In their molten state, copper ions are missing one electron, giving them a positive charge, while sulfur ions are carrying two extra electrons, giving them a negative charge.
The desired reaction in an electrolysis cell is to form elemental atoms, by adding electrons to metals such as copper, and taking away electrons from sulfur. This happens when extra electrons are introduced to the system by the applied voltage.
The metal ions are reacting at the cathode, a negatively charged electrode, where they gain electrons in a process called reduction; meanwhile, the negatively charged sulfur ions are reacting at the anode, a positively charged electrode, where they give up electrons in a process called oxidation.
In a cell that used only copper sulfide, for example, because of its high electronic conductivity, the extra electrons would simply flow through the electrolyte without interacting with the individual ions of copper and sulfur at the electrodes and no separation would occur. The Allanore Group researchers successfully identified other sulfide compounds that, when added to copper sulfide, change the behavior of the melt so that the ions, rather than electrons, become the primary charge carriers through the system and thus enable the desired chemical reactions.
Technically speaking, the additives raise the bandgap of the copper sulfide so it is no longer electronically conductive, Chmielowiec explains. The fraction of the electrons engaging in the oxidation and reduction reactions, measured as a percentage of the total current, that is the total electron flow in the cell, is called its faradaic efficiency. The new work doubles the efficiency for electrolytic extraction of copper reported in the first paper, which was 28 percent with an electrolyte where only barium sulfide added to the copper sulfide, to 59 percent in the second paper with both lanthanum sulfide and barium sulfide added to the copper sulfide.
We were able to make rhenium, and we were able to make molybdenum. The Allanore laboratory also used molten electrolysis to produce zinc, tin and silver, but lead, nickel and other metals are possible, he suggests. The amount of energy required to run the separation process in an electrolysis cell is proportional to the faradaic efficiency and the cell voltage.
For water, which was one of the first compounds to be separated by electrolysis, the minimum cell voltage, or decomposition energy, is 1. Sahu and Chmielowiec identified the cell voltages in their cell as 0. At the cell operating temperature and at an applied potential of 0. Separate experiments also proved the ability to selectively reduce rhenium or molybdenum without reducing copper, based on their differing decomposition energies.
Important strategic and commodity metals including, copper, zinc, lead, rhenium, and molybdenum are typically found in sulfide ores and less commonly in oxide-based ores, as is the case for aluminum.
A lot of engineering has gone into that for the aluminum industry, so we would hopefully piggyback off of that. Sahu and Chmielowiec conducted their experiments at 1, C, about degrees Celsius above the melting point of copper. It is the temperature commonly used in industry for copper extraction. To improve their cell efficiency, Sahu says, they may need to modify the cell design to recover a larger amount of liquid copper.
The electrolyte can also be further tuned, adding sulfides other than barium sulfide and lanthanum sulfide. That work continues. It can be used on ore with as little as 0.
Another important source of copper is recycled scrap, described as secondary copper production. To read more about copper recycling, click here. An ore is a rock containing enough valuable mineral to make it worth extracting. In the case of copper, it is worth extracting when there is about 2 kg of copper per 1, kg of ore 0. Copper minerals are found in over one hundred varieties, although only a few have been worked for copper on a large scale.
The most abundant ores are chalcopyrite and bornite, which contain both copper and iron sulphides. By continuing to use the site, you agree to the use of cookies. Find out more by following this link.
Copper and Copper Alloys Processes. Processes: copper mining and production Copper is found in natural ore deposits around the world. Copper mining The following gives an overview of how copper is extracted from its ore and converted into pure metal. Mining The ore is removed from the ground in either open pit or underground mines.
The ore An ore is a rock that contains enough metal to make it worthwhile extracting. Grinding The ore is crushed, then ground into powder. Concentrating The ore is enriched using a process called froth flotation. The leaching reagent dilute sulfuric acid is sprayed through sprinklers on top of the heap pile and allowed to trickle down through the heap, where it dissolves the copper from the ore. The second step is solvent extraction , in which two immiscible un-mixing liquids are stirred and allowed to separate, causing the cooper to move from one liquid to the other.
The pregnant leach solution is mixed vigorously with a solvent. The copper migrates from the leach solution into the solvent.
The two liquids are then allowed to separate based on solubility, with copper remaining in solution in the solvent, and impurities remaining in the leach solution.
The leftover leach solution is then recycled, by adding additional acid and sending it back to the sprinklers in the heap leaching process. The last step is called electrowinning , a type of electrolysis. An electrical current passes through an inert anode positive electrode and through the copper solution from the previous step, which acts as an electrolyte. Positively-charged copper ions called cations come out of solution and are plated onto a cathode negative electrode as Sulfide ores are generally processed using pyrometallurgy , the extraction and purification of metals by processes involving the application of heat.
This process uses a series of physical steps and high temperatures to extract and purify copper from copper sulfide ores, in four basic steps: 1 froth flotation, 2 thickening, 3 smelting, and 4 electrolysis.
Following mining, transporting, and crushing to a consistent gravel or golf ball-size, the crushed ore is further processed at a mill using secondary crushers, and reduced to pebbles, and finally to fine sand. After the copper ore is crushed, liquid is added to make it a slurry. The slurry is placed in a tank and a process called froth floatation is used to separate the copper minerals from the gangue. Pipes are used to blow air into the bottom of the tank to create bubbles, which rise to the surface, taking the waterproof copper sulfide particles along.
The froth of copper-rich bubbles at the top of the tank is then skimmed off for further processing. The gangue sinks to the bottom of the tank to be removed or disposed of as mine tailings. The next stage after froth flotation is the thickening stage. The froth is poured into large tanks called thickeners.
0コメント