Gold recovery from e-waste

Post-consumer electronic waste contains a large range of valuable elements that can potentially be recycled.  An analysis by the UN e-waste coalition reports that 7% of the world’s gold reserve may be contained in e-waste and there is 100x more gold in a tonne of smart phones compared to a tonne of gold ore, leading to increasing interest in ‘urban mining’ to recover and recycle it.

Researchers at The University of Queensland (UQ) have developed a hydrometallurgical process for leaching gold from electronic waste (such as printed circuit boards) and then collecting the gold by electrodepositing it onto electrodes.

Compared to other leaching processes, the process is highly selective for gold and leaching is fast, ensuring rapid processing.  Compared to smelting, capex and operating costs are both low, and modular plant construction can be scaled according to the size of the incoming waste stream.

Key features

  • Highly selective for gold; other metals can also be recovered
  • Low cost, modular plant design allows easy facility scaling
  • Clean process – most leachate recycled.

 

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High frequency/low voltage pulsed power for dewatering mineral tailings

The use of tailing storage facilities often requires extensive plant equipment and large areas of land, as well as risk management plans should a tailing dam rupture leading to pollution of surrounding areas. There is a need to develop an alternative method for dewatering of mineral tailings whether for storage in a tailings dam or via dry stacking.  There is also a need for in-situ recovery of water from deposited tailings in water stressed areas.

Researchers at The University of Queensland (UQ) have invented a method for dewatering mineral tailings using high frequency and low voltage pulsed power.

Key features

  • Methods and/or systems for dewatering mineral tailings that comprise a mineral component with water bound within
  • Subjecting mineral tailings to a pulsed electric field to liberate the water bound within or to the mineral component of the mineral tailings
  • Utilises high frequency and low voltage pulsed power to separate water from mineral tailings such as copper, coal, red mud and diamond slime.

 

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Lodomat

Lodomat consists of a suite of technologies that involve the use of free nitrous acid (FNA) for the treatment of wastewater sludge to enhance volatile solids destruction, enhance biogas production in anaerobic sludge digestion, to improve sludge dewaterability and to improve biological nitrogen removal.

Key features

  • Lodomat is an advanced system for wastewater treatment of sludge utilising anaerobic digestion, free nitrous acid, partial nitration and mainstream deammonification
  • Lodomat technologies were developed at the Advanced Water Management Centre at the University of Queensland
  • Lodomat AD, NP, NIT and MD have continued to improve on each technology to reduce biosolids to be disposed of and recover energy in the form of methane or biogas.

 

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Alkaline digestion of waste glass

There is a narrow range of reaction conditions under which the alkaline digestion of soda-lime glass and separation of resultant products is able to proceed in a commercially relevant way.  UQ researchers have optimised digestion conditions and product processing, such that glass can now be used to produce a range of high-value products including liquid alkali-silicates in all commercially relevant concentrations and ratios, high purity silica gel and Calcium Silicate Hydrate (CSH).

Key features

  • Simple process developed for the extraction of sodium silicate from soda-lime glass, characterised by a high utilisation of the raw materials and energy embodied in glass
  • Suitable for the low-value fraction of waste glass which is too small to be optically sorted (by colour) and remade into glass products
  • Significant commercial (reduced capex and opex) and social benefits (reduce landfill and consumption of virgin materials) when compared to conventional production routes of sodium silicate.

 

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