State-owned minerals research organisation Mintek and the e-Waste Association of South Africa (eWasa) will later this month start testwork on the Urban Mining Project, subsequent to their signing a five-year memorandum of understanding (MoU) late last year to jointly tackle the growing challenge of metal-bearing waste in South Africa.

This testwork phase will entail demon- strating the relevant high-temperature beneficiation technologies that will be used for the treatment of metal-bearing waste on a pilot scale in Mintek’s pilot furnace facilities, which can treat 1 t/d of material.

The Urban Mining Project, which involves the so-called process of ‘urban mining’ – a type of mining beneficiation involving the extraction of value from any and all types of metal-bearing waste streams – will focus on the recovery and beneficiation of all sources of metal-bearing waste, which include electronic waste (e-waste) and industrial waste, as well as mine tailings and residues in South Africa, to recover a greater portion of the metal value from metal-bearing waste and residues.

Mining Weekly reported in November that Mintek research and development GM Dr Makhapa Makhafola said Mintek and eWasa had many common objectives for the Urban Mining Project.

“The collaboration over the next five years will enable us to collectively develop technologies that will change the way in which e-waste is collected and treated in South Africa, with the potential to export the technology elsewhere on the African continent and worldwide.

“Currently, an enormous amount of value recovered from the beneficiation processes in South Africa is lost, as e-waste fractions are exported for treatment offshore. One of our aims in signing the MoU is to ensure that the technology Mintek supplies or develops will be put to good use locally to ensure that communities and the country maximise the beneficiation flows,” said Makhafola.

The reason for bolstering the recovery and recycling of metal-bearing waste is twofold, says Mintek business development GM Peter Craven.

Firstly, the global exploitation of primary ore resources cannot continue at the current rate, as primary ore resources will not be able to sustain this exponential increase. Subsequently, the only way forward is substitution by way of replenish- able resources, such as industrial waste recycling and the treatment of mining waste.

Secondly, countries are turning to recycling because of the possible negative environmental impact of metal-bearing waste. “Removing more metal values from the waste will mean that the environmental impact will be less in the longer term,” he explains.

This recovery and recycling process also enables the extraction of value from waste collected in the form of several metals and minerals that will be fit for use again. These recycled metals and minerals can then be reused in the production processes as secondary raw materials. This activity also creates green jobs, diverts waste from landfill and, therefore, also protects the environment, eWasa chairperson Keith Anderson adds.

The value chain of waste treatment entails the collection and transport of the waste to a central location, followed by the selection of suitable technology to treat that material and, eventually, the sale of the recycled material to the traditional metal markets.

Partnership
As part of its mandate under this partnership, eWasa has committed itself to providing the partnership with statistical data, contacts and market intelligence, which will facilitate interaction and collaboration with the collection networks in the waste treatment industry and identify opportunities for training, awareness and job creation opportunities in the sector.

Mintek, which has many years of experience in the mining sector through its minerals technology research, can play a role in the middle of the waste value chain. This role will involve selecting suitable technologies from its range of existing beneficiation technologies or developing new technologies for the treat- ment of different types of metal-bearing waste and the subsequent recovery of its valuable components.

Craven explains that because metal-bearing waste consists of a vast mix of elements and metals, highly sophisticated metallurgical techniques are required to separate the various elements, which are also in close proximity to one another.

Beneficiation Technology
Craven tells Mining Weekly that there is no single technology that can be applied to beneficiate all the types of metal-bearing waste. Therefore, selecting appropriate technologies for treating specific metals, or developing a suitable technology should one not already exist, is therefore important.

He adds that many of the technologies that Mintek is in the process of developing will be used to treat specific metal types and can be applied to extract different metals from metal- bearing waste.

In e-waste, specifically, there is a dynamic mixture of elements and metals that require sophisticated metallurgical techniques to separate the respective elements from one another, as the difference in the individual characteristics of the elements is not enough to allow for individual separation.

These techniques entail using pyrometallurgy and hydrometallurgy processes.

Craven explains that after the e-waste is shredded and the metallic elements are sepa- rated from the nonmetallic elements, the metallic elements need to be homogenised to produce a homogenous material. This usually involves a pyrometallurgical stage, which entails smelting the metals. During this process, all of the metals lose their original identity and they become a mere chemical component of a homogenous mix.

After smelting, a hydrometallurgical process gets under way. This involves dissolving a metal from a solid state into a liquid state using a leaching agent. Once all the elemental species are in solution, components such as ion-exchange solvents and resins, or selective precipitation, are used to separate one component from another.

“Most of the time, this is the type of technology that has to be used to treat metal-bearing waste,” says Craven, adding that the technologies that will probably be employed to treat e-waste will be complex and the most sophisticated of all the metallurgical technologies.

He further cites ageing technology as a challenge that Mintek and eWasa will face in developing a mineral and metal treatment technology, as technology that is efficient now will not necessarily be efficient in the next few years.

This is a result of changing ore types and the declining grade of ore types, explains Craven. New technologies will, therefore, have to constantly be developed to treat those future changing ore types and grades.

Additional Challenge
Another challenge facing the collection and beneficiation of South Africa’s metal-bearing waste is overcoming the logistics problem currently facing the nascent sector.

Collecting and transporting the waste to a location for processing is problematic as the quantity of waste produced is not nearly as high as that of high-metal-intense countries. South Africa’s geographical locations are also much further apart.

These factors contribute to making the collection and economical viability of collecting waste difficult.

Further, transport costs add greatly to the cost of managing the waste in an environmentally sound manner, highlights Anderson. “Addressing the need to dispose of materials in rural areas in a cost-effective way is part of the reason for the eWasa-Mintek collaboration,” he adds.

Craven further remarks that metal-bearing waste, such as industrial waste, e-waste and mine tailings, is bulky to transport, which increases transport costs. This sparks the question of whether to transport the waste to a processing facility or establish a processing facility near the collection point.

Resolution
Craven insists that a likely course of action that will serve as a trade-off between the most technically feasible and economical option, and one that suits the South African context best, will probably be chosen.

He adds that when one has the economies of scale inherent in a large central processing facility, the transport costs associated may be too high.

“What I can [envisage], at this stage, is establishing a series of upfront preliminary treatment facilities to shred the waste to produce a product that is easier to transport. We may even treat some of the waste on a regional basis. However, our ultimate aim is to establish central refineries for the bene- ficiation of the metal-bearing waste,” says Craven.