Why is it so attractive? Well the reason is that gold is high value noble metal, and the high cost of mining for gold gives us enough reason to recycle this noble metal.
While recycling of gold jewellery is high dependent upon market conditions and prices for the metal, the electronics industry is a steady source of recyclable gold-containing waste. We all need to know that production process for making electronics needs gold without asking for price.
Computer circuit boards, cell phone boards, contact pins, integrated circuits and various other electronic components all contain minute amounts of gold that, if effectively collected, can be processed to extract gold as well as other precious and base metals. Gold is gold, whoever use it and it has value depended on global market status.
Once electronic or other gold-containing scrap material is collected, it must be pre-processed in order to remove unwanted parts that are often made with plastic and composite materials, which could affect the chemical recycling process.
The next step is to identify and sort material depending on purity and the presence of certain impurities, particularly hazardous or regulated substances.
Proper identification of materials and recognition of composition is critical not only to ensuring that the recycling process is profitable, but also those hazardous materials such as cadmium or mercury are properly treated and disposed.
Gold contained in electronic waste is often categorized as:
Very high grade - gold content with a minimum of 400ppm
High grade - gold content with a minimum 200ppm
Medium grade - gold content with a minimum of 100ppm
Low grade - gold content with a minimum content of 50ppm
Very low grade - gold content with a maximum content of 50ppm
Methods of sorting include spectrometry analysis, sample taking and electrolysis.
Assays are produced that indicate the quantity and purity of gold as well as any other credits for precious metal like silver or platinum. The assay is used to settle accounts between suppliers and the recycling facility.
Depending on the form, grade and composition of the source material, gold can be recovered through various methods. These are expertise and you should leave them to the experts.
Just to mention each one, keep reading this article:
Burning with high heat can isolate gold from the other components. This method is very simple in that the gold can be collected while other un-wanted materials are burned off as fumes. However, the presence of toxic and heavy metals in many electronics can make this a dangerous method and, so, it is rarely used in commercial operations.
Cyanide leaching is one of the easiest, most cost effective and toxic methods for extracting gold. The process involves immersing the electronic devices in a solution containing cyanide. Cyanide is element which interacts with gold, forming gold ions, which can then be distilled into gold dust or gold powder. The powder can then be collected and melted into gold bullion at near 99 percent purity. This method is often employed in developing countries, as a cheap and quick way to extract valuable gold from electronic components. Health and environmental concerns spurred by the use of cyanide leaching in developing countries have resulted in the Basel Convention addressing the trans-border movement of electronic waste.
Aqua regia is a mixture of hydrochloric and nitric acids. These acids have the ability to dissolve gold. Nitric acid reacts with gold to oxidize and strip it from other metals like silver, copper, and nickel, allowing these to be collected for recycling. In order to stop the oxidizing process and precipitate the gold from the mixture, hydrochloric acid must be added. Now, the gold molecules can be collected and filtered. The recovered gold is washed with acetone and water before being cast as solid gold.
A more complicated method to recover gold involves reverse electroplating. This process involves creating an electrolytic cell in order to 'win' back gold via electrolysis, effectively reversing the process of electroplating the gold onto the electronic component.
