高银金泥精炼工艺研究

针对高银金泥性质,采用有机酸除杂—氯化溶金—金分步还原、氯化溶金渣中氯化银铁粉置换—熔铸—电解精炼工艺分步精炼提纯金、银,并考察了酸浓度、反应温度、除杂时间等因素对金泥除杂率及金、银回收效果的影响。结果表明:在获得的最佳除杂工艺条件下,有机酸除杂效果较好,金泥除杂率约为8.2%;除杂后的富金银渣采用氯化溶金工艺处理时,金直收率为93.56%;该工艺可获得满足国标要求的金、银产品,且金、银回收率较高。

Thermodynamic equilibrium of bismuth hydrometallurgyin chloride and nitrate solutions

Simultaneous equilibrium was applied to the thermodynamic analysis and calculation of Bi（Ⅲ）-X（Cl-, NO-3）-H2O systems, based on which the diagrams of the logarithm of equilibrium concentration of Bi（Ⅲ） of series precipitation vs pH value of these two systems at 25 ℃ were obtained, and the pH ranges of the stable zones of various precipitations were analyzed and determined. In Bi（Ⅲ）-Cl--H2O system, the variations of c0(Bi3+) and （c0（Cl-）） have little effect on the equilibria of Bi（OH）3-solution and BiOOH-solution, but has great influence on the （equilibrium） of BiOCl-solution. However, in Bi（Ⅲ）-NO-3-H2O system, the variations of c0(Bi3+) and c0（NO-3） have little effect on equilibria of Bi（OH）3-solution, BiOOH-solution and Bi2O3-solution. When pH value is high, Bi2O3 is the thermodynamic stable phase, its stable zone is the widest, almost including the stable zones of BiOCl or （BiONO3,） （Bi（OH）3） and BiOOH. Bi（OH）3 cannot be obtained from Bi（Ⅲ）-Cl--H2O system, even strong alkaline media. Bi2O3 can be obtained from the solution directly, and highly pure BiOCl or BiONO3 can also be obtained through strictly controlling pH value.

Corrosion Resistance ofAA6063-Type AI-Mg-Si Alloy by Silicon Carbide in Sodium Chloride Solution for Marine Application

The present work focused on corrosion inhibition of AA6063 type Al-Mg-Si alloy in sodium chloride （NaCI） solution with a silicon carbide inhibitor, using the potentiodynamic electrochemical method. The aluminium alloy surface morphology was examined, in the as-received and as-corroded in the un-inhibited state, with scanning electron microscopy equipped with energy dispersive spectroscopy （SEM-EDS）. The results obtained via linear polarization indicated a high corrosion potential for the unprotected as-received alloy. Equally, inhibition efficiency as high as 98.82% at 10.0 g/v silicon carbide addition was obtained with increased polarization resistance fRy）, while the current density reduced significantly for inhibited samples compared to the un-inhibited aluminium alloy. The adsorption mechanism of the inhibitor aluminium alloy follows the Langmuir adsorption isotherm. This shows that the corrosion rate of aluminium alloy with silicon carbide in NaCI environment decreased significantly with addition of the inhibitor.

DFT Study of the Interaction of Cu（II）, Zn（II）, Sn（II） with Carbohydrates in Aqueous Solution

In the present work, authors studied the interaction between carbohydrates as ligands such as L1： fructose, L2： glucose and L3： sucrose with metal（II） halides such as CuCl2, ZnCl2, SnCl2. Also authors compare the stability of the metal-ligand bond strength. DFT （density functional theory） was utilized using the B3LYP functional and the 6-31G（d） basis set. This level of calculation was used for optimization of geometry of ligands and exploring electronic properties such as ionization potential （I）, electron affinity （A）, chemical potential （μ）, hardness （η）, band gap （HOMO （highest occupied molecular orbital）-LUMO （lowest unoccupied molecular orbital））. The local reactivity was analyzed by the fukui function indices and the indices local of nucleophilicity in order to predict the sites of attack of carbohydrates. In addition, the strength of interaction has been evaluated by energy lowering and charge transfer using DFT at the B3LYP level employing the basis set Lan2DZ. As a result, the sequence of high stability of metal-ligand bond for ligands is in the following order; sucrose 〉 glucose 〉 fructose. Furthermore, the sequence of high stability for metal halides is in the following order, CuCl2 〉 SnCl2 〉 ZnCl2. We advise person who carries a dental amalgam do not exceed the consommation of monosaccharides, because their complexes are not sufficiently stable and hence these ions are not ejected easily outside the human body.

Chloride Stress Corrosion Cracking of 316 Austenitic Stainless Steel

SCC （stress corrosion cracking） is environmentally well-known as a failure caused by exposure to a corroding while under a sustained tensile stress. SCC is most often rapid, unpredictable. Failure can occur in a short time as a few hours or take years and decades to happen. Most alloys are liable to SCC in one or more environments requiring careful consideration of alloy type in component design. In aqueous chloride environments austenitic stainless steels and many nickel based alloys are common to perform poorly. SCC of austenitic stainless steels of types 316 was investigated as a function of applied stress at room temperature in sodium chloride solutions using a constant load method. The experiment uses a spring loaded fixture type and is based on ASTM G49 for experiment method, and E292 for geometry of notched specimen. The stress depends on fracture appearance and parameters of time to cracking, and cracking growth. The results explained in terms of comparison between the two concentrations of sodium chloride solutions.

A Highly Efficient and Selective Water-Soluble Bimetallic Catalyst for Hydrogenation of Chloronitrobenzene to Chloroaniline

Selective hydrogenation of chloronitrobenzene(CNB) to chloroaniline(CAN) catalyzed by water-soluble Ru/Pt bimetallic catalyst in an aqueous-organic biphasic system was studied. It was found that the catalytic activity increased obviously due to the addition of platinum. Ru/Pt bimetallic catalysts exhibited a strong synergistic effect when the molar ratio of Pt was in the range of 5%—80%. Under the mild conditions including a temperature of 25 ℃, a hydrogen pressure of 1.0 MPa and a Pt molar ratio of 20%, the conversion of p-chloronitrobenzene(p-CNB) reached 99.9%, with the selectivity to p-chloroaniline(p-CAN) equating to 99.4%. The Ru/Pt catalyst also showed high activity and selectivity for the hydrogenation of other chloro- and dichloro-nitrobenzenes with different substituted positions. In addition, the catalyst can be recycled five times without significant loss of activity.