> chemistry > techniques-et-matériel > amateur-lab-equipment-reverse-osmosis-deionization-systems-for-purifying-water-nurdrage

Amateur Lab Equipment: Reverse Osmosis Deionization Systems for Purifying Water

NurdRage - 2020-06-13

In this video we discuss the components, usage, and science behind a Reverse Osmosis Deionization unit for purifying water.



Most sources of water that an amateur chemist may use (like tap water) contain dissolved salts. These salts usually consist of sodium, calcium, or magnesium carbonates, chlorides and sulfates. Water containing significant quantities of these minerals is often called "hard water". And they can be easily observed by letting a quantity of water evaporate completely. While these minerals are usually very low in concentration and inconsequential for most domestic purposes like drinking, cooking or bathing, they are a contaminant for performing chemistry. This can be particularly detrimental to sensitive experiments like analytical chemistry, crystal growing, or electrochemistry. So removal is preferred. 



The historical technique for removing non-volatile mineral contaminants is distillation. For very small quantities distillation is cheap and effective as most amateur chemists already have distillation equipment. But for larger quantities, distillation is very energy intensive and expensive due to electricity costs. It's also extremely slow. 



Reverse Osmosis Deionization is now the standard for making purified water as such systems are much easier to purchase in the modern era. A basic system has a carbon prefilter that takes in water and neutralize the chlorine normally added to sterilize. This is done to ensure the chlorine cannot damage the reverse osmosis membrane. The water then proceeds to the membrane that consists of a rolled envelope of polyimide plastic. This membrane passes water, but resists the passage of minerals and salts. The wastewater that contains the leftover minerals is discarded, while the permeate water with most of the minerals removed is sent to a column of deionization resin. This resin is made of a special ionically charged plastic that swaps out mineral ions in the water for hydronium or hydroxide ions. Those ions neutralize to become water and the result is purified water with all the minerals removed. While not strictly necessary, purified water improves the quality and reproducibility of amateur chemistry experiments so a reverse osmosis system is a recommended addition to an established amateur lab.


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Explosions&Fire - 2020-06-13

Hey cool video! But as you might be aware from the view numbers, this isn't coming up on my subscription list? Good luck getting it fixed, I know it's been a problem that's plagued your channel a bit over the years

NurdRage - 2020-06-13

This time it's my fault. I uploaded multiple videos, deleted some, changed others, and set some to unlisted and private. Totally messed things up. Next video should be a bit more straightforward.

Explosions&Fire - 2020-06-13

@NurdRage still strange that this video is stuck in purgatory somewhere between unlisted and public, it shouldn't even be possible for that to happen

Dismissing - 2020-06-13

I was wondering why I couldn't see this in my subscription page. Thanks for clearing things up!

Kenny Adams - 2020-06-24

I always thought you watched nurdrage! Big inspiration of my chemistry quest. Especially using households

Jos J - 2020-06-23

As a ship engineer this type of system is widely used on most cargo ship to create potable water from sea water.
When you change filters in this kind of system please make sure they are straight and do not use the wrench to tighten the filters.
These kind of filters are mostly pressure locking and only need to hand tight. When using a wrench to close it you will break the plastic over extended periods of time.
I hope this helps and sorry for the bad grammer

NurdRage - 2020-06-24

Interesting! i'll keep that in mind :)

Nate D. - 2020-06-26

I was looking for this comment. There are a few videos out there on creating your own system, without having to purchase an expensive system, for use on smaller boats.

Kitty 折衝子 Black - 2020-12-16

@Nate D. u can find exactly this type of filter on ebay for around 50$ add maybe 60-70$ for the storage watertank and you should have a good set. search in the aquaristic section, thats where i found it :)

Cameron Bigley - 2020-06-14

I never knew how reverse osmosis worked. I'm glad to be taught it by my favorite science channel. Thanks for the interesting content, as always!

Aqua Mayne - 2020-06-24

This video is great, I am obsessed with learning about RO water and this video has been the most extensive

SV Chineel, Junk-Rigged Schooner Sailing - 2021-07-31

This system is very different to what you need for seawater RO, in case you were wondering.

Archis - 2020-06-19

ThermoFischer came to my lab to install a deionizer. While installing the cartridge some of the black stuff looked yellow. I asked the service man and he said it's normal for it to be that way.
I'm pretty sure he was peddling a spent cartridge because we got the purifying system with a discount. Fuckers.

Marta - 2020-06-13

Well it was a good lesson, I don't mind watching it all over again.

Chris Carley - 2020-06-13

Doc, extremely informative and thank you for making us think more. I'm glad you're back.

Doc Mangler - 2020-06-29

Thank you so much for posting this, I'm already familiar with these components, it's really great to see how it works chemically.

Libor Tinka - 2020-07-06

Thanks a ton! This saves me a lot of time when choosing the water filtration system.

ajayalmighty - 2020-06-24

Looking forward to a more detailed video about the ion exchange resins!

Quinn Hughes - 2020-06-17

Always glad to see you posting! Like always such a great video and I can't wait to see more

Dejay Rezme - 2020-06-13

Thank you very much, I'm quite interested in living "off grid" on a boat. This video explains the basics first. I realize the water makers for boats probably have more or different steps.
I'm also somewhat fed up with the hard water we have here, you constantly get lots of residue when cleaning or cooking or boiling water.

PS: I'd really love it if you'd expand on this topic, regeneration of filters, how to add a pressure booster, how to increase efficiency, how to dial in the water input/output pressure, maybe pumps that can use the energy of the clean output water to increase energy efficiency.

Of course I'm just lazy, just have to learn all this myself ;)

Alex Blair - 2020-06-14

I live in an area with extremely hard water, and while I ended up getting a full system for the house at large, it's after all my outdoor taps. Eventually, I found a similar cartridge to the deionizaton one, but it's built as a water softener cartridge, that can be regenerated by dumping it into a 5 gallon bucket of saturated water softener salt. We use this and a couple of adapters to soften the water when cars are getting washed. Might be a good option for you if you're dealing with particularly hard water. I've also found that softening the input water makes my reverse osmosis membranes last way longer. The RO system I use for hydroponics, drinking water, and the occassional bit of electronics cleaning, and the suggested replacement is 3 months for all filters other than the RO membrane, which is 1/year.

Liam Cg - 2020-07-10

i just want to say that your videos have helped immensely to improve my understanding of certain things in chemistry and given me a very significant amount of information that has helped me a lot with home chemistry, i really appreciate the amount of time and work that you put into your videos and really hope that you continue. definitely one of the best.

Chlorate - 2020-06-21

Excellent video, I actually had no idea how reverse-osmosis filters worked until now.

Алексей Московец - 2021-03-19

Thanks for the great video! This is very useful for me to understand the practical side of the RO and DI.

KOR - 2020-06-16

Nice video. I am looking forward to the regeneration of the deionization resin video.

Mokou Fujiwara - 2020-06-22

I have to separate into 2 sessions to fully watch this video. Nonetheless, this is a very good lesson.

Rodney Vinen - 2020-06-13

Brilliant. You did a fantastic job on this video. Thank you for sharing your great work and knowledge.

madxenomorph - 2020-06-24

Thank you for explaining it. I live off a well and water is plentiful but I started off with limited filters and are living with delivered bottled water. This video helps explain what I can/should do to feed better water into my softener/non-drinking system AND what the actual reverse osmosis system I plan on getting will do.

thejumperkin - 2020-06-24

I'm glad you made this video even if it doesn't include any of your usual experiments. This is some awesome information. I'm sure everyone else appreciates it as well!

John Gilmer - 2020-06-27

You might want to "promote" the post carbon filter to the pre-filter position and install a new filter it its place.

orhan tokur - 2020-10-22

Thank you for the video. We have a similar system in our laboratory. My question is: Do you think that these filters can be reused after cleaning with high pressured water?

UDtheAesir - 2020-06-14

Yay, NurdRage's back!

G A - 2020-06-14

Great video, thanks
I used to work in a lab and the process there was: potable tap water pushed through large (separate) cation & anion beds which were regenerated with hydrochloric acid and sodium hydroxide. This was then distilled and then put through a reverse osmosis polishing unit with carbon, resin & uv. I shudder at the costs involved but have to say that it was very pure (18 megohm)

texasdee slinglead - 2020-06-16

You ought to see kidney centers , and type 1 water production . Both are insanely expensive .
A kidney center can process 150 gallons of r.o. per hour, typically . The system for such volume is huge and very specifically tailored and modified to deal with unique incoming municipal source . Government oversite is crazy on those systems .
Type 1 water is far more expensive to produce , but not quite as regulatory to produce .
Basic pharmacy and lab sample RO systems are so pleasent to tinker with when compared to the industrial sized beast versions .

Martin Špina - 2020-06-19

I’ve been waiting for this video long time. Thank you

Johnavon Joseph Jin - 2020-06-16

Over the months and years I have realised that the number of subscribers for this channel has been decreasing despite the increase in quality and depth of his videos. This is just sad to know that a sizeable portion of the subscribers were just here for the pop science. Keep up the good work. Been a faithful viewer since 2012 :)

Succulent Lord - 2020-06-21

Huge thanks for making this. A while back, I started researching RO and it was incredibly difficult to find practical information like this that covered the full range of applications and filtration tools. It seems like water filter companies and plumbers try to obfuscate information for marketing purpose...

Timothy Manley - 2020-06-21

the best free source of free information relating to RO design is dow chemicals reverse osmosis design manual. its very tightly written but scientifically oriented...not very engineer friendly but its exhaustive.

purolite also publishes a series of papers on ion exchange specifically. beyond this you will need to spend money on amazon for industry specific and general topic type design manuals.

Penot - 2020-06-21

I'd love a video on ionic exchange resins

Cerise Author - 2020-06-20

I just rebuilt the 18Mohmcm system in my lab, it's surprising how cheap non ozone uv and .05 micron filters are now. On a small lab scale it's not as expensive as you'd think to pump water in a loop (post ro) instead of installing down stream components. If the volume the loop pushes is much higher than the output then you can maintain 18 Mohcm purity.

David Hülsmann - 2020-06-13

Thanks for this informative video. I consider installing one of those systems 😉 greetings from Germany

Kitty 折衝子 Black - 2020-12-16

die sind wirklich gut, findest die bei ebay in der aquarium sektion, heißen auf deutsch umkehr osmosefilter und am günstigsten fährst du mit filter und tank für filterwasser seperat. achja, isoliertape nicht vergessen, des weiße gummiartige ausm baumarkt und nit zu fest schrauben sonst bricht das plastik ;)

Dane - 2020-08-05

Alternating spin magnetic stirrers would exponentially increase rate of reaction

PoWnAy Productions by JR - 2020-08-17

Hi NurdRage, great video as always ....I was just wondering if the RO membrane was polyamide and not polyimide? I’m used to hearing of polyamide RO membranes.

bobmoandfriend - 2021-05-01

I lol'd at 'after all, as chemists, we should take advantage of the few times when we know what we're doing' xD

Sam Woo - 2021-06-16

Thanks. Great description of purifying and deionizing water. Is there any advantage of connecting more than 1 RO filter in series to improve the purity of the water? Seems like this should reduce any impurities although it would waste more water.

Google User - 2020-06-13

I used an ro unit for weekly, partial water changes in my freshwater aquarium.

LandOfSigh - 2020-06-17

This video reminded me of my first Ion Exchange Chromatography lab. It went.... much slower than I expected.

batenkait0s - 2020-07-24

interesting to see how these things work. ive been wanting to obtain or create one myself since carnivorous plants can be somewhat sensitive to the minerals in water (their natural habitats often have low mineral concentrations in the soil so they often aren't well adapted to them) so it would be nice to have one of these myself but it's also interesting to look at the schematics of these systems and try to come up with improvements.

Joe C - 2020-06-19

I'm looking forward to more details on the Ion exchange resin. I need to exchange a Potassium Ion for a more water soluble Sodium Ion for a project. I think an indicating Cation exchange resin will do the trick.

Garbled User - 2020-06-21

Indeed! How do you regenerate a mixed bed resin?

mrtini102 - 2020-06-24

@Garbled User With an acid and base flush. Something like NaOH and HCl one after the other with a rinse in between. Haven't done it for a while so might not be 100% correct but its the basic principal

Brian Whalen - 2020-06-26

@mrtini102 It's best to separate the resins before regenerating

William Eagan - 2020-07-01

Good video. How does rain water compare with distilled, deionized and tap water for quality?

Kirby Wilkerson - 2020-06-24

Excellent video. I was going to ask a question about the RO system we had at work for an anodize process line which had the water softener before the RO input, but I think you answered it. It had a booster pump so the pressures were much higher and I think the calcium was more likely to block the membranes at that pressure. It then had what we called polishing bottles after the RO system. I now know more about the system then I did before. Thanks!

buggsy5 - 2021-03-06

If it has steel filters, it probably was running at around 150 psi. If there was a water softener before the RO unit, then there shouldn't be significant calcium getting to the RO filter.

lightdark00 - 2020-06-23

This video also explained how a zero water filter works. It’s all resin and activated carbon in the filter.

JR - 2020-07-12

Excellent content.. Thanks.. I learnes a lot

Denis O'brien - 2020-09-24

"tap water is rarely perfectly clear" .. laughs in scottish. our tap water here is phenominal, often nicer than bottled water.

Bob Werner - 2020-06-13

this is very helpful.......on the other hand I have questions that I need help with I guess I should be a patron LOL as always you do give great info Thanks

matsaa93 - 2020-06-21

the waste water would be good for hydroponics as the consentration of minerals is much it better, and might not need to use as much micro nutrients for the plants.

Retiree Chemistry - 2020-11-10

Very nice video covering all the aspects. Keep it up

GCM - 2020-06-23

14:00 this blew my mind... goes to show how weak of a force gravity actually is

Leo Curious - 2020-06-27

Only on this very small scale. On even smaller scales suddenly other forces are much more relevant, eg. elektrostatic forces. On larger scales like industry/earth/... gravity clearly takes over.

Kenny Adams - 2020-06-24

Yay! Your back! I've been watching your vids for like 10 years

Bemused Indian - 2020-06-18

Phenomenal, Period

TheDoctor - 2020-06-21

Freaking youtube turned off my notifications for this channel again! Just found this vid.