# Metachrylate-Based Polymeric Sorbents for Recovery of Metals from Aqueous Solutions
## 8 Adsorption on Magnetic Polymeric Sorbents  
There is a growing interest in the application of magnetic nanoparticles for the removal of heavy metals from wastewater since they possess a whole range of advantages in comparison with traditional sorbents, such as small particle size, large surface area, and easy separation after treatment by applying an external magnetic field [1; 36; 70; 71; 72; 73]. However, magnetic nanoparticles tend to aggregate, which decreases the surface area and reduces the removal capacity. Stabilization of these particles can be achieved by surface coating or grafting with an organic layer (surfactant or polymer), coating with an inorganic layer (silica or carbon), and incorporating magnetic nanoparticles in polymer matrices (Scheme 2). In order to provide stabilize these particles, surface modification is required [1; 51; 139]. A wide range of different magnetic materials was used as metal sorbents. For example, [PERSON] et al. used polyglycidyl methacrylate graft copolymer (PGMA) and polymer-supported magnetic nanoparticles (PGMAFe) as Cr(VI) sorbent [140]. Both adsorbents were useful for removing Cr(VI) from an aqueous solution over a wide pH range. The resulting graft copolymer and its Fe\({}_{3}\)O\({}_{4}\) nanoparticles-coated form were highly effective for Cr(VI) sorption in column experiments, with a short contact time, up to 30 min. The column was efficiently regenerated with NaOH (10%, _w/v_) solution. However, PGMAFe had higher Cr(VI) adsorption capacity compared to PGMA, presumably as a consequence of the combined effects of Fe oxide and amine groups. Better correlation with experimental data was observed for both PGMA and PGMAFe sorbents. The maximum Cr(VI) adsorption capacities of PGMA and PGMAFe sorbents obtained at pH 4 were 132.5 and 162.9 mg/g, respectively. It was concluded that both samples were effective adsorbents for Cr(VI) in a wide pH range with relatively high adsorption capacity. [PERSON] et al. prepared magnetic methacrylate/divinylbenzene particles with a magnetite core and post-functionalized with ethylenediamine, diethylenediamine, and tetraethylenemamine. Synthesized magnetic core-shell polymer particles samples were tested as Hg(II) sorbent [141]. The Hg(II) sorption capacities of polymeric sorbent were found to be in the range 2.1-4.8 mmol/g. [PERSON] et al. prepared magnetic GMA sorbents, crosslinked with divinylbenzene (GMA/DVB-en) or \(N\),\(N^{\prime}\)-methylenebisacrylamide (GMA/MBA-en) and functionalized with tetraethylenediamine [98]. The sorption behavior towards molybdate anions was studied. The Mo(VI) adsorption capacities of 4.24 and 6.18 mmol/g were obtained for GMA/DVB-en and GMA/MBA-en, respectively. The adsorption followed the pseudo-second-order model. Regeneration efficiency up to 90-96% was reached using an ammonia buffer. [PERSON] et al. used magnetic terpolymer poly(glycidyl methacrylate-methyl methacrylate-ethylene glycol dimethacrylate) functionalized with ammonia for Hg(II) ions removal from aqueous solution in static conditions and in a magnetically stabilizedfluidized bed (MFB) reactor [142]. The optimum removal of Hg(II) ions was observed at pH 5.5, with a maximum adsorption capacity of 124.8 mg/g. [PERSON] et al. studied the influence of different magnetite content on the porosity parameters, morphology, and magnetic properties of magnetic macroporous PGME copolymer (mPGME). The copolymer was post-functionalized by a ring-opening reaction with diethylene triamine. The amino-functionalized magnetic mPGME\(-\)data, was studied as molybdenum, Mo(VI), and rhenium, Re(VII) sorbent from binary solutions [130]. The influence of pH, ionic strength, and coexisting cations (Ni\({}^{2+}\), Cd\({}^{2+}\), and Cu\({}^{2+}\)) and anions (Cl\({}^{-}\), NO\({}_{3}\)\({}^{-}\) and SO\({}_{4}\)\({}^{2-}\)) on Mo(VI) and Re(VII) oxyanion sorption on mPGME-data were investigated. Langmuir model was proven to be the most appropriate adsorption isotherm model, assuming monolayer adsorption at specific homogenous sites on the mPGME-data surface.