Resin is usually composed of two parts: one is a three-dimensional web properties generated by polymerization of monomer and crosslinking agent, which is also called resin properties; The other part is a special functional group attached to the properties.
The three-dimensional structure type and structure determine the main physical properties of the resin, such as stability, pore structure, density, swelling degree, etc. The special functional groups connected on the three-dimensional skeleton play a decisive role in the application of the adsorbed substances.
Resin can be divided into the following types according to the types and properties of functional groups connected on the properties:
This kind of resin does not contain special ions and functional groups. When interacting with other substances, it mainly depends on the van der Waals force between molecules without forming chemical bonds. The adsorption selectivity of different substances mainly depends on the polarity of the adsorbed molecules. Non-ionic resins have strong adsorption on weak polar and non-polar organic compounds. These resins are widely used in drug separation, pigment extraction and other fields.
Metal ion coordination resin
Metal ion coordination type resin skeleton with special coordination groups and coordination ions, and metal ions can be complex reaction, so that the formation of coordination bonds between the two, resin and adsorbed material through coordination bond interaction and adsorption on the resin, the adsorption process for chemical adsorption. These resins, also known as chelating resins, are used for selective separation and enrichment of transition metal ions in aqueous solution. The functional group of chelating resin is a functional group containing one or more coordination atoms. All the coordination atoms have the property of providing electron pairs. The common coordination atoms are mainly atoms of O, N, S, P and other elements. When these atoms interact with the adsorbed substance, they can provide the lone electron pair of coordination. Therefore, the chelating resin can also be divided into oxygen chelating resin, nitrogen chelating resin, sulfur chelating resin and so on according to the type of coordination atoms. The chelating functional groups containing oxygen atoms are: — OH (alcohol, phenol), — COOH (carboxylic acid), — O — (ether, crown ether), — CO — (aldehyde, ketone, quinone), — COOR (ester, salt), — NO2 (nitro), — NO (nitroso), etc. The chelating functional groups with nitrogen as coordination atom include — NH (amine), 2>C=NH (imine), >C=N — R (Schiff base), >C=N — OH (oxime), — CONH2 (amide), — N=N — azo, etc.
The tubular energy groups connected to the properties of the ionic resin are one or several functional groups with chemical activity, which can dissociate some cations (such as h+ or na+) or anions (such as OH – or Cl -) in the aqueous solution. After dissociation, the ionic groups on the properties can interact with different counter ions through electrostatic attraction to adsorb the ionic substances with opposite charges onto the resin.
When interacting with other ionic groups in aqueous solution, the original paired counter ions are replaced by new ions due to competitive adsorption. The types of chemically active groups in resins determine the main properties and types of resins. According to the exchanged ions, ion exchange resins can be divided into cation exchange resins and anion exchange resins. Cation resins can be divided into strong acidic and weak acidic, and anion resins can be divided into strong alkaline and weak alkaline.
The strong acidic functional group of ionic resin band has sulfonic acid group (- SO3H), which has exchange function in alkaline, neutral and even acidic medium; Weakly acidic functional groups include carboxyl (- COOH) or phosphate (- Po (OH) 2). These functional groups have ion exchange capacity only in alkaline or nearly neutral media with ph=5~6; The strongly basic functional group has quaternary amine group (NR3), which can exchange ions in acidic, alkaline and neutral media; Weakly basic functional groups include primary amine (- NH2), secondary amine (- NHR) and tertiary amine (- NR2). These functional groups can only exchange ions in neutral or acidic media.
In addition, resins can also be divided into polar and non-polar resins according to their chemical structures. Nonpolar resin refers to the resin polymerized by nonpolar monomers, such as divinylbenzene. Polar resins can be divided into strong polar, polar and medium polar resins. The strong polar resin contains pyridine group and amino group; Medium polar resins are generally polymerized from monomers containing ester and carbonyl groups; Polar resins are usually polymerized from monomers containing amido, sulfoxide and cyano groups.