## 3 Types of Adsorbents Made from Polyacrylonitrile
### Polyacrylonitrile in Ion Exchange Resins
Potentiometric titration curves were used to study the acid-base characteristics of the anion exchangers by calculating the acidity variables. These ion exchange fibers contained at least four different functional groups and their ion exchange capacity was around 3.5 med/g. The ion exchange value of resin containing strong base quaternary amino groups (pK\(\cong\) 2) was 2.5 med/g. The nitrile groups in the polyacrylonitrile underwent hydrolysis and introduced carboxylic acid moieties in the ion exchange fibers. [PERSON] et al. (2004) developed ion exchanger beads for the extraction of Sr\({}^{2+}\) and Ag\({}^{+}\) ions in acidic conditions ([PERSON] et al., 2015). Potassium titanate (K\({}_{2}\)Ti\({}_{4}\)O\({}_{9}\)) and nickelferrocyanate (Ni\({}_{2}\)Fe(CN)\({}_{6}\)) powders were utilized to form inorganic ion exchanger beads. These powders were dissolved in the solvent dimethylsulfoxide with a small amount of TWEEN-80 surfactant, mixed at 50\({}^{\circ}\)C. The polyacrylamide powder was then mixed in a known quantity of the above homogeneous solution at a temperature of 323 K to obtain a uniform solution. The diffused air in the solution was removed and a composite solution was passed through a dual nozzle to obtain sphere-shaped beads. It was found that nickelferrocyanate ion exchangers were more selective for Ag\({}^{+}\) ions in comparison with potassium titanate, while potassium titanate ion exchangers showed more affinity for Sr\({}^{2+}\) ions than Ag\({}^{+}\) ions. Chelating resin belongs to the category of ion exchange resins and contains functional groups connected to the backbone of the main chain polymer. It has one or more electron donor atoms, such as nitrogen, sulfur, oxygen, and phosphorous, that can form coordinate bonds with most of the poisonous heavy metals. A chelating resin containing amidoxime groups was utilized to extract copper ions ([PERSON] et al., 2015). This resin was synthesized by the aqueous suspension copolymerization of acrylonitrile and divinyl benzene and subsequent modification of cyano groups by reaction with hydroxyl amine. Another poly(acrylamide) chelate resin was reported by [PERSON], [PERSON], and [PERSON], (1982), synthesized through redox polymerization of acrylonitrile and divinyl benzene and then reacted with hydroxylamine hydrochloride to generate a functional moiety ([PERSON] et al., 2015). Poly(acrylamide) resin's complex formation properties were discovered to be viable for the extraction of lanthanum, cerium, and neodymium from wastewater. Polyacrylonitrile copolymers containing cysteine groups were synthesized by reacting polyacrylamide with L-cysteineand 1,6 hexanediol. This resin was much more selective towards Ag\({}^{+}\), Hg\({}^{2+}\), Au\({}^{3+}\) and Pt\({}^{4+}\) in diluted acidic conditions; the highest adsorption values were found to be 0.97 millimole, 0.65 millimole, 1.22 millimole, and 0.39 millimole per gram of resin [40]. In another experiment, substituted polyamides were formed by reacting acrylonitrile-vinylacetate-divinylbenzene copolymer with amino guanidine bicarbonate for effective removal of gold cyanide (49.3 mg/g) in a butanol-water mixture [41]. Various resins with guanidyl groups are also reported. [PERSON] et al. reported the adsorption of copper by the resin containing guanidine ligand derivatives [42]. The aminolysis of poly(acrylonitrile-vinylacetate-DVB) was carried out by utilizing ethylene-diamine or hydroxyl amine hydrochloride after their reaction with dicyandiamide, cyanamide, and sodium dicyanimide. The resultant resins had biguanidyl, guanidyl, or nitrilguanidyl derivatives in the polymer side chain, respectively. The structure of ligand complexes with copper ions was determined through electron paramagnetic resonance spectroscopy. [PERSON] and [PERSON] (2005) have reported ethylenediamine containing polyacrylamide for the extraction of toxic ions [43].