Removal and Recovery Through Chelate Ligand Modified Nanoparticles – A Case for Thiosemicarbazones

Abstract In the last decades, wastewater has developed from a burden to an essential part of water, energy, and nutrient supply. The curing of wastewater, especially the removal of toxic metal ions is thus important, and several technologies are currently employed. Amongst these technologies, adsorption is promising and the design of efficient and selective adsorbents is an important research area. The combination of high adsorption capacities with high selectivity might become feasible through anchoring of chelate ligands onto nanoparticles (NPs). Here, the typical NP characteristics as high surface areas, biocompatibility, and simple removability, were combined with specific properties of chelate ligands such as denticity and hard/soft donor sets allowing selective metal ion binding. Thiosemicarbazones (TSCs) with their general formula RR’C–N = N–C(S)–NR’’R’’’ are attractive chelate ligands for the recovery of soft metal ions because they contain an N^S chelate binding pocket and the ease of modifying TSCs at the four position for substitution (R to R’’’) allows to even increase the number of donor atoms. Additionally, the same four positions can be used for functionalization towards covalent anchoring (conjugation) on NPs. In the first part of the review, in Chapters 1 to 4, general aspects of covalent binding (conjugating) of Ligands on NPs for metal recovery and removal is presented works. Chapter 5 then focusses on the idea of conjugating TSCs on NPs and presents recent progress in this field. Finally, some ideas are presented to further develop the field of TSC-modified NP for metal recovery and removal in Chapter 6. Graphical Abstract