Ions are electrically charged atoms or molecules found in water that have either a net negative or positive charge.
Ions with a positive charge are called Cations and ions with a negative charge are called Anions.
Whenever forming pure water, that is not an ion, Ion exchange resins are used to exchange non desirable cations and anions with hydrogen and hydroxyl. Remember, these resins are small plastic beads that are composed of organic polymer chains that have charged functional groups built into the resin bead. Ion exchange resins are used to produce deionized water. You should take this seriously. In order to produce deionized water, cation resin is regenerated with Hydrochloric Acid. The anion resin is regenerated with sodium hydroxide. The Hydrogen is positively charged and therefore attaches itself to the negatively charged cation resin bead. So cations are exchanged for hydrogen, as positively charged cations flow across cation resin beads.
As negatively charged anions flow across anion resin beads, likewise the anions are exchanged for hydroxyl.
Calcium is more strongly attracted to a cation resin bead than sodium is.
The hydrogen on the cation resin bead and the hydroxyl on the anion resin bead do not have a strong attraction to the bead. Different ions are attracted to a resin bead with different strengths. This is what allows ion exchange to take place. Most of the exchange sites on the cation and anion resin beads are used up and the tank no longer produces deionized water. Demineralization therefore requires using at least two ion types exchange resins to produce deionized water. The negatively charged anions are not attracted to the cation resin bead and pass through. Seriously. While forming hydrochloric acid, The hydrogen, that has a positive charge, will attach itself to the chloride ion. You should take it into account. We need to examine calcium chloride in the feed water. As a result, in solution, the calcium ion is positively charged and will attach itself to the cation bead and will release a hydrogen ion.
The chloride has a negative charge and therefore shouldn’t attach itself to the cation resin bead.
All positively charged cations are attracted to the cation resin bead and exchanged for hydrogen, as city water enters the tank filled with cation resin.
In a dual bed system, the cation resin is always first in line. The effluent from the cation resin will consist of strong and weak acids. Consequently, the anion resin will attract negatively charged anions like chloride and exchange them for hydroxyl. This acidic water will hereafter enter a tank filled with anion resin. It combines with hydroxyl to form sodium hydroxide which has a high conductivity, So in case sodium leaks past the cation exchange tank. Needless to say, in reality, a dual bed system does not produce true H20 due to sodium leakage. Sodium leakage is addressed because of the sheer number of repeated cation/anion exchanges taking place.
This effectively makes the mixed bed tank act like thousands of dual bed units in one tank.
The cation/anion exchange is taking place over and over within the resin bed.
In a mixed bed system, the strong acid cation and strong base anion resin are intermixed. Electrical current passes through water using ions as stepping stones.
Ions conduct electricity. Less ions in the water will make the passage of electricity more difficult. By measuring the electrical conductance of water can tell us what the ionic content of the water is.