A study of factors influencing the kinetics of copper cementation during atmospheric leaching of converter matte
The kinetics of copper cementation during atmosphere leaching of a Ni-Cu matte in CuSO4-H2SO4 solution was studied as a function of initial copper ion concentration, initial acid concentration, temperature, stirring rate, particle size distribution and pulp density. It was found that all these process variables influenced the rate of cementation. A two-stage rate of reaction was observed in most of the experiments, with the rate of cementation in the initial stage being slower than that of the subsequent second stage. The increased rate of cementation in the second stage was attributed to the enhancing effect of the surface deposit. The cementation process was found to take place by two different rate-controlling mechanisms. At a temperature range of 50i?½70i?½C, an activation energy of 74.6 kJ/mol was obtained, indicating a surface reaction controlled process. At higher temperatures (70i?½80i?½C) a lower value of activation energy was observed (18.2 kJ/mol), indicative of a process controlled by diffusion through surface layers. The structural characteristics of the cemented deposit could not be determined in the investigated system where the deposit was mixed with the leach solid residue.
Bioleaching of electronic waste using acidophilic sulfur oxidising bacteria
Abstract Bioleaching of copper-rich electronic waste material was carried out using mesophillic Acidithiobacillus thiooxidans . The leaching behaviour of copper was investigated using three methods: abiotic chemical leaching using inorganic sulphuric acid, indirect leaching using bacterially generated sulphuric acid and by direct leaching using the acidophilic bacteria. The yield of bacterially generated sulphuric acid used for both indirect and direct leaching was 14.9 g/dm 3 grown in a medium containing 25 g/dm 3 of elemental sulphur and basalt salts for 14 days at 30 °C. This acid was diluted to achieve various pHs for the leaching tests. The variables tested were solution pH, temperature, time, pulp density and copper concentration in the waste. The results indicated that copper dissolution is influenced by passivation and galvanic coupling, both of which reduced the Cu yield and resulted in slower leaching. Increasing the acid concentration, copper concentration in the waste, higher temperature and prolonged leaching favoured higher yields and higher copper selectivity. e-waste toxicity had little effect on direct bioleaching at the pulp density used (10 g/dm 3 ). However the growth medium containing partially oxidised sulphide compounds promoted copper surface passivation resulting in lower Cu recovery (60%) relative to abiotic leaching (98%).
Study on Electrical Explosion Mechanism and Ignition Characteristics of Copper and Aluminum Powder Under Ignition Solid Propellant
In order to study the characteristic of the electrical explosion of copper and aluminum powders, a multilayer generator was designed, an experimental system was set up, and the parameters of metal powder electrical explosion were measured and analyzed. The results show that the duration of the electrical explosion process increases significantly due to the addition of metal powder. The duration of aluminum powder electrical explosion jet flow is ~86.36 ms due to its self-sustained combustion, which releases a large amount of energy, and a small fraction of aluminum powder particles is not burned. The duration of copper powder electrical explosion jet flow is ~15.84 ms, and most of the copper powder particles are in the solid state. The current pause process is absent; instead, the first discharge process is connected to the second discharge process. The effect of copper powder on the first discharge process is greater than that of aluminum powder. Furthermore, the ignition ability of copper powder electrical explosion to solid propellant is stronger than that of aluminum powder in a closed bomb experiment. These results are indubitably meaningful for the application of metal powder electrical explosion and ignition of solid propellant in an electrothermal chemical gun.