Guo-qu Zheng

Electrodeposition and corrosion behavior of nanostructured Ni-TiN composite films

Abstract The Ni-TiN nanocomposite film was successfully electrodeposited on brass copper substrates. The microstructures of the Ni-TiN nanocomposite film were investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Its average grain size was analyzed through X-ray diffraction (XRD), and its anti-corrosion property was studied through potentiodynamic scanning curves and electrochemical impedance spectroscopy (EIS). The results show that the morphology of Ni-TiN composite film is sensitively dependent on the electroplating current density, TiN nanoparticle concentration, solution stirring speed, bath temperature and pH value of solution. The average grain size of the optimized nanocomposite film is about 50 nm. Meanwhile, the Ni-TiN nanocomposite films are much more resistant to corrosion than pure Ni coatings.

Preparation of pure SbCl3 from lead anode slime bearing high antimony and low silver

A novel treatment process of lead anode slime bearing high antimony and low silver was developed by a potential-controlled chloridization leaching and continuous distillation. The experimental results show a high Sb3+ concentration, 489.2 g/L, in the leaching solution for two-stage countercurrent leaching process, and the leaching rates of Sb, Cu, Bi more than 99% when the potential is controlled at 450 mV. When the leaching solution is distillated and concentrated at 120 °C, almost all the silicon compound is evaporated into the concentration distillate and exists as amorphous hydrated silica. By the continuous distillation, high pure SbCl3 could be prepared, and AsCl3 is enriched in the distillate while metals Bi, Cu are enriched in the continuous distillation residue. As a result, the recovery rate of Sb is more than 95%.

Thermodynamic analysis of separating lead and antimony in chloride system

In chloride system, thermodynamic analysis is a useful guide to separate lead and antimony as well as to understand the separation mechanism. An efficient and feasible way for separating lead and antimony was discussed. The relationships of [Pb(superscript 2+)][Cl(superscript -)]^2-lg[Cl](subscript T) and E-lg[Cl](subscript T) in Pb-Sb-Cl-H2O system were studied, and the solubilities of lead chloride at different antimony concentrations were calculated based on principle of simultaneous equilibrium. The results show that insoluble salt PbCl2 will only exist stably in a certain concentration range of chlorine ion. This concentration range of chlorine ion expands a little with increasing the concentration of antimony in the system while narrows as the system acidity increases. The solubility of Pb(superscript 2+) in solution decreases with increasing the concentration of antimony in the system, whereas increases with increasing the concentration of total chlorine. The concentration range of total chlorine causing lead solubility less than 0.005 mol/L increases monotonically.

Electrodeposition of As–Sb alloy from high arsenic-containing solutions

Abstract As–Sb alloy was electrodeposited from high arsenic-containing solutions. The influences of current density, Sb 3+ concentration, reaction temperature and HCl concentration on the electrolyte composition, cell voltage and current efficiency were investigated. The surface morphology, composition and structure of the deposits were analyzed by scanning electron microscopy (SEM), inductively coupled plasma mass spectrometry (ICP-MS) and X-ray diffraction (XRD), respectively. The results show that the prepared As–Sb alloy shows an amorphous structure under all conditions. Under the optimized condition, i.e., 10 g/L As 3+ , 2 g/L Sb 3+ , 4 mol/L HCl, current density of 4 mA/cm 2 and temperature of 20 °C, desired As–Sb alloy with a composition of 70.26% As and 29.74% Sb (mass fraction) is obtained. What is more, the current efficiency is as high as 94.74% and high arsenic removal rate is achieved under this condition.

Effective cementation and removal of arsenic with copper powder in a hydrochloric acid system

This work investigated the removal and cementation of arsenic from a hydrochloric acid system with copper powder. Thermodynamic analysis and cyclic voltammetry test were conducted to evaluate the feasibility of cementation. The effect of reaction temperature, mole ratio of Cu to As(III), stirring rate, reaction time and HCl concentration on the cementation efficiency of arsenic were investigated systematically. 94.75% of the arsenic could be removed under optimized conditions: mole ratio of Cu/As = 8 at 45 °C for 60 min. The structure and morphologies of the cement products were characterized by X-ray diffraction and scanning electron microscopy, respectively. The results show that the reaction temperature has little influence on the morphology of the cement products which consist of particles with various sizes, but has a great influence on the cementation efficiency. During the cementation process, the rate-controlling mechanisms are changed at different temperatures. It is diffusion controlled at the high temperature region (45–50 °C) with an activation energy of 26.7 kJ mol−1, while it is surface reaction controlled at the lower temperature region (30–45 °C) with an activation energy of 145.7 kJ mol−1. Ammonium citrate can efficiently inhibit the evolution of arsane, while has little influence on the cementation efficiency of arsenic.

Nucleation/growth mechanism of electrocrystallization for As–Sb alloy in hydrochloric acid system

Abstract The initial electrocrystallization of As–Sb alloy on glass carbon (GC) electrode in hydrochloric acid system was studied via cyclic voltammetry (CV) and chronoamperometry measurements. Current transients were presented in dimensionless formation, which showed that the initial nucleation/growth process of As–Sb alloy followed three-dimensional nucleation model with diffusion-controlled growth. Relevant nucleation parameters were calculated by analyzing related current transients. Particular attention was paid to the effect of Sb(III) concentration on the nucleation process during the co-electrodeposition. The quantitative results showed that Sb(III) played a positive effect on enhancing the nucleation rate of As–Sb alloy, leading to the evolution of alloy surface morphology from grain structure to compact layer structure.