Win a copy of Compost Teas for the Organic Grower this week in the Composting forum!
  • Post Reply Bookmark Topic Watch Topic
permaculture forums growies critters building homesteading energy monies kitchen purity ungarbage community wilderness fiber arts art permaculture artisans regional education experiences global resources the cider press projects digital market permies.com private forums all forums
this forum made possible by our volunteer staff, including ...
master stewards:
  • Nicole Alderman
  • r ranson
  • Anne Miller
  • paul wheaton
  • Joseph Lofthouse
stewards:
  • Mike Jay
  • Jocelyn Campbell
  • Devaka Cooray
garden masters:
  • Steve Thorn
  • Dave Burton
  • Dan Boone
gardeners:
  • Joylynn Hardesty
  • Mandy Launchbury-Rainey
  • Mike Barkley

Hydrogels in solar stills?

 
gardener
Posts: 2406
Location: SW Missouri
696
goat cat fungi books chicken earthworks food preservation cooking building homestead ungarbage
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Read an interesting article this morning, anyone have any clue what these hydrogels are and whether they are toxic?

New solar technology could produce clean drinking water for millions in need

 
gardener
Posts: 2386
Location: Central Texas zone 8a
381
cattle chicken bee sheep
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
That is interesting. I have no idea about toxicity. I would guess there would be no toxicity in the finished water because that is what evaporation/condensation does. It leaves the icky stuff behind.

So the question is what happens to the solids left behind. If seawater is used, the byproduct is sea salt. But this sea salt would have these polymers mixed in.

Since the water is distilled it lacks any minerals. Common sense would say add a little bit of the solids (sea salt) back into the water for that reason. Mineralize it.



 
garden master
Posts: 2585
Location: Central Oklahoma (zone 7a)
487
forest garden trees woodworking
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
In general the hydrogels themselves are "considered" non-toxic, but I recently discovered that the long-chain polymers that go into them tend to have toxic breakdown products:

Soil-additive hydrogels (water gels, water crystals) contain AND break down into toxic gick

Now, the common hydrogels are polyacrylamides; the breakdown products include acrylamide, a lethal neurotoxin.  The article suggests the solar still is using polyvinyl alcohol instead of polyacrylamides; so maybe that bullet is dodged but from what we know of vinyl, this stuff won't have pleasant breakdown products either.

As Wayne points out, the water produced by the still ought to be chemically pure.  But what about the sludge left behind?  It's going to be full of this stuff and its breakdown products, and it's going to be a disposal problem; every time the still gets dumped, washed, cleaned, or otherwise maintained, these chemicals will be going somewhere.  So I am not sanguine, even though I'm not enough of a chemist to evaluate how PVAs (polyvinyl alcohols) break down.
 
Pearl Sutton
gardener
Posts: 2406
Location: SW Missouri
696
goat cat fungi books chicken earthworks food preservation cooking building homestead ungarbage
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
My first guess was they'd break down into nasty chemicals. But, if they don't, wow, what a cool thing, if it made solar stills work better.
Hope someone who is a chemist chimes in here. I think it's such a neat thing, to up the output speed... but not at the expense of gick. That's why I distill water to start with, to eliminate gick and gack.
 
This is my favorite show. And this is my favorite tiny ad:
permaculture bootcamp - learn permaculture through a little hard work
https://permies.com/wiki/bootcamp
  • Post Reply Bookmark Topic Watch Topic
  • New Topic
Boost this thread!