Principle of anion exchange resin

　　Junior high school chemistry should be introduced in this regard, Yin and Yang principles are the same.

　　The reaction is as follows:

　　Ion exchange method can remove cations and anions in water. NaCl is used to represent inorganic salts in water. The basic reaction of water desalination can be expressed by the following equation:

　　1. Cation Exchange Resin: R-H+Na+R-Na+H+

　　2. Anion Exchange Resin: R-OH+Cl-R-Cl+OH-

　　The general reaction formulas of cation and anion exchange resins can be written as follows:

　　RH+ROH+NaCl-RNa+RCL+H2O

　　It can be seen from this that NaCl in water has been replaced by H + and OH - on the resin respectively, and the reaction product is only hydrogen peroxide, so it can remove salt from water.

　　(1) Strong acidic cation exchange resin

　　These resins contain a large number of strong acidic groups, such as sulfonate-SO3H, which is easy to dissociate H+, so they are strong acidic. After resin dissociation, the negative groups contained in the bulk, such as SO3-, can adsorb other cations in the solution. These two reactions make H + in resin exchange with cations in solution. Strong acidic resin has strong dissociation ability and can dissociate and produce ion exchange in acidic or alkaline solution.

　　After the resin is used for a period of time, it should be regenerated, that is, the ion exchange reaction is carried out in the opposite direction with chemicals, so that the functional groups of the resin can be restored to their original state for reuse. If the cationic resin is regenerated with strong acid, the resin releases the adsorbed cations and then combines with H + to restore the original composition.

　　(2) Weak acid cation exchange resin

　　这类树脂含弱酸性基团，如羧基－COOH，能在水中离解出H+ 而呈酸性。树脂离解后余下的负电基团，如R-COO－(R为碳氢基团)，能与溶液中的其他阳离子吸附结合，从而产生阳离子交换作用。这种树脂的酸性即离解性较弱，在低pH下难以离解和进行离子交换，只能在碱性、中性或微酸性溶液中(如pH5～14)起作用。这类树脂亦是用酸进行再生(比强酸性树脂较易再生)。
　　(3) 强碱性阴离子交换树脂

　　These resins contain strong alkaline groups, such as quaternary amines (also known as tertiary amines) - NR3OH (R is hydrocarbon group), which can dissociate OH - in water and show strong alkalinity. The positive group of the resin can be combined with the anion adsorption in solution to produce anion exchange.

　　The resin has strong dissociation and can work normally at different pH. It is regenerated with strong alkali (such as NaOH).

　　(4) Weak basic anion exchange resin

　　These resins contain weak basic groups, such as primary amino group (also known as primary amino group) - NH2, secondary amino group (secondary amino group) - NHR, or tertiary amino group (tertiary amino group) - NR2, which can dissociate OH - in water and show weak alkalinity. The positive group of the resin can be combined with the anion adsorption in solution to produce anion exchange. In most cases, this resin adsorbs the whole other acid molecules in the solution. It can only work under neutral or acidic conditions such as pH 1-9. It can be regenerated with Na2CO3 and NH4OH.