Microemulsion Systems for Fiber Deconstruction into Cellulose Nanofibrils

Abstract

A new method to produce cellulose nanofibrils (CNF) is proposed to reduce the energy demand during deconstruction of precursor fibers suspended in aqueous media. Microemulsions were formulated with aqueous solutions of urea or ethylenediamine and applied to disrupt interfibril hydrogen bonding. Compared to typical fibrillation of lignin-containing and lignin-free fibers, pretreatment with microemulsion systems allowed energy savings during microfluidization of 55 and 32%, respectively. Moreover, microemulsion processing facilitated smaller-scale CNF structures (higher degrees of deconstruction), with higher water retention value (WRV) and surface area. Urea-containing microemulsions were found to be most effective in reducing energy consumption and in weakening the cellulosic matrix. Films prepared from CNF processed after pretreatment with urea-containing microemulsions presented a more uniform fiber network and produced films with smoother surfaces compared to those based on ethylenediamine. The lignin-containing CNF (LCNF) produced denser films than those obtained from lignin-free CNF. The mechanical properties of films obtained after application of microemulsion pretreatment were compared, and the benefits of the proposed approach were further confirmed. Overall, fiber deconstruction after microemulsion treatment is a step toward energy-efficient production of nanocellulose.

Preparation and evaluation of high-lignin content cellulose nanofibrils from eucalyptus pulp

“…The average diameter size was 13 ± 8 nm, thereby corroborating the nanoscale of the fibrils obtained. Carrillo et al obtained similar size fibril bundles when preparing LCNF from Kraft digestion of eucalyptus using aqueous solutions of urea (Carrillo et al 2014). The nanopaper produced were observed by AFM and FE-SEM in order to measure roughness and observe surface structure.…”

Recent Strategies in Preparation of Cellulose Nanocrystals and Cellulose Nanofibrils Derived from Raw Cellulose Materials

“…The maximum thermal decomposition temperature was 343 ∘ C, while it was 310 ∘ C for the CNFs prepared without the NaOH pretreatment. Since urea and ethylenediamine have the ability to loosen the hydrogen bonds and solubilize cellulose, they could be applied to pretreat cellulose [190]. Before further mechanical disintegration, a microemulsion (surfactant-oil-water systems) including urea or ethylenediamine was applied to treat kraft pulps.…”

“…Before further mechanical disintegration, a microemulsion (surfactant-oil-water systems) including urea or ethylenediamine was applied to treat kraft pulps. It was found that urea and ethylenediamine pretreatment could effectively accelerate the isolation of CNFs [190].…”

Aqueous morpholine pre-treatment in cellulose nanofibril (CNF) production: comparison with carboxymethylation and TEMPO oxidisation pre-treatment methods

“…It has been shown that the presence of the charged groups bring about electrostatic repulsion and fibre swelling which reduces the effect of hydrogen bonding and hydrophobic interactions, thereby easing fibrillation (Nechyporchuk et al 2016a). In addition, a multicomponent microemulsion system containing either urea or ethylenediamine was used to ease the delamination of cellulose and lignocellulosic fibres (Carrillo et al 2014). The authors attributed the reduction in energy demand for CNF production to the ability of the microemulsion system to reduce the hydrogen bonding effect on cellulose.…”