Ok, so I did a STB where I added potasium metabisulfite from the local brew store. I used a 1:6 shredded MHRH bark to water ratio mentioned in the paper in the first post (50g of bark and 300ml of water) then slowly added ~10% NaOH (30g) and 20% (60g) Potasium Sulfite. This was mixed well and run in the PC for two hours at 15 PSI, then allowed to cool below 100F and pulled 3x with naphta.
Notes/Results
- Part of the bark turned into a thick muddy slush and a distinct "pulp" like core. Seems consistent with the lignin breakup to release the cellulose story, but I can't say for sure.
- During the naphta pulls a burnt tan/orange color appeared in the naphta (see first image below). Usually with NaOH only looks more yellow.
- This orange color is difficult to get rid of. It remained after a few re-X (it only slowly fades). It is a bit problematic honestly (assuming it is unwanted). Right now this is a downside compared to doing STB with NaOH only (from previous experience).
- On the plus side, yield was surprisingly high after only 3 pulls (1.008g ~ 2%, however the product is now white yet - see second picture). I usually get less with a simple STB after 3 pulls (1.5% to 1% range). Will do a few more pulls to see if anything else comes out.
So sulfites could be helping break up the bark?
Overall I think this is worth a few more tests. If we find a way around the new orange color (e.g. a FASA/I step) it would be worth doing the direct sulfite/no-sulfite split keeping all else the same (same PC run, same ionic strength using NaCl on the control) to compare yields.
Also, I may have overdone it. It could be that with sulfites less NaOH is needed, etc. But first, will need to figure out the orange color and then check yields. If no benefit at that point it would not be worth fine tuning this process.
Loveall attached the following image(s):
IMG_20190925_074315751.jpg
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