Most people think of nuggets and such, but the truth is that very little comes from nuggets – nearly all newly indeed gold comes from ores mined from the natural hard rocks that contain gold in tiny, even microscopic particles. Various separation and refinement processes are used to extract the gold for profitable use. Some of the main processes include: Froth Floatation/ Separation floatation Filtration Precipitation reaction Smelting Froth Floatation / separation floatation – Gold extraction 1 .
The Ore containing small particles of ore are transferred to a mill, where it is ground down to ultra-fine “sand-like” particles. 2. The ground particles are then mixed with a liquid mixture with frothing agents to induce separation of there constituents and the gold. The frothing agents include: a. Amyl alcohol b. Camphor c. Phenols d. Essential oils 3. A collection agent is then added to the frothing mixture. The collection agent bonds with the gold particles by forming an oily film that collects onto air bubbles for frothing.
This is known as “floatation”, as gold floats above the liquid 4. Organic chemicals added to the mixture. These chemicals prevent other contaminants adhering to the air bubbles. Carbon is often used which bonds to the contaminants leaving gold to bond to the air bubbles. 5. Liquid solution is aerated then froth is separated from the water bath. The gold concentrate floats on top but in a different cell for easy collection. Water waste is collected from the bottom of the cell and taken to a tailing site 6. Cyanide is added to the gold to remove impurities (sulfides) 7.
The gold concentrate is then sent for gold refinement so it can meet the official standard Of 99. 9% purity before being used for commercial use precipitation reaction and federation -? Gold Refinement There are actually a few different methods of refining gold. Depending upon the quantity of gold you are working with and the desired level of purity, the woo most common methods for refining gold are the use of high temperature flame and the use of chemicals to refine the gold. 1. Unrefined gold is placed in a heavy-gauge plastic buckets or Pyrex Vision Ware pots 2.
Nitric acid is added to the gold and allowed to react for 30 minutes. 30 millimeters of Nitric acid is used for every ounce Of gold in the container 3. Hydrochloric acid is added to the mixture to assist in the dissolution of the gold. 120 millimeters of hydrochloric acid is required for every 1 gram of gold 4. The mixture is filtered and poured out into another large container. The mixture should eve and emerald green color. 5. A precipitant is added to the mixture while it is boiling to induce the separation of gold into a solid. Lbs of a urea and distilled water is added to the mixture which neutralizes the nitric acid but not the hydrochloric acid in the solution 6. The “gold mud” sediment at the bottom of the mixture is separated from the remaining acid and is rinsed multiple times with distilled water and aqua ammonia to clean any other contaminants 7. The “gold mud” is gradually heated on a hot plate until it turns into powder-like consistency. 8. The gold powder is placed into a rapport crucible and smelted at extremely high temperatures, then poured into a mold to be shaped.
Waste from extraction and refinement process Overburden: Is the term given to describe the soil and rock which is displaced in order to access the ore deposits. The overburden during gold extraction is normally piled at certain sites in the mine where it will not impede expansion, due to the fact it is often expensive to relocate it to a different site and dispose of it. Overburden has a low environmental impact and can often be used for mine closure after mining is finished. Additionally overburden is moieties used and sold for landscape contouring.
Tailings: Is the term given for the finely ground rock, mineral waste and chemical waste from processing. During gold separation and refinement nitric acid, hydrochloric acid and large amounts of cyanide are used, these products are deposited into tailing ponds in the form of waste sludge. Offshore tailing used to be extremely common before the detrimental effect on the environment where realized. Due to inefficiencies in the extraction process, large volumes of sulfides often end up going into the tailings. Over time, the sulfides start o oxidize as they’re exposed to wind, snow and temperature changes, creating sulfuric acid.
The sulfuric acid mixes with rainwater and eventually works its way out of the tailings and into waterways, where it can change the pH of the water and precipitate harmful heavy metals. Enclosed dams are now used to hold tailings although it is considerably more expensive. Slag’s: Is the term given for the non-metallic by products from smelting. Slag’s have a very low impact on the environment and often have many other uses, increasingly being used for concrete and road construction. Conclusion In conclusion gold is an extremely precious and versatile element held in high demand in society.