Process for cobalt separation and recovery in the presence of nickel from sulphate solutions by Cyanex 272

The present paper deals with the extraction of cobalt from a solution containing cobalt and nickel in a sulphate medium similar to the leach liquor obtained by the dilute sulphuric acid pressure leaching of the Pacific Ocean nodules matte followed by copper extraction. The commercial extractant Cyanex 272 (bis (2, 4, 4-trimethylpentyl) phosphinic acid) is used for this purpose. The leach liquor used for the present study contains Co =1.78 g/L and Ni=16.78 g/L. Before cobalt extraction, impurities, such as copper and iron, are removed from the leach liquor by the precipitation method. Increasing the concentration of Cyanex 272 increased the extraction percentage of cobalt due to the increase of equilibrium pH. Cobalt extraction efficiency of >99.9 % is achieved with 0.20 M Cyanex 272 in two counter-current stages at an aqueous: organic (A:O) phase ratio of 1.5∶1. Complete stripping of cobalt from the loaded organic containing 2.73 g/L Co was carried out at pH 1.4 by a synthetic cobalt spent electrolyte in two stages at an A:O ratio of 1∶2. The enrichment of cobalt during extraction and stripping operations was about 3.5 times. A complete process flowsheet for the separation and recovery of cobalt is presented.     

加氢裂化装置生产工业白油的技术开发与工业应用

目的 降低炼厂的柴汽比,提高企业经济效益。方法 对惠州石化4.0 Mt/a蜡油加氢裂化装置生产5号工业白油的可行性进行了分析,认为通过提高柴油馏分初馏点实现生产5号工业白油产品是可行的。前期,装置已通过主分馏塔降压调整、增设蒸汽汽提塔和原柴油汽提塔再沸器改蒸汽汽提工艺3种方式提高柴油初馏点,均未取得良好的运行效果。鉴于以上3种工艺的局限性,开发了热氮气气提工艺,工艺采用热氮气气提替代柴油汽提塔塔底再沸器,主分馏塔塔顶排出不凝气,以维持塔压稳定。结果 该工艺实施后,装置生产合格白油60 t/h,航煤产量增加14 t/h,不凝气产量增加1.3 t/h,不再产柴油产品;白油产品开口闪点由85℃提高至126℃,解决了开口闪点低和产品含水问题。结论 采用该工艺生产的5号工业白油产品性质稳定,满足行业指标的要求,装置改造工程量小,经济效益显著,对国内外同类装置的生产优化具有重要的借鉴意义。     

氨气提工艺尿素生产中操作的改进

实验证明,由Snam公司提供的尿素操作方法与实际状况出入很大。为此,通过降低高压系统 的氨碳比、关闭中压氨冷凝器至液氨贮槽的气相切断阀、提高低压分解温度、改进二氧化碳压缩机 、水解装置和高压甲铵泵的操作方法等措施,使尿素装置达到了安全、稳定、经济运行的目的。     

湿法磷酸汽提法脱氟技术研究

在饲料级磷酸氢钙生产过程中,湿法磷酸中的磷氟比（五氧化二磷与氟的质量比）≥250才能符合生产要求。采用汽提法脱氟技术,研究了汽提方式、汽提时间、磷酸温度、磷酸浓度及真空度对湿法磷酸脱氟效果的影响。实验表明：采用减压脱氟,将质量分数为50%的浓磷酸加入圆底烧瓶中,加入氟含量2倍的白炭黑,将磷酸温度升高至100 ℃,真空度控制为20 kPa,脱氟1 h,可使磷酸的磷氟比达到286.97,满足饲料级磷酸氢钙对湿法磷酸的要求。     

Sensor-containing microspheres of chitosan crosslinked with 8-hydroxyquinoline-5-sulphonic acid for determination of Cu(II) in instant coffee

A novel carbon paste electrode containing chitosan microspheres for the determination of Cu(II) in instant coffee by anodic stripping voltammetry was developed. Chitosan was crosslinked with the chelating agent 8-hydroxyquinoline-5-sulphonic acid and glutaraldehyde. The microspheres of the crosslinked chitosan biopolymer were obtained by the spray drying technique and employed in the construction of the sensor. In acetate buffer solution (0.1 mol L⁻¹, pH 6.0), the calibration curve obtained was linear for concentrations of 5.0 × 10⁻⁷ to 1.4 × 10⁻⁵ mol L⁻¹ (r = 0.9990); the detection limit was 5.5 × 10⁻⁸ mol L⁻¹. The relative standard deviation (n = 8) was lower than 3.0% for solutions containing 6.0 × 10⁻⁶, 5.0 × 10⁻⁵ and 1.5 × 10⁻⁴ mol L⁻¹ of Cu(II). The method was successfully employed for determination of Cu(II) in instant coffee and the results obtained showed good agreement when compared with those using electrothermal atomic absorption spectrometry.     

生物可利用铅的铋膜电极微分电位溶出法测定研究

研究了镀铋膜电极替代镀汞膜电极的微分电位溶出分析法(DPSA)测定铅的方法,考察了同位镀铋膜测定铅的条件.结果表明,在HAc-NaAc介质中铅可在镀铋膜电极上得到灵敏的微分电位溶出峰,结合三步连续萃取利用标准加入法对城市污泥样品中的生物可利用铅进行测定,避免了镀汞膜电极带来的健康与环境危害,结果较满意.     

Preparation of Pt/multiwalled carbon nanotubes modified Au electrodes via Pt–Cu co-electrodeposition/Cu stripping protocol for high-performance electrocatalytic oxidation of methanol

Pt nanoparticles well dispersed on multiwalled carbon nanotubes (MWCNTs) were prepared for high-performance electrocatalytic oxidation of methanol in both acidic and alkaline media via the co-electrodeposition/stripping (CS) protocol, namely, co-electrodeposition of Pt and Cu followed by electrochemical stripping of Cu, as examined by cyclic voltammetry (CV), electrochemical quartz crystal microbalance (EQCM), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The Pt catalyst prepared by the CS protocol on MWCNTs (Pt_cs/MWCNTs/Au) exhibited a specific electrocatalytic activity of 519 and 2210 A g⁻¹ toward cyclic voltammetric electrooxidation (50 mV s⁻¹) of methanol in 0.5 M CH₃OH + 0.5 M H₂SO₄ and 0.5 M CH₃OH + 1.0 M NaOH media, respectively, which are larger than those prepared by conventional electrodeposition from chloroplatinic acid on Au and MWCNTs/Au, as well as that by a CS protocol on Au. The Pt_cs/MWCNTs/Au electrode also possessed the highest stability, which maintained 91% and 90% of its initial catalytic activity after 120-cycle CV in 0.5 M CH₃OH + 0.5 M H₂SO₄ and 0.5 M CH₃OH + 1.0 M NaOH, respectively. The electrode kinetics of methanol oxidation is also briefly discussed. The nanosubstrate-based CS protocol is simple, convenient and efficient, which is expected to find wide applications in film electrochemistry and electrocatalysis.     

Determination of aflatoxins B1 and B2 by adsorptive cathodic stripping voltammetry in groundnut

In this study, adsorptive stripping voltammetry was proposed for determination of aflatoxins B1 (AFB1) and B2 (AFB2) using hanging mercury drop electrode (HMDE) as the working electrode. Both aflatoxins were found to adsorb and undergo irreversible reduction reaction at the working mercury electrode. The experimental conditions were optimised by one-at-a time and experimental design to obtain the best characterised peak in terms of peak height with analytical validation of the method for each aflatoxin. The calibration curves for aflatoxins AFB1 and AFB2 were linear in the ranges of 0.4–40 ng ml⁻¹ and 0.2–70 ng ml⁻¹ with the limit of detections (LOD) 0.15 and 0.10 ng ml⁻¹, respectively. The proposed method was applied for the analysis of aflatoxins in groundnut samples and the results were compared with those obtained by the HPLC technique.