As electronics turn out to be extra commonplace, the disposal of printed circuit boards (PCBs) poses environmental considerations. Conventional strategies of gold restoration from PCBs contain harsh chemical substances that may be dangerous to the atmosphere. Nevertheless, it’s attainable to extract gold from PCBs with out using dangerous chemical substances, making the method extra environmentally pleasant.
One such methodology includes using electrolysis. This course of includes submerging the PCB in an answer containing water and a small quantity of salt. A optimistic electrode is then linked to the gold-plated contacts on the PCB, whereas a detrimental electrode is linked to a bit of metallic. When an electrical present is handed by way of the answer, the gold ions within the plating are dissolved and migrate in direction of the detrimental electrode. The gold ions are then deposited on the detrimental electrode, forming a pure gold coating. This course of will be repeated a number of instances till all the gold has been faraway from the PCB.
One other methodology for eradicating gold from PCBs with out chemical substances includes using a gold stripping answer. This answer is usually composed of a mix of nitric acid and hydrochloric acid. The PCB is submerged within the answer, and the gold ions within the plating are dissolved. The gold ions can then be recovered from the answer by precipitation or electrolysis. This methodology is extra environment friendly than electrolysis, however additionally it is extra hazardous because of using robust acids.
Ultrasonic Cavitation for Gold Elimination
Ultrasonic cavitation is a non-chemical course of that makes use of high-frequency sound waves to separate gold from circuit boards. This system includes submerging the circuit boards in a liquid bathtub and exposing them to ultrasonic waves. The sound waves create cavitation bubbles, which quickly broaden and collapse. Because the bubbles collapse, they generate high-pressure shock waves that dislodge the gold from the circuit board.
Course of Parameters
The effectiveness of ultrasonic cavitation for gold removing will depend on a number of course of parameters, together with:
- Frequency: Greater frequencies (20-40 kHz) produce smaller bubbles and extra intense shock waves, leading to improved gold removing effectivity.
- Depth: The facility of the ultrasonic waves influences the dimensions and depth of the cavitation bubbles. Greater intensities result in extra vigorous cavitation and enhanced gold removing.
- Temperature: Elevated temperatures can improve the cavitation exercise and facilitate gold dissolution.
- Liquid Tub: The selection of liquid bathtub (e.g., water, solvents) can have an effect on the cavitation course of by altering the sound wave propagation and bubble formation.
Benefits
Ultrasonic cavitation affords a number of benefits over chemical strategies for gold removing:
- Non-chemical: Eliminates using hazardous chemical substances, lowering environmental considerations.
- Selective: Targets gold with out damaging different elements on the circuit board.
- Scalable: Can be utilized for processing giant volumes of circuit boards with excessive gold yields.
- Price-effective: In comparison with chemical strategies, ultrasonic cavitation generally is a extra cost-efficient answer in the long term.
Thermal Decomposition
Thermal decomposition includes heating the circuit board to extraordinarily excessive temperatures, usually above 1,000 levels Celsius. This course of causes the gold on the board to vaporize, separating it from the opposite elements. The gold vapor is then condensed and picked up.
Advantages: Thermal decomposition is a comparatively simple course of that may be carried out utilizing normal laboratory tools.
Drawbacks: The excessive temperatures concerned in thermal decomposition can injury different elements on the circuit board, making this methodology unsuitable for salvaging different supplies.
Vacuum Distillation
Vacuum distillation is a extra refined course of that includes putting the circuit board in a vacuum chamber and heating it to a decrease temperature than thermal decomposition, usually between 400 and 600 levels Celsius. The gold on the board vaporizes underneath vacuum and is collected in a condenser.
Advantages: Vacuum distillation is a gentler course of that doesn’t injury different elements on the circuit board, permitting for the restoration of a number of supplies.
Drawbacks: Vacuum distillation requires specialised tools and a extra complicated setup in comparison with thermal decomposition.
Comparability of Thermal Decomposition and Vacuum Distillation
| Methodology | Temperature | Execs | Cons |
|---|---|---|---|
| Thermal Decomposition | 1,000+ levels Celsius | Easy setup | Damages different elements |
| Vacuum Distillation | 400-600 levels Celsius | Light course of, recovers a number of supplies | Complicated setup, requires specialised tools |
Hydrometallurgical Processes
Hydrometallurgical processes make use of chemical reactions in aqueous options to extract gold from circuit boards.
Cyanidation
Cyanidation is essentially the most broadly used hydrometallurgical course of for gold extraction. It includes treating the circuit boards with an answer of sodium cyanide (NaCN) and oxygen:
4Au + 8NaCN + O2 + 2H2O → 4Na[Au(CN)2] + 4NaOH
The gold dissolves into the answer because the tetracyanoaurate (III) complicated [Au(CN)2]–, which might then be recovered by precipitation or electrolysis.
Thiosulfate Leaching
Thiosulfate leaching is an alternative choice to cyanidation. It includes treating the circuit boards with an answer of sodium thiosulfate (Na2S2O3):
2Au + 3Na2S2O3 → Na3[Au(S2O3)2] + Na2S
The gold dissolves into the answer because the dithiosulfatoaurate (III) complicated [Au(S2O3)2]–, which will be recovered by precipitation or ion alternate.
Comparability of Hydrometallurgical Processes
| Course of | Benefits | Disadvantages |
|---|---|---|
| Cyanidation | Excessive gold restoration charges, comparatively low value | Poisonous chemical substances, environmental considerations |
| Thiosulfate leaching | Much less poisonous chemical substances, extra environmentally pleasant | Decrease gold restoration charges, greater value |
How To Take away Gold From Circuit Boards With out Chemical compounds
There are a couple of methods to take away gold from circuit boards with out utilizing chemical substances. One is to make use of a mechanical methodology, corresponding to scraping or submitting. One other is to make use of a thermal methodology, corresponding to heating the board with a torch. Lastly, you should use {an electrical} methodology, corresponding to electrolysis.
Mechanical strategies are the most typical strategy to take away gold from circuit boards. Scraping or submitting can be utilized to take away gold from the floor of the board. Nevertheless, these strategies will be time-consuming and may injury the board.
Thermal strategies are one other strategy to take away gold from circuit boards. Heating the board with a torch can soften the gold and permit it to be poured off. Nevertheless, this methodology may injury the board.
Electrical strategies are essentially the most environment friendly strategy to take away gold from circuit boards. Electrolysis makes use of {an electrical} present to dissolve the gold and take away it from the board. This methodology just isn’t as damaging to the board as the opposite strategies.
Folks Additionally Ask
How a lot gold is on a circuit board?
The quantity of gold on a circuit board varies relying on the dimensions and kind of board. Nevertheless, most circuit boards include between 0.01 and 0.1 grams of gold.
Is it price it to take away gold from circuit boards?
Whether or not or not it’s price it to take away gold from circuit boards will depend on the worth of gold and the quantity of gold on the board. If the worth of gold is excessive and there’s a important quantity of gold on the board, then it might be price it to take away the gold.
