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I am attempting to design/enhance a system which applies direct current to a soil for the electro-kinetic remediation of organic/metal contamination. My current plan is to try enhancing conventional EK-treatment by concurrently heating the soil using microwave frequency radiation distributed in-situ through a co-axial antenna.

My question is whether the microwaves will interact with my DC field in any way, and if anyone could suggest some resources to me for exploring this idea

To help visualize the problem, I plan to utilize an anode on the left of the soil cell, a microwave antenna centrally located in the soil, and a cathode on the right of the soil cell. I cannot seem to find information on how these two components may interact.

(I apologize if this is a silly question, I come from a Civil Eng. background so electricity is quite foreign to me)

Austin Pelletier
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  • As someone with no background in civil engineering, such cross-domain questions are always very interesting! Now, I'm a bit surprised microwave should help: Just like in your microwave oven, I'd only expect a heating up of (wet) soil; the same effect could probably be had cheaper with more DC. Can you enlighten us about the physical / chemical things happening during EK-treatment and what you expect microwave radiation to do? – Marcus Müller Jul 02 '18 at 22:31
  • Aside from heating, microwaves do change some chemical processes. e.g. Acid digestions proceed faster with microwave heating, than plain external heat, all things being equal. – Henry Crun Jul 02 '18 at 23:31
  • BTW, there is also a lower frequency, 27.12MHz used for RF welding, diathermy and other heating. This might have deeper ground penetration., or offer other options. – Henry Crun Jul 02 '18 at 23:55
  • What happens if you add a high AC voltage to the same electrodes to get increased heating. What exactly is the DC supposed to do in the bulk, as opposed to at the electrodes where there will be ion exchange with them? – Neil_UK Jul 03 '18 at 05:45

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It won't affect the flow of DC current (as a first order electrical effect).

However the strong microwave signals will be picked up by the electrodes and cables, and carried back to the DC power supply circuits. Or leakage from the microwave generator/coaxial cables might couple to the DC power supply you stacked it right on top of.

RF might upset the operation of the power supply: the voltage and current go up or down.

If this is the case you need to do something about it. quarter wave stubs, coiled leads, shielding, ferrite sleeves. Entirely solvable if it happens.

A tip: old fashioned coil+needle meters might be more reliable indicators of current/voltage under strong radio fields, than digital types.

An issue with what you are trying to do is getting power into the soil, and not reflected back to the transmitter by mismatch. Reflected power/VSWR meters show you this.

Henry Crun
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