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Bleaching WVO/biodiesel

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  • Bleaching WVO/biodiesel

    I've had reason to need to bleach a batch of WVO before esterification with methoxide and just wanted to share some of my findings with others and outline an alternate work around should the requisite bleaching clay be unavailable.

    There has been a lot of talk about using magnesium silicate type bleaching agents and some have suggested using talc. Talc is actually a hydrated form of magnesium silicate and is not acid activated unlike the commercial products hence the poor results.

    Although it may be possible to acid activated talc I chose calcium bentonite (smectite) type clays because the procedure called for this. The clay I actually used was sold is a thixotrope and had other compounds like alkyl amine tallowates but I disregarded these knowing I was going to treat with concentrated sulphuric acid.

    NOTE: There are swelling and non swelling clays, what is needed is a NON SWELLING type clay, although they may actually both be acid activated, the swelling type has a tendency to froth and foam excessively. Not a good idea with conc H2SO4.


    1. Add 330 g of Ca/bentone clay to one liter of DI water and mix until homogenous.

    2. Bring temp up to about 60 C and slowly add conc. H2SO4 equal to 35%
    of total solution volume.

    3. Increase temperature to between 100 and 120 C and heat for six to twelve hours. CAUTION: MONITOR FOAMING AS THERE MAY BE A LOSS OF CONTAINMENT

    4. Filter solution and wash with DI until pH is neutral

    5. Oven dry at 100 C for four hours or overnight at 40 C

    6. Crush dried filter cake to -75 um, about the same size as a kitchen sieve

    And thats it.

    All you need to do know is add this to your WVO or meth ester at 10% and heat to 100 C for about six hours, then cool and filter.

    All filtering should be done down to about 10 um, anything above this size can wreak havoc on an engine, its like sandblasting it from the inside!

    I haven't actually used my home made bleaching clay so I really can't talk about its efficacy (drying as I write this) but I'll update the thread next week (with pics) when I've had a chance to try it out. From all reports though, this recipe should bleach veg oils equally as good as the best bleaching clays on the market.

    Lastly none of this work would be possible if not for 250downunder who supplied me with a free 100L waste soy sample and has been more than generous with his advice and expertise in the area of both bio production and bleaching

    Happy bleaching all!



  • #2
    Re: Bleaching WVO/biodiesel

    What do you mean by "bleaching" WVO, and why is it done?


    • #3
      Re: Bleaching WVO/biodiesel

      I use magnesium silicate to purify my biodiesel. It works by adsorption. Wikipedia gives; Adsorption- is the physical adherence or bonding of ions and molecules onto the surface of another phase (e.g., reagents adsorbed to solid catalyst surface). The stuff I want to remove sticks to the insoluble magnesium silicate, which is then filtered out. It has been working for me. But I've only done very small quantities. Magnesium silicate, brand name Magnesol was used to clean up vegetable oil in restaurants. We used it at a fish and chips restaurant I worked at. Bleach-refers to a number of chemicals that remove color, whiten, or disinfect, often via oxidation. I don't understand why you use the term bleaching?


      • #4
        Re: Bleaching WVO/biodiesel

        Originally posted by Dr Mark View Post
        What do you mean by "bleaching" WVO, and why is it done?
        There are industrial uses for Methyl Esters [other than fuel] that require a product that is both clear and free of colour [carotenes]. Soy Methyl Ester, having superior solvent properties, is the material of choice.


        • #5
          Re: Bleaching WVO/biodiesel

          Hi 250, thaks for chimming in.

          Guys, I was merely using the commercial name for the process. Also theres good evidence that acid activation helps breakdown the corotenoids (red and yellow pigments) so the process is both chemical and physiochemical (adsorptive) in nature.

          The commcercial products claim to clear up to 98.5 % based on spectrometric analysis of wavelengths specific to the carotenoids. Could you roughly estimate (visually) how effective Magnesol is WesleyB, can you show us some pictures?

          There are a ton of manufacturers for these clays on the market.



          • #6
            Re: Bleaching WVO/biodiesel

            ,When I used magnesium silicate to help purify orange, acorn derived methyl biodiesel, the biodiesel went from orange to clear yellow. I had assumed the bright yellow color was due to unsaturation in the fatty acids. I don't know if I can post pictures of it. Maybe my brother has the equipment and know how to do it. I think what I removed from my acorn biodiesel was tannic acid using magnesium silicate.
            Donating Member
            Last edited by WesleyB; 29 October 2011, 05:50 PM. Reason: added a comma


            • #7
              Re: Bleaching WVO/biodiesel

              Is there some confusion here ? Looks like Bioboy uses the bleaching product to remove color from the Biodiesel to use it for another reason other than for fuel.
              Magnesol is used to remove impurities from biodiesel to use in the car , not take the color out.

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