Additive Behavior in Copper Electrorefining

This paper reports on the mode of action of two different organic additives—gelatine and thiourea—during the electrorefining of copper from acid copper sulfate solutions. Gelatine increases the cathode current efficiency and produces smoother deposits up to a certain level of concentration, beyond which, however, these effects are diminished by the steric hinderance of bulky molecular entities adsorbed to the electrode surface. Thiourea decreases the cathode current efficiency when present at concentrations around 5 mg/1. Nonetheless, it improves deposit quality. In higher concentrations, thiourea increases the cathodic current efficiency but also promotes nodule formation and rough deposits. The degradation and/or hydrolysis of both additives and the various interactions with the electrode surface and with cupric ions in solution are also examined.     

Effects of cobalt, temperature and certain impurities upon cobalt electrowinning from sulfate solutions

The effects of cobalt concentration, temperature and the presence of zinc, copper and iron ions in the electrolyte on current efficiency and cathodic quality were investigated by cyclic voltammetry and galvanostatic methods during cobalt electrowinning. The results showed that high cathodic efficiency of cobalt deposition was obtained from solutions containing cobalt concentration in the range 30–60 g l^–1. Current efficiency increased from 94% to 97% with increase in cobalt concentration to 60 g l^–1 at 20 °C. It was also found that increase in temperature to 50 °C enhanced the cobalt deposition reaction, along with the rate of hydrogen evolution, resulting in little change in current efficiency. The presence of foreign cations in the electrolyte not only adversely affects current efficiency but also promotes cracking and peeling.     

Resource and power allocation for achieving rate fairness in D2D communications overlaying cellular networks

Wireless Networks - This paper presents a novel resource and power allocation scheme for device-to-device (D2D) communications overlaying cellular networks. The proposed scheme is implemented in...     

Removal of cadmium from simulated wastewaters by electrodeposition on spiral wound steel electrode

The electrowinning of cadmium from dilute sulphate solutions was studied by voltammetry and chronopotentiometry in a conventional three-electrode cell using a rotating glassy carbon and spiral wound steel electrodes. The polarization curves provided valuable information about the electrolytic cadmium reduction as well as of the respective current densities. The results of the recovery of cadmium by using a flow-by cell with spiral wound steel high-surface-area cathode were also described. The cell was operated in a continuous recirculated batch process. This reaction system was found to be extremely effective in reducing metal concentrations to the permissible range. Cadmium recovery of 30% at 250 μA cm⁻² increases sharply to 99.95% at 400 μA cm⁻².     

Chitosan/MCM‐41 nanocomposites for efficient beryllium separation

Chitosan nanoparticles (Ch NPs) with individual particles 10–30 nm in size and average aggregate sizes of 240 nm were prepared via ionic gelation. Ordered mesoporous Mobil Composition of Matter No. 41 (MCM‐41) with a surface area of 1590 m²/g was prepared via a sol–gel method. The nanocomposites were prepared via the in situ dispersion of MCM‐41 in chitosan followed by ionic gelation with a multivalent anion to produce MCM‐41‐impregnated Ch NPs or via the mixture of dispersed MCM‐41 with preprepared Ch NPs to produce Ch NPs supported on MCM‐41. The beryllium‐uptake efficiency was studied with different pH values, contact times, and initial Be(II) concentrations. The maximum achieved uptake efficiencies of the nanocomposites (95% and 96%) were superior to that of MCM‐41 (38%) and higher than that of Ch NPs (90%). The nanocomposite formulas facilitated post‐treatment separation while maintaining a high beryllium‐uptake efficiency. The Be(II)‐uptake process for all of the materials followed the pseudo‐second‐order kinetic model and both the Langmuir and Freundlich isotherms. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46040.