Feedback of Ramzi Khiari: guest researcher at Glyco@Alps

on the August 29, 2019

Ramzi Khiari, researcher at Faculty of Sciences of Monastir, Tunisia received a Glyco@Alps grant as a guest researcher. He stayed two months at LGP2.
Ramzi Khiari:

"First of all, I would like gratefully acknowledge the support the GlycoAlps for the financial support. I would like also to thank Prof. Evelyne Mauret, Prof. Didier Chaussy and Prof. Naceur Belgacem for their advice and helps.

Many studies have been carried out on cellulose fiber pretreatment for nanofibrillation and today up to 10 pretreatments are available, such as, TEMPO oxidation, cationization, phosphorylation, carboxymethylation, sulfoethylation, or deep eutectic solvent. Among all these pretreatments, enzymatic and TEMPO oxidation are the oldest and the best known. Used industrially today, they lead to CNF of good quality, but they present some drawbacks. Enzymatic hydrolysis allows a significant reduction in energy consumption but does not offer the possibility to make other modifications. Hence, new fiber modifications methods have been proposed in recent years. These pretreatments are very promising. For example, surface cationization of cellulose fibers using epoxy propyltrimethyl ammonium chloride (EPTMAC) leads to antimicrobial surfaces and allows a large decrease in energy consumption (from 11,000 to 3,000kWh/t). Periodate oxidation of cellulose fibers, leading to dialdehyde cellulose, offers a large variety of possibilities for grafting other molecules, as reported several times. After ring opening using periodate oxidation, many molecules can interact and modify the properties of the cellulose, such as NaBH4 reduction, Girard reactant, or diamine. Nowadays, others researchers propose to use a deep eutectic solvent based on choline chloride and urea to produce CNF with an environmentally friendly process. Even if the mechanism for this treatment is unknown, they obtained CNF of 2-5nm width and a Young’s modulus around 8 GPa. Others news chemical pretreatments were also examined such as phosphoric component: (NH4)2HPO4 is grafted to the fiber, which confers flame retardant properties and were also aiming to produce phosphorylated CNF using different procedures.
In the same context, our work focuses mainly on founding new grafting which can be reduce the high energy consumption during the mechanical processes in order to produce to nanofibrillated cellulose. A new green way to produce CNF using environmentally friendly cellulose carbonate produced according to our develop method. Figure 1 illustrates the various steps leading to the preparation of CNF using cellulose carbonate and a Supermasscolloider ultra fine friction grinder.

The resultant CNF suspension was successfully prepared and characterized in terms of fibrillation yield, transparency, rheological behavior, morphological features, and quality index. This novel chemical approach for the production of CNF seems to hold promises not only for its green features but also for its lesser and cleaner effluent discharge, and low cost of reagents".

Published on August 29, 2019