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Thread: using the principles of electroplating

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    using the principles of electroplating

    Just wondering if you could hook up a low amp battery charger and attache negative leads one with copper,one with steel,one with magnesium,aluminum and zinc, etc....and draw the deposition of dissolved metals onto these negatively charged diodes ( not sure if that's the word I'm looking for)...But you get the idea.

    If it would work....it would be a great business to start as a relatively inexpensive service clearing residential and commercial pools of their dissolved metals staining problems.

    Whutcha think?
    11000 gal L shaped gunite pool with and aggragate plaster
    Pentair cartridge filtration with 1.5 hp pump
    only have 3 returns and one dedicated vacuum line
    manifold to pump is three valve

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    Re: using the principles of electroplating

    The negative plate (cathode) would generate hydrogen gas, just as it does in a saltwater chlorine generator. If it were that easy to remove metals, then saltwater chlorine generator pools that used metal ion algaecides or had other metal staining issues would be able to simply run as normal and plate out all the metal. That doesn't happen, at least not enough to be viable to remove metals from the water. It's not that plating out metal doesn't work, but that when the metal concentrations are low, it becomes impractical because the rate of plate-out drops too low unless one has huge plate areas and currents.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
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    Re: using the principles of electroplating

    Actually i think it could be done reasonably efficiently.I was more curious as to whether it would involve adding more chemical solutions ..acids and such that you wouldn't want in your pool at all for any reason.

    I'd also think you wouldn't want moving water during the process....still water and positive ionized metals depositing onto a negative charged plate of metal....or maybe I have that in reverse.

    If it simply means adding an acid like AA or some alkaline solution...that problem could be worked out I think.
    But I was also wondering if each cathode would need to be of Like metal that you are trying to take out of solution...ie: 12" x 12" 12ga copper plate to draw out copper....or would you be able to draw all dissolved metals and deposit them onto one cathode.

    I just came across a rather expensive product...I think it is called CU-Lator....it is a packet of polymers that you place in the skimmer basket and supposedly precipitated the dissolved metals and minerals inside this packet without added negative or positive charge.

    I don't see how that is possible. I knew I should have studied up more on alchemy.

    My idea I think would work......the only real problem I see is the dangers of electricty and water....the safety of people.The pool area would need to be babysat during the process to ensure no one got zapped.

    If it would require the addition of certain acids or potassium cyanide to the pool water....then....I'd not mess with it.
    11000 gal L shaped gunite pool with and aggragate plaster
    Pentair cartridge filtration with 1.5 hp pump
    only have 3 returns and one dedicated vacuum line
    manifold to pump is three valve

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    JasonLion's Avatar
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    Re: using the principles of electroplating

    I agree with chem geek, there is no way you can get that to work quickly enough to be of any use. The metal concentrations involved are extremely low, and that slows the reaction rates down dramatically.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Re: using the principles of electroplating

    You will be limited in the rate of plating by the conductivity of the water and your plate area, but mostly by the fact that the metal ion concentration is so low. As I wrote, even saltwater chlorine generator pools don't plate out metals fast enough and they have 3000 ppm salt (so higher conductivity) and enough plate area to be able to generate sufficient amounts of chlorine. What you are proposing is simply not practical. If you had strong solutions of metal ions, then plating is reasonable, but we're talking about levels in the 0.2 to 1 ppm range and that is VERY low concentration in terms of plating.

    You absolutely would want the water to be moving, otherwise the metal ions in the water would only get to the plate by diffusion which is VERY slow. As for trying to "attract" the metal ions to the plate by charge, you are forgetting that there are much higher concentration of other positive ions in the water, namely sodium and calcium. Though these won't plate out due to their thermodynamics, they will migrate to balance charge. Likewise, hydroxyl ions generated at the plate will migrate away.

    The cathode does not need to be of like metal in order to have plating occur, but it is true that different metals will have different over-voltages so some will be more likely to plate than others. However, all of this is swamped by the fact that primarily hydrogen gas will be produced since that it more thermodynamically favorable (at least for iron, as shown below).

    CuLatorâ„¢ has had mixed reviews so far so the jury is out on this product. It works by essentially having a metal sequestrant chemical bound in a polymer so that it stays on the surface of plastic balls in the bag rather than being dissolved in the water (see How It Works as well as this patent). So as metal ions in the water flow through the bag they attach to the sequestrant in the bag. No mystery here and it's a reasonable approach, but as I wrote we don't have enough positive info to recommend this yet.

    TECHNICAL DETAILS OF THERMODYNAMICS OF PLATING AT CATHODE:

    The relevant half-reactions at the cathode are the following:

    2H+ + 2e- --> H2(g) ..... E0 = 0.000V
    Fe3+ + 3e- --> Fe(s) ..... E0 = -0.037V
    Cu2+ + 2e- --> Cu(s) ..... E0 = +0.3419V

    To figure out the actual reduction potential, one needs to use the Nernst Equation to account for concentrations of reactants and products:

    E = E0 - (RT/zF)*ln(ared/aox) = E0 - (8.314*300/(2*96485))*ln(ared/aox) = E0 - (0.0129)*ln(ared/aox)

    At a pH of 7.5, [H+] = 3.47x10-8 M and at 1 ppm (mg/L) [Fe3+] is 1.79x10-5 M and [Cu2+] is 1.57x10-5 M. Hydrogen gas has a Henry's constant of 7.8x10-4 M/atm and a normal partial pressure in the atmosphere of 0.55 ppmv (5.5x10-7 atm) so the normal concentration in water is 4.29x10-10 M. So using the Nernst equation, the actual reduction potentials for the above are the following:

    2H+ + 2e- --> H2(g) ..... E0 = +0.056V
    Fe3+ + 3e- --> Fe(s) ..... E0 = -0.178V
    Cu2+ + 2e- --> Cu(s) ..... E0 = +0.199V

    The above ignores over-voltages, reaction rates (including ion diffusion rates) and the fact that hydrogen gas concentration in the water will rise especially near the plate so will be less favorable than indicated. Based on the above, it would seem that it is unlikely for iron to plate out, but possible for copper to do so, albeit slowly.

    Perhaps the saltwater chlorine generator folks can comment on whether they see any plating of copper onto their cathodes in pools with copper ions, though the reversal of the salt cell will tend to minimize any long-term accumulation.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

  6. Back To Top    #6

    Re: using the principles of electroplating

    Definitely a thorough explanation of the problem.Thank you Chem Geek.

    It's sometimes too bad that all metals aren't magnetic...it would be so easy to set up a 30 gallon seguestration tank with an electromagnet.Although I think I've read somewhere that everything is susceptible to magnetic attraction.
    11000 gal L shaped gunite pool with and aggragate plaster
    Pentair cartridge filtration with 1.5 hp pump
    only have 3 returns and one dedicated vacuum line
    manifold to pump is three valve

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