Bruno Chabot

Phosphorylation of Kraft fibers with phosphate esters.

Phosphate esters, derived from two different long-chain aliphatic alcohols, were used as phosphorylating reagents for Kraft pulp fibers. High phosphorus contents and almost non-degraded fibers were obtained by following this pathway. The phosphorylation efficiency was influenced by the alkyl chain length of PEs since the phosphorus content in modified fibers was higher for the shorter chain reagent. Due to the heterogeneous reaction environment, the amount of grafted phosphorus was found to be almost three times higher at the surface than in the bulk of the fibers. Analyses also indicated that the phosphorus was bonded to fibers as a phosphate-like structure. Furthermore, the situation seemed to be different for the fiber surface where significant amounts of phosphorus were present in more complex structures like pyrophosphate or even oligo-phosphate.

The Use of Weissler Method for Scale-Up a Kraft Pulp Oxidation by TEMPO-Mediated System from a Batch Mode to a Continuous Flow-Through Sonoreactor

The efficiency of cellulose oxidation mediated by the 4-acetamido-TEMPO radical under ultrasonic cavitation was investigated using two ultrasonic systems: a batch lab scale ultrasonic bath with a glass reactor and a semi-continuous flow-through sonoreactor. The main objective was to explore the possibility of scaling up the production of oxidized cellulose under ultrasound, from a lab scale process to a pilot plant process, which served as a precursor for producing nanofibrils cellulose. It was found that under acoustic cavitation, the efficiency of TEMPO-mediation oxidation of native cellulose was significantly improved, particularly in the flow-through sonoreactor. In comparison with the glass reactor, the flow-through sonoreactor reduce the applied energy by 88% while increasing 7.8 times the production rate of radicals. These results enable a possibility of producing oxidized fibers for industrial applications.

The Use of Sodium Chlorite in Post-Oxidation of TEMPO-Oxidized Pulp: Effect on Pulp Characteristics and Nanocellulose Yield

Abstract Presence of aldehydes on cellulose nanofibers (alternatively called nanocellulose) produced from TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyle)-oxidized pulp could interfere with the grafting of selected compounds on the carboxyls group of the oxidized pulp or of the nanofibers produced from such pulps. A simple protocol, called post-oxidation, utilizing sodium chlorite under acidic conditions has been developed for TEMPO-oxidized native cellulose to oxidize the aldehydes to carboxyls. The chemical nature, degree of polymerization, nanocellulose yield, and brightness stability of the post-oxidized pulp was characterized and compared with those of pulps prepared by the post-oxidation methods published in the literature. A sodium chlorite charge of 10% was sufficient for the oxidation of the TEMPO-oxidized pulp, which had a residual aldehydes content of ∼100 mmol/kg. We had observed an increase in degree of polymerization, nanocellulose yield, and brightness stability due to post-oxidation. It was found that aldehyde groups contributed significantly to the brightness reversion and yellowing of the TEMPO-oxidized pulp.

Development and treatment procedure of arsenic-contaminated water using a new and green chitosan sorbent: kinetic, isotherm, thermodynamic and dynamic studies

Abstract Arsenic is classified as one of the most toxic elements for humans by the World Health Organization (WHO). With the tightening drinking water regulation to 10 μg L−1 by the WHO, it is necessary to find efficient sorbent materials for arsenic. In this work, the removal of arsenic(V) from water is achieved with an insoluble chitosan sorbent in the protonated form obtained by a simple heating process. Kinetic studies show a very fast sorption (less than 10 min). The Langmuir isotherm model is best describing experimental data with a capacity of 42 mg g−1 at pH 8. The sorption process is based on anion exchange (chemisorption) determined from the Dubinin-Radushkevich model. The sorption efficiency of the chitosan sorbent is 97% at low concentrations (e.g. 100 μg L−1). Thermodynamic analysis reveals that the sorption process is exothermic and is controlled by enthalpic factors. Breakthrough curves (BTC) were acquired in real-time by instrumental chromatography and was better described by the Thomas model. BTC from column sorption and desorption with a salt solution suggest that this sorbent is relevant for large scale applications. With this new renewable product, it will be possible to treat arsenic contaminated water at low cost and with little waste (concentration factor of 1500).

Spectroscopic Study of Tempo-Oxidized Deinked Pulp

Abstract Deinked pulps are not currently used in value-added paper manufacturing. To implement their use, both strength and optical properties must be improved. TEMPO oxidation has been shown to improve strength properties of thermomechanical and deinked pulps. However, a significant reduction of the pulp brightness results due to yellowing of mechanical fibers. Spectroscopic techniques were used to investigate the effect of TEMPO oxidation on deinked fiber properties. Fourier transform infra-red (FTIR) spectroscopy and UV/VIS spectrum showed that oxidation conditions are driving important chemical reactions that affect optical properties. Results indicated that ortho-quinone compounds as well as carboxylic groups are generated depending on oxidation conditions resulting in pulp brightness decrease. Spectroscopic studies also revealed that residual ink detachment from fiber surfaces is occurring during oxidation contributing to improve pulp brightness.