蛇纹石中微量钯的提炼

介绍了蛇纹石的熔融，酸解等处理过程，重点叙述了从蛇纹石中提取微量贵金属钯的工艺流程和操作方法。钯的提取率为９０．５％。     

蛇纹石中钯的萃取

为了探讨蛇纹石中钯的有效萃取方法,进行蛇纹石浸出液萃取条件选择及萃取物还原实验。在盐酸介质中,以二(2 乙基己基)二硫代磷酸(D2EHDTPA)为萃取剂,浸出液pH为1,萃取时间为30min,钯的提取率达98%。     

蛇纹石热处理研究进展

蛇纹石类矿物具有耐磨、隔热、隔音、抗腐蚀等性能,是一种常见的天然无机材料。近年来我国对于蛇纹石资源的开发利用取得一系列新的研究成果,但蛇纹石资源的开发和利用尚处于起步阶段。在介绍蛇纹石矿物结构的基础上,总结了蛇纹石常见的热处理方式,即水热法和干热法。总结了蛇纹石水热条件生长机理,干热相变特征以及实际热处理的生产应用,提出蛇纹石热处理现存的问题,为蛇纹石更深一步研究提供参考。     

蛇纹石及温石棉的热分析

蛇纹石矿物为1:1型三八面体的层状硅酸盐。归属于高岭石—蛇纹石族中的蛇纹石亚族。据Brindley和Brown(1980),本亚族矿物包括斜纤蛇纹石(clinochrysotile)、正纤蛇纹石(ortho-chrysotile)、对纤蛇纹石(parachrysotile)、叶蛇纹石(antigorite)、镁利蛇纹石(magnesianlizardite)、镁绿泥石或称镁铝蛇纹石(amesite)、铝利蛇纹石(aluminian lizar-dite)、镍利蛇纹石—暗镍蛇纹石系列的矿物(nickelianlizardite—nepouite series)、磁     

蛇纹石尾矿固体废弃物资源化的途径

蛇纹石尾矿是蛇纹石开采、利用过程中产生的固体废弃物,是我国排放量较大的矿业固体废弃物之一,也是可回收利用的二次资源。本文介绍了蛇纹石尾矿对环境的危害,分析了蛇纹石尾矿的物理化学性质,总结出资源化利用的途径。     

利用氟化钠消除蛇纹石对黄铁矿浮选不利影响的机理研究

通过浮选试验、Zeta电位测试、SEM-EDS测试、X射线光电子能谱(XPS)测试研究了氟化钠在蛇纹石/黄铁矿体系中的作用机理。蛇纹石是硫化铜镍矿中的主要脉石矿物,不仅会抑制硫化矿物的浮选,而且会进入浮选精矿使后续的冶炼成本增加,因此需要利用氟化钠来消除蛇纹石对黄铁矿浮选的不利影响。研究结果表明,氟化钠可以显著改变蛇纹石的表面电位,使蛇纹石和黄铁矿由原来的静电吸引变为静电排斥,使黄铁矿在蛇纹石存在条件下的浮选回收率由41.2%提升至82.5%。其机理是氟化钠可以与蛇纹石表面的Mg(OH)_(2)反应生成MgF_(2),减少蛇纹石表面暴露的Mg^(2+),从而改变蛇纹石的表面电位,提高黄铁矿的浮选回收率。     

蛇纹石石棉纤维表面活性及生物持久性研究进展

蛇纹石石棉是重要的矿产资源,但其安全性问题一直制约其广泛应用。综述了蛇纹石石棉的流行病学和细胞毒性研究结果,蛇纹石石棉的理化性质与表面活性之间的联系及蛇纹石石棉纤维的生物持久性作用,并通过比较蛇纹石石棉浸蚀产物与SiO_2颗粒的毒性作用效果,指出从矿物物理化学角度揭示石棉表面活性特性、持久性与生物安全性之间的本质联系对蛇纹石石棉的安全使用具有重要意义。     

蛇纹石的性质与利用的研究进展

综述了自2011年起至今几年来国内对蛇纹石的研究进展状况,介绍从蛇纹石中有效成分的提取与利用和蛇纹石的表面性质导致其对矿石浮选过程的影响。蛇纹石的表面性质的研究已有进展,进一步的研究方向为寻找更加低廉并且高效的分散剂;对蛇纹石中有效成分的提取和利用仍处于探索阶段,还有很大的发展空间与发展前景。     

羧甲基纤维素对微细粒蛇纹石的絮凝及抑制作用

通过浮选实验、沉降实验、吸附量测试及红外光谱测试研究不同种类抑制剂在蛇纹石浮选中的作用,并考察其作用机理.结果表明,蛇纹石表面亲水,可浮性较差,微细粒级蛇纹石能够通过泡沫夹带上浮进入精矿.高分子抑制剂羧甲基纤维素(CMC)能完全抑制细粒级蛇纹石的浮选,而抑制剂水玻璃不能抑制细粒级蛇纹石的浮选.机理研究表明,CMC和水玻璃均能在蛇纹石表面吸附,而高分子抑制剂CMC能对细粒级蛇纹石产生絮凝作用,增大蛇纹石颗粒表观粒度,降低泡沫夹带,从而实现细粒级蛇纹石的完全抑制.     

合成纤蛇纹石润滑油添加剂的研究

分别利用三种实验方法进行了蛇纹石的水热合成.制备的粉体分别用X射线衍射仪(XRD)、透射电子显微镜(TEM)进行成分与形貌的表征分析.结果表明以滑石与氧化镁为反应物的方法在220℃、pH=13、反应30 h条件下成功合成出纤蛇纹石纳米管,并讨论了水热合成条件对产物的影响.含有纤蛇纹石的合成产物及天然蛇纹石分别经表面修饰剂修饰后进行四球摩擦磨损实验来研究其摩擦性质,人工合成蛇纹石表现出比天然蛇纹石更好地减摩抗磨效果.     

多组分废催化剂中钯的分离工艺研究进展

简述了废催化剂中钯分离回收的基本过程和方法,指出多组分废钯催化剂具有很高的回收价值,但存在组分多、分离困难的问题。对于多组分废钯催化剂中钯与贵金属金、银、铂、铑等,以及与非贵金属铜、钴、镍、铁等的分离技术分别进行了简要介绍与评价。结果表明,化学沉淀法、溶剂萃取法、还原法、置换法是目前多组分废钯催化剂常用的回收方法。其中化学沉淀法是使用最多的方法,但存在回收周期长、复杂、成本较高的问题,而溶剂萃取法具有分离效果好、过程简单的优点,成为最具发展前景的方法。因此选择性高、无污染并适合大规模工业化的萃取新工艺成为未来的发展方向。     

Evaluation of reaction variables in the dissolution of serpentine for mineral carbonation

The sequestration of CO₂ through the employment of magnesium silicates, olivine and serpentine, is beyond the proof of concept stage. Serpentine has been chosen as the feedstock mineral due to its abundance and availability. Although the reactivity of olivine is greater than that of serpentine, physical and chemical treatments have been shown to greatly increase the reactivity of serpentine. A sulfuric acid leaching stage has been shown to alleviate the rate limiting step of magnesium removal, thereby accelerating the overall carbonation process. Varying reaction conditions can significantly influence the results for the dissolution process with an extreme reaction environment providing desirable results. However, a more careful assessment of the reaction variables under milder conditions is needed for a better understanding of the reaction processes and potential pathways for high extraction yields under more modest conditions. Accordingly in this work, a statistical design of experiments was conducted to ascertain the effect of acid concentration, particle size and reaction time and temperature on the leaching of magnesium from serpentine using sulfuric acid. Results demonstrated that acid concentration provided primary control on the dissolution via the removal of water, which is closely correlated with the extraction of magnesium from serpentine. Particle comminution to a median size less than 163 μm remained an important consideration in increasing reactivity and liberating magnetite. Single variable experimentation demonstrated dissolution enhancements with increased reaction time and temperature. An increase in magnesium dissolution of 46% and 70%, over a baseline test, occurred for increased reaction time and temperature, respectively.     

Extraction–electrodeposition (EX–EL) process for the recovery of palladium from high-level liquid waste

Extraction–electrodeposition (EX–EL) process has been developed for the quantitative recovery of palladium from nitric acid medium and fast reactor-simulated high-level liquid waste (FR-S-HLLW). The process exploits some characteristic properties of room temperature ionic liquid, tri-n-octylmethylammonium nitrate (TOMAN), for quantitative and favorable recovery of palladium. Extraction of palladium (II) from FR-S-HLLW and nitric acid medium by a solution of 0.5 M TOMAN in chloroform has been studied in detail. More than 60% of palladium was extracted in a single contact of equal volumes of organic and aqueous phases and nearly five contacts were required for quantitative extraction. The electrochemical behavior of palladium (II) present in the organic phase was investigated at stainless steel electrode by cyclic voltammetry. A surge in cathodic current occurring at a potential of –0.5 V (vs. Pd) was due to the reduction of palladium (II) to palladium (0). The kinetics of electrodeposition was followed by the UV–VIS absorption spectrum of palladium present in organic phase and under the given conditions nearly 20 and 35 h were required for the quantitative deposition of palladium from organic phase, which was obtained after extraction of palladium from 4 M nitric acid and FR-S-HLLW, respectively. Decontamination of palladium from other fission products during extraction and electrodeposition was studied and the results are reported in this article.     

EXTRACTION MECHANISM OF PALLADIUM WITH DIDODECYLMONOTHIOPHOSPHORIC ACID IN HEPTANE DILUENT

ABSTRACT

Kinetic study of the extraction of palladium(D) with didodecylmonothiophosphoric acid in n-heptane diluent was carried out using a stirred transfer cell to clarify the extraction mechanism. The effect of surfactants on the kinetics of palladium extraction was also investigated, to elucidate the role of surfactants used in liquid surfactant membranes. Moreover, the interfacial tension between the organic and aqueous phases was measured to elucidate the adsorption equilibrium of the surfactants. It was found that the interfacial activity of each surfactant is higher than that of the extractant. In the kinetic study of palladium extraction, the experimental results of the extraction rate was analyzed by the interfacial reaction model, taking into account of the adsorption of the surfactant and extractant. The rate-determining step of palladium extraction was the complex formation between four chloro-palladium complexes and the extractant at the interface, and the extraction rate constants of each palladium species were obtained. The extraction rate of palladium in n-heptane diluent was much faster than that in toluene. Additionally, it was suggested that there was particular interaction between the surfactant and extractant at the interface. The effect of the surfactant on the extraction rate was explained by taking into account the adsorption of the surfactant at the interface.     

Extraction rate of palladium using divinylbenzene microcapsules containing tri-n-octylamine as the extractant

The extraction of palladium(II) from an aqueous hydrochloric solution was carried out using divinylbenzene microcapsules containing tri-n-octylamine as the extractant. The preparation of these microcapsules was affected by the preparation conditions, such as the concentrations of the divinylbenzene, tri-n-octylamine and diluent. In the case of extremely low or high concentrations of divinylbenzene, and for the high concentration of tri-n-octylamine, the matrix-type microcapsules could not be prepared. The morphologies the prepared of microcapsules were spherical and the surface of the microcapsules was very smooth. The adsorption of palladium(II) onto the microcapsules was negligible compared to the extraction of palladium(II), and it found that the adsorption of palladium(II) onto the microcapsules did not occur. The extraction of palladium(II) into the microcapsules was affected by the characteristics of microcapsules such as, the surface area, pore diameter and volume, and the encapsulation efficiency of the tri-n-octylamine. The extraction of palladium(II) into the microcapsules seemed to have three steps. The first extraction step is caused by the tri-n-octylamine existing near the surface of the microcapsules. The second step is caused by the internal diffusion. The final step is the extraction equilibrium. Based on these results, the microcapsule that has a high encapsulation efficiency of tri-n-octylamine and small pore diameter seems to show the high extraction performance.     

钯分离富集方法研究进展

综述了近几年来分离富集钯的主要方法,包括液-液萃取法、吸附法、分子识别法、沉淀法、离子交换法、固相萃取法、液膜法、置换法等。并对一些新的方法做了评述。     

钯的二苄基硫醚固相萃取分离研究

基于二苄基硫醚与钯的配合反应,建立了一种高选择性固相萃取吸附钯的方法。在0.1 mol/L的盐酸介质中,钯可以被二苄基硫醚树脂吸附富集并形成1∶2稳定配合物,该配合物可用20 g/L酸性硫脲洗脱,洗脱液经处理后用分光光度法测定,柱可以再生和重复使用,且萃取剂流失少。二苄基硫醚对钯的吸附是配位萃取机理;方法用于吸附分离钯选择性高,钯的回收率达95%以上。     

Droplet-based microreactor system for stepwise recovery of precious metal ions from real metal waste with calix[4]arene derivatives

ABSTRACT

Stepwise recovery of silver(I), palladium(II) and platinum(IV) with suitable calix[4]arene extractants was carried out by investigating the extraction and stripping process using a droplet-based microreactor system. The highest percentages of silver, palladium (100%) and platinum ion (37.2%) were extracted from a real waste only within 4.00s using a microreactor system compared with 24 and 72 h to reach extraction equilibrium in a batch method. Fourier transform infrared spectroscopy studies revealed a very good relation in peak shifts on the metal complexation with calix[4]arene derivatives after extraction and stripping. The droplet-based microreactor system emerges as an effective tool to be applied in metal recovery.     

Separation of palladium from high level liquid waste of PUREX origin by solvent extraction and precipitation methods using oximes

Separation of palladium from high level liquid waste (HLLW) solution originated from the reprocessing of spent fuel by PUREX process is carried out by solvent extraction and precipitation methods using oximes. In solvent extraction, palladium is extracted from the waste using 1.1×10⁻²M α-benzoin oxime in Solvesso 100 as extractant. The loaded organic phase is scrubbed with water prior to the stripping of palladium using the strippants 0.05 M thiourea in 0.1 M HNO₃ and 4 M NH₄OH separately. The recovery of the method is found to be >99.5%. The method has been used to recover Pd in sub mg quantities from actual waste solution originated from the reprocessing of spent fuel from pressurised heavy water reactor (PHWR-HLLW). Studies are also carried out for the separation of palladium using an aqueous solution of sodium salt of dimethyl glyoxime (0.1% w/v) as precipitant. Various parameters which influence the precipitation of palladium such as concentration of the precipitant, concentration of nitric acid in the feed and the behaviour of uranium, plutonium and other fission products at the concentration level encountered in the waste are studied in detail. Under the optimized precipitation conditions separation of Pd is carried out from a synthetic PHWR-HLLW and the recovery is found to be >99.9%. The palladium product obtained from both the methods show high decontamination factors with respect to other fission products and constituents of the waste. Based on these results a scheme has been proposed for the recovery of palladium from HLLW.