Influence of processing parameters on regeneration kinetics and morphology of porous cellulose from cellulose–NaOH–water solutions

Abstract

The kinetics of cellulose regeneration in acetic acid bath from cellulose-8% NaOH-water solutions and gels is studied as a function of gelation conditions, acid concentration and bath temperature. The diffusion coefficient of NaOH from cellulose solution or gel into regenerating bath was calculated. It does not depend either on gelation mode or on acid concentration. On the contrary, cellulose regeneration from non-gelled solutions is slower than from a gel. The increase in bath temperature induces diffusion coefficient increase obeying Arrhenius law. Scanning electron microscopy images of regenerated swollenin-water freeze-dried cellulose and of the same samples dried in supercritical CO 2 show highly porous morphology.

Influence of lignin on cellulose-NaOH-water mixtures properties and on Aerocellulose morphology

“…Cellulose-NaOH solutions were prepared as described elsewhere (Gavillon and Budtova 2008;Sescousse and Budtova 2009). Briefly, an aqueous solution of 12% wt NaOH was cooled down to -6°C.…”

“…The samples were then rinsed with water to remove acid and then washed in acetone to remove water which is not compatible with CO 2 . Swollen-in-acetone samples were dried in supercritical CO 2 conditions as described earlier (1 L autoclave, 80 bar, 35°C) by Gavillon and Budtova 2008;Sescousse and Budtova 2009. After depressurisation (4 bar per hour at 37°C), light brown samples of ligno-Aerocellulose were extracted and analysed.…”

“…Gelation of cellulose-8%NaOH solution in the presence of lignin was investigated. Cellulose-lignin dry porous samples were then prepared according to the procedure developed for making Aerocellulose, pure cellulose ultra-light aerogel-like materials (Gavillon and Budtova 2008;Sescousse and Budtova 2009). They were made from the gelled mixtures followed by cellulose regeneration in water or acid baths and drying in supercritical conditions.…”

Cellulosic materials as biopolymers and supercritical CO2as a green process: chemistry and applications

“…The influence of the addition of a surfactant (Simulsol) on the porosity has been studied showing that the higher the concentration of the surfactant, the larger the pore size and the lower the density of the aerogels obtained ( Figure 4). Regeneration of these materials using acetic acid and scCO 2 drying has been reported by the same authors (Sescousse and Budtova 2009). In these studies, a solvent exchange of water with acetone or ethanol prior to scCO 2 drying was used to avoid water/scCO 2 immiscibility.…”

Cellulosic and Polyurethane Aerogels

“…Jin et al were the first to use nonderivatized cellulose in 2004 to produce very porous film-like materials by dissolution and regeneration of cellulose in aqueous solution of calcium thiocyanate followed by regeneration and carefully controlled freeze-drying procedures [11]. Then, various routes were developed, among others, with cellulose-NMMO (N-methylmorpholine N-oxide solutions) [12], cellulose-NaOH/urea solutions using epichlorohydrine as crosslinker [49], aqueous cellulose-NaOH solutions (Figure 10.19) [14,50], aqueous cellulose carbamate-NaOH solutions [51] or with cellulose dissolved in hydrated calcium thiocyanate melts [52] and even with aquagels of cellulose nanofibers [53]. Very recently, a brand new class of cellulosic aerogels based on the all-composite concept [54] has been prepared by partial dissolution of microcrystalline cellulose in LiCl/DMAc (N,N-dimethylacetamide) solutions followed by precipitation in water before freeze-drying [55].…”