## 3 Types of Adsorbents Made from Polyacrylonitrile
### Polyacrylonitrile in Ion Exchange Resins
A biosorbent was produced by immobilizing dead fungal biomass on polyacrylonitrile to examine the ability of microorganisms to extract metal ions from solution [53]. This adsorbent was used for the extraction of hazardous metals such as Cu\({}^{2+}\), Zn\({}^{2+}\), and Ni\({}^{2+}\) from the mixtures. The metal removal capacities of the adsorbent (concentrations 50%) were 16 mg/g, 7 mg/g, and 0.25 mg/g at pH 7 for Zn\({}^{2+}\), Cu\({}^{2+}\), and Ni\({}^{2+}\), respectively. The adsorption values of PAN (concentrations of 75%) were 18, 7.9 mg/gand 0.25 mg/g for Zn\({}^{2+}\), Cu\({}^{2+}\), and Ni\({}^{2+}\) ions, respectively. [PERSON], [PERSON], and [PERSON] (2007) used an \(\gamma\)-ray irradiation technique to connect a partially deacetylated chitin (deacetylation degree of around 40%) to acrylonitrile. The maximum binding value of acrylonitrile onto the pre-irradiated chitin at 25 \(\pm\) 1.2 kGy was 114% for an acrylonitrile concentration of 40% (\(v/v\)) in dimethylformamide at 343 K for eight hours. The mixture ratio of 0.1 N hydroxylamine hydrochloride to 0.1 N sodium hydroxide was chosen to be 7:3 (\(v/v\)) for the conversion of cyano groups on grafted chitin (Chi-g-AN) into amidoxime. The equilibrium value of As\({}^{3+}\) on Chi-g-AN converted amidoxime (Chi-g-AN-C) was well fitted in the Langmuir model and its highest adsorption value was 19.724 mg/g. Different polymeric materials were reported by [PERSON] et al. for the extraction of Ag\({}^{+}\) and Pb\({}^{2+}\) ions from synthetic solutions ([PERSON] et al., 2016). They treated the polyacrylamide with triethylenetetramine (PAN-TETA 50 and 100) using different amounts. Polyacrylonitrile-triethylenetetramine and their metal complexes were investigated through FT-IR and SEM. At pH 6.0, the highest uptake values for Ag\({}^{+}\) and Pb\({}^{2+}\) ions were 108.14 mg/g and 99.01 mg/g, respectively. Desorption of Ag\({}^{+}\) and Pb\({}^{2+}\) ions were done in 0.5 M HCl acidic solution and the desorption value was found to be 91%. In another study, a permeable acrylonitrile (AN)/methyl acrylate (MA) copolymer was prepared through the suspension emulsion polymerization method and the resultant copolymer was functionalized with hydroxylamine hydrochloride to form an amidoxime group to extract toxic ions from wastewater ([PERSON] et al., 2016). The results confirmed that amidoxinated AN/MA beads showed good adsorption values for Hg\({}^{2+}\), Ag\({}^{+}\), and Cu\({}^{2+}\) with great selectivity for Hg\({}^{2+}\) ions. The equilibrium adsorption values of amidoxinated AN/MA copolymer for various ions were found to be 2.68 mmol/g for mercury ions, 1.35 mmol/g for silver ions, 2.01 mmol/g for copper ions, 0.74 mmol/g for iron ions, and 0.06 mmol/g for lead ions, with the initial concentration of metal ions solutions being 5.0 mM. On the other hand, untreated AN/MA did not show any removal efficiency. The equilibrium was attained within 10 h through adsorption kinetics. Another study reports the development of crosslinked acrylic acid (AA)-acrylonitrile (AN) resin through the suspension polymerization method by using poly(vinyl alcohol) as a suspending agent and \(N\),\(N\)-methylenebisacrylamide (MBA) and divinylbenzene (DVB) as crosslinkers ([PERSON] et al., 2016). Acrylonitrile and acrylic acid were used in a mole percent ratio of 95:5, while various ratios of crosslinking agents (2.0, 5.0, and 10.0 weight percent) were used during the formation of the copolymer. The adsorption of uranium took place in HNO\({}_{3}\), HCl, and H\({}_{2}\)SO\({}_{4}\) solutions. This paper also discusses the impact of different parameters such as pH, time to adsorb toxic ions, kind of acid, nature of crosslinking agents, their amounts, and desorption phenomena. In another study, the synthesis of imniodiacetate functionalized acrylonitrile-divinylbenzene (AN-DVB) copolymers by using crosslinkers at amounts of 10 and 15 weight percent is reported.