Multipurpose material based on biopolymers

The purpose of the current thesis is to devise, develop and tests novel material for the removal, recover and recycle of metal cations from different sources, ranging from natural waters to used lithium-ion battery (LIB) cathodes. On this account, a particular attempt was made to follow as much as possible the principles of green chemistry in order to provides new, greener approach to the abovementioned problem while sticking to the modern concept of circular economy. Poly lactic acid (PLA), cellulose derivatives and bergamot pomace (BP) all falls under the definition of biocompatible and renewable resources. All three can also be easily obtained as products of a recycle process from different industrial source. Bergamot pomace is an outstanding example of a material given a new life. Throughout this work, these materials will be described as they are presented in the most recent state-of-art and studied from multiple perspective in order to present the reader with an array of uses, advantages and withdrawal for each one of them. Further in the work, a class of material named polymer inclusion membranes (PIMs) will be thoroughly discussed as a tool for the removal of metal cations. The study conducted in this work on this class of membranes, specifically aim to replace the most common polymers adopted for the preparation of such membranes, namely: poly vinyl chloride (PVC) and cellulose triacetate (CTA) with the above-mentioned PLA. The novelty in the formulation does not stop at the polymer. As will be thoroughly explained further in the text, also the used auxiliary chelating agent, namely citric acid and GLDA were never used before. In fact, the first membranes prepared in this work, were made using GLDA as the auxiliary chelating agent. The goal was to obtain a membrane able to perform chelation through different functional groups, namely R4N+ and COO-. This concept was specifically designed having Cd(II) in mind since this cation can be found under many forms, ranging from positive (e.g., Cd2+, CdCl+) to negative (e.g., CdCl3-, CdCl42-) species in respect to pH and chemical environment. This specific formulation, comprising of both positive and negative chelating groups, was devised to be able to interact with differently charged metal species. Moreover, GLDA, was chosen for its inherent biocompatibility and its acid base/chelating properties. As a matter of fact, the reduction of the environmental impact of PIMs could be the cornerstone for future study and industrial applications on larger scale. To be more specific and avoid any confusion further in the discussion, the material employed is poly -L- lactic acid (PLLA). In this work, PIMs were not studied only as sequestering material but also as a tunable multipurpose platform. The use of an enantiomeric pure polymer as the bulk of the membrane, for example, was studied for application as an enantioselective separation device. Bergamot pomace was chosen as a material for similar reasons, in fact not only it is very biocompatible but also respect the principles of circular 8 economy whereas this material would only be disposed of. This work investigates the possibility to use it as a sorption material with nearly no treatment nor chemical modification. Such green option would also represent a novelty in the field of environmental remediation. As discussed, the primary objective of the present work was to prepare different sustainable materials as possible sorbent towards metal cations for remediation and/or recovery purpose. For all the sorbents the preparation or synthesis procedure are reported along with the FT-IR and NMR characterization. The novel polymer inclusion membrane presented hereafter was further investigated as a multipurpose platform after showing an interesting releasing kinetic and possible enantioselective properties. BP is a recycled material from the agro-food industry that was tested in as a sorption material for metal ions of strategical economic importance such as Ni(II), Mn(II), Co(II) and Li(I). The aim of these tests was to determine its sorption ability for the above-mentioned metals in a solution prepared from spent LIB cathodes (defined as NMCL). Succinated cellulose (Cell-Succ) was also devised to work as an easy-to-remove sorption material for dangerous metal ions such as Cd(II) and Pb(II). Multiple characterization techniques were employed on the studied materials. FT-IR ATR and XPS were used for the determination of functional groups and possible metal binding sites, respectively. qNMR and UV-Vis spectroscopy provided important data both for the materials characterization and the in-solution behavior for compound materials (like PIM). The study of the acid-base properties and the formation of complexes between the target cation and the materials was conducted potentiometrically. Tests to evaluate the sequestering capacity were carried in the fashion of sorption isotherm experiments, by placing different aliquots of each material in contact with an aqueous solution containing the target cation(s), under stirring for a set amount of time in a thermostated chamber at 298.15 K. The residual concentration of cation(s) in the filtered solution was measured by voltammetry and/or ICP-OES. These data were employed for the quantification of the sequestering capacity of each material using models the most common isotherm models such as Langmuir, Freundlich and SIPS. Moreover, PIMs were also studied in multiple applications such as drug delivery and enantioselective separation.