
Synthesis of Chelating Resin
The resin with quaternary ammonium group reacts with iminodiacetic acid to obtain a "semi EDTA" based chelating resin without monoacetate group. The produced dimethylaniline can be recovered and used to prepare quaternary ammonium resin. The above reaction can be carried out almost quantitatively, and the performance of the product is also very good.
IDA resin can also be obtained by using chloromethylated cross-linked polystyrene as raw material, amination with nitrogen based acrylate or iminodiacetonitrile, hydrolysis, or amination with industrial amine diethanol, and oxidation with nitric acid.
Hydrophobic chloromethyl crosslinked polystyrene is difficult to react with water-soluble nucleophilic reagent amino carboxylic acid, so it cannot be aminated with such reagent to directly obtain IDA resin. However, the chloromethylation intermediate is partially aminated with trimethylamine first, and then iminodiacetic acid can be used for direct amination to obtain IDA resin with an exchange capacity of 1.9mmol/g for Cu2+.
When IDA resin is prepared by the above methods, the chlorocarboxylic acid used can be B-chloropropionic acid, r-chlorobutyric acid, etc. in addition to chloroacetic acid; The amino carboxylic acid ester used can be methylamino acetate, amino triacetate, iminodipropionate, etc.
There are other methods for preparing imine carboxylic acid resin. But the styrene IDA is still the most important. The selection order of metal ions is:
Cu2+>Pb2+>Fe3+>A13++>Ni2+>Zn2+>Co2+>Cd2+>Fe2+>Ba2+>Ca2+>Na+
However, in many synthesis methods, the structure of the group obtained is not very clear, so its performance may not be completely the same as that of the "semi EDTA" group with double five membered ring structure.
8-hydroxyquinoline resin is also a N, O coordination chelating agent, and there are many synthetic methods. The simplest is to polycondensate 8-hydroxyquinoline with formaldehyde under acidic conditions.
Spherical chelating resin can be obtained by chloromethylation of 8-hydroxyquinoline and reaction with primary amine resin for 1h at 100 ℃.
Using 5-chloromethyl-8-hydroxyquinoline to react with macroporous crosslinked polystyrene under the catalysis of SnC14, 8-hydroxyquinoline resin can also be obtained. The exchange capacity of Cu2+reached 2.16meq/g.
Schiff bases are also a large class of N, O chelating resins. Basically, it is formed by condensation of primary amine and aldehyde. In structure, it is required to have a coordination group such as 0H or SH near the Sifo bond to form a chelate structure.
This kind of chelating resin includes polyamines, pyridines, oximes, pyrazole, imidazole, guanidine, schiff bases and many other varieties.
Polyamine chelating resin is also an anion exchange resin, which has many types of styrene, acrylic and polycondensation structures. Such resins are complexed with metal ions by primary or secondary amine groups.
The corresponding chelating resin can be obtained by the reaction of guanidine and pyrazole compounds with chloromethylated crosslinked polystyrene.
When a large number of metal ions are splashed on the resin, the adsorption recovery rate of Au3+is still more than 90%, and the adsorption rate of Au is 100% in the range of 0.2~6molHCI.
When the degree of crosslinking was 8, the conversion of the reaction was 65% at 8 h. Resin to Au (III) The adsorption capacity of Ag (I) is 170 and 177mg/g.
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