## 3 Types of Adsorbents Made from Polyacrylonitrile
### Polyacrylonitrile in Ion Exchange Resins
The highest and lowest metal adsorption values were 5.2 millimole per gram for Ni\({}^{2+}\) at pH 5.0 and 1.5 millimole per gram for Co\({}^{2+}\) at pH 1.0, respectively. [PERSON], [PERSON], and [PERSON] (2005) investigated functionalized copolymers by reacting poly (vinyl benzyl chloride-acrylonitrile-divinyl benzene) matrix with ethylene diamine, bis(aminopropyl) amine, bis(aminohexyl) triamine, and tris(2-amino ethyl) amine followed by reaction with 5-ethylthiourea to obtain a copolymer having 2.8-5.0 millimole of amino moiety per gram of resin [44]. The adsorption value of the above copolymer for gold, platinum, and palladium chloro complex were determined in 0.1 M HCl acidic solution and were found to be 190 mg/g, 245 mg/g, and 280 mg/g of resin, respectively. Another chelating resin, polyacrylamide-amino-1,3,4-thiadiazole (PAN-ATD) was developed through a single step reaction and its composition was described through FT-IR [45]. The adsorption of mercury ions by the resultant copolymer was examined through batch and column techniques. The results obtained through the batch method demonstrated that polyacrylamide-amino-1,3,4-thiadiazole had an affinity for mercury ions and the highest adsorption value assessed from the Langmuir method was 526.9 mg/g at 308 K. Moreover, this resin was more selective for mercury ions in the mixture of metal ions such as Hg\({}^{2+}\), Ni\({}^{2+}\), Cu\({}^{2+}\), Cd\({}^{2+}\), Pb\({}^{2+}\), and Zn\({}^{2+}\) at the same pH. [PERSON] and [PERSON] (2015) synthesized thioutrea- and glutaraldehyde-modified polyacrylonitrile adsorbents [46]. The parameters affecting the adsorption process, such as pH range (0.70 to 2.00) and adsorbent dose (100 to 800 mg), were studied for different time intervals. The optimum pH for the extraction of platinum and palladium was found to be 1.5. The Langmuir isotherm model illustrates the adsorption of toxic ions by the adsorbent much more precisely compared with the Freundlich model. It was found that the extraction rate for platinum and palladium reached around 93% in 0.50 M HCl-0.50 M thiourea solution and no noteworthy decline after 5 adsorption-desorption cycles was obtained. The adsorption of Cu\({}^{2+}\) and Cr\({}^{2+}\) on pumice and a polyacrylamide/pumice composite was examined by [PERSON] et al. (2008) by utilizing a batch technique at room temperature, and their adsorption properties were evaluated on pumice and the composite [47]. The sorbent's adsorption rates were discovered to vary with their properties, such as surface functionalization, preliminary concentration of metal ions solution, adsorption kinetics, and solution pH. The time needed to remove metal ions from wastewater was six hours, and solution concentrations were in the range of 100-500 mg/g of resin. Langmuir and Freundlich isotherm models were utilized to determine the amount of adsorption of Cu\({}^{2+}\) and Cr\({}^{3+}\) on the adsorbent and results were found to fit in the Langmuir models. The Langmuir and Freundlich isotherm models were utilized to determine the amount of adsorption of Cu\({}^{2+}\) and Cr\({}^{3+}\) on the adsorbent, and the results were found to fit in the Langmuir models. The extraction of Cu\({}^{2+}\) and Cr\({}^{3+}\) from the metal ion mixture was greater in the composite than in pumice. The adsorption values of the sorbents pumice and polyacrylamide/pumice composite observed from the isotherm equations were 0.055 and 0.065 for Cu\({}^{2+}\) and 0.031 and 0.268 mmol/g for Cr\({}^{3+}\) ions, respectively. In another study,the amidoximated chitosan-grafted polyacrylonitrile (CTS-g-PAO) was reported to adsorb UO\({}_{2}\)\({}^{+}\) from aqueous solution [48]. The adsorption capacity of CTS-g-PAO was found to be 312.06 mg/g and equilibrium was attained within 120 min. Maximum loaded uranium on CTS-g-PAO (more than 80%) was desorbed through 0.1 M HCl or EDTA-Na, CTS-g-PAO, and reutilized for at least three cycles. [PERSON] et al.