# Novel Polymer Sorbents with Imprinted Task-Specific Ionic Liquids for Metal Removal
## 4 Conclusions  
Based on the conducted research, it was shown that the proposed procedure of the copolymer of vinylbenzyl chloride and divinylbenzene modification through quaternization in toluene as well as halogen exchange according the S\({}_{N}\)2 mechanism (poly(vinylbenzyl bromide-co-divinylbenzene) synthesis) enabled us to obtain novel ionic liquid-imprinted polymer sorbents. The sorption studies clearly show that the sorption properties depended not only on the type of metals ions and on the functional group structure (ketone or oxime substituent located at 3- or 4-position in pyridine ring as well as chloride or bromide counter ion for pyridinium nitrogen) but also on the pH, temperature, and initial concentration of metal ions. Both pH as well as temperature sorption increases with the increase in values of the parameters. The pH dependence indicated the sorption of cationic forms of metals, which at a pH below 2 competed with free H\({}^{+}\). This effect also indicated the ease of desorption, e.g., with diluted acid. The temperature effect indicated that the process was exothermic or that the increased temperature increased the availability of the active centers capable of coordinating to the metals ions. This indicated, in conjunction with thermogravimetric analysis, a high sorption potential of the resins at higher temperatures than 25 \({}^{\circ}\)C. The results obtained also showed that, regardless of the structure of the functionalities, the metal sorption was very fast and equilibrium was reached even within 1 min of shaking. The fitting to the selected isotherm models indicated that sorption takes place on the homogeneous surface as a result of complexation (coordination by the imine moiety or the oxime OH). Among the selected compounds, there was none that turned out to be the most effective for all absorbed metal ions, e.g., for Zn(II) sorption, the most efficient was VBC-Ox4.10 (84 mg/g); for Cd(II) sorption, the most efficient was VBBr-Ox3.10 (63 mg/g); and for Cu(II) sorption, the most efficient was VBC-K3.10 (69 mg/g). Moreover, the possibility of reusing the sorbent allowed us to state that these materials could be successfully used for Cu(II), Cd(II), and Zn(II) removal.  
The following are available online at [[https://www.mdpi.com/article/10.3390/ma14175008/s1](https://www.mdpi.com/article/10.3390/ma14175008/s1)]([https://www.mdpi.com/article/10.3390/ma14175008/s1](https://www.mdpi.com/article/10.3390/ma14175008/s1)), Figure S1: DSC thermogram of the VBBr-Ox3.10 sorbent, Figure S2: Values of the zeta potential measured as a function of pH, Table S1. Values of the isoelectric point and contact angle of fabricated sorbent series VBC and VBBr, Table S2: Isotherms parameters of different models for the sorption of Cu(II), Zn(II), and Cd(II) onto VBC-K3.10, VBBr-K3.10, VBC-K4.10, and VBBr-K4.10, Table S3: The isotherm parameters of different models for the sorption of Cu(II), Zn(II), and Cd(II) onto VBC-Ox3.10, VBBr-Ox3.10, VBC-Ox4.10, and VBBr-Ox4.10.  
Conceptualization, K.W.; methodology, K.W., T.B., M.N. and A.M.; investigation, K.W., P.D., K.F., T.B., M.N., A.L. and A.M.; formal analysis and writing--original draft preparation, K.W., P.D., T.B., M.N. and A.M.; writing--review and editing, K.W.; visualization, K.W., K.F., T.B., M.N., A.L. and A.M.; supervision and funding acquisition, K.W. All authors have read and agreed to the published version of the manuscript.  
This work was financed by the National Science Centre (Poland) (grant No. 2017/27/B/STS/01484).  
Not applicable.  
The authors thank the funding institution for support.  
The authors declare no conflict of interest.