The Influence of Ionic Strength on the Electroassisted Filtration of Microcrystalline Cellulose

Abstract

The production of materials such as microfibrillated cellulose and cellulose nanocrystals is gathering significant research interest by combining mechanical strength and toughness with a low density, biodegradability and renewability. However, one of the challenges with production on an industrial scale is to obtain an energy-efficient solid–liquid separation which is difficult because of the high specific filtration resistance of these materials. This study investigates electroassisted filtration as a method to facilitate the dewatering of cellulosic materials and the influence of ionic strength on the electrofiltration behavior. Electroassisted filtration is found to improve the dewatering rate of the studied cellulosic material, and the potential improvement compared to pressure filtration increased with the specific surface area of the solid material. Increasing the ionic strength of the system increased the power demand of the electroassisted filtration, and the major potential for industrial application is thus for systems with a limited ionic strength.

Electroosmotic dewatering of cellulose nanocrystals

“…The energy demand of systems with a high degree of electrical conductivity, e.g. suspensions of high ionic strength, will increase as the intensity of the current required to maintain the electric field increases (Wetterling et al 2017a). Moreover, the energy demand will also be influenced by the electrode separation as this influences the electrical resistance of the system and the strength of the electric field for any given voltage that is applied.…”

“…Electroosmotic dewatering is an assisted filtration technique that can be used to increase the solid content of suspensions of materials with charged surfaces (Iwata et al 2013;Mahmoud et al 2010). It has proved to be useful in increasing the solid content of cellulosic materials with high specific surface areas (Wetterling et al 2017a), such as microfibrillated cellulose suspensions (Heiskanen et al 2014), and has also shown potential for use in the dewatering of both biopolymers (Gözke and Posten 2010;Hofmann et al 2006;Hofmann and Posten 2003) and hydrogels (Tanaka et al 2014). Using electroosmotic dewatering prior to drying can decrease the total energy demand of the dewatering operation (Larue et al 2006;Loginov et al 2013;Mahmoud et al 2011) and is therefore also attracting significant research interest in the treatment of wastewater sludge (Citeau et al 2012;Mahmoud et al 2011;Olivier et al 2015).…”

Towards sustainable production and utilization of plant-biomass-based nanomaterials: a review and analysis of recent developments

“…In electrofiltration, an electric field is applied to influence the filtration of negatively charged CNCs by inducing an electrophoretic force in the direction of the anode, thereby influencing the filter cake growth. At the same time, it also induces motion of the fluid in the direction of the cathode, which drives solid–liquid separation [ 243 , 244 ]. In this process, the electric field is a dominant factor influencing the dewatering rate, exceeding the effect of modifying suspension conditions.…”

Dewatering of Cellulose Nanofibrils using Ultrasound

“…(1-4hrs/100ml suspension) (Iwamoto et al 2005;Sehaqui et al 2010). Electro-assisted filtration for microfibrillated cellulose (MFC) helps tackle this issue (10-30 mins/100 ml of diluted suspension) but only through an increase in the overall energy consumption (Wetterling et al 2017). Electroosmotic filtration for CNC has been demonstrated to be energy efficient as compared to the thermal methods, however, higher dewatering rates increases these energy requirements and their applicability to CNF remains unknown (Wetterling et al 2018).…”