[Posted pics of pH strips and washed solvent samples in the link below]

Will be using this post to test the used solvent washing treatments discussed in Ethyl acetate approach [CIELO] - Preparation - Welcome to the DMT-Nexus

Treatments

After washing with sodium carbonate-water solution, then settling, 4 samples of used solvent were treated follows:

A. Decant and dry with sodium carbonate.

B. Freeze, remove puck and ice shards

C. Decant and dry with sodium carbonate, freeze, remove ice shards

D. Freeze, remove puck and ice shards, dry with sodium carbonate

These 4 treatments, plus a fresh EA sample, were run using the standard approach, scaled down for 15g cactus powder runs, with six pulls, and passive crystallization.  The only change to the recipe posted on the wiki, was scaling down the citric acid from 5g, instead of the posted 2.5g amount.  Processing times were as stated in the wiki.

Specifically:

Cactus powder - 15g

Pickling Lime - 3.75g

Distilled Water - 45mL

Stir, fold, mash - 8 minutes

Rest in covered french press - 10 minutes

After resting, all pastes were “chopped up” with mixing spoon before adding solvent

Six 3-minute pulls (1 minute stir of 70-90 revolutions, 2 minute rest) per pull, strained through french press strainer into coffee filter on collection jar, combined pulls rested for 1 hour til clear and no water drops/layer

1st pull Ethyl Acetate volume 36mL; 22mL per pull for pulls 2 - 6

Citric Acid - 0.75g, stirred briefly

Passively crystallized for 48 hrs; jar and filtrate filtered and rinsed with two 10mL washes of fresh EA; after jar dried, jar washed into evap plate with two 5 mL hot distilled water washes, then evap’d and scraped.

Processing Observations:

All pastes were my normal consistency of cookie dough/playdough, and consistent color

All pastes became consistency of applesauce within one or two pulls

All runs had solvent pull recovery of 90+%

Combined pulls for all washed solvent treatments were a similar hue, slightly darker than the fresh solvent pulls (as might be expected)

None of the combined pulls had sediment or water droplets/layer after 1 hour settling.

Yields after filtering at 48hrs:

A 0.235g, B 0.234g, Fresh EA 0.201g, C 0.215g, D 0.221g

These resulls are not final, but my general interpretation is that weights greater than Fresh EA represent amount of citrical that precipitated from washed used solvent.  Seems to make sense since this is consistent with C & D having slightly lower weights, after having additional treatment.

Incremental yields after final filtering at 72hrs:

A 0.001g, B 0.000g, Fresh EA 0.004g, C 0.004g, D 0.003g

Jars dried, then rinsed with 2 x 5mL hot distilled water, evap’d. Incremental wash residue yields: A 0.005g, B 0.006g, Fresh EA 0.006g, D 0.006g, D 0.006g.

Total yields: A 0.241g, B 0.240, Fresh EA 0.210g 1.4%, C 0.231g, D 0.230g

Earlier unwashed reused solvents precipitated significant amounts of dissolved solids during subsequent extraction runs (the precipitate is believed to be calcium citrate), the solvents “washed” in this trial represent a major improvement, that neutralizes pH and removes solids to levels near that of fresh solvent.

There appears to be no difference in the A & B treatments for removing the sodium carbonate and water, as well as additional dissolved solids, after the initial solvent wash  (approx 14% non-M appears to subsequently precipitate), with a further slight improvement, but again similar effectiveness, when doing the C & D treatments (approx 10% non-M appears to subsequently precipitate).

Longer settling times at various stages before and/or after washing treatments may further reduce subsequent non-M precipitation. 

Fractional distillation would, fully purify the used solvent, but would involve significantly more work, increase safety issues, and perhaps lead to additional recovery losses.