Finer points of e-scrap

Pictured above, from left: Hyunju Lee and Brajendra Mishra in a Worcester Polytechnic Institute
lab working on the “Recovery of Valuable Metals from Flue Dust and Other Fines from
Mechanical Treatment of E-Scrap” project.

Electronic scrap (or e-scrap, which can refer to a variety of electronic products that have met their end of life) is one of the fastest growing discarded material streams in the world.

With the advancement of the technological age, industry and consumers are continuously disposing of cellphones, computers, monitors, laptops, televisions, VCRs, stereos, copiers, fax machines and other types of equipment, often without any clear direction on how to prevent environmental contamination.

According to Solving the E-waste Problem (StEP), an international initiative created to develop solutions to address issues associated with Waste Electrical and Electronic Equipment (WEEE), the world produced nearly 54 million tons of used electrical and electronic products in 2012.

StEP forecasts that number to have been 33 percent higher, or 72 million tons, in 2017, according to an article on the LiveScience website. Clearly, we have a global waste minimization and disposal issue that needs to be addressed.

Multi-university research

While e-scrap generation cannot be prevented, environmental consequences have driven global government policies to explore alternative solutions, such as the reuse and recycling of electronics that can lead to zero-waste processing.

This is where the Center for Resource Recovery & Recycling (CR³), a global, multiuniversity National Science Foundation collaborative, is playing a pivotal role. CR3 is located at Worcester Polytechnic Institute (WPI) in Massachusetts in the United States. Other universities in the collaborative include the University of Tokyo; KU Lueven in Belgium; and the Colorado School of Mines, also in the U.S.

CR³ explores technologies that recover, recycle and reuse materials throughout the manufacturing process. These advancements help industry reduce energy costs and increase profitability while protecting our natural resources.

More specifically, CR³ brings together key constituencies in the resource recovery and recycling area to develop comprehensive technology transfer pathways to industry.

The primary focus of CR³ is on key sectors of iron and steel, nonferrous structural metals, light metals, rare earths and photovoltaic metals, high-value refractory metals and electronic materials where technology development will address the product manufacturing byproducts, post-consumer scrap, instrumentation, sensors and controls, design for disassembly and conversion of trash to treasure.

CR³ is exploring ways to safely recover and reuse the valuable metals, such as gold, silver, copper, iron and zinc, found in the fine particles that are generated during mechanical processing and in flue dust collected in smelting operations of the electronic scrap.

Although e-scrap also can contain substances considered toxic, including lead, mercury and arsenic, it has high percentages of valuable metals, including iron, copper, aluminum, silver and gold. It is in this area that CR³ is focusing its efforts.

A research study titled Recovery of Valuable Metals from Flue Dust and Other Fines from Mechanical Treatment of E-Scrap is being conducted at CR³, under the direction of Brajendra Mishra, Kenneth G. Merriam Professor of Mechanical Engineering at Worcester Polytechnic Institute (WPI) in Massachusetts and the director of CR³. Hyunju Lee, a post-doctoral student at WPI, is the lead researcher.

“Up until this point, the recovery process of flue dust from the e-waste smelting process has not been fully understood, because there is insufficient information about the constituents of the dust,” says Mishra. “This project will evaluate the potential for cost-effective and technologically viable methods for recovering valuable metals from the flue dust generated in e-waste by using physicochemical methods, which will help industry address the e-waste challenge.”

The recovery of flue dust from the e-scrap smelting process is not well-known because there is insufficient information about the constituents of the dust. This is what researchers at the Center for Resource Recovery & Recycling (CR³) are exploring.

Step by step

CR³ began working on its research project in the fall of 2015 and is on track to complete the project later in 2018.

Researchers analyzed the content of precious metals such as silver and gold and base metals such as iron and copper.

Flue dust samples were provided by a CR³ supporter, a worldwide leader in copper production. Size separation of the nine sample types was performed to analyze the composition for metal value segregation. Composition and crystal phase identification were done using ICP (inductively coupled plasma) mass spectrometry and XRD (X-ray diffraction), respectively.

Researchers conducted magnetic separation to separate magnetic and non-magnetic materials in the size fractions found to contain high metal value.

The research team also has conducted selective leaching for gold, silver and copper using acid solutions. Gold and silver leaching efficiency is approximately 90 percent, and 100 percent through one-step leaching. Through a two-step process, gold and silver leaching efficiency is obtained at about 98 percent and 100 percent, respectively.

Currently, the researchers at CR³ are conducting extraction experiments for gold and silver. An economic analysis will be completed to evaluate which process is most cost-effective and technologically viable for recovering metals.

The high content of valuable and precious metals in these types of waste fines and the easy application of leaching and precipitation steps that allow almost complete selective recoveries provide very high confidence in the economic viability. Thus, the scheme is easily adaptable by e-scrap recyclers.

There are a number of other key industry challenges in the area of resource recovery and recycling that CR³ is addressing. Specifically:

• scarcity of virgin feedstock materials and the increasing cost of some material resources;
• increasing amounts of byproducts and scrap from industrial processes as well as end-of-life products;
• a need for solutions for resource recovery, reuse, and recycling of critical materials; and
• the need for energetically favorable, environmentally compatible and economically viable industrial processes.

More information about this research project or about membership in CR³ can be obtained by emailing Brajendra Mishra at bmishra@wpi.edu.

The author is the marketing director at the Metal Processing Institute of Worcester Polytechnic Institute and can be reached at vbirkhill@wpi.edu.