Dewatering Cellulose Nanomaterial Suspensions and Preparing Concentrated Polymer Composite Gels via Reverse Dialysis

Abstract

Cellulose nanomaterials (CNMs) are typically produced in aqueous suspensions at low concentrations, which require subsequent dewatering to reduce transportation cost or as a preprocessing step for applications that require higher CNM loadings such as rheological modifiers and composites. Reverse dialysis is an effective method that avoids common dewatering issues like irreversible aggregation and sample heterogeneity. In this study, samples for dewatering were placed inside a dialysis bag and immersed in poly­(ethylene glycol) (PEG) solution. The water removal process is driven by the osmotic pressure difference. Dewatered TEMPO-cellulose nanofibril (TEMPO-CNF) was redispersible after allowing for time to rehydrate; the original viscosity was recovered after a dewatering-redilution cycle. The generalizability of reverse dialysis was demonstrated by also dewatering suspensions of cellulose nanocrystal and chitin nanofiber. Furthermore, concentrated and well-dispersed poly­(vinyl alcohol) (PVA)/TEMPO-CNF composite gels were obtained via reverse dialysis at loadings that were difficult to achieve by other methods. Reverse dialysis thus increases the processing range for these sustainable nanomaterials while preserving their beneficial morphological properties. Reverse dialysis can be added to manufacturing processes; recycling of the PEG solutions via ultrafiltration can be used to create an energy-efficient, sustainable, closed-loop dewatering process for cellulose nanomaterials that are hard to redisperse.

Understanding Nanocellulose–Water Interactions: Turning a Detriment into an Asset

“…For example, Reverse dialysis in poly(ethylene glycol) (PEG) has been shown to be a safe dewatering method via osmotic dehydration, without causing irreversible aggregation and sample heterogeneity. 907 Santmarti et al used low molecular weight PEG as a replacement for the water phase in nanocellulose aqueous gels. These gels had solid contents of up to 70% without interfibril hornification.…”

“…There are strategies to reduce the volume of nanocellulose gels for preservation and transport. For example, Reverse dialysis in poly­(ethylene glycol) (PEG) has been shown to be a safe dewatering method via osmotic dehydration, without causing irreversible aggregation and sample heterogeneity . Santmarti et al used low molecular weight PEG as a replacement for the water phase in nanocellulose aqueous gels.…”

Spontaneous Co-Assembly of Cellulose Nanocrystals and TiO2 Nanorods Followed by Calcination to Form Cholesteric Inorganic Nanostructures

“…The pH was monitored by narrow range test strips (pH test paper 9.2–10.6, Hydrion). Reverse dialysis according to Liao et al . in polyethylene glycol (PEG) aqueous solution at pH = 10 was performed to concentrate the suspensions up to around 16 wt %.…”

“…The pH was monitored by narrow range test strips (pH test paper 9.2−10.6, Hydrion). Reverse dialysis according to Liao et al 22 in polyethylene glycol (PEG) aqueous solution at pH = 10 was performed to concentrate the suspensions up to around 16 wt %. In a typical setup, PEG of a molecular weight of 35,000 g/mol was dissolved in water to form a solution at 20 wt %, and the pH was adjusted to about 10 with TMAH.…”

Bubble-blowing-inspired sub-micron thick freestanding silk films for programmable electronics

“…To get silk fibroin with high concentrations, the purified silk solution was concentrated through a reverse dialysis method. 42,43 In a typical process, 10 wt% polyethylene glycol (M w = 10 000) aqueous solution was prepared at first. Then a proper amount of silk fibroin solution was filled into a dialysis membrane (MWCO 3.5 kDa, Spectra/Por, USA).…”