Selective Oxidation of Cellulose—A Multitask Platform with Significant Environmental Impact

Abstract

Raw cellulose, or even agro-industrial waste, have been extensively used for environmental applications, namely industrial water decontamination, due to their effectiveness, availability, and low production cost. This was a response to the increasing societal demand for fresh water, which made the purification of wastewater one of the major research issue for both academic and industrial R&D communities. Cellulose has undergone various derivatization reactions in order to change the cellulose surface charge density, a prerequisite condition to delaminate fibers down to nanometric fibrils through a low-energy process, and to obtain products with various structures and properties able to undergo further processing. Selective oxidation of cellulose, one of the most important methods of chemical modification, turned out to be a multitask platform to obtain new high-performance, versatile, cellulose-based materials, with many other applications aside from the environmental ones: in biomedical engineering and healthcare, energy storage, barrier and sensing applications, food packaging, etc. Various methods of selective oxidation have been studied, but among these, (2,2,6,6-tetramethylpiperidin-1-yl)oxyl) (TEMPO)-mediated and periodate oxidation reactions have attracted more interest due to their enhanced regioselectivity, high yield and degree of substitution, mild conditions, and the possibility to further process the selectively oxidized cellulose into new materials with more complex formulations. This study systematically presents the main methods commonly used for the selective oxidation of cellulose and provides a survey of the most recent reports on the environmental applications of oxidized cellulose, such as the removal of heavy metals, dyes, and other organic pollutants from the wastewater.

Polysaccharide-Based Composite Hydrogels as Sustainable Materials for Removal of Pollutants from Wastewater

“…Particularly, for water purification, CS stands out as a highly sustainable raw material in fabricating numerous low-cost composite sorbents with remarkable mechanical properties, chemical stabilities, and sorption performances [ 181 ]. On the other hand, the chemical modification of Cel by grafting different multifunctional ligands or monomers is extensively studied worldwide as a means to produce soluble derivatives [ 183 ], aiming to broaden the use of Cel-based materials in many advanced applications [ 184 , 185 , 186 ].…”

Insights on Some Polysaccharide Gel Type Materials and Their Structural Peculiarities

“…Aerogels present an increased permeability, a great specific pore-size, greater density, and proper robustness as mechanical performance making them suitable for a diverse range of applications [ 193 ]. Related to the above-mentioned, it is of real significance the relative ease of applying alteration of cellulose structure through chemical processing [ 194 ] in order to enhance the durability and peculiarities conferred by the structure of resulted aerogel-type materials (e.g., oxidation using TEMPO). Xerogels —which are obtained by applying evaporation drying method, which reduces gels’ wetness, presents increased permeability, a great specific pore-size, and a structure similar to aerogels obtained through drying using supercritical solvents [ 195 , 196 , 197 , 198 ].…”

“…Aerogels present an increased permeability, a great specific pore-size, greater density, and proper robustness as mechanical performance making them suitable for a diverse range of applications [ 193 ]. Related to the above-mentioned, it is of real significance the relative ease of applying alteration of cellulose structure through chemical processing [ 194 ] in order to enhance the durability and peculiarities conferred by the structure of resulted aerogel-type materials (e.g., oxidation using TEMPO).…”

“…Other characterization methods, such as isothermal thermogravimetry in a kinetic mode associated with the time-resolved infrared spectroscopy, were used to confirm the role of solvent, especially when the solvent was water, in the formation and properties of polysaccharide gels [ 194 ].…”

Chitosan Schiff-Base Hydrogels—A Critical Perspective Review

“…In this regard, it seems particularly advantageous to use sodium periodate, a specific reagent, to oxidize the OH groups contained in the majority of polysaccharides. The unique property of this selective and specific reagent is that it simultaneously oxidizes the secondary OH groups of the glycosidic unit and breaks the bridge between C2 and C3, resulting in a reaction product with two aldehyde groups on the structural unit [ 10 , 29 , 42 , 43 , 44 , 45 ], Figure 2 .…”