_Applied_  
_sciences_  
_Article_  
**Recovery of Heavy Metal Ions Using Magnetic Glycine-Modified Chitosan--Application to Aqueous Solutions and Tailing Leachate**  
**[PERSON] 1,*2, [PERSON] 1,2, [PERSON] 3,4,6, [PERSON] 5,6 and [PERSON] 7,*2**  
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The accumulation of contaminants, such as heavy metals, in the food chain may explain the special attention they have received from the community and regulators. Decreasing the levels of metal ions in water bodies is not only critical for ensuring the availability of drinkable water for human and animal feed, but also for the recycling of water flows. The recovery of metals (especially strategic and valuable elements) is also strongly encouraged to optimize their use from finite resources (based on availability but also on geopolitical criteria). Therefore, the valorization of metal resources from secondary reserves (tailings, waste materials, and so on) is of critical importance, with strong political incentives for developing recycling facilities. Depending on the water flow, metal concentration, complexity of solutions and final objective (recovery optimization vs. effluent decontamination), different methods can be used for metal recovery. Solvent extraction [1,2] is usually preferred for the recovery of valuable metals from high-concentration solutions, while precipitation techniques are more appropriate for treating high flow rates (at the expense of the production of huge amounts of metal-contaminated sludge that are poorly valuable). For the decontamination of water sources at drinkable levels, membrane techniques are more appropriate, but these techniques are frequently very expensive, and are preferred for the treatment of limited flow rates with low initial metal concentrations. Extractant impregnation of porous resins has also been investigated for metal removal; the immobilization of the extractant prevents the release and the loss of hazardous and expensive reagents with optimized transfer properties (driven by the porosity of the supports [3, 4, 5]). This is an intermediary technique between solvent extraction process and sorption on functional resins. Sorption processes using ion-exchange or chelating resins [6,7], carbon-based sorbents [8,9], inorganic supports [10, 11, 12, 13] or biosorbents [14, 15, 16, 17, 18] have attracted great attention from both the research community and industrial sectors, especially for the treatment of low-concentration effluents or as polishing techniques. Chitosan (aminopolysaccharideaccharide) and alginate are emblematic examples of supports used for metal recovery from dilute solutions. They are mainly extracted from marine resources (shrimp shell and algal biomass, respectively). These biopolymers are very versatile both physically (elaborating different shaping and conditionings) and chemically (reactivity of functional groups for chemical reaction and grafting of specific reactive groups) [19, 20, 21, 22, 23, 24]. Chitosan is characterized by the presence of hydroxyl groups (providing hydrophilic behavior) and amine groups, which are highly reactive for metal binding. The sorption of metal ions may proceed through: (a) chelation of metal cations on electronic doublet of N (from free amine groups) in near neutral solutions, or (b) electrostatic attraction and ion-exchange mechanisms for the removal of metal anions on protonated amine groups in acidic solutions [25]. Chitosan is usually characterized by weak porosity (except when hydrogels are dried using expensive procedures such as drying under supercritical CO\({}_{2}\) conditions to form aerogels [26, 27, 28]); therefore, in order to reduce diffusion limitations, it is preferable to use small-size particles at the expense of increasing difficulties in solid/liquid separation.