Sustainable Electrochemical Machining for Metal Recovery, Elimination of Waste, and Minimization of Water Usage

Abstract

This paper will discuss progress in development by Faraday of an integrated technology to recover and recycle metals from electrochemical machining (ECM). ECM is suited for low mass removal, high value-added manufacturing steps that cannot be easily performed using conventional machining, whether due to workpiece material properties, tooling limitations, or high surface integrity requirements. Sludge byproducts formed during conventional ECM processes are difficult to recover from the electrolyte, and discarding the sludge results in the loss of potentially valuable “waste” metal as well as entrained electrolyte salts and water. Results will be presented demonstrating a “Recycling ECM” technology, which is based upon patented cell designs and pulsed waveforms, targeting alloys including: C18000 copper, SAE4150 alloy steel, 316L stainless steel, and INCONEL® 718. These metals were machined in electrolyte to concentrations between 800-3500 ppm and subsequently recovered by electrowinning in solid, metallic form devoid of hydroxides/hydrated oxides, without intermediate electrolyte processing.

Perspective–Opportunities for Industrial Applications of Pulse Electrolytic Processes Beyond Plating and Surface Finishing

“…32,33 Due to the electrolyte flexibility of PRC and PC, the combined PRC ECM and PC EW processes utilized a common electrolyte and for a specific ECM operation, we estimated 1) water usage would be reduced from 85,000 to 3,000 gal yr −1 , 2) ~500 MT of metal containing sludge to landfill would be eliminated, and 3) $56,000 in metal recovery would be accrued. 34 The author suggests that PC/ PRC ECM combined with PC EW is a promising technology for the wider implementation of ECM.…”

Sustainable Green Processes Enabled by Pulse Electrolytic Principles

“…The process recovers valuable metals such as nickel and copper; is estimated to reduce water consumption from ~85,000 gal to 3,000 gal; and is estimated to eliminate ~ 500 metric tons of sludge. 50 In summary, pulse/pulse reverse current enable an environmentally friendly electrochemical machining/electrowinning process, which recovers metals, reduces water usage, and eliminates sludge. Two patents have issued directed to the recycling electrochemical machining process and apparatus.…”

Accelerated Electrochemical Machining Tool Design via Multiphysics Modeling

“…The model domain used for these simulations is shown in Figure 5 analysis of the domain extents. An electrolyte conductivity of 100 mS cm -1 was assumed, which is representative for electrochemical processing of this type (4,5). A DC operating potential of 3 V was assumed for the simulation, which was selected to approximate the average effective potential of the pulse-reverse waveform actually used in machining the part.…”

“…Consistent with conservation principles regarding management of natural (metals, water, energy) resources, such as the "Net Zero" vision of the U.S. Army (3), Faraday has recently developed a patent-pending process (4) which recovers metals, recycles electrolyte and reduces water usage. This process addresses two of the remaining four research challenges, (i) sludge disposal and (ii) electrolyte processing (5). The work described herein is a first step toward addressing the final two challenges: (iii) tool design and (iv) machining accuracy.…”