Optimal Synergistic Extraction of Cr(VI) from Aqueous Acidic Media Using Alamine 300/Aliquat 336 and Di-n-octyl Amine/Tributyl Phosphate Mixed Reagents

Data for the extraction of chromium(VI) from aqueous sulfate solutions by Alamine 300/Aliquat 336 and di–n–octyl amine/tributyl phosphate (DOA/TBP) have been subjected to formulation of an optimization structure for an effective Cr(VI) separation based on the derivative variation method. Both experimentally and analytically defined optimum Cr(VI) removal efficiencies are ranging about 83–99%, 71–93%, and 60–73% for Alamine 300/Aliquat 336, DOA/TBP, and DOA, respectively. Modeling efforts based on mass-action law methodology and non-homogeneous differential approach have shown considerable success yielding a 10% mean error, and satisfies established limiting behavior of the physical event.     

镀铬故障排除实例

通过对10个镀铬生产故障实例的分析,说明了电镀产品的形状、电极的形态、挂具的形状、零件在挂具上的分布、镀槽的大小和形状等因素对镀铬生产的影响,提出了故障原因查找和故障处理的方法。指出了镀铬生产线预防同类故障发生的技术措施和故障判别经验。     

Chromate Binding and Removal by the Molybdate‐Binding Protein ModA

Effective and cheap methods and techniques for the safe removal of hexavalent chromate from the environment are in increasingly high demand. High concentrations of hexavalent chromate have been shown to have numerous harmful effects on human biology. We show that the E. coli molybdate‐binding protein ModA is a genetically encoded tool capable of removing chromate from aqueous solutions. Although previously reported to not bind chromate, we show that ModA binds chromate tightly and is capable of removing chromate to levels well below current US federal standards.     

Nanomechanical properties of gas-borided layer produced on Nimonic 80A-alloy

Diffusion borided layers, fabricated on Ni-based alloys, were characterized by improved hardness and wear resistance. In this paper, gas boronizing in N₂–H₂–BCl₃ atmosphere was proposed to produce the ceramic phases (borides) on Nimonic 80A-alloy. This process was carried out at 920 °C (1193 K) for 2 h. The microstructure was studied in detail using scanning electron microscope and energy-dispersive X-ray microanalysis. The boride layer consisted of a mixture of nickel borides (Ni₃B, Ni₂B, Ni₄B₃, NiB) and chromium borides (CrB, Cr₂B). The nanomechanical properties (Young's modulus and hardness) were examined using the nanoindenter with a Berkovich diamond tip. The load-displacement curves and the indentation images were shown for the selected measurements. The identified phases in microstructure were very fine, therefore it was impossible to measure the hardness and Young's modulus of a defined phase. However, the percentage of chromium and nickel borides’ mixtures was calculated based on the measurements of indentation hardness (H_IT) compared to the previous work. It enabled to calculate Poisson's ratio for a specified indentation. As a consequence, the indentation moduli E_IT were determined. The higher values of H_IT and E_IT were obtained in case of indents, performed in the areas of higher percentage of chromium borides.     

Early Fixation of Cobalt-Chromium Based Alloy Surgical Implants to Bone Using a Tissue-engineering Approach

To establish the methods of demonstrating early fixation of metal implants to bone, one side of a Cobalt-Chromium (CoCr) based alloy implant surface was seeded with rabbit marrow mesenchymal cells and the other side was left unseeded. The mesenchymal cells were further cultured in the presence of ascorbic acid, β-glycerophosphate and dexamethasone, resulting in the appearance of osteoblasts and bone matrix on the implant surface. Thus, we succeeded in generating tissue-engineered bone on one side of the CoCr implant. The CoCr implants were then implanted in rabbit bone defects. Three weeks after the implantation, evaluations of mechanical test, undecalcified histological section and electron microscope analysis were performed. Histological and electron microscope images of the tissue engineered surface exhibited abundant new bone formation. However, newly formed bone tissue was difficult to detect on the side without cell seeding. In the mechanical test, the mean values of pull-out forces were 77.15 N and 44.94 N for the tissue-engineered and non-cell-seeded surfaces, respectively. These findings indicate early bone fixation of the tissue-engineered CoCr surface just three weeks after implantation.     

辅助成膜剂对锌酸盐镀锌蓝白钝化外观的影响

镀锌蓝白钝化膜的颜色相比彩色钝化单一,钝化膜的颜色更易受到金属离子的影响,辅助成膜剂可以提高镀锌钝化膜的致密性和耐蚀性,改变钝化膜的颜色。研究发现,在三价铬基础钝化液中添加适量的硫酸钴,能增加蓝白钝化膜的蓝色并延长硫酸铜点滴试验的变色时间,但对增强钝化膜的抗盐雾性能不明显;加入适量的氯化镍,能改善蓝白钝化膜的外观,但不显著;加入0.5~2.0 g/L的镧离子对蓝白钝化膜外观没有明显的改善作用。硅酸钠虽然能提高钝化膜的耐蚀性,但增大了钝化试样的杂色,使得钝化膜的颜色不均匀。     

提高低质量浓度Cr(Ⅵ)检测准确度的方法

采用二苯碳酰二肼分光光度法,对两种超纯水机制备的超纯水、市售饮用蒸馏水、电镀废水等样品及其低质量浓度加标样品进行检测。结果表明,采用标准检测方法所用的单波长法和分析步骤,即样品中先加混合酸,后加显色剂进行显色及测定,低浓度纯水加标样品的回收率介于16%~92%;而采用先加显色剂,后加混合酸时,回收率介于94%~114%。推测其中机理,先加酸时,在酸性环境下,Cr(Ⅵ)与显色剂的显色反应和Cr(Ⅵ)对有色化合物的褪色反应同时存在,导致结果偏低;而在中性或弱碱性条件下,先加显色剂时,Cr(Ⅵ)与显色剂可先形成中间产物,中间产物在酸性环境下较完全地形成了紫红色化合物。以上方法结合参考波长为660 nm的双波长法可进一步提高检测的准确度。     

Rheological and thermal stability of novel weak gels based on sulfonated polyacrylamide/scleroglucan/chromium triacetate

The present study deals with weak gels based on sulfonated polyacrylamide (SPA)/scleroglucan (SC)/Cr³⁺ with an exceptional thermal stability in electrolyte media. The rheological results showed that on increasing the SC concentration the shear viscosity and storage modulus of the SPA/SC/Cr³⁺ system were increased and the dependence of the storage modulus on frequency became weaker. The yield stress of the SPA/SC/Cr³⁺ system was higher than that of the corresponding SPA/SC system. The thermochemical stability increased with increasing relaxation time. The SPA/SC/Cr³⁺ semi‐interpenetrating network exhibited the lowest viscosity loss in electrolyte media; therefore this system may be a potential candidate for enhanced oil recovery applications. © 2016 Society of Chemical Industry     

微波消解-火焰原子吸收法测定水泥原料中的总铬

建立了微波消解-火焰原子吸收法测定水泥原料中总铬的方法。采用微波消解的方法对样品进行前处理,以硝酸-盐酸为消解体系,在特定的消解程序下对样品进行消解,经过排酸的步骤,加入氯化羟胺掩蔽其他元素的干扰,火焰原子吸收法测定总铬。在浓度范围0~1.0mg/L时呈现良好的线性,总铬的回收率在90.5%~99.0%,相对标准偏差为:0.32%,方法的检出限为:0.01mg/L,运用所建立的方法对5个水泥原料中的总铬进行检测,结果显示该方法选择性强、灵敏度高,前处理方法简单、快速、安全,适合水泥及原料中总铬的测定。     

新型合成气甲烷化催化剂La2O3-ZrO2-Ni/Al2O3的制备与性能

针对常规合成气甲烷化催化剂高热结构稳定性差、活性低、适应性差等不足,本文创新地引用稀土金属氧化物La₂O₃复配过渡金属氧化物ZrO₂作为多功能复合助剂,利用反向沉淀法制备了新型合成气甲烷化催化剂La₂O₃-ZrO₂-Ni/Al₂O₃,同时制备催化剂Cr₂O₃-Ni/Al₂O₃作为参照组。采用X射线衍射（XRD）、透射电子显微镜（TEM）表征了催化剂的微观结构,并利用N₂吸附仪（BET）测量催化剂经高温水热处理前后的微孔结构参数,以考察催化剂的高热结构稳定性。结合国内某大型煤制天然气项目工艺特征和运行实践,应用Aspen Plus软件模拟了四段甲烷化工艺理论平衡值。基于自主固定床合成气甲烷化评价实验装置,考察了反应压力、空速和原料气H₂O(g)含量等因素对La₂O₃-ZrO₂-Ni/Al₂O₃催化性能的影响,并开展了1000h长周期寿命评价实验。结果表明,La₂O₃-ZrO₂-Ni/Al₂O₃比Cr₂O₃-Ni/Al₂O₃具有更优的高热结构稳定性;可使CO和CO₂反应达到或接近催化剂床层出口温度下的理论平衡状态,呈现显著的宽温活性;活性组分NiO晶粒尺寸介于7~10nm,分散度较高;对反应压力、空速和原料气H₂O(g)含量的变化不敏感,具有良好的操作弹性;1000h反应后仍能保持较高的活性和稳定性。