封闭溶矿-分光光度法测定铀矿石中的亚铁

介绍了用封闭溶矿 分光光度法测定铀矿石中的亚铁。140℃恒温条件下,在聚四氟乙烯封闭溶样器中,用氢氟酸 硫酸混合溶液分解矿样,分解后溶液中的Fe(Ⅱ)用邻菲罗啉分光光度法测定。在pH5 0的醋酸 醋酸钠缓冲介质中,Fe(Ⅱ)与邻菲罗啉形成稳定的橙红色配合物,其最大吸收波长为510nm,摩尔吸光系数ε510nm=1 1×104L·mol-1·cm-1,Fe(Ⅱ)质量浓度在0～2 0mg/L范围内符合朗伯 比尔定律。本法用于测定矿石中0 005%～5 0%范围内的Fe(Ⅱ),相对标准偏差优于±5%,标准加入回收率为97 6%～102%。方法操作简单、快速,结果令人满意。

封闭溶矿测定岩石矿物中亚铁

岩石矿物中亚铁的测定,经典方法是采用HF-H2SO4铂坩埚溶矿测定。文献[1]中给出了几种溶矿方法,此方法简便、快速,但采用铂坩埚价格昂贵,且Fe2+在溶矿过程中易被空气氧化使测定结果偏低。有采用塑料坩埚溶矿测定和聚四氟乙烯为内衬的铝压热器密闭溶矿法。本工作将矿样在硬质聚丙（乙）烯塑料中溶解后测定岩石矿物中的FeO,获得比较理想的效果。 1 方法原理采用封闭瓶于水浴加热溶矿分解岩石矿物试样测定FeO中必须有少量CO2存在,否则测定结果偏低,虽然利用CO2充气法在较大程度上防止了Fe2+氧化,但操作不当结果准确度也不理想。本文利用在HF-H2SO4混合酸中加入少量NaHCO3来直接产生CO2气驱赶空气后再经封闭水浴溶矿后用K2Cr2O7法测定FeO。

微细粒浸染型金矿金的赋存状态研究

某金矿系属于微细粒浸染型矿床 ,矿床赋存于三叠系底部一套粉砂岩与粘土岩组成的沉积岩中 ,物质组成简单 ,自然金是唯一的有用矿物 ,金的颗粒极其微细 ,多数呈非游离不可见金 (超显微粒状金 ) ,主要赋存在毒砂、黄铁矿等硫化物中 ,次为粘土或石英中。常规光学显微镜下鉴定极为困难 ,根据矿石特点 ,采用以选择性溶解试验为主与镜下鉴定的试验相结合的研究方法 ,基本查明了金的赋存状态及工艺特性。解决了单一镜检从半定量、相对含量提高到绝对量的高标准 ,从而为选冶工艺提供更可靠的数据。

黑龙江省中部森林沼泽区超低密度深穿透地球化学调查采样介质的确定

通过对王水溶矿法与四酸溶矿法的对比,元素在泛滥平原A层、B层沉积物及水系沉积物中的分配,以及这3种介质圈定的异常对比等综合因素的研究,确定了泛滥平原A层沉积物是黑龙江省中部森林沼泽区开展超低密度深穿透地球化学调查的有效采样介质。

森林沼泽区富含有机质样品中金的存在形式及对分析的影响

为探讨中国东北森林沼泽地区富含有机质样品中金偏低的原因,采用了王水溶矿法和四酸溶矿法的AAS分析来测定样品中的Au。用四酸溶矿法驱除硅胶,明显地提高金的测定值,特别是对含量大于10-9的样品,2种分析方法的差别更大。通过以上研究发现,在森林沼泽区的富含有机质样品中,金除以有机质结合形式存在于介质中,还可能以胶体或纳米形式存在于样品中,并被SiO2胶体所包裹,在高浓度有机酸的保护下,金能在水溶液中呈活动形式做长距离迁移;但用王水溶矿法不能测定出这种被SiO2胶体包裹形式的金。

Transformation of hematite in diasporic bauxite during reductive Bayer digestion and recovery of iron

The reductive Bayer digestion by using iron powder as reductant is proposed to convert hematite to magnetite and further to dissociate iron minerals from sodium aluminosilicate hydrate(desilication product,DSP)based on the differences of their surface properties.The results show that the differences of surface properties between magnetite and DSP in zeta potential,wettability and solvation trend facilitate magnetite to agglomerate,grow up and thus to dissociate from DSP.The increments of reductant amount and alkali concentration favor the transformation of hematite in digestion with the relative alumina recovery of98.91%.Processing the resultant red mud can obtain qualified iron concentrate with iron grade of approximate60%and recovery of about86%through magnetic separation,resulting in reduction of red mud emission higher than70%.The results are potential to develop a novel technology for processing high iron diasporic bauxite efficiently and provide references for comprehensive utilization of high iron red mud.

Hazard development mechanism and deformation estimation of water solution mining area

Based on the hazard development mechanism, a water solution area is closely related to the supporting effect of pressure-bearing water, the relaxing and collapsing effect of orebody interlayer, the collapsing effect of thawless material in orebody, filling effect caused by cubical expansibility of hydrate crystallization and uplifting effect of hard rock layer over cranny belt. The movement and deformation of ground surface caused by underground water solution mining is believed to be much weaker than that caused by well lane mining, which can be predicted by the stochastic medium theory method. On the basis of analysis on the engineering practice of water solution mining, its corresponding parameters can be obtained from the in-site data of the belt water and sand filling mining in engineering analog approach.

Role and maintenance of redox potential on chalcopyrite biohydrometallurgy:An overview

Chalcopyrite is one of the most important copper minerals;however,the extracted efficiency of chalcopyrite is still not satisfactory in hydrometallurgy owing to its high lattice energy which leads to its low dissolution kinetics.To overcome the difficulties,many advanced technologies have been developed,including the selection of high effectively bacteria,the inhibition of the passivation film adhered onto the minerals surface,and the maintenance of solution redox potential under an optimum range.Up to date,considerable researches on the first two terms have been summarized,while the overview of the last term has been rarely reported.Based on corresponding works in recent years,key trends and roles of solution redox potential in copper hydrometallurgy,including its definition,effect and maintenance,have been introduced in this review.

Synthesis and characterization of water-soluble magnetite nanocrystals via one-step sol-gel pathway

Water-soluble magnetite nanocrystals have been prepared by one-step non-alkoxide sol-gel method.The magnetic properties of magnetite nanocrystals obtained are size dependent.The experimental results also reveal that 2-pyrrolidone not only serves as solvent,but also involves surface coordination which renders the magnetite nanoparticles water-soluble and colloidal solution stable.Although the current synthetic approach is a small modification to the non-alkoxide sol-gel method,it allows us to directly obtain high-quality water-soluble magnetic nanocrystals.In addition,we realize that this method could be easily extended to preparation of many other transition and main group metal oxide water-soluble nanocrystals only from simple metal ion salts.

Directing nucleation and growth kinetics in solution-processed hybrid perovskite thin-films

A heightened understanding of nucleation and growth mechanisms is paramount if effective solution processing of organic-inorganic perovskite thin-films for optoelectronic applications is to be achieved. Many fabri- cation techniques have been utilized previously to develop high-performance perovskite layers but there remains an absence of a unifying model that describes accurately the formation of these materials from solution. The present study provides a thorough analysis of nucleation and growth kinetics underpinning the development of hybrid organic-in- organic perovskite thin-films. Through precise control of the perovskite growth conditions the spacing of heteroge- neous nucleation sites was varied successfully from several hundred nanometers to several hundred microns. The crystalline regions surrounding these nuclei were found to comprise clusters of highly-oriented crystal domains exceed- ing 100 pm in diameter. However, no beneficial correlation was found between the size of these well-oriented grain-clus- ters and the optoelectronic performance. The formation of the perovskite microstructure features characteristics of both classical and non-classical growth mechanisms. The insights into perovskite thin-film growth developed by the present study provide clear implications for the development of future hybrid perovskite microstructures.

Magnetite/Reduced Graphene Oxide Nanocomposites： One Step Solvothermal Synthesis and Use as a Novel Platform for Removal of Dye Pollutants

A simple one step solvothermal strategy using non-toxic and cost-effective precursors has been developed to prepare magnetite/reduced graphene oxide （MRGO） nanocomposites for removal of dye pollutants. Taking advantage of the combined benefits of graphene and magnetic nanoparticles, these MRGO nanocomposites exhibit excellent removal efficiency （over 91% for rhodamine B and over 94% for malachite green） and rapid separation from aqueous solution by an external magnetic field. Interestingly, the performance of the MRGO composites is strongly dependent on both the loading of Fe304 and the pH value. In addition, the adsorption behavior of this new adsorbent fits well with the Freundlich isotherm and the pseudo-second-order kinetic model. In further applications, real samples--including industrial waste water and lake water--have been treated using the MRGO composites. All the results demonstrate that the MRGO composites are effective adsorbents for removal of dye pollutants and thus could provide a new platform for dye decontamination.

Theoretical limiting concentration for mineralization of trichloromethane and dichloromethane in aqueous solutions by AOPs

It is widely stated that most organic contaminants could be completely mineralized by Advanced Oxidation Processes(AOPs). This statement means that the concentration of the organic contaminant at equilibrium(limiting concentration,LC)is low enough to be neglected.However,for environmental safety,especially drinking water safety,this statement needs to be verified from chemical engineering thermodynamic analysis.In this paper,trichloromethane(CHCl3)and dichloromethane(CH2Cl2) are selected as the model systems,and the equilibrium concentration(theoretical limiting concentration,TLC)for the mineralization of chlorinated methanes in aqueous solutions at the different initial concentrations of chlorinated methanes,pH values and·OH concentrations by AOPs are investigated by thermodynamic analysis.The results in this paper show that the TLC for the mineralization of CHCl3 and CH2Cl2 with·OH increases with increasing initial concentrations of CHCl3 and CH2Cl2,decreases with increasing concentration of·OH,and the TLC for the mineralization of CHCl3 decreases with increasing pH values except that the pH value changes from 3.0 to 3.5.For the mineralization of CH2Cl2 with·OH,at the concentrations of·OH obtained from the literature,there is no obvious change of the TLC with pH values,while as the concentrations of·OH increase by 10 and 100 times,the TLC decreases with the increasing pH values from 2.0 to 3.0 and from 3.5 to 4.5,and increases with the increasing pH values from 3.0 to 3.5 and from 4.5 to 5.0.The investigations in this paper imply that high concentration of·OH,a bit higher pH values(4.0–5.0)in acid environment and low initial concentrations of the organic contaminants are beneficial for the complete mineralization of chlorinated methanes by AOPs.

Facial synthesis of highly stable and bright CsPbX(X=Cl,Br,I)perovskite nanocrystals via an anion exchange at the water-oil interface

Cesium lead halide perovskite nanocrystals(NCs)have attracted unprecedented attention owing to their compelling properties for optoelectronic applications.Compared with the classical hot-injection method,the roomtemperature(RT)synthetic strategy is more facile and tender,but it is hard to obtain stable CsPbI3 NCs and it usually uses polar solvents that sometimes reduce the stability and properties of NCs.Here,we reported a simple approach to synthesize highly efficient and stable CsPbI3 as well as other colortunable CsPbX3 NCs with high quantum efficiency at room temperature via an anion exchange at the water-oil interface,in which the as-synthesized pristine CsPbBr3 NCs in toluene were treated in aqueous solutions of HX(X=Cl,Br,and I)and protonated oleylamine(OAm)acted as a carrier.The synthesized CsPbI3 NCs had an emission at 680 nm and even showed excellent colloidal stability after being stored for 32 d.The high efficiency and stability of the obtained CsPbX3 NCs were ascribed to the facts that:(ⅰ)the polar reagents were almost removed from the surface of NCs;(ⅱ)the defect-related nonradiative recombination was suppressed efficiently by surface passivation.