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Silver Capture and Recovery from Microelectronics Wastewater

Background

Microelectronics manufacturing uses diverse raw materials, chemicals, and processes. As part of the production finishing process, chemistries diluted with deionized water (DI) are used to remove particles, residues, metallic impurities, and organic contamination from the sensitive components in rinsing baths. While assuring quality and longevity for the manufactured components, this rinse requires wastewater treatment to address the dissolved metals removal for asset recovery and discharge compliance regulations placed on the facility. Silver metal found in the rinse water was targeted for treatment and disposal according to EPA and local regulatory guidelines. Recovery of the silver is highly desirable due to its value. Ion-exchange (IX) was the traditional treatment method, which required heavy amounts of processing and media/vessel changeouts to capture the silver asset.

Challenges

A large printed circuit board (PCB) manufacturer produces silver-laden wastewater from rinse baths, also called drag-out baths. The site was using ion-exchange to remove the silver to meet NPDES permit limits and selling the saturated resins to a smelter to reclaim only 55% of the silver value, or $449/kg. Production for the plant was forecasted to increase, which translated to an increase in resin change out frequency and associated costs.

Proven Results | Case Study

The manufacturing process of a microelectronics manufacturer produced waste byproducts containing elevated levels of silver of 40 ppm – 80 ppm and varying amounts of organic compounds. The site permit allowed for 0.1 ppm in the effluent discharge. Site expectations are to recover the silver for recycling while meeting discharge compliance. ElectraMet’s automated process was implemented in phases to control the changeover from ion-exchange, resulting in an 8-week implementation and approval process.

Over an 8-week period, the site was able to:

  • Increase vale of recycled silver by $343/kg
  • Eliminate ion-exchange (IX) resin replacement and chemistry
  • Reallocate 1/2 FTE to production site
ElectraMet’s automated solution uses an electrochemical process to selectively remove and recover silver from complex process water or wastewater streams. The system is modular and can be scaled and interfaced as production grows. The system consumes very little power of < 0.12 kWh/m3 treated. With its capture and recycling technology, ElectraMet’s chemical-free process presents a circular solution for handling silver in process/waste streams, benefiting the plant, its employees, the surrounding community, and the environment.

Additional observed benefits include:

  1. eliminated > 20,000 pounds of annual IX consumption,
  2. reduced operator hours due to automation and analytics which informed adjustments,
  3. analytics-informed upstream process troubleshooting maximized uptime and production quality, and
  4. increased personnel time spent on preventative maintenance for other systems.
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