Design and development of functional biopolymeric materials for environmental applications

Abstract

The naturally derived polymers have attracted extensive research interest for large abundance, biodegradability, high mechanical properties, and good biocompatibility. Biopolymers are the class of biodegradable polymers, produced by living organisms. In addition to this, some polymers can also be extracted from biological sources such as sugars, proteins, amino acids, and oils, which can also be described as biopolymers. Compared to synthetic polymers, biopolymers have more defined and precise three dimensional structures. Chitosan, cellulose, sodium alginate, and gelatin are some of the biopolymers, which can be derived from biomass sources such as animal residue, industrial residue, agriculture residue, sewage, etc (Figure 1). A large number of functional groups and reactive sites are present over the biopolymer, which can be chemically modified accordingly for desired applications. Chapter-1 Biopolymers are a kind of material that can be used to adjust, control, or participate in the various parts of the living system, to facilitate the operation and function of the living system. They can be used individually or as a part of a complex system. In this whole thesis work, biopolymeric materials were used with the inclusion of metal NPS, ionic liquids, and covalent organic framework for various environmental applications including catalysis, sensing, active food packaging, antimicrobial membranes, and water purifications (Figure 2). Chapter-2 Herein, a cationic hydrogel was designed and synthesized using a simple and facile method yielding excellent adsorption capacity, thereby enabling the rapid removal of organic dyes, nitrite anions, and Pb2+ from polluted water, as well as oil–water separation. The backbone of the hydrogel was composed of CS and poly(vinyl alcohol) (PVA) with glutaraldehyde as the crosslinker. An ionic liquid (IL) was grafted onto the backbone via a radical reaction. The synthesized hydrogel was optimized by varying the amounts of crosslinker, monomer, temperature, reaction time, initiator, and solvent to obtain maximum adsorption affinity. The interstitial voids and cationic charge on the hydrogel increased its binding affinity for organic dyes and anions (Figure 3). The positively charged hydrogel electrostatically interacted with the dyes and nitrite (NO2 ), facilitating their removal from wastewater. Chapter-3 Chapter-3A: In this study, cellulose was extracted from rice straw, and a highly active solid-supported catalytic model (ASC-1) was developed. Cellulose conjugated with poly(ethylene-co-vinyl acetate) (PEVA) followed by insertion of AgNPs. The process involved the reduction of silver nanoparticles in the presence of sodium-borohydride. The synthesized catalytic hybrid was successfully applied to Willgerodt Kindler's reaction of aromatic aldehydes, amines, and sulfur for the formation of thioamides in excellent yields (Figure 3). Chapter-3B: Herein magnetically removal of IL1-2@Fe3O4 heterogeneous catalysts was developed, which were further used for the synthesis of polymers via willgerodt kindler reaction with a simple and facile method (Figure 4). Fe3O4 NPs have high affinity towards the functional groups, present in ionic liquid and we found that IL1 2@Fe3O4 performs high catalytic properties for synthesis of thioamide-based polymers and recycled with minimum loss of activity. Chapter-4 This chapter deals with the synthesis of Au NPs embedded solid support catalyst (Au@CIL) for selective reduction of Nitro compounds, with a simple and facile method. Abundant hydroxyl groups present on the surface of ionic liquid functionalized cellulose help in the adsorption of Au NPs. Ionic liquid stabilized the solid support system by a combination of electrostatic protection layers. Because of variation the size of Au NPs makes them are used as heterogeneous catalysts in wide applications. We found that Au@CIL performed excellent catalytic properties for selective reduction of NO2 group and recycling with minimum loss of catalytic activity (Figure 5). Chapter-5 Chapter-5A: In present work, we developed a polymeric matrix from biopolymers with inclusion of ionic liquid which have potential to increase shelf life of food. In this regard, an ionic liquid was synthesized from 1-methyl imidazole and salicylate anion, where anionic moiety showed excellent antioxidant properties and cationic moiety has potential towards antibacterial action (Figure 6). Furthermore, ionic liquid also works as a cross-linker between the gelatin and CMC to strengthen the polymeric matrix. Chapter-5B: In this chapter smart sensing strips and antimicrobial active food packaging films were synthesized to monitor the food quality. For smart sensing of food spoilage, 2D covalent organic frameworks (COFs) were synthesized from 2,4,6 triformylphloroglucinol (TFP) and p-phenylenediamine. Thereafter, COF was incorporated into sodium alginate polymeric material to obtain sensing strips with highly colorimetric response and augmented mechanical properties (Figure 7). The smart sensing strips were demonstrated on packaged poultry meat. Sensing strips are highly pH-responsive and their color changes according to pH of the surroundings. Chapter-6 Includes the overall summary of thesis work, where various functions of biopolymers with inclusion of metal nanoparticles, ionic liquids, and covalent organic framework have been developed. Synthesized materials have potential for environmental remediation applications including catalysis, removal of dyes, toxic metal ions, oil, toxic anions from wastewater, smart sensing, and active packaging of food.