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Although ink waste (mixed colors of different inks for printing) is 90% water, separating the inks appears to be problematic. We have tried membranes, RO, electrolysis, boiling, and solidifying with kitty litter. Membranes do not trap the dyes, electrolysis is slow and expensive, boiling is expensive and messy, and litter makes too much waste. I would like to separate out the water and decimate (reduce by 90%) the waste. Any other process ideas? I have worked on precipitating the ink but I am not much of a chemist and there are all kinds of different components.

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  • $\begingroup$ What sort of scale are we talking here? How many litres per minute/hour/day of 'clean' water do you need to get out, or ink are you putting in, and what % recovery rate is the minimum requirement? $\endgroup$ – Jonathan R Swift Mar 20 '18 at 9:34
  • $\begingroup$ Are you trying to recover the water or just avoid violating effluent rules in your outflow? $\endgroup$ – Carl Witthoft Mar 20 '18 at 15:51
  • $\begingroup$ The scale is approx. 5 gal per day. We do not want to recover the water and we consider ourselves a green company, so we want to follow the disposal rules. Our goal is to reduce waste cost. $\endgroup$ – Kirt Haden Apr 10 '18 at 22:16
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many dyes and pigments can be decomposed by buffering the ink to either acid or base, depending on their molecular structure. you can then dewater the resulting effluent with the right RO membrane.

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Low pressure desalination is a known technique to avoid high temperatures, the same problem that appears to hinder you in boiling.

I wouldn't aim for a single process, though. As you noted, boiling will concentrate the result and give you sticky solution to work with. At that point you may want to switch to that litter-based solution - most of your intial volume will have been boiled off as pretty clean water vapor. (If your ink contains alcohols, they'll boil off preferentially and can be condensed out before the water vapor.)

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