Chemical Leaching

 

Chemical leaching

Introduction:

Chemical leaching technology can be used to recover valuable critical raw material from industrial mixed waste materials (e.g. sludges, slags, ashes). The concept will integrate innovative environmental friendly chemical leaching procedures that allow for the valorisation of both valuable critical raw materials and matrix materials of the waste material.

incinerator ashes


steel slags


shredder waste

 

Potential:

The technology has the potential to remove contaminating (heavy) metals which pose environmental treats with regard to the reuse of the matrix materials (large bulk of the waste) and to recover valuable metals from the matrix by advanced leaching (small amount, high value).

Aim:

The aim is to reach a proof-of-concept of the chemical leaching process on a range of different mineral waste streams.

Difference to BAU technology/approach:

Traditionally mineral waste is landfilled without recovery of heavy metals or low concentrations of valuable metals. Environmental leaching under the influence of contact with surface, ground or rain water of heavy metals from landfilled mineral waste can pose environmental threats.
The chemical leaching technology aims to recover the heavy metals from mineral waste. In an integrated process both the metals and the matrix material are recovered.

Input stream requirements:

Inorganic metal-containing sludges, slags and ashes, such as phosphorous, steel, boron and lead slags, shredder waste, filter cake, incineration ashes, dredging sludge.

historic steel slags


lead slags


filter cake

 

Available quantity:

Large amounts are available at various landfill sites, brownfields and sometimes unknown, forgotten locations. Quantity of the most valuable input streams still has to be determined.

Drivers for treating this stream:

The  main drivers for treating these input streams are environmental (environmental threats of leached metals prevent a material from being reused) and economic (recovery of valuable metals from waste instead of ores, reclamation of landfill sites close to populated areas with high land prices). From a legislative viewpoint, drivers can be the forced closure of a landfill site (which means that solution for waste material that are still produced needs to be provided).


Landfill mining: reclaming materials from old landfill sites

Potential environmental risks related to this waste stream:

Landfilled mineral waste (mono landfill) can pose environmental threats when leaching heavy metals.

Economic/technical barriers to collect this stream:

The identification of the (most) valuable landfill sites is needed.  The data with regard to location, amount and quality (composition) of the waste is often partially or not available.

Output stream:

Critical raw materials and valuable metals, e.g. Zn, As, Cd, Co, Mn, Mg, ...

Potential uses of this output stream:

Valuable metals are recycled and recovered matrix material can be re-used, e.g. as construction material.

 

Potential environmental risks/benefits related to this output stream:

Recovery of metals and matrix material from mineral waste streams avoids the extraction and treatment of primary metal ores. Also possible environmental issues (leaching of heavy metals) can be avoided.

Economic barriers/drivers for market introduction of this output stream:

Metal prices of recovered metals, treatment costs and the current and future landfill cost of the waste material determine the profitability of the process.

Technical barriers for market introduction of this output stream:

The separation and recovery of valuable metals can be a technological challenge: fine grained mineral waste is difficult to handle and separate physically, and the embedded metals can be thermodynamically stable such that (chemical) recovery can be hindered.

Legislative barriers for market introduction of this output stream:

Local waste legislation makes cross-border treatment of waste difficult (transport, treatment,…).

Pilot description:

The pilot consists of a lab-scale leaching set-up. In-house testing (chemical and physical analyses) of the contaminant-rich waste materials and treated fractions takes place to determine separation and recovery efficiencies.

Installation:

Lab-scale leaching tests setup.

 

Capacity:

At this moment only lab-scale tests can take place (a few 100 gr up to 0,5kg per hour).

Scale of the equipment:

Lab scale

Main technological barriers for market introduction:

Hydrometallurgical metal recovery from mineral waste materials is relatively new; although knowledge from existing mineralogical technologies, applied on primary ores, can be used, secondary ores are generally more complex and low grade materials. Therefore, new technology is needed whereby metals can be recovered in an even more selective way, at a low cost, environmentally friendly and without altering the properties of the matrix material too much, since valorisation of this material is also needed. 

Main economic barriers/drivers for market introduction:

There is a high competition with primary ores. However, the ore grades of many primary ores is dropping and the cost of mining and treating lower grade ores is increasing. 

Research steps:

Development of new, highly selective and cost effective metal recovery routes from mineral waste materials.

Economic steps:

Facilitate the exploitation of old landfill sites as “secondary mines” and render the landfilling of mineral waste materials, which can be treated, more difficult.

Legislative steps:

See economic steps

Other:

Enhance the symbiosis of companies in a fully circular material value chain by introducing new business models.

Contact details:
Organisation: VITO

Department: Sustainable Materials Management

Leading researcher: Jeroen Spooren

Phone number: +32 14 33 56 33

E-mail: jeroen.spooren@vito.be

          

 

Documentation:

Presentation: Mineral waste as a materials resource: technological approaches and challenges, VITO, Jeroen Spooren, RENEW Technology Foresight Conference 24/04/2013