Nuclear Magnetic Resonance Investigation of the Fractionation of Water–Ethanol Mixtures with Cellulose and Its Cross-Linked Biopolymer Forms

Abstract

Cellulose (CE) was cross-linked with epichlorohydrin (EPI) at variable compositions, and the fractionation properties were investigated in binary water−ethanol (W−E) solutions, including the pure solvent systems. The relative uptake of each solvent was measured using quantitative 1 H nuclear magnetic resonance (qNMR) spectroscopy. This study highlights the utility of qNMR as a rapid screening method for estimation of solvent selective fractionation in binary mixtures. The uptake properties of CE−EPI cross-linked polymers with ethanol and water were well-described using the Sips isotherm model. Modeling shows that the monolayer surface coverage (Q m ) of ethanol and water onto the polymer materials covers a range (1.13−2.44 g/g) of values with heterogeneous adsorption behavior, in agreement with the Sips exponential fitting parameter (n s ≠ 1). The CE−EPI adsorbents display unique fractionation with water and ethanol from binary solutions, as evidenced by the relative selectivity (R selectivity ) value in binary W−E solvent systems. The R selectivity [Q m (W)/Q m (E)] values at saturative conditions varied (from 1.10 to 2.03) and further illustrate that CE materials display molecular selective solvent fractionation in binary W−E solutions. This study provides a greater molecular level understanding for the adsorptive uptake properties of CE that are relevant to developing CE-based adsorbent technology for the fractionation of biofuels and related chemical separations.

A Spectroscopic Study of Solid-Phase Chitosan/Cyclodextrin-Based Electrospun Fibers

“…The HPCD content of the fiber samples was estimated using a quantitative NMR (qNMR) method that was adapted from a previous report [33]. A 1% (w/w) THF/DMSO-d 6 solution was prepared by adding a desired amount of THF to DMSO-d 6 to which ca.…”

Spectroscopic and Thermodynamic Study of Biopolymer Adsorption Phenomena in Heterogeneous Solid–Liquid Systems

“…6 Biopolymer adsorbent technology that utilize starch and cellulose (CE) has gained increasing attention due to its relative abundance, low-cost, and low energy inputs with minimal infrastructure requirements for adsorptive-based fractionation. 7 In a previous study, 8,9 we reported the unique adsorption-based fractionation of water (W) from binary mixtures of water and ethanol (W–E) using biopolymer sorbents and their modified forms. Elsewhere, we reported on the unique adsorption of water vapor using starch biopolymer adsorbents.…”

“…9,12,13 In a recent isotherm study of starch–water vapor systems, 10 the importance of biopolymer–solvent (s–l) interactions was shown by markedly different thermodynamic properties of starch-based adsorbents. By comparison, the heterogeneous fractionation of water from W–E binary solutions using starch- and cellulose-based adsorbents was reported 8,9,14−16 that extends beyond the pioneering work of Ladisch and Dyck. 17 However, there is a limited molecular-level understanding of the factors that govern hydration and solvent-selective fractionation in solid-solution (s–l) sorption processes, especially for native and modified (cross-linked) biopolymer systems.…”

“Pillaring Effects” in Cross-Linked Cellulose Biopolymers: A Study of Structure and Properties

“…While there are various strategies for the synthetic modification of cellulose, cross-linking is known to alter the physicochemical properties due to pillaring effects [4,5]. Previous studies have shown that the introduction of cross-links within a biopolymer network alters the textural, hydration, and mechanical properties, along with the chemical stability toward biodegradation [6][7][8][9][10]. The structure and physicochemical properties of cross-linked polymers related to adsorption (e.g., morphology, thermal stability, solvent swelling, crystallinity, and surface chemistry) differ compared with unmodified (native) polymers.…”

“…In turn, a greater understanding of the physicochemical properties of cellulose and its cross-linked forms will advance the science and technology of such materials. We envisage that such biopolymer materials can be synthetically engineered for specialized solid phase extraction (SPE) of steroids or lipids for analytical to biotechnology applications to address chemical separations in complex media such as urine to water/alcohol mixtures [7,25].…”