How do you extract gold from circuit boards using the borax method

What Is the Borax Method?

The borax method is a flux-based smelting process that uses sodium borate (commonly called borax) to lower the melting point of metals and bind impurities into a slag layer. When applied to gold-bearing materials such as circuit board scraps, the method separates pure gold from other metals and contaminants by creating a molten mixture where impurities float to the top and gold settles at the bottom.

Borax has become popular in small-scale recycling because it avoids the use of toxic mercury, making it a safer alternative for individual operators. The process requires only basic equipment: a heat-resistant crucible or clay bowl, a blowtorch or furnace capable of reaching 800°C to 1000°C, and a supply of borax powder.

Preparing Circuit Boards for Gold Extraction

Before applying the borax method, circuit boards must be properly prepared. Gold in PCBs is typically found on connector fingers, plated pins, and integrated circuit packages. The preparation stage involves:

• Sorting: Separate gold-plated components from steel, aluminum, and plastic parts. A magnet helps remove ferrous metals.
• Stripping: Remove gold fingers and clean circuit board sections that contain visible gold plating.
• Crushing: Break down the sorted material into smaller pieces to increase surface area and improve melting efficiency.

Some operators use a chemical pre-treatment step involving hydrogen peroxide and muriatic acid to dissolve base metals and concentrate the gold-bearing material before smelting. This step requires proper safety gear including rubber gloves, goggles, and ventilation, and should only be performed outdoors or in a fume hood.

The Borax Smelting Process

Once the material is prepared, the borax smelting process can begin. A typical procedure follows these steps:

1. Mixing: Combine the gold-bearing material with borax at a ratio of approximately three parts borax to one part concentrate. Add a small amount of water to form a thick paste.
2. Heating: Place the mixture in a clay bowl or crucible and heat it using a blowtorch or charcoal furnace. The temperature must reach at least 800°C for the borax to activate.
3. Slag formation: As the mixture melts, the borax binds with impurities such as copper, nickel, and iron oxides, forming a glass-like slag layer that floats on top.
4. Gold separation: Pure gold, being denser, sinks to the bottom of the crucible beneath the slag layer.
5. Cooling and collection: Allow the crucible to cool, then break away the slag to reveal the gold bead underneath.

The resulting gold is rarely 100 percent pure after the first smelting. Multiple iterations may be necessary to achieve higher purity, and each cycle involves reheating the gold with fresh borax to remove remaining impurities.

Challenges and Limitations

While the borax method works in principle, applying it to circuit boards presents significant practical challenges. Circuit boards contain a complex mixture of metals, plastics, fiberglass, and chemical coatings. The gold content in most consumer electronics is extremely low, often measured in grams per ton of material. This means operators must process large volumes of boards to recover meaningful quantities of gold.

Additionally, the manual process is time-consuming, labor-intensive, and potentially hazardous without proper training and equipment. Fumes from burning plastics and fiberglass can release toxic compounds, and improper handling of acids during pre-treatment poses serious health risks. Environmental regulations in many countries also restrict open burning and backyard smelting of electronic waste.

The Case for Professional Circuit Board Recycling Equipment

For businesses and recycling facilities handling circuit boards in bulk, manual borax smelting is neither efficient nor economical. Professional circuit board recycling equipment offers a far more effective solution. Mechanized recycling plants can process hundreds or thousands of kilograms of PCBs per hour, using automated crushing, separation, and refining technologies to recover not only gold but also copper, silver, palladium, and other valuable materials.

Modern circuit board recycling plant systems use a combination of mechanical shredding, air separation, electrostatic sorting, and wet separation to break down boards into their constituent materials without the need for hazardous open burning or manual acid baths. These systems significantly improve recovery rates while reducing environmental impact and labor costs.

Investing in an e-waste recycling machine allows operators to handle diverse electronic waste streams beyond circuit boards, including cables, batteries, and refrigerator components, creating multiple revenue streams from a single facility.

San Lan Technologies: Your Partner in E-Waste Recycling

San Lan Technologies Co., Ltd has been manufacturing WEEE recycling machinery since 2007. Based in Ganzhou, Jiangxi Province, China, the company specializes in designing and building complete recycling plants for circuit boards, lithium batteries, lead acid batteries, cables, and other electronic waste streams.

San Lan's circuit board recycling systems are available in multiple configurations, with capacities ranging from 300 kg/hour to 2000 kg/hour or more. Their dry separation plants achieve copper powder purity levels of 96 to 98 percent, while wet separation systems offer environmentally friendly water-based processing with no dust pollution. Each plant can be customized to meet specific customer requirements.

With customers in over 21 countries, San Lan provides comprehensive support including installation, commissioning, operator training, and ongoing technical assistance. Their engineering team holds master's degrees in mechanical engineering and brings more than 15 years of experience in e-waste recycling equipment design.