难处理金精矿含元素硫的酸浸渣加石灰氧压浸金

实验研究了难处理金精矿含元素硫的酸浸渣加石灰氧压浸金过程，论述了石灰加入量、浸出时间和浸出温度对浸金的影响规律，发现最佳石灰加入量应使浸渣中元素硫与OH的摩尔比为0.8~1.1，在85°C和0.1~0.3 MPa氧压下浸出3~5 h，金的浸出率可达90%，此时终pH在5~8范围内. 根据实验结果分析，推断浸出过程中元素硫在一定pH值范围内氧化生成的S2O32–是主要的浸金剂.     

The Adsorption of Gold,Palladium, and Platinum from Acidic Chloride Solutions on Mesoporous Carbons

Studies on the adsorption characteristics of gold, palladium, and platinum on mesoporous carbon (CMK-3) and sulfur-impregnated mesoporous carbon (CMK-3/S) evaluated the benefits/drawbacks of the presence of a layer of elemental sulfur inside mesoporous carbon structures. Adsorption isotherms collected for Au(III), Pd(II), and Pt(IV) on those materials suggest that sulfur does enhance the adsorption of those metal ions in mildly acidic environment (pH 3). The isotherms collected in 1 M HCl show that the benefit of sulfur disappears due to the competing influence of large concentration of chloride ions on the ion-exchanging mechanism of metal ions sorption on mesoporous carbon surfaces. The collected acid dependencies illustrate similar adsorption characteristics for CMK-3 and CMK-3/S in 1-5 M HCl concentration range. Sorption of metal ions from diluted aqueous acidic mixtures of actual leached electronic waste demonstrated the feasibility of recovery of gold from such liquors.     

Recovery of Gold from Hydrochloric Acid by means of Selective Coagulation with Persimmon Extract

Abstract

Gold was selectively precipitated with solution of persimmon extract which contains persimmon tannin, a kind of polyphenol. Quantitative recovery of gold was achieved in the concentration range of hydrochloric lower than 0.5 mol · dm^?3. X-ray diffraction analysis and a digital micrograph of the filtered cake indicated the formation of gold particle during recovery process. High selectivity of persimmon extract is ascribed to the reduction of Au(III) to elemental form.     

蛋氨酸与化学增感剂的相互作用机理

运用X射线光电子能谱（XPS）的ESCA扫描技术研究了蛋氨酸与不同化学增感剂相互作用及其中的硫、金、碳和氧等元素的化学形态和相对含量的变化规律。发现蛋氨酸与不同的化学增感剂的反应机理是不尽相同的,蛋氨酸与S增感剂不会发生任何化学反应,它们可以稳定地共存于同一体系之中;蛋氨酸可以将全部Au^3 增感剂还原为Au,其自身部分被氧化为蛋氨酸亚砜,并且在其脱质子的羟基部位与Au形成Au－O－C结构的金属配合物,向蛋氨酸体系中加入S＋Au增感剂后,体系中的氧化还原反应发生在外加的Au^3 和S2O3^2-之间,此时蛋氨酸的作用是将被S增感剂还原的Au络合,亦形成Au－O－C结构的配合物。     

锌湿法冶炼硫渣中硫磺化学富集工艺

对锌精矿富氧直浸产生的硫渣中硫磺进行化学富集. 基于硫渣物理化学性质分析,得出影响硫磺品位的主要杂质是SiO2和FeS2,并进一步提出了HF溶液脱除SiO2, Fe2(SO4)3酸性溶液分解FeS2以提高硫磺品位的技术思路,研究了相应的技术条件. SiO2脱除的较佳条件为：HF溶液浓度20%(w)、温度55℃、时间3 h、液固比4 mL/g;FeS2分解的较佳条件为：Fe3+离子浓度1.5 mol/L、H2SO4浓度1.5 mol/L、Fe2(SO4)3用量为理论量2倍、温度98℃、时间5 h. 硫渣经两步处理后,硫磺含量可从70%提高至86.2%. 该工艺具有一定的工业应用价值.     

Reaction of Au(111) with Sulfur and Oxygen: Scanning Tunneling Microscopic Study

The reaction of sulfur and oxygen with the gold surface is important in many technological applications, including heterogeneous catalysis, corrosion, and chemical sensors. We have studied reactions on Au(111) using scanning tunneling microscopy (STM) in order to better understand the surface structure and the origin of gold’s catalytic activity. We find that the Au(111) surface dynamically restructures during deposition of sulfur and oxygen and that these changes in structure promote the reactivity of Au with respect to SO₂ and O₂ dissociation. Specifically, the Au(111) herringbone reconstruction lifts when either S or O is deposited on the surface. We attribute this structural change to the reduction of tensile surface stress via charge redistribution by these electronegative adsorbates. This lifting of the reconstruction was accompanied by the release of gold atoms from the herringbone structure. At high coverage, clusters of gold sulfides or gold oxides form by abstraction of gold atoms from regular terrace sites of the surface. Concomitant with the restructuring is the release of gold atoms from the herringbone structure to produce a higher density of low-coordinated Au sites by forming serrated step edges or small gold islands. These undercoordinated Au atoms may play an essential role in the enhancement of catalytic activity of gold in reactions such as oxygen dissociation or SO₂ decomposition. Our results further elucidate the interaction between sulfur and oxygen and the Au(111) surface and indicate that the reactivity of Au nanoclusters on reducible metal oxides is probably related to the facile release of Au from the edges of these small islands. Our results provide insight into the sintering mechanism which leads to deactivation of Au nanoclusters and into the fundamental limitation in the edge definition in soft lithography using thiol-based self-assembled monolayers (SAMs) on Au. Furthermore, the enhanced reactivity of Au after release of undercoordinated atoms from the surface indicate a relatively insignificant role of an oxide support for high reactivity.     

Activated carbon sorbent with thioetheric sites—preparation and characterization

An activated carbon sorbent containing thioetheric sites (ACTS) was prepared by modification of the activated carbon with 2,2′-thiodiethanol. The specific surface area, pore volume, concentration of oxygen-containing groups and sulfur content of the sorbent were determined. The sorption behavior towards ions of some precious metals—Au(III), Pt(IV), Pd(II) and heavy metals—Ni(II), Zn(II), Fe(III), Cu(II), Pb(II), Cd(II) and Co(II) was studied. Selectivity towards gold, palladium and platinum in the pH range 1–9 was observed. The capacity for gold was 80 mg g⁻¹. The sorption of Au(III) at pH 1 is not affected by milligram amounts of Ni(II), Zn(II), Fe(III), Cu(II), Pb(II), Cd(II) and Co(II). The sorbed gold species is Au(0).     

Use of gold tracer in the study of atmospheric oxidation of sulfur dioxide

A technique using gold particles as a conserved tracer has been developed in an effort to determine experimentally the oxidation of sulfur dioxide in sour gas plant plumes. A helicopter was used for plume sampling at distances up to 4 km downwind of the stack. The concentration of sulfur dioxide gas in the plume sample was determined by the West-Gaeke method. Neutron activation analysis was used to determine the concentration of gold particles in the plume sample. Since gold particles do not react chemically with plume gases, any decrease in their concentration along the plume path was due to turbulent dispersion. This parameter allowed an accurate estimation to be made of the decrease in the sulfur dioxide concentration within the plume sample that had occured due to physical dilution alone. Any further decrease in concentration could therefore be attributed to loss by chemical reaction. The experimental results indicated that, within the range studied, there is no measurable oxidation of sulfur dioxide in sour gas plant plumes.     

Recovery of gold by electroless precipitation from acid solutions using polyaniline

The oxidation of the leucoemeraldine (LM) and emeraldine (EM) states of polyaniline (PAN) and the subsequent reprotonation and reduction of the nigraniline (NA) and pernigraniline (PNA) in acid gold solution were utilized for the spontaneous and sustained reduction of gold. The rate of Au reduction is strongly dependent on the intrinsic oxidation state of the polymer and the polymer surface area. The rate also increases with decreasing pH of the chloroauric solution to about pH ～ 1. X-ray photoelectron spectroscopic (XPS) results indicate that only elemental gold or Au(0) accumulates on the polymer surface. The N1s core-level spectra of the protonated and base form of EM films after Au reduction confirm that the intrinsic structure of the polymer remains intact. The process, however, is limited by the decreasing effective surface area of the polymer due to Au deposition. The results indicate that an LM film accumulated up to five times its own weight of Au (Au/monomer mole ratio > 2) before the recovery rate was significantly retarded.     

栲胶脱硫过程中单质硫生成机理

采用循环伏安法研究了栲胶脱硫过程中HS-和V5＋之间的氧化还原反应。实验结果表明：在栲胶脱硫过程中,HS-和V5＋之间的反应有多硫离子Sx2-生成,多硫离子是反应过程中的活性中间产物,其进一步转化可生成单质硫S8。随着反应物V5＋浓度的增加,单质硫的生成速率增加。最后,提出了一种硫氢根HS-和V5＋反应生成单质硫S8的自由基机理。     

The effects of different manufacturing techniques on the availability of sulfate to pasture from mixtures of elemental sulfur with either triple superphosphate or partially acidulated reactive phosphate rock

Six different preparations of elemental sulfur incorporated into triple superphosphate and a single mixture of elemental sulfur with partially acidulated reactive phosphate rock were evaluated for the rate of release of sulfatesulfur to pasture at two sites.The method of preparing the mixtures affected the size of sulfur particles released on dispersion of fertilizer granules. The rates of release of sulfate from oxidation of the elemental sulfur was controlled by the fineness of the particles of elemental sulfur. For rapid release of sulfate by oxidation a mixture prepared by sintering elemental sulfur with mature triple superphosphate was the most effective. It contained sulfur particles of diameter less than 75 m. The mixtures which comprised synthetic blends of elemental sulfur of particle size less than 150 m or 150–250 m, each with mature triple superphosphate, released sulfate at a progressively slower rate than that with particles less than 75 m. However, both proved effective sulfur fertilizers releasing sulfate over a 1–2 year period. In contrast, mixtures prepared by adding molten elemental sulfur during the process of manufacturing triple superphosphate resulted in a coarser distribution of sulfur particles and a slow release of sulfate to plants.The incorporation of sulfur into a mixture with partially acidulated reactive phosphate rock was made via the dispersion of molten sulfur into phosphoric acid which was then used to partially acidulate phosphate rock. The resultant sulfur particles ranged from finely divided (e.g. 38% < 150 m) to moderately fine (81% < 500 m), and the release of sulfate was predictable based on the particle size distribution.Differences between the two experimental sites in uptake of plant sulphate reflected the different pastures grown. At the cool temperate coastal site a ryegrass/clover pasture rapidly took up sulfate as it was released into the topsoil. Inland, in the summer-dry environment, the uptake of released sulfate by the deep-rooted lucerne pasture was delayed for 12–18 months, indicating that the sulfate uptake increased after the nutrient had leached beyond the surface soil layer.     

元素硫的歧化反应动力学研究

本文研究了在pH 6—10、温度130—170℃条件下元素硫在水溶液中的歧化反应,确定了反应式为4S+6OH~-→2S~(2-)+S_2O_3~(2-)+3H_2O.参考了伴有化学反应的相间传质模型,本文中导出伴有快速化学反应的相间传质模型,即-In(1-a)=k_tt.在pH6—7.5范围内进行动力学测定所得结果与该模型相符,且发现此歧化的化学反应速度与〔OH~-〕成正比,求得表观反应活化能为24.0千卡/克分子.同时,还研究了Cu~(2+)对元素硫在水溶液中歧化反应的影响.     

Factors Influencing The Adsorption Of Gold-Iodide Onto Activated Carbon

Abstract

Activated carbon has found increasing application during the past decade as an adsorbent for gold from cyanide leached pulps. As result of practical and theoretical advancements in recent years, the carbon-in-pulp (CIP) process has become the preferred method for gold extraction from cyanided slurries. Lately, environmental considerations have led to the investigation of alternative leaching processes. One group of lixiviants studied is the halogens, such as bromine, chlorine, and iodine. It is the aim of this paper to investigate the factors influencing the adsorption of gold from iodide solutions onto a coconut-shell-type activated carbon. Equilibrium loadings on the carbon indicated clearly that gold-iodide has a higher loading profile than has gold cyanide. The Freundlich isotherm fitted the equilibrium curve for gold-iodide adsorption on carbon. The experimental results indicated that the pH level, iodide, and dissolved oxygen concentration had little or no influence on the kinetic and equilibrium parameters in a film diffusion model. However, the initial gold, iodine, and tri-iodide concentrations altered both the rate and equilibrium of gold-iodide adsorption significantly. Scanning electron microscopy showed that elemental gold deposited on the carbon surface influences the high film transfer coefficients obtained for gold-iodide adsorption.     

钙基脱硫剂用于冶炼烟气脱硫的模拟与实验

提出了一种应用钙基脱硫剂脱除冶炼烟道气中高浓度SO₂并回收硫单质的方法。通过热力学模拟多种硫化物与SO₂之间的反应,筛选得出硫化钙（CaS）适合作为化学链脱硫技术的脱硫剂,它在400～650℃范围内可将SO₂还原为单质硫,生成的固相产物为CaSO₄而非CaO。通过固定床反应器内的脱硫实验,发现温度对脱硫率和硫单质回收率影响较大。在400～650℃范围内温度越高,脱硫率和硫单质回收率越大;当温度高于600℃时,脱硫率和硫单质回收率基本相等。提高空速,则会降低脱硫率和硫单质回收率,但两者的差值随空速增大逐渐减小。当烟气中SO₂浓度小于1%时,脱硫率维持在99.8%基本不变;SO₂浓度升至3.45%后,平均脱硫率急剧下降至92.1%;SO₂浓度越高,平均脱硫率越低。硫单质回收率随SO₂浓度增大存在一最佳范围。在脱硫反应后期,粒径较大的脱硫剂颗粒脱硫性能较低。SEM照片表明了脱硫剂颗粒随反应温度的升高团聚现象更为明显,XRD表征证明了反应中SO₂气体被还原为升华硫颗粒。     

用198Au示踪法研究季铵盐体系萃取金

The solvent extraction of KAu(CN)2 from alkaline solution by quaternary ammonium salts (trialkylmethylammonium chloride or cetyltrimethylammonium bromide) waw investigated by means of ^198Au radioactive tracer method. Various parameters,such as the gold (I) concentration in aqueous phase,the modiffer,emulsifiation at the interface of two phases, and phase ratio used in the extraction of gold (I) were studied. The results demonstrate that almost all gold (I) in the aqueous phase was practically extracted into the organic phase. The water content in the organic phase decreased significantly with increase of gold (I) concentration using long chain alcohol as modifier,in contrast with the system with tributyl phosphate (TBP) as modifier. Emulsification at the interface of two phases decreases with an increase of modifier concentration in the organic phase or with the addition of a small amount of lysozyme into the aqueous phase. The method with ^198Au tracer can be directly used to determine the Au(I) concentration both in aqueous and organic phases, which is especially suitable for the low concentration of Au(I).     

Effect of CaSO4 Pelletization Conditions on a Novel Process for Converting SO2 to Elemental Sulfur by Reaction Cycles Involving CaSO4/CaS – Part II: Reduction of SO2 with CaS

A new process for converting sulfur dioxide to elemental sulfur by a cyclic process involving calcium sulfide and calcium sulfate without generating secondary pollutants, developed at the University of Utah, was described in Part I of this series. In this process, sulfur dioxide is reacted with calcium sulfide to produce elemental sulfur and calcium sulfate; the latter is reduced by hydrogen to regenerate calcium sulfide. Here, in Part II, the effects of different pelletization conditions for the initial reactant calcium sulfate on the reactivity of CaS pellets produced from calcium sulfate pellets toward sulfur dioxide were studied. Experiments were performed to investigate the effects of temperature in the range 1023–1173 K, pellet size, cycle repetition, and water vapor or carbon dioxide content in the sulfur dioxide stream. The binder amount and the presence of nickel catalyst did not significantly affect the reaction rate.     

Structure and Composition of Au–Cu and Pd–Cu Bimetallic Catalysts Affecting Acetylene Reactivity

Au–Cu and Pd–Cu bimetallic model catalysts were prepared on native SiO₂/Si(100) substrate under ultra high vacuum (UHV) by employing buffer layer assisted growth procedure with amorphous solid water as the buffer material. The effect of the bimetallic nanoclusters (NCs) surface composition and morphology on their chemical reactivity has been studied with acetylene decomposition and conversion to ethylene and benzene as the chemical probe. It was found that among the Au–Cu NCs compositions, Au_0.5Cu₃ NCs revealed outstanding catalytic selectivity towards ethylene formation. These NCs were further characterized by employing TEM, XPS and HAADF-STEM coupled EDX analysis. With CO molecule as a probe, CO temperature programmed desorption has been used to investigate the distribution of gold on the top-most surface of the supported clusters. Surface segregation at high relative elemental fraction of gold leads to a decreased activity of the Au–Cu NCs towards ethylene formation. In contrast to the Au–Cu NCs, the Pd–Cu bimetallic system reveals reduced sensitivity to the relative elemental composition with respect to selectivity of the acetylene transformation toward ethylene formation. On the other hand, remarkable activity towards benzene formation has been observed at elemental composition of Cu₃Pd, at comparable rates to those for ethylene formation on clean Pd NCs.     

Preparation and surface-enhanced Raman performance of electrospun poly(vinyl alcohol)/ high-concentration-gold nanofibers

A facile approach to prepare electrospun poly(vinly alcohol) (PVA) nanofibers with high concentration of gold nanoparticles (Au NPs) on the fibers, had been developed. These PVA/Au nanofibers could be used as flexible surface-enhanced Raman scattering (SERS) substrates. Relatively high concentration of PVA aqueous solution (10 wt %) was used as the stabilizing agent for gold salt precursor, as well as the starting solution for electrospinning. This method was demonstrated to be effective to prepare high-concentration-gold nanoparticles without aggregation and precipitation by reducing high concentration of gold salt in the presence of PVA aqueous solution. SEM and TEM images showed that both the amount and the size of Au NPs which embedded in PVA nanofibers, increased with increasing the gold salt content, while the gap between the adjacent NPs decreased. Raman spectra showed an apparent enhancement in the signal of 4-mercaptobenzoic acid (4-MBA) molecules pre-absorbed from its ethanol solution onto the PVA/Au nanofibers. The high SERS activity to 4-MBA in solution with a relatively low concentration (10⁻⁶ M), could be mainly attributed to the reduced gap of Au NPs.     

微生物燃料电池处理模拟含硫废水的初步研究

采用微生物燃料电池(Microbial fuel cell,MFC)处理模拟含硫废水,硫化物能全部被氧化戍单质硫或硫酸盐.MFC的最大功率密度达到(20±1)W·m~(-3),库仑效率为(20±2)%.阳极中有机质的氧化与硫化物的氧化存在一定竞争关系,进水碳硫比是影响单质硫生成率的关键因素.试验中,进水碳硫质量比大于1250:1,S~(2-)质量浓度为50mg·L~(-1)时,硫化物氧化成单质硫的转化率可达61%～77%.此外,阳极表面单质硫的积累很可能是造成MFC电极失效或运行不稳定的原因之一.     

Ligand‐Free Buchwald–Hartwig Aromatic Aminations of Aryl Halides Catalyzed by Low‐Leaching and Highly Recyclable Sulfur‐Modified Gold‐Supported Palladium Material

A stable heterogeneous catalyst precursor, sulfur‐modified gold‐supported palladium material (SAPd), has proved to be an excellent source of leached, ligand‐free, Pd for the amination of aryl bromides and chlorides. The reaction‐enabling catalyst is provided in situ as leached Pd in low catalyst loading (0.21±0.02 mol%). This allows the precatalyst (SAPd) to be filtered off and used for a minimum of ten reaction cycles without loss of catalytic activity. SAPd released only trace amounts, less than 0.6 ppm, of highly active Pd during the reaction without any aggregation.