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Comment PDF Separation Processes

Urban Mining Offers Good Prospecting

By Gerald Ondrey |

As the volume of discarded electronic gadgets grows, efforts are underway to recover the precious resources trapped inside

It should come as no surprise that the fastest growing part of the world’s domestic waste stream is e-waste — discarded products with a battery or plug (see box below, “The Growing Need for Recycling”). Because e-waste contains valuable resources, efforts around the word to collect and recycle such waste — so-called urban mining — are growing. But it is more than simply mining for profit. “Waste electrical and electronic equipment (WEEE, or e-waste) is a complex mixture of materials; it is a source of secondary raw materials, including precious metals, but, at the same time, it also contains hazardous substances that give rise to environmental and health problems if not adequately managed,” according to WEEE Forum (Brussels, Belgium; www.weee-forum.org).

It was with this in mind — that e-waste is hazardous waste — that E.U. legislators adopted directive 2002/7967/EC on waste electrical and electronic equipment (WEEE) back in 2002. At that time, there was no specialist WEEE de-polluting and recycling industry to speak of. There were few WEEE designated collection facilities. Citizens were not aware of the hazards associated with discarding WEEE, and no targets or responsibilities were in place, according to the WEEE Forum. Since then, progress has been made, but there is still a lot of work to be done.

 

Plant expansions

Umicore N.V. (Brussels, Belgium; www.umicore.com) operates one of the world’s largest metals-recycling plants in Hoboken, Belgium. This plant recovers precious (Ag, Au, Pt, Pa, Pd, Rh, Ir, Ru) and specialty metals (In, Se, Te) from a wide variety of materials from over 200 complex input streams from around the world (Chem. Eng., April 2015, pp.18–23: www.chemengonline.com/new-frontiers-metals-recycling). The company recently invested €100 million to expand its capacity by 40%, and is now ramping up from 350,000 metric tons per year (m.t./yr) to 500,000 m.t./yr.

Meanwhile, last May, Hereaus Precious Metals, a global business unit of the Hereaus Group (Hanau, Germany; www.hereaus.com) inaugurated a 30,000-ft 2 expansion of its precious-metals recycling plant in Wartburg, Tennessee. The multi-million dollar expansion project, which began in the spring of 2016, increases the plant’s pre-processing capacity to meet growing demand from the chemical, electronics, automotive and jewelry industries. Established in 2004, the Hereaus Wartburg plant is a treatment and storage facility for both hazardous and non-hazardous materials containing precious metals. The company says it has made significant investments in new recycling technologies and capabilities, including specialized converters, furnaces (Figure 1) and processing equipment (Figure 2). One of the newest innovations at Wartburg is its pyrometalurgical recycling converter, which uses a highly specialized process to recover precious metals faster and more economically, says the company. The converter will primarily focus on the recovery of platinum-group metals. “Processing and recovering precious metals has become extremely complex. But today we have a state-of-the-art facility and a world-class team of talented employees at Wartburg to meet our customers’ recycling challenges,” said Andre Christl, president of Heraeus Precious Metals, during the ribbon-cutting ceremony.

urban mining

Figure 1. Hereaus employee working on the new furnace at the Wartburg, Tenn. facility
Hereaus Precious Metals

Figure 2.  Hereaus workers discussing the production process at the Wartburg plant Hereaus Precious Metals

Figure 2. Hereaus workers discussing the production process at the Wartburg plant
Hereaus Precious Metals

The 358-year-old company operates a global network of trading offices, processing facilities and recycling sites in Germany, Switzerland, China, South Africa, India, Hong Kong and the U.S.

In March, the Alba Group (Berlin, Germany; www.alba.info) opened its Hong Kong WEEE-Park, a new facility for processing and recycling WEEE. Located in the city’s EcoPark north of the airport, the new processing plant is said to be the most modern in all of Southeast Asia, and the biggest combined facility for processing such a wide range of WEEE in the world. Initially, the plant will have a capacity of 30,000 m.t./yr, with the option to expand to 56,000 m.t./yr.

In addition to the construction and operation of the plant, Alba Group’s contract — the largest in its history — includes the development and operation of a city-wide collection system with five satellite collection centers and a fleet of heavy goods vehicles (HVGs) over 10 years. The facility will handle “legally regulated” electronic waste, comprising large household devices, including air conditioners, refrigerators, television sets, washing machines and computers.

 

Figure 3.  The new recycling facility in Hong Kong is said to be the largest of its kind in the world Alba Group

Figure 3. The new recycling facility in Hong Kong is said to be the largest of its kind in the world
Alba Group

Emerging process technology

While traditional processing plants continue to expand, efforts are also underway to develop new processes for recovering valuable resources from e-waste. For example, Mint Innovation (Auckland, New Zealand; www.mintinnovation.co) is developing a hybrid approach that combins hydrometallurgy and biotechnology to recover gold from printed circuit boards (PCBs). “We take comminuted PCBs, put them through a leach process, and contact the resulting pregnant lixiviant with select microorganisms,” explains chief scientific officer Ollie Crush. “These microbes are able to specifically biosorb precious metals, like gold, and enable both the purification and concentration of metal in one step. The process runs at ambient pressure and temperature and doesn’t utilize cyanide.”

“Because gold accounts for approximately half of the metallic value of PCBs, this is our process’ primary target, followed by palladium and copper,” says Crush. The aim for Mint is to commercialize a low-CAPEX, low-OPEX process that can be deployed economically at a range of scales, explains Crush. “This will enable individual cities or regions to be able to capture value from locally-generated WEEE, as opposed to landfilling or exporting it. In comparison to large-scale specialized smelters, this distributed approach will allow aggregators of WEEE to achieve higher returns, as well as shorten payment timeframes and reduce uncertainty. It is also hoped that our process can be deployed in developing nations in order to displace rudimentary (and hazardous) small-scale processing,” he says.

Since December 2017, the company has been operating a pilot plant, located at Level Two (www.leveltwo.tech) in Auckland. The pilot plant can process tens of kilograms of ground PCBs at a time in 100-L batches, and Crush envisages a semi-continuous process at commercial scale. Mint has partnered with Remarkit Solutions Ltd. (Auckland, New Zealand; www.remarkit.co.nz) to build a demonstration plant that will recover precious metals from up to 200 m.t./yr of scrap PCBs. Construction is slated for early 2019, with commissioning taking place in stages over that year, says Crush.

Last April, the world’s first e-waste microfactory started up at the University of New South Wales (UNSW; Sydney, Australia; www.unsw.edu.au). Using technology developed at UNSW’s Center for Sustainable Materials Research and Technology, the microfactory transforms components from e-waste, such as discarded smartphones, laptops and printers, into valuable materials for re-use.

The discarded devices are first placed into a module to break them down. The next module may involve a special robot for the identification of useful parts. Another module then involves using a small furnace that transforms these parts into valuable materials by using a precisely controlled temperature process.

These transformed materials include metal alloys (copper-tin, for example) and a range of micromaterials. The micromaterials can be used in industrial-grade ceramics, while the specific quality plastics from computers, printers and other discarded sources can be put through another module that produces filaments suitable for 3-D-printing applications. The metal alloys can be used as components for new or existing manufacturing processes, says UNSW.

“These microfactories can transform the manufacturing landscape, especially in remote locations where typically the logistics of having waste transported or processed are prohibitively expensive,” says professor Veena Sahajwalla. “This is especially beneficial for the island markets and the remote regions of the country.”

The technology was developed with support of the Australian Research Council and is now in partnership with a number of companies, including e-waste recycler TES (Singapore) Pte Ltd. (www.tes-amm.com) and mining manufacturer Moly-Cop (Waratah, Australia; www.molycop.com).

In another effort towards zero-waste solutions for e-waste, Ronin8 Technologies Ltd. (Richmond, B.C., Canada; www.ronin8.com) has developed a process to separate metal from the nonmetal matrix of PCBs using physical processes, as an alternative to chemical or thermal treatments that destroy the nonmetallic resources. The remaining nonmetal fraction, which usually end up in the landfills, can also be recovered in the process for secondary usage, and thus provides a closed-cycle solution for e-waste recycling, says the company.

Ronin8 has been working with the Ph.D. candidate Amit Kumar and professor Maria Holuszko at the Urban Mining Innovation Center (UMIC) at the University of British Columbia (UBC; Vancouver; www.ubc.ca) for one year to characterize and process the obtained nonmetal fraction for the suitability for secondary use. Most e-waste recycling firms focus on recovering useful metals like gold, silver, copper and palladium, which can be used to manufacture other products. But nonmetal parts like fiberglass and resins, which make up the bulk of cellphones’ PCBs, are generally discarded because they’re less valuable and more difficult to process. They are either fed to incinerators or landfilled, where they can leach hazardous chemicals into groundwater, soil and air.

Holuszko and Kumar developed a process that uses gravity separation and other simple physical techniques to process cellphone fiberglass and resins in an environmentally neutral fashion. “The separated fiberglass can then be used as a raw material for construction and insulation. In the future, if we can find a way to improve the quality of the recycled fiberglass, it may even be suitable for manufacturing new circuit boards,” says Kumar.

Meanwhile, researchers from Rice University (Houston; www.rice.edu) and the Indian Institute of Science (Bangalore; www.iisc.ac.in) have shown that another possible way to separate the materials in PCBs is by cryogenic milling into nanopowders. Described in a March 2017 issue of Materials Today, the process uses a ball mill, with argon atmosphere operated at 154K, to break down the waste into nano-sized particles of metals, oxides and polymers. Because of the small size of the resulting dust (20–100 nm), the different powders behave as separate phases, which can then be easily separated.


The growing need for recycling

Umicore_sidebarIn 2016, 44.7 million metric tons (m.t.) of e-waste — everything from end-of-life refrigerators and television sets, to solar panels, mobile phones and computers — was generated globally, according to The Global E-waste Monitor 2017, which was published last December. The report, compiled by the United Nations University (UNU; Bonn, Germany; www.unu.edu), the International Telecommunications Union (ITU; Geneva, Switzerland; www.itu.int) and the International Solid Waste Association (ISWA; Vienna, Austria; www.iswa.org), shows an 8% increase in e-waste generation compared to 2014, and experts foresee a further 17% increase to 52.2 million m.t. by 2021 — the fastest growing part of the world’s domestic waste stream, says UNU.

The report also says that only 20% of 2016’s e-waste is documented to have been collected and recycled, even though the waste contains rich deposits of gold, silver, copper, platinum, palladium and other materials — with a conservative estimated value $55 billion, says UNU. Most of the 2016 waste (76%, or 34.1 million m.t.) actually ended up being incinerated, thrown into landfills, or remains stored in households.

Europe (including Russia) is the second-largest generator of e-waste per inhabitant, with an average of 16.6 kg per inhabitant, but Europe also has the highest collection rate (35%), according to UNU. This could be due to the progress made since 2002, when the E.U. legislators adopted directive 2002/7967/EC on waste electrical and electronic equipment (WEEE).

According to the WEEE Forum (Brussels, Belgium; www.weee-forum.org), quantities of WEEE collected by the producer responsibility organizations (PROs) rose from 292,550 m.t. in 2002 to 2.1 million m.t. in 2016. However, recycling rates for most critical raw materials (CRMs) have remained low over the last 15 years, says WEEE Forum. “The recycling rate for CRMs, such as rare earth elements, is currently estimated at less than 1%,” WEEE Forum reported in its 15-year anniversary brochure, published in 2017.
One initiative to capitalize on this lost resource is the development of a centralized database, with easy access to primary and secondary raw materials data on a single platform. Launched in January 2018, The Urban Mine Platform (www.urbanmineplatform.eu) was created by 17 partners in the ProSUM project (Prospecting Secondary Raw Materials in the Urban Mine and Mining Wastes). The database reveals the amount of valuable materials recovered or lost in the E.U.’s scrap vehicles, batteries, computers, phones, gadgets, appliances and other high-tech products discarded every year. “Three years in the making, this consolidated database is the world’s first ‘one stop shop’ knowledge data platform on CRMs in waste products — easy to access, structured, comprehensive, peer-reviewed, up-to-date, impartial, broad in scope, standardized and harmonized, and verifiable, says,” Pascal Leroy, secretary general of the WEEE Forum and ProSUM project coordinator.

According to the ProSUM consortium, a smartphone contains around 40 different CRMs, with a concentration of gold 25 to 30 times that of the richest primary gold ores. Furthermore, mining discarded high-tech products produces 80% less CO2 emissions per unit of gold, compared with primary mining operations.

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