Effect of Stabilizer on Gold Leaching with Thiourea in Alkaline Solutions

The present work investigated the comparison of the effects of Na2SO3 and Na2SiO3 on thiourea stabilization, and a systematic study was undertaken to establish the effects of these stabilizers on the stability of alkaline thiourea, both qualitatively and quantitatively. The effects of these stabilizers on the activation energy of alkaline thiourea gold leaching was also studied. The results showed that sodium silicate was more suitable as a stabilizer in this system than sodium sulfite because the peak current of gold dissolution with sodium sulfite was higher than that with sodium silicate, but the inhibition of thiourea decomposition by the former was less obvious than that of sodium silicate in the cyclic voltammetry curve. The quartz crystal microbalance results showed that the quality decreased to about 100 ng cm2 in the presence of a stabilizer, while it increased to 300 ng cm2 in the absence of the stabilizer. It is inferred that gold can be dissolved by alkaline thiourea in the presence of a stabilizer, while it cannot without a stabilizer because of the decomposition of thiourea. This assumption was confirmed by atomic force microscopy measurements. The surface activation energy of Au dissolution decreased from 183.76 to 98.07 kJ/moL with the addition of sodium silicate, indicating that Au dissolution was promoted with the chemical.

Study on Electrochemical Stripping Method of Graphene Electrode and Its Capacitive Properties

Graphene has excellent properties, such as excellent conductivity, more pores, stable chemical and structural properties, high specific surface area, so it is usually used in the battery fields. In order to further explore the capacitive properties of graphene, this experiment used electrochemical stripping method, the electrochemical electrode was characterized by constant potential treatment methods, cyclic voltammetry curve, and constant current charging–discharging curve. The capacitive performance of modified graphene at different potentials was compared. If a constant potential peeling treatment is performed, the interlayer spacing of graphene increases, and this time, the specific surface area is enlarged, and the electrical properties of the graphene electrode material are correspondingly improved. Cyclic voltammetry curve results show that the graphene electrode exhibits better capacitance performance after being treated with a constant potential in neutral electrolyte. When treating with 3.1 V constant potential and voltage range of -1.1 V–1.1 V, capacitance can reach 327.273 F. The chronopotentiometry curve results show that 3.1 V graphene electrode mass ratio capacitance can reach 218.182 F/g under voltage range of -0.3 V–0.3 V, meeting the energy storage requirements of the battery industry, and it is expected to become an ideal electrode material in the field of supercapacitors.

Effect of a Small Amount of Iron Impurity in Sphalerite on Xanthate Adsorption and Flotation Behavior

Through industrial testing at the Huize lead-zinc mine, it was found that the floatability of sphalerite varied greatly with the iron impurity content. Three kinds of Huize sphalerites with iron contents of 2.30 wt.%, 3.20 wt.% and 4.66 wt.%, were used to study the influence of small amounts of iron impurity in the sphalerite on xanthate adsorption and flotation behavior. The flotation experiments showed that the flotation recovery increased with the increase in iron impurity content. Fourier Transform infrared spectroscopy (FTIR) and Ultraviolet–visible (UV-VIS) spectra showed that the adsorbed products of xanthate on the surface of three kinds of sphalerite were metal xanthate. The adsorption capacity measurements showed that the saturation absorption of xanthate on sphalerite increased with the increase in iron impurity content. The cyclic voltammetry curve and Tafel curve showed that with the increase in iron impurity content, sphalerite was more easily oxidized and the adsorption rate of xanthate on the surface of sphalerite increased obviously. To summarize, a small amount of iron impurity was beneficial to the recovery of sphalerite.

A Novel Electrochemical Method for Protionamide Determination Based on Its Interaction with Alizarin Red S

The interaction of protionamide with alizarin red S (ARS) and its analytical application were carefully investigated in this contribution. The interaction conditions were carefully studied and optimized by cyclic voltammetry. Under the optimum conditions, the cyclic voltammetry curve of ARS showed an oxidation peak with the peak potential of 0.57 V. After the addition of protionamide to the ARS solution, the peak potential was negatively moved, and meanwhile the oxidation peak current decreased apparently to the concentration of protionamide and then a new method for the protionamide determination was established. The linear equation between the decreasing current (Δip) and protionamide concentration was got as Δip (μA) = 0.01514C(mg/L) −0.01553 (n=9; r=0.991)with the linear range of 10.0~50.0 mg/L, and the detection limit (3σ) was got as 8.25 μg/mL. The effects of coexisting substances on the determination were carefully investigated and the protionamide artificial and tablet samples were detected with satisfactory results.

Study on the Cyclic Voltammetry Curve of Electrode in the Electrolytic Process of Seawater Pretreatment

The performance of the electrode is the core technology of the electrolytic process of seawater pretreatment, and has the decisive influence on the systematic technological process and water quality. In the initial stage of electrolytic technology being applied in seawater pretreatment, soluble anodes, which use the aluminum, ferrum or other metal elements as the main ingredient, are chosen for most cases. And this method can effectively reduce the turbidity of raw seawater and sludge density index (SDI). While applying a variety of methods, the proportion of electrolytic aluminum, ferrum and other metal elements in the water can be effectively controlled. And this can increase the ratio of hydrolysate, but will also introduce the composition of soluble electrode into the seawater inevitably. This study uses electrodes which contain a variety of precious metal (such as Ti, Ru, and Ir) oxide in the seawater pretreatment process, which is different from traditional chlor-alkali industry.

Multi-Walled Carbon Nanotubes as Electrocatalyst Supports for H2O2 Reduction Reaction

This work studies the use of Multi-walled carbon nanotube (MWCNT) as catalyst supports for H2O2 electro-reduction in acid media. Using impregnation-chemical reduction method, we prepared Pt-Ag/CNTs, Pt-Co/CNTs, Pt-Ag/C and Pt-Co/C nanocatalysts. Four catalysts were analyzed by XRD and TEM. Their electrochemical performance was studied via cyclic voltammetry curve. The results show that: the nanoparticles have a better dispersion on CNTs substrate than on XC-72 carbon substrate. Comparing with Pt-Ag and Pt-Co on XC-72 carbon substrate, the H2O2 reduction reaction activation energy of catalysts on CNTs substrate is bigger, and the peak current densities of catalysts on CNTs substrate are larger than that on XC-72 carbon.

The Effect of Sintering Temperature on Microstructure and Electrocatalytic Capability of RuO2-IrO2-TiO2/Ti Anode

The anodes of RuO2-IrO2-TiO2/Ti were prepared by Pechini method. The surface morphology and electrocatalytic capability of anodes were studied by SEM, EDX, XRD, polarization curve, cyclic voltammetry curve and accelerated life test. It has been shown that the anodes have uniform surface composition, and the surface density of the anodes were increased as the sintering temperature increased, some active elements were crystallization grains at the surface of the anode when sintering temperature ≥500°C. The chlorine evolution capability of anode had a tendency to increase firstly then fall down afterwards as the sintering temperature increased. But the electrocatalytic capability of anodes showed an opposite tendency. The RuO2-IrO2-TiO2/Ti anode prepared at 500°C presents the longest service life.

The Effect of Acid Etching Process on Surface Morphology and Electrocatalytic Capability of RuO2-IrO2-TiO2/Ti Anode

Titanium substrate was etched by oxalic acid and hydrochloric acid respectively. Then the anodes of RuO2-IrO2-TiO2/Ti were prepared by Pechini method. The surface morphology of anodes was studied with SEM, EDX and XRD. The electrocatalytic capability of anodes was studied by polarization curve and cyclic voltammetry curve. The effect of Acid etching process on anode life was studied by accelerated life test. The results show that there was an obvious effect of acid etching on surface morphology of the anodes. The result indicates that the anode with hydrochloric acid etching have the better electrocatalytic capability and accelerated life.

Anodic Behavior of Copper in 1-Hydroxyethylene-1, 1-Diphosphonic Acid (HEDPA) Baths

The electrochemical behavior of anodic dissolution of copper electrode was investigated in non-cyanide alkaline electrolyte containing 1-hydroxyethylene-1, 1-diphosphonic acid (HEDPA) as a complexing agent. Electrochemical behavior of copper electrode was studied by cyclic voltammetry. X-ray photoelectron spectroscopy was used to study morphologies of copper electrode after dissolution under different potentials. The results showed that in cyclic voltammetry curve of the 1-hydroxyethylene-1,1-diphosphonic Acid(HEDPA) baths, the first peak of copper anode was diffusion-controlled, associated with the formation of Cu2O. The second oxidation peak came from generating CuO and the third peak was the formation of CuO/Cu(OH)2 compound.