栲胶脱硫溶液中总钒测定新方法——单宁酸比色法

我们在研究橡椀栲胶单宁与四价钒络合物组成时,发现试剂单宁酸(即鞣酸,Tannic Acid)与四价钒所形成的蓝色络合物具有很好的稳定性,因而提出将这种试剂用于栲胶脱硫溶液中总钒的测定。在测定了络合物组成、稳定常数、克分子吸光系数的基础上,又进行了条件试验和分析方法对比试     

旋转盘膜剪切强化络合-超滤处理含镉废水

以聚丙烯酸钠(PAAS)为络合剂,通过旋转盘膜过滤系统,研究了络合超滤处理含镉废水的工艺条件,以及络合物PAA-Cd在剪切场中的稳定性。研究了pH值,聚合物/金属离子质量比(P/M),转速对镉离子截留率的影响,并获得了络合物PAA-Cd的临界剪切速率,以其为指导通过剪切诱导解络进行了PAAS的回收。结果表明,在pH值为6,P/M为30时,镉离子截留率几乎为100%。在pH值为5、5.5、6时,络合物PAA-Cd的临界剪切速率分别为5.9×10~4s~(-1),1.01×10~5s~(-1),1.31×10~5s~(-1)。     

氧化淀粉络合能力的测定

利用钙离子选择电极和化学分析法对淀粉氧化物的络合能力进行了测定。考察了氧化淀粉加入量、pH值及温度对钙离子络合能力的影响。结果表明,在实验条件下,温度升高,氧化淀粉的络合能力增加,在35℃时达最大值;在pH值为9~10范围内,随着pH值增加,络合能力增加较小,在9.8时达最大值;随着氧化淀粉加入量的增加,氧化淀粉的络合能力增加,加入的质量分数超过0.02时,单位量的玉米淀粉氧化物的络合能力下降。淀粉氧化物对钙离子的络合量可达到92.25 mg/g。离子选择性电极法与化学分析法测定的结果基本相同,是一种快速、准确而又操作简单的检测方法,可用在在线检测,能较准确、快速测定玉米淀粉氧化水解反应进行的程度。     

可见分光光度法测定阿司匹林中水杨酸含量的探究

研究了用分光光度法快速、准确测定阿司匹林（ASP）中水杨酸（SA）含量的方法。以FeCl3为显色剂,通过测含杂质的阿司匹林溶液的吸光度来测定其中SA含量,考虑了pH、温度、反应时间、显色剂用量等因素对络合物生成量及稳定性的影响,确定了最适宜的测定条件,并绘制了标准工作曲线。结果表明,在pH值=3的CH3COOH—CH3COONa缓冲溶液中,Fe3＋与SA生成较稳定的络合物,络合比为1：1,常温下10min即可络合完全,该络合物的最大吸收波长为512nm。该定量方法测量误差在2．5％以内。     

聚合温度和料浆pH对电镀级焦磷酸钾品质的影响研究

采用两步法工艺研究了聚合温度和料浆pH对电镀级焦磷酸钾品质的影响。研究表明:电镀级焦磷酸钾的聚合温度需控制在530℃以上;随着聚合温度的升高,产品络合指数逐步增大,在550~560℃范围,产品的络合指数达到最大值,之后随着温度的升高,产品的络合指数开始下降;聚合温度在550~560℃范围,产品的赫尔槽试验效果最佳;料浆pH为9.2时,所得焦磷酸钾含量最高;生产高含量(大于99%)焦磷酸钾需控制料浆pH在8.9~9.4。     

鞣酸-硫代乙醇酸分光光度法测定催化剂中的钒

研究了鞣酸—硫代乙醇酸与钒的反应 ,发现显色酸度pH值为 4 ,最大吸收波长λmax为 6 0 0nm ,反应络合物稳定性好。测定催化剂中钒的含量 ,结果令人满意。     

漆树漆酶催化单宁酸的氧化反应研究

用分光光度法考察漆树漆酶催化单宁酸的氧化情况,探讨了pH值、反应温度、单宁酸浓度、有机酸和金属离子等对催化反应的影响.结果表明,当反应温度为30℃时,漆树漆酶催化反应效果较好;在pH值为4.2～ 9.8的范围内,反应速率随pH值增大而加快;单宁酸浓度在1.47×10-5 ～ 2.94×10-4 mol·L-1时,反应速率随底物浓度的增大呈线性增加;Cu2 、Mg2 和Ni2 三种金属离子对催化反应有激活作用,其中Cu2 影响最大;而柠檬酸和乙二胺四乙酸对酶催化反应均有抑制作用.     

五倍子单宁酸吸附甲醛的特性研究

采用五倍子单宁酸作为吸附剂,考察了反应温度、p H值、降解温度等因素对五倍子单宁酸吸附甲醛性能的影响,实验结果表明:反应温度为40℃、p H值=12、降解温度为65℃时,五倍子单宁酸对甲醛的吸附性能最好,其对应的甲醛除去率分别为33. 3%、72. 1%、52.4%;其中pH对五倍子单宁酸吸附甲醛的影响最大。红外光谱、TG-DSC以及气质联用对五倍子单宁酸与甲醛反应前后的试验分析表明,五倍子单宁酸与甲醛发生了类似酚醛缩合的反应,反应后五倍子单宁酸的热稳定性有所降低。     

阿斯匹林精氨酸中游离水杨酸测定方法的摸索——pH对水杨酸铁络合离子的影响

微量的水杨酸可与铁离子生成带色的水杨酸铁络合离子,其最大吸收峰为520毫微米,可用比色法测得水杨酸之含量,水杨酸铁络合离子显色是随pH值不同而异。一般说来,pH1.8～2.5时显紫红色;pH4～8时显橙色;pH8～11.5时显黄色:当pH为12时,有机络合物被破坏而生成Fe(OH)_3沉淀。即     

用pH电位法测定Yb(Ⅲ)-苹果酸络合物的稳定常数

在分析化学中所使用的大部分络合配位基,多为中强碱,在一定的pH下可以质子化。金属离子与已质子化的配位基形成络合物而同时释放出质子,因此,测量滴定过程中体系pH的变化,根据酸碱平衡与络合平衡,可测得络合物的稳定常数。苹果酸为二元弱酸(H_2L),与Yb(Ⅲ)络合形成[YbL~ ],[YbL_2~-]和[YbL_3~(3-)]络合物。根据电荷等衡与质量等衡,可计算出在不同中和度a下,体系中游离配位基的浓度[L~(2-)]及平均配位数n,按照实验获得的各个[L~(2-)]和n值,绘制-log[L~2]和n的关系曲线,由半值点法确定各级稳定常数。为了获得更为精确的数值,可用松弛法对实验数值进行校正。苹果酸与Yb(Ⅲ)所形成络合物的第一级稳定常数K_1,在研究了测定体     

栲胶脱硫工艺操作条件的优化

采用正交实验法,分别将2 h和4 h的脱硫效率及碱耗作为评价指标,考察了碱度、栲胶浓度、偏钒酸钠浓度及温度的影响。结果表明,对脱硫效率的影响程度为碱度>温度>栲胶浓度=钒浓度,对碱耗的影响却是随时间变化的;栲胶浓度和钒的浓度对脱硫效率及碱耗的变化趋势相同;胶钒比宜控制在1.5~1.7,温度在25~30℃。     

含钒渣对铝碳材料的侵蚀

为了探讨含矾渣对铝碳材料的侵蚀机制,用动态感应抗渣法研究了w(V2O5)=10%、碱度2.8,w(V2O5)=6%、碱度2.8,w(V2O5)=6%、碱度1.44的3种含钒渣对铝碳材料的侵蚀。结果表明:随着V2O5含量(w)由6%增加到10%,铝碳材料的熔损指数增加;随着碱度的增加,铝碳材料的熔损指数也增加;添加电熔镁砂有助于提高铝碳材料的抗侵蚀性能。显微分析表明:V、Ti元素渗透能力强,渗透深,而尖晶石可固溶少量V2O5、MnO及FeO。     

Thermodynamic investigation of vanadium oxide in CaO–SiO2–VOx system at 1873 K

Owing to the complexity of the multivalence states of vanadium oxides in slag systems and experimental difficulties, thermodynamic properties of vanadium oxides have not been established yet. In the present study, the mixed-valence states and activities of the vanadium oxides in CaO–SiO₂–VO_x slag were investigated experimentally at 1873 K and oxygen partial pressures of 3.2 × 10^–9 and 3.1 × 10^–7 atm. After the CaO–SiO₂–VO_x slag had equilibrated with a platinum strip, the mixed-valence states of the vanadium oxides in the slag were estimated by performing X-ray photoelectron spectroscopy, and the activities of the vanadium oxides in the slag were calculated using the activity of vanadium in the platinum strip at equilibrium using thermodynamic equations. At an oxygen partial pressure of 3.2 × 10^–9 atm, V³⁺ was the dominant ion and V⁴⁺ was the second most abundant ion. With increasing VO_x content or basicity (CaO/SiO₂ ratio), the fraction of V³⁺ decreased, whereas that of V⁴⁺ increased. The activity of VO_1.5 was greater than those of the other vanadium oxides. On the other hand, when the oxygen partial pressure increased to 3.1 × 10^–7 atm, V⁴⁺ became the dominant ion. As the slag basicity increased, the fraction of V⁴⁺ increased further, whereas that of V³⁺ decreased to less than that of V⁵⁺. The activity of VO_1.5 was greater than those of the other vanadium oxides, limiting the effect of the slag basicity. Consequently, the valence state of vanadium oxide was affected by the slag basicity at a low oxygen partial pressure by acting as a network modifier. In contrast, at a higher oxygen partial pressure, the activity of vanadium oxide increased further but was not affected by the slag basicity because of its contribution to the network structure formation. The present findings can be applied to optimize the slag composition in steel refining or vanadium pentoxide production processes to increase the yield rate of vanadium.     

赤泥酸浸提钒

采用H2SO4, HCl, HNO3三种浸出剂提取赤泥中的钒,考察了酸浓度对钒浸出率的影响,对赤泥、浸出液和浸出渣进行了分析,研究了钒溶液的热力学,绘制了不同价态钒浓度对数与pH值关系图. 结果表明,H2SO4最适合赤泥酸浸提钒,在液固比5 mL/g、反应温度90℃、反应时间1 h和H2SO4浓度5.5 mol/L条件下,钒浸出率为88%. 经H2SO4浸出后,赤泥中的板钛矿、钙钛矿、白云石、赤铁矿和白云母均一定程度溶解,出现硬石膏物相. 浸出液pH=0.47,溶液呈蓝色,钒呈4价,钒浓度为0.006773 mol/L,赤泥中的V(IV)与SO42-形成VOSO4,提高了钒的溶解度,拓宽了其稳定存在区间. 随H2SO4浓度升高,VO2更易溶解且溶解产物VOSO4更稳定.     

钒矿石活化焙烧-酸浸新工艺的研究

对河南某钒矿进行了活化焙烧-酸浸实验,系统考察了添加剂种类与用量、焙烧温度、焙烧时间、浸取酸度、液固比、浸取温度及时间对钒浸取率的影响。实验结果表明:焙烧过程中,采用氧化钙为添加剂,控制添加量为10%,850～900℃下焙烧3h,矿样的活化效果较好;酸浸过程中,硫酸酸度为5%,液固比为2.5∶1,70～80℃,浸出3h的条件下,钒的浸出率最高,可达80%以上。     

Physical and Optical Properties of Borobismuthate Glasses Containing Vanadium Oxide

Glasses with compositions 20BaO · 10Bi2O3 · (70 – x)B2O3 · xV2O5 with x = 0, 0.2, 0.4, 0.6, 0.8 and 1 mol % were prepared by melt quenching technique. The amorphous nature was established by X-ray diffraction studies. Fourier transform infrared studies carried out for samples and it exhibit absorption bands for oxides in various structural units. Physical parameters viz., density, molar volume, molar refraction, dielectric constant, electro negativity, polaron radius and oxygen packing density were calculated. Theoretical optical basicity was estimated and is increasing with vanadium content shows increasing polarizability of samples. Metallization criterion decreases shows the metallic nature of samples, this implies that prepared glass samples can be used as amorphous semiconductors and could be used in electronics and memory switching devices. Using UV-vis spectra optical band gap energy (Eopt) calculated and is decreased from 2.998–2.453 eV, linear refractive index is measured from Eopt. Increase in Urbach energy (Eu) with vanadium component is observed.     

钒钛磁铁矿钙化焙烧-酸浸提钒过程中钒铁元素的损失

在理论分析的基础上,以钒钛磁铁矿为原料,硫酸钙为钙化剂,系统研究了钙化焙烧和硫酸酸浸过程的钒、铁等有价组元的损失。研究结果表明:钙化焙烧-酸浸提钒工艺在理论上是可行的;焙烧过程中,烧结产物中的钒损失率随温度的升高而升高;尽管焙烧过程损失了部分钒元素,但焙烧后钒元素更易于溶解浸出;钒浸出率随焙烧温度的升高先升高后降低且1450 K时达到最大值;当硫酸浓度增加时,钒浸出率变化不大;当焙烧温度高于1450 K时,浸出渣中铁的损失率快速上升,硫酸浓度增加时,其值随之增大;控制适当条件可强化钒的有效迁移,目前实验室研究条件下,钒的浸出率最大可达79.08 %,而此时铁的损失率为3.32%。     

Preferential extraction of gallium from Bayer liquor using ion exchange chelating resin containing hydroxamic acid functional group

Gallium extraction studies were carried out using resin containing an hydroxamic acid functional group. Extraction was dependant on reaction time and alkali concentration. The resin did not extract aluminium. Vanadium extraction kinetics were slower than those of gallium. The gallium and vanadium separation efficiency increased with decreasing contact time with extractions of 64% and 32% respectively after 1 min. Gallium extraction was independent of alkali concentration up to 250 g dm^?3 and thereafter decreased with increasing alkali concentration. Vanadium extraction decreased with increasing alkali concentration. Cyclic batch and column studies were carried out with synthetic as well as actual Bayer liquor to test the stability and preferential extraction of gallium using the resin. It was observed that using resin partially loaded with gallium, the co‐extraction of vanadium could be minimised. Copyright © 2003 Society of Chemical Industry     

Vanadium redox cell electrolyte optimization studies

The stability of the positive electrolyte of the vanadium redox cell has been studied at various temperatures and at different solution compositions and solution state-of-charge (SOC). It has been found that at elevated temperatures for extended periods, V(V) can slowly precipitate from solution, the extent and rate of which being dependent on temperature, vanadium and sulphuric acid concentration as well as the SOC of the electrolyte. A H₂SO₄ concentration of 3–4m has been found to be more suitable than 2m, not only from the point of view of increased stability, but also because of the higher electrolyte conductivity which leads to increased voltage efficiencies during battery cycling.     

Poly(squaryl amides)

The solution polycondensation of squaric acid with p-phenylenediamine in selected protic, aprotic or strongly acidic solvents furnishes linear polyamide structures possessing units with 1,2- as well as those with 1,3-orientation of the substituent links on the four-membered ring system. The relative occurrence of these two unit types as assessed by infra-red spectroscopy depends on the basicity of the medium, the extent of 1,2-orientation decreasing with increasing solvent basicity. The same type of polyamide results from a solution polycondensation of the diamine with diethyl squarate. These findings, contradicting earlier results of other workers, are in accord with more recent non-polymeric squaric acid amidation studies. A reference polyamide with maximum content of units possessing the 1,2-substituent orientation is synthesized from p-phenylenediamine and squaryl dichloride under low temperature solution polymerization conditions. Polymer inherent viscosities range from about 10 to 30ml/g, highest values being obtained under conditions of homogeneous polymerization.