荷醇呋喃酮2-环戊烯酮,较大直径的分子易受到孔壁表面更强的吸附作用力,与表面吸附就更牢,相应的分子的脱附活化能就越大。     

用SDS滴定奶粉中蛋白质的实验研究

目的:研究用十二烷基硫酸钠(sodium dodecyl sulfate,SDS)快速测定奶粉中蛋白质含量的实验条件。方法:一定量的奶粉用蒸馏水溶解后,在一定介质中用0.1000%的SDS溶液滴定,当被滴定溶液析出凝乳状的白色沉淀时,即为终点。研究了温度、pH值及奶粉中淀粉、蔗糖含量对测定的影响,确定了SDS溶液的滴定量与蛋白质含量的关系。结果:用该方法对同一奶粉测定8次,RSD=0.53%,用本法和凯氏定氮法对8份不同奶粉中的蛋白质含量测定,结果无显著性差异(p>0.05)。结论:该方法简便、准确、可靠,适合于奶粉中蛋白质的快速检测,检验一个样品仅仅用4min。