超临界CO2络合萃取重金属研究进展

超临界流体萃取作为一种新型分离技术,不能直接萃取重金属等离子型物质,但能萃取离子与配合剂反应生成的配合物。将配合反应与超临界CO2流体萃取结合形成了又一门新型的萃取技术—超临界CO2络合萃取。在总结国内外文献的基础上,介绍了超临界CO2络合萃取重金属的原理、影响因素以及最新进展情况。     

Enthalpy recovery of gases issued from H2 production processes: Activity and stability of oxide and noble metal catalysts in oxidation reaction under highly severe conditions

Oxidation activity and stability under reaction was investigated for a series of mixed oxide catalysts, doped or not by a precious metal (Pd, Pt). The reaction feedstock, containing CO, H₂, CH₄, CO₂ and H₂O, simulated gases issued from H₂ production processes for fuel cells. Contrarily to conventional noble metal catalysts, mixed oxide samples present generally good stability under reaction at high temperature. The activities measured for the perovskite and hexaaluminate catalysts, are however largely lower than that of the reference Pd/Al₂O₃ catalyst. High activities were obtained after impregnation of 1.1 wt.% Pd or 0.8 wt.% Pt on the hexaaluminates samples. Even if Pd/Al₂O₃ was found to present a high activity, this sample suffered from drastic deactivation at 700 °C. Better stability were obtained on perovskite. Furthermore, doping hexaaluminate by Pt led to samples with good activities and high stability. Even if better activities were obtained by doping the hexaaluminate samples by Pd, the Pd/BaAl₁₂O₁₉ strongly deactivated, as it was previously observed for the reference catalyst. Interestingly, this Pd deactivation was not observed when Pd was impregnated on the Mn substituted hexaaluminate, leading to a stable and active catalyst. This suggests that it is possible to stabilize the palladium in its oxidized form at high temperature (700 °C) on the surface of some supports.     

Redox properties of CeO2 and Pt-Rh/CeO2 studied by TAP method

Redox properties of CeO₂ and Pt-Rh/CeO₂ were studied by temporal analysis of products (TAP) method using alternative pulses of CO and O₂. A portion of pulsed CO was oxidized to CO₂ and a portion of CO was adsorbed on the surface. Pulsing ¹⁸O₂ onto the catalyst which has surface species derived from CO, evolved CO₂ contained no ¹⁸O suggesting that the surface species will be carbonate ions.     

Dependence of oil stability index of fatty compounds on their structure and concentration and presence of metals

During storage and use, vegetable oil-derived industrial products such as biodiesel and biodegradable lubricants can be subjected to conditions that promote oxidation of their unsaturated components. The materials arising during oxidation and subsequent degradation can seriously impair the quality and performance of such products. Therefore, oxidative stability is a significant issue facing these vegetable oil-derived products, and enhanced understanding of the influence of various components of vegetable oils and storage parameters is necessary. In this work, the oil stability index (OSI) was used for assessing oxidation of monoalkyl esters of FA by varying several parameters. Neat fatty compounds and prepared mixtures thereof were studied for assessing the influence of compound structure and concentration. Small amounts of more highly unsaturated compounds had a disproportionately strong effect on oxidative stability. The recently developed concept of bis-allylic equivalents correlated more closely than the iodine value with the OSI times of mixtures of fatty esters. The OSI times of free acids were shorter than those of the corresponding alkyl esters. The presence of copper, iron, and nickel also reduced oxidative stability, but their effect was less than the presence of more highly unsaturated fatty compounds. Of these metals, copper had the strongest catalytic effect on OSI time. OSI may be an alternative to long-term storage tests for determining the influence of extraneous materials such as metals on oxidative stability.     

重金属在宽叶香蒲人工湿地系统中的分布与积累

本文通过对广东韶关凡口宽叶香蒲（Typha latifolia)人工湿地系统的进出水口，土壤剖面及四种优势植物体各部分器官中Pb,Zn,Cu和Cd含量进行分析。结果表明；重金属主要库存于土壤中。从水平上看，全量的重金属含量从进水口到出水口呈上升趋势，而有效态则相反；从土壤剖面的垂直分布上看，全量和有效态重金属含量都随土壤深度的增加而递减，四种植物都具有较强的吸收和富集重金属的能力，且主要富集在植物的地下部分。     

Removal of metal ions using lignite in aqueous solution—Low cost biosorbents

Turkish lignite can be used as a new adsorption material for removing some toxic metals from aqueous solution. The adsorption of lignite (brown young coals) to remove copper (Cu²⁺), lead (Pb²⁺), and nickel (Ni²⁺) from aqueous solutions was studied as a function of pH, contact time, metal concentration and temperature. Adsorption equilibrium was achieved between 40 and 70 min for all studied cations except Pb²⁺, which is between 10 and 30 min. The adsorption capacities are 17.8 mg/g for Cu²⁺, 56.7 mg/g for Pb²⁺, 13.0 mg/g for Ni²⁺ for BC₁ (Ilg?n lignite) and 18.9 mg/g for Cu²⁺, 68.5 mg/g for Pb²⁺, 12.0 mg/g for Ni²⁺ for BC₂ (Beysehir lignite) and 7.2 mg/g for Cu²⁺, 62.3 mg/g for Pb²⁺, 5.4 mg/g for Ni²⁺ for AC (activated carbon). More than 67% of studied cations were removed by BC₁ and 60% BC₂, respectively from aqueous solution in single step. Whereas about 30% of studied cations except Pb²⁺, which is 90%, were removed by activated carbon. Effective removal of metal ions was demonstrated at pH values of 3.8–5.5. The adsorption isotherms were measured at 20 °C, using adsorptive solutions at the optimum pH value to determine the adsorption capacity. The Langmuir adsorption isotherm was used to describe observed sorption phenomena. The rise in temperature caused a slight decrease in the value of the equilibrium constant (K_c) for the sorption of metal ions. The mechanism for cations removal by the lignite includes ion exchange, complexation and sorption. The process is very efficient especially in the case of low concentrations of pollutants in aqueous solution, where common methods are either economically unfavorable or technically complicated.     

城市污泥流化床中低温空气气化及重金属迁移特性

利用自行搭建的流化床热态实验装置，系统研究了污泥的中低温气化及重金属迁移特性。研究表明，对冷煤气效率和碳转化率影响最大的是气化温度，其次是空气当量比，而一二次风配比和流化数影响较弱。污泥中低温气化的焦油产率较之高温气化明显增加。随着二次风占比和空气当量比的提高，焦油产率单调下降。气化温度由600℃升至850℃，冷煤气效率和碳转化率均呈升高趋势；空气当量比由0.2升至0.4，冷煤气效率呈先升高后下降的趋势，在0.3时达到最大值，而碳转化率则呈单调升高趋势。随着气化温度的升高，污泥中重金属转移至产气、焦油及飞灰的迁移率升高。随着空气当量比的升高，Ni、Cu的迁移率降低，Cr升高，Cd、Zn、As和Pb等其他重金属的迁移率几乎不变。     

GaN基LED与Si键合技术的研究

采用金属键合技术结合激光剥离技术将GaN基LED从蓝宝石衬底成功转移到Si衬底上。利用X射线光电子谱(XPS)研究不同阻挡层对Au向GaN扩散所起的阻挡作用,确定键合所需的金属过渡层。利用多层金属过渡层,在真空、温度400℃和加压300 N下实现GaN基LED和Si的键合,通过激光剥离技术将蓝宝石衬底从键合结构上剥离下来,形成GaN基LED/金属层/Si结构。用金相显微镜及原子力显微镜(AFM)观察结构的表面形貌,测得表面粗糙度(RMS)为12.1 nm。X射线衍射(XRD)和Raman测试结果表明,衬底转移后,GaN基LED的结构及其晶体质量没有发生明显变化,而且GaN与蓝宝石衬底间的压应力得到了释放,使得Si衬底上GaN基LED的电致发光(EL)波长发生红移现象。     

钼矿尾矿铜铅重金属离子溶出规律研究

为了评估钼矿尾矿的环境危害,通过105 d连续静态浸泡试验,定期监测钼矿尾矿浸泡液的pH值及其铜铅重金属离子浓度,研究了尾矿的离子溶出规律.结果表明,尾矿对酸性溶液有很强的中和能力,可将pH=3.5～6的酸性溶液在8 d内中和到pH=7的中性状态,并维持不变.液固比为1:10的浸泡液中Cu~(2+)和Pb~(2+)的浓度都在25 d内达到最大值(分别为29.52和9.40μg/L),此后浓度下降,并发生震荡,但Cu~(2+)和Pb~(2+)的浓度随时间的变化趋势不同.浸泡液中Cu~(2+)和Pb~(2+)的平均浓度分别为19.37和4.29μg/L,尾矿中Cu和Pb的平均溶出率分别为0.097%和0.043%.钼矿尾矿可在中性条件下长期释放Cu~(2+)和Pb~(2+),且Cu比Pb更容易溶出.     

桂柳高速公路两侧土壤重金属分布特征

选择桂柳高速公路上的4个调查剖面和1个对照剖面测试了公路两侧农田土壤中Pb、Cd、Cr、Hg和As的含量分布。结果表明,公路交通对路两侧土壤重金属含量有一定的影响,运行期较长的对照路段桂黄公路两侧土壤中的Pb、Cd和As的含量明显高于运营期较短的桂柳高速公路段,而Cr、Hg与公路运行期长短的关系不是非常密切;重金属含量在横向上都有随距路肩距离的减小而增大的趋势,Pb、Cd在路肩两侧200m范围内含量的变化较小。以广西水稻土土壤背景值为评级标准,采用单因子指数法评价了路侧土壤的环境质量：所测路段和剖面的Cd、Hg污染均较严重;Cr基本上还处在非污染水平;桂黄公路段Pb的污染指数高于高速公路段。