Metal recycling and recovery are two sides of the same coin. Recycling is reprocessing scrap or waste metal into new products. Recovery is the process that extracts purified metal from scrap. Recycling and recovery of metals such as brass, bronze, copper, lead, zinc, and aluminum can come from scrap or from slag that is left over from a primary smelting operation.
In fact, aluminum is infinitely recyclable. Nearly 75% of all aluminum ever produced is still in use today.1 This matters because although aluminum is the most abundant metal on Earth (making up 8.1% of the planet’s crust2), it is locked in minerals such as bauxite. And, the typical smelting process for producing commercially usable aluminum metal is carbon intensive.
Recovered and recycled metals: Manufacturing and environmental benefits
Recycling and recovery of metals provide significant advantages for industry and the environment:
- Recovered and recycled metals are available at a fraction of the cost of virgin metals
- Scrap provides a continuous source of material
- Energy consumption for recovery and recycling is dramatically less than purifying metal ore: Recycling aluminum and copper, for example, uses 85-95% less energy than producing new metal3-4
- Manufacturers can source recycled metals closer to home, through local or regional scrap sources
The power of borates in metal recovery and recycling
Producing a pure metal product from scrap requires removing all oxides and extraneous impurities. Borates help by acting as fluxes during melting, combining with metallic oxides at relatively low temperatures to bring them to the surface of the melt as a slag that can be decanted or skimmed off.
The flux effect is different for different metals—and in different processes. For example, in aluminum recovery-refining, boron in the form of fluoboric acid (HBF4) is used as flux for aluminum reduction. During aluminum production, boric oxide added to the pot lining has shown to be a suitable reactant to decrease the formation of cyanide, a hazardous waste. Boron is also widely used as a grain refiner in aluminum and can indirectly increase strength through grain refinement.
An anhydrous borate (such as Dehybor®) easily forms a liquid flux that actually helps dissolve oxides, silica, and other non-metallic impurities.
Borates are not the only flux agent that can facilitate metal recovery processes. Other fluxes include lead carbonate, soda ash, silica, scrap iron, or combinations of multiple fluxes. However, borates offer marked advantages over these flux agents. Borates:
- Produce a high-solvent action on metal oxides and siliceous materials, resulting in a purer metal product
- Reduce liquidus temperature, enabling formation of highly fluid slags and the extraction of more metal from the slag
- Enable easier slag thickening and skimming depending on metal chemistry
- Reduce manufacturer’s energy costs because a lower melting point is required in the furnace
- Reduce the leaching effect of lead sulfate from slag in lead recovery, which enables improvements in the cooled, more solidified slag
- Are easy and safe to handle
- Are non-combustible and have minimal fuming tendency
Your choice of borates for metal recovery and recycling matters
Given the nature of a fluxing agent in metal recovery, it might seem that any borate could do the job. Any superfluous materials would simply be carried away in the slag, right? However, the type of borate product you choose can influence the safety of people, equipment, and the environment. Selecting the right borate concentration, purity, and particle size makes the difference between high-quality recycled metals and an inconsistent product prone to cracking or pitting.
Neobor® (a hydrated borate) is the most common form of sodium borate used in industry. It might seem like a simple choice for a smelting operation. And in many operations, it is. However, the effects of Neobor and Dehybor in the smelting process are quite different.
As Neobor’s sodium borate heats up, it dehydrates slowly and forms a melt that tends to bubble and sputter as it loses additional moisture. In smelting operations, Dehybor helps to avoid sputtering—and even potential steam explosions—making it a safer choice.
In metal recovery smelting, Dehybor improves both process quality and safety. It is an excellent solvent for metallic oxides at high temperatures. In addition:
- Hydrated borates may be more corrosive to refractory brick because of the water they emit.
- Because Dehybor is already dehydrated, less product is required per ton of recycled material, which may help save on cost.
- As a refined borate, Dehybor contains the lowest possible amount of toxic elements such as arsenic. As a result, it releases fewer toxins into the environment during smelting.
- In gold recovery, the formation, purity, and consistent granulometry of borates are important. Dehybor’s consistency makes it ideal for preventing “spit and crackle” problems and facilitating the proper melt.
Borate supplier expertise
U.S. Borax is known for our products’ quality and consistency. Our borates undergo comprehensive quality testing so they deliver high borate concentration and uniform particle size.
But we go beyond the sale, offering technical support to help ensure you have the right product for your application and facility. Turn to us for guidance on the function of borates in your process, samples for testing, and recommendations for formulations based on our extensive research and experience.
Together, we can ensure the efficient use of metals—and solve one of the significant challenges of modern living.
References
1. Aluminum’s Sustainability. The Aluminum Association.
2. Periodic Table: Aluminium. Royal Society of Chemistry.
3. Aluminium recycling saves 95% of the energy needed for primary aluminium production. International Aluminium.
4. Recycling. International Copper Association.
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