SEM TECH: Salt Electro Mining Technology

SEM TECH is Rowow’s open-source platform that uses saltwater and electricity to extract, concentrate, and refine metals from ore, mine tailings, e-waste, slag, and industrial waste. The leaching chemistry (hydrochloric acid plus sodium chlorate) is derived from saltwater and regenerated electrochemically every cycle. The system runs closed loop, so there is no repeated chemical makeup and no waste acid stream.

Periodic table of SEM TECH recoverable elements — 53 of the 60 US critical minerals are extractable in a single leaching solution.

How the closed loop works: the CMU

In the Continuous Mining Unit, the acidic leaching solution is regenerated at the anode and flows to a leaching tank where it digests the ore. Solids are separated from the liquid, and the metal rich leachate is pumped to the cathode side, where dissolved metals are reduced and plate out as powder. The depleted solution then returns to the anode through a cation exchange membrane, and the cycle repeats. The solution holds an oxidizing redox potential of over 1.5 V at pH 0, strong enough under chlorine-rich conditions to dissolve noble metals such as rhodium, platinum, and gold.

Continuous electrochemical leaching closed-loop diagram — The Continuous Mining Unit: leach chemistry is regenerated in-loop while metals precipitate as powder.

Selective refining: the CRU

The Continuous Refining Unit uses the same architecture with different solutions, for example nitric and acetic acid, to selectively dissolve base metals out of CMU powder, dore bars, and mixed metal feedstocks while precious metals stay behind for continuous concentration. Our CRU has leached a complex vanadium-chrome dore bar, similar to Hastelloy, that traditional nitric acid would not touch.

Continuous electrochemical refining diagram — The Continuous Refining Unit: selective leaching with precious metals retained by filtration.

Results so far

Up to 99% recovery at costs as low as $50 per ton at bench scale
53 of the 60 US critical minerals extractable and concentratable in a single leaching solution
Third party assay confirmed rhodium recovery, a metal that aqua regia leaves untouched
Clear mining waste had its heavy metals reduced within 5 to 10 minutes at about $5 per ton, while the acid was recovered and regenerated
Membranes field tested for months in harsh acidic mining conditions with no observable decline in performance
Validated in-house with a Rigaku NEX DE lab spectrometer, detecting elements from sodium through uranium

Rare earth oxide concentrate produced by the CMU on a lab scale — Rare earth oxide concentrate recovered by SEM TECH.

The membrane that makes it possible

Commercial ion exchange membranes can cost up to $400 per square foot. Ours is made from pulverized water softener resin dispersed in PVC cement and costs under $1 per square yard. We filed U.S. non-provisional patent application #19/531,984 to anchor the work, then released the design to the public domain under CC0 1.0 so anyone can build on it.

Build it yourself: the open-source membrane repository

Where this is going

SEM TECH runs today at lab and small prototype scale, validated on real ore, tailings, and liquid mine waste. The next step is a pilot scale system in a portable shipping container configuration processing 2 to 5 tons per day, the threshold where mining and e-waste feedstocks become economic. If you have a feedstock, a waste stream, or a project that might fit, we would like to hear about it.

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