I want to remove water hardness using Ion exchange resin filter. Does anyone tried this method I want to know if this method really lowers the hardness. What is the best method of regenerating resin filter? How much water it uses for regenerating process?
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2$\begingroup$ That is a standard water softener in the US :The resin exchanges Na+ for Ca++ , typically. $\endgroup$– blacksmith37Feb 22, 2020 at 15:55
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2 Answers
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The ion exchange resin works pretty well. It removes the hardness. This is the standard method for producing demineralized water in practice. If you want to regenerate the used resin, you treat it with concentrated hydrochloric acid, and then wash it with plenty of water until the water is not acidic any more when getting out of the resin. You may also replace HCl by a concentrated solution of sodium chloride. But in this case it is difficult to know when the regenerating process is finished and the refreshed resin ready for use.
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1$\begingroup$ Or you buy a new cartridge, avoiding the hazardous waste if you don't run a chemical laboratory with a hazardous waste management plan. $\endgroup$– Karsten ♦Feb 22, 2020 at 16:29
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1$\begingroup$ @KarstenTheis I wonder if the kitchen you or / and your friends use has a dishwasher. All the models I encountered so far regenerate(d) their water softening resin by adding just sodium chloride to the correct opening (en.wikipedia.org/wiki/Dishwasher_salt). Hydrochloric acid is something for larger scale application, but even the dishwasher in the lab regenerates multiple times with salt before its hip-high cartrige then is regenerated at the plant. $\endgroup$ Feb 22, 2020 at 18:53
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Yes - the process works
If you are just looking to remove hard water salts (divalent, trivalent) the sodium chloride regenerable resin ("softener" resin) works fine and you can regenerate and put the waste to sewer.
If you want to remove all metals, then you'll need to acid regenerate and neutralise the wash before discharge or treat as hazwaste.
If you want to remove both cations and anions then you'll need either mixed bed or separate cation and anion resin. Don't try to regen mixed bed resin at home - it's a PITA.
Or you can step up to the plate to spend some real money :
- Carbon filter - removes organics and breaks down hypochlorite found in most town water
- Reverse osmosis - concentrates and dumps 90+% of dissolved ions -> take permeate and follow by
- UV sterislisation (technically unneccessary - but, hey, belts and braces) follwed by
- PFOS specific resin followed by
- separate cat/an resin beds followed by
- mixed bed nuclear grade resin into sealed, nitrogen blanketed tank
Tada - 18MOhm sterile analytical grade water.
(if you REALLY want to go all out - package it and then gamma irradiate - take no prisoners!)