金精矿碘化浸出过程动力学

采用碘-碘化物体系对金精矿进行浸出,通过实际矿石的浸出试验考察搅拌速度、浸出温度、碘浓度及碘离子浓度对金精矿碘化浸出反应动力学的影响。结果表明:提高搅拌速度对金的浸出有不利影响;通过对影响该体系动力学参数的考察,发现其符合核收缩模型,反应过程总体由界面化学反应控制,其表观活化能为31.674kJ/mol,碘浓度和碘离子浓度的反应级数分别为1和0.5,建立了金精矿碘化浸出过程的反应速率方程。     

碘化物对金精矿碘化浸出过程的影响

采用碘-碘化物浸出体系,从碘初始含量、碘与碘化物摩尔比和浸出液pH值3个影响因素入手,考察不同碘化物(碘化铵、碘化钾和碘化氢)对金精矿碘化浸出过程的影响。结果表明:在碘初始含量为1%,碘与碘化物摩尔比为1:8,浸出液pH值为7,液固比为4:1,搅拌速度为600 r/min,浸出时间为4 h,温度为25℃的条件下,用碘化铵或碘化钾作为碘化浸金的络合剂,金的浸出率均能达到90%左右,而用碘化氢(其水溶液为氢碘酸)作络合剂时,金的浸出率仅有75%。考虑到不同碘化物浸金效果差异及工业应用的可行性等因素,确定碘化钾为适宜的金精矿碘化浸出络合剂。     

钯—硫醚及■叶立德配合物的合成和表征

氯化-3,3-二氟-2-丙烯基二甲基锍及溴化乙氧甲酰甲基二甲基锍分别与钯的卤化物反应,生成双(3,3-二氯-2-丙烯基二甲基锍)四氯钯(Ⅱ)和双(乙氧甲酰甲基二甲基锍)六溴二钯(Ⅱ)。进一步反应转变为配合物。二氯双(3,3-二氟-2-丙烯基甲基硫醚)合钯(Ⅱ)和二溴双(二甲基乙氧甲酰甲基■叶立德)合钯(Ⅱ)。开通过元素分析、红外光谱、核磁共振谱等测试结果确定了它们的结构。     

电解法从废弃印刷线路板的碘化浸金液中沉积金

研究电解法从废弃印刷线路板的碘化浸金液中沉积金.结果表明,电解法从废弃印刷线路板的碘化浸金液中沉积金的最佳工艺条件为:碳棒作阴极,钛板作阳极,阴离子交换膜隔开电解槽,阳极碘液中碘的质量分数为0.1%～0.8%,n(I2):n(I-)=1-10,槽电压为10～14 V,阴极碘化浸金液中金的浓度为15～50 mg/L,电解时间为1～4 h,金的电解沉积率大于95%.电解实验后,阳极碘液可以重复作为电解质使用或再次用来从废弃印刷线路板中浸取金.     

碘化浸出液电沉积金工艺

针对碘化浸出液中金回收效率低、电能消耗高等问题,采用电沉积法从碘化浸出液中电沉积金。考察阴极液金浓度、阳极液碘质量分数、阳极液n(I_2):n(I~-)、槽电压对金沉积率的影响。采用响应面法以阳极液碘质量分数、阳极液n(I_2):n(I~-)、槽电压为变量因素,金沉积率为响应值,研究各变量因素之间的交互作用以及对金沉积率的影响规律。结果表明:阳极液碘质量分数、阳极液n(I_2):n(I~-)和槽电压与金沉积率的主效应关系为:槽电压阳极液n(I_2):n(I~-)阳极液碘质量分数,并得出了以金沉积率为响应值的二阶回归方程。优化后工艺条件为:阴极液金浓度10 mg/L、阳极液碘质量分数0.58%、阳极液n(I_2):n(I~-) 1:6.5、槽电压12 V、电解时间2 h,三次验证实验的金沉积率均值为97.83%,与模型预测值98.15%十分接近,证明响应面法优化得到的二次多项式模型具有可行性。同时,该工艺条件适用于实际应用,金沉积率仍可达97%以上。     

NaF—CaF2熔盐溶液结构的分子动力学模拟研究

使用分子动力学方法,研究了NaF—CaF_2熔盐体系给出了体系各离子间的偶对分布函数和各种健角几率分布,并在此基础上讨论了体系中的桥和络合模拟结果表明,Ca~(2+)离子周围的F~(-)离子未形成四面体配位,出现象CaF_4~(2-)这样小的络合原子团的可能性不大Ca~(2+)离子周围F~(-)离子排布的一种可能的结构是3个Ca~(2+)离子通过F~(-)离子桥联成一个正三角形,正三角形中心上下各有一个F~(-)离子,每个Ca~(2+)离子在三角形外侧还各有2个F~(-)离子     

基于同时平衡原理的Au-I~--H_2O系热力学分析

采用同时平衡原理对Au-I--H2O系的浸金热力学进行分析,分别研究溶液与固体Au以及Au I沉淀与固体Au平衡时的φ-p H关系、Au I存在条件和溶液中含金组分的变化规律。结果表明:随着溶液中含金组分的总浓度cT(Au)的降低或含碘组分的总浓度cT(I-)的增加,还原电位φsol/Au迅速降低,Au3+/Au2O3的平衡p H值增大,非常有利于金的碘化浸出;随着溶液中cT(I-)逐渐增加,出现Au I沉淀且其沉淀量呈先增大后减小的趋势;在cT(Au)为1×10-4 mol/L的条件下,当溶液中cT(I-)浓度大于0.0021 mol/L时,可避免Au I沉淀的生成,金主要以Au I2-络合离子形式存在。Au-I--H2O系的浸金热力学分析为金的高效碘化浸出提供了理论依据。     

丁二腈基分子塑晶固态电解质的电化学性能

通过向丁二腈分子塑性晶体中加入固体碘盐和碘分子,制备了碘体系丁二腈基分子塑晶固态电解质。研究了不同阳离子的固体碘盐对丁二腈基固态电解质的相变、扩散系数以及离子电导率的影响。最终以碘化N-乙基吡啶作为固体碘盐与碘分子及丁二腈的摩尔比为2:1:100配制的固态电解质I-和I3-的扩散系数在室温达到1.83×10-6 cm2·s-1与1.22×10-6 cm2·s-1,固态电解质的离子电导率在30℃为1.7 m S·cm-1,制备的电池效率达1.57%。碘化N-乙基吡啶同时又是一种低成本和高成本效能的固体碘盐,更加具有商业应用价值。     

Thermodynamic Study on Synthesizing Rhodium Iodide by Direct Synthesis Method

采用直接合成法使铑粉和碘粉反应合成碘化铑.首先对碘的气化过程进行热力学计算,确定铑粉和碘粉反应的最高温度为600℃;通过吉布斯(Gibbs)自由能与温度的计算,得出该反应的适宜温度为500℃.在500℃温度下碘和铑能充分反应生成活性碘化铑.     

Li+掺杂TiO2薄膜的制备及晶化行为

本文采用DTA,XRD,SEM及Raman光谱等测试手段,研究了利用溶胶-凝胶法制备LiNO3掺杂的TiO2薄膜的相变行为,提出了通过加入Li+离子降低薄膜从无定形到锐钛矿、锐钛矿到金红石的相转变温度的方法.并通过甲基橙水溶液的光催化降解实验表明在600℃热处理温度下的LiNO3掺杂的TiO2薄膜的光催化效率高于未掺杂的TiO2薄膜.     

白云母对氰化浸金的吸附效应研究

采用多种手段研究了金矿石中白云母对氰化浸出液中的金吸附效应。吸附试验考察了不同粒级白云母对溶液中金吸附率的影响,结果表明,白云母粒度越细,溶液中金的吸附率越高,吸附率由1.29%提高至5.35%;电化学溶解实验表明,白云母粒度越小,金的溶解速率越大;对浸金产物的扫描电镜(SEM)和能谱(EDS)分析表明,金的氰化络合物易吸附在白云母端点处;红外光谱分析显示,金氰化物与白云母存在化学吸附。密度泛函理论(DFT)模拟计算结果显示,金氰化物与白云母(001)表面的吸附强度为[Au(CN)2]^-?AuCN。     

Solid-phase extraction gold from alkaline cyanide solution with quaternary ammonium surfactant

The solid-phase extraction(SPE) technique applied to the extraction of organic compound was creatively used as the extraction of inorganic gold in the paper.Two types of techniques were proposed and explored,namely the SPE and the liquid–liquid extraction(LLE) of the quaternary ammonium surfactant [cetytrimethyl ammonium bromide(CTMAB),cetyl pyridine bromide(CPB),benzyl dimethyl dodecyl ammonium chloride(BDMDAC),and dodecyl trimethyl ammonium chloride(DTMAC)].The surfactant could react with Au(CN)_2~-to form the ionic complex,and the compound could be extracted by SPE column of reversed-phase bonded silica gel.Hence,a new method of SPE was proposed to extract gold with these features of the high selectivity,the reliability,and the simplicity.The experimental result shows that the recovery rate of gold is more than 98 %,and the solid-phase extraction column is not easily damaged and it can be repeatedly used.The new method can be used as the extraction process of gold from alkaline cyanide solution as well.Besides,the paper also puts forward a new process of gold extraction.     

A spectroscopic and electrochemical investigation of the oxidation pathway of glycyl-d,l-methionine and its N-acetyl derivative induced by gold(III)

The ¹H nuclear magnetic resonance spectroscopy was applied to study the reaction of the dipeptide glycyl-d,l-methionine (H-Gly-d,l-Met-OH) and its N-acetylated derivative (Ac-Gly-d,l-Met-OH) with hydrogen tetrachloridoaurate(III) (H[AuCl₄]). The corresponding peptide and [AuCl₄]^– were reacted in 1:1, 2:1, and 3:1 molar ratios, and all reactions were performed at pD 2.45 in 0.01 M DCl as solvent and at 25°C. It was found that the first step of these reactions is coordination of Au(III) to the thioether sulfur atom with formation of the gold(III)-peptide complex [AuCl₃(R-Gly-Met-OH-S)] (R=H or Ac). This intermediate gold(III) complex further reacts with an additional methionine residue to generate the R-Gly-Met-OH chlorosulfonium cation as the second intermediate product, which readily undergoes hydrolysis to give the corresponding sulfoxide. The oxidation of the methionine residue in the reaction between H-Gly-d,l-Met-OH and [AuCl₄]^– was five times faster (k ₂ = 0.363 ± 0.074 M^-1s^-1) in comparison to the same process with N-acetylated derivative of this peptide (k ₂ = 0.074 ± 0.007 M^-1s^-1). The difference in the oxidation rates between these two peptides can be attributed to the free terminal amino group of H-Gly-d,l-Met-OH dipeptide. The mechanism of this redox process is discussed and, for its clarification, the reaction of the H-Gly-d,l-Met-OH dipeptide with [AuCl₄]^– was additionally investigated by UV-Vis and cyclic voltammetry techniques. From these measurements, it was shown that the [AuCl₂]^– complex under these experimental conditions has a strong tendency to disproportionate, forming [AuCl₄]^– and metallic gold. This study contributes to a better understanding of the mechanism of the Au(III)-induced oxidation of methionine and methionine-containing peptides in relation to the severe toxicity of anti-arthritic and anticancer gold-based drugs.     

Separation of precious metals using selective mesoporous adsorbents

The mesoporous NH₂-MCM-41 adsorbent prepared by grafting aminopropyls on MCM-41 is selective towards gold and palladium adsorptions and can separate these precious metals from complex solutions containing other metal ions such as cobalt, nickel, copper and zinc. Adsorption is rapid and the adsorbent’s capacity for gold is better or comparable to most carbonaceous adsorbents including activated carbons. Furthermore, NH₂-MCM-41 can separate palladium from gold solution at pH1.0 with excellent selectivity and capacity. Thus, it is possible to design a two steps separation process for the separation of palladium and then gold from the complex solution. A simple acid wash was sufficient to recover the adsorbed palladium and gold as concentrated, high purity (i.e., > 95%) metal salt solutions and the regenerated adsorbent was reused without lost of performance.     

Oxygen-free precursor for chemical vapor deposition of gold films: thermal properties and decomposition mechanism

Thermal properties of oxygen-, phosphorus-, and halogen-free dimethylgold(III) diethyldithiocarbamate complex (CH₃)₂AuS₂CN(C₂H₅)₂ (gold, dimethyl(diethylcarbamodithioato -S,S′)-) having excellent storage stability and the mechanism of its decomposition to elemental gold were studied. Saturated vapor pressure was found to be ~10⁻³–10⁻¹ Torr at 50–90°C. Decomposition of the vapor on the surface starts at T = 210°C. The temperature dependence of gas phase composition was studied using the original mass spectrometric technique, it was established that the decomposition of the compound on the surface in vacuum follows three main pathways. Two of them result in the formation of elemental gold, saturated C2–C4 alkanes and (1) protonated ligand or (2) methylated ligand. The third one results in elemental gold and gaseous products: C2–C3 alkylmercaptanes and CH₃SCN(C₂H₅)₂. The formation of gold as a sole solid product within the temperature range 210–240°C was confirmed by X-ray photoelectron spectroscopy analysis. It was shown that the compound exhibits the best combination of volatility, thermal, and storage stability among volatile organogold complexes and thus it may be a promising precursor for obtaining gold films by chemical vapor deposition.     

Gold(I) and gold(III) complexes with anionic oxygen donor ligands: hydroxo, oxo and alkoxo complexes

The chemistry of gold(I) and gold(III) hydroxo, oxo and alkoxo complexes containing organic co-ligands is reviewed. Due to the high reactivity of the gold-oxygen bond most of these species can be employed as useful intermediates in many important processes. Alkoxides are by far the most numerous class among these species, and both gold(I) and gold(III) complexes are known with a variety of alkoxides. The recent discovery of the catalytic activity of some gold(I) and gold(III) fluoroalkoxides has enlivened the interest towards this class of compounds leading to new applications for previously known complexes, as is the case for a gold(III) siloxo complex which has found use as a precursor for CVD, as well as for the synthesis of new alkoxo derivatives. Another well represented and well known class of compounds are the gold(I) oxo complexes [O(AuPR₃)₃]⁺ which are the most effective aurating reagents. Gold(III) oxo complexes have been synthesized only recently and much of their chemistry is still largely to be explored. Preliminary studies suggest their potential in the transfer of oxygen atoms. Finally, some cationic gold(III) hydroxo complexes are found to display significant,and in some cases relevant, cytotoxic effects on cancer cell lines.     

Influence of iodide ions on corrosion of dual‐phase steel in sulfuric acid solution

Potassium iodide was studied for its corrosion inhibition property on the corrosion of dual‐phase steel in 0.5 M sulfuric acid at 25°C by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. Scanning electron microscopy was used to characterize the steel surface. The inhibition efficiency increases with the concentration of iodide ions. The thermodynamic parameters K_ads and ΔG⁰_ads are calculated and discussed. The probable inhibitive mechanism is proposed from the viewpoint of adsorption theory.     

Der Einfluβ Der Spezifischen Adsorption Von Halogenidionen Auf das Elektrochemische Verhalten der Nickel-Elektrode

Small additions of the halide ions (F^?, Cl^?, Br^?, I^?) to 1N H₂SO₄ result in marked deviations of the current density/potential curves as well as the capacitance/potential curves from nickel, compared with those obtained in pure H₂SO₄. The different actions are explained by the varying tendency of the halide ions to specific adsorption at the nickel surface.The time-dependence of the capacitance demonstrates the existence of a two-stage process for the adsorption of iodide ions.In the presence of iodide ions the influence of their concentration was measured with respect to current density and capacitance.     

高岭石对氰化浸金的影响及助浸研究

采用电化学实验研究了在氰化浸金过程中常见矿物高岭石对金溶解速率及对溶液中金的吸附效果的影响。结果表明,高岭石的存在会使金的溶解速率加快,随着高岭石粒度逐渐降低金的溶解速率提高,且高岭石对溶液中金的吸附率增加。氰化浸出实验结果表明,高岭石存在时金的浸出率由93.21%降低到91.76%,采用柠檬酸三钠、过氧化镁和十二烷基硫酸钠助浸时,金浸出率升高至94.42%。能谱分析(EDS)发现浸出物中高岭石表面有金元素存在,表明高岭石会吸附溶液中的金。红外光谱分析和密度泛函理论计算表明,高岭石与金发生化学吸附作用,氢原子为高岭石的活性位点,C6H5O7^3-会优先吸附于高岭石(001)表面,加入助浸剂可降低高岭石与金的吸附强度,提高金的浸出率。     

Catalytically active gold sites: nanoparticles, borderline sites, clusters, cations, anions? FTIR spectra analysis of12CO and of12CO-13CO isotopic mixtures

The analysis of FTIR absorption spectra of CO and of¹²CO-¹³CO isotopic mixtures is reported for gold catalysts supported on a number of oxides. Relationships between the nanostructure and the CO adsorbing properties of the different gold catalysts are discussed. In particular, on titania supported gold, where particles of metallic nature are present, two kinds of surface sites do adsorb CO, the 6-coordinated corners and the 7- coordinated edges, while the terrace sites, 8 coordinated, are not able to adsorb even at 90 K. Moreover, the adsorbing sites are not isolated, but mutually interacting. On zirconia supported gold, the adsorbing sites, mutually interacting, are exposed at the surface of non metallic gold nanoclusters. Almost isolated and negatively charged gold adsorbing nanoclusters have been highlighted on the sample supported on reduced ceria, and, finally, isolated cationic sites on oxidized gold supported on a mixed ceria-titania oxide have been detected.