title: Translational Entropy and Dispersion Energy Jointly Drive the Adsorption of Urea to Cellulose.
abstract: The adsorption of urea on cellulose at room temperature has been studied using adsorption isotherm experiments and molecular dynamics (MD) simulations. The immersion of cotton cellulose into bulk urea solutions with concentrations between 0.01 and 0.30 g/mL led to a decrease in urea concentration in all solutions, allowing the adsorption of urea on the cellulose surface to be measured quantitatively. MD simulations suggest that urea molecules form sorption layers on both hydrophobic and hydrophilic surfaces. Although electrostatic interactions accounted for the majority of the calculated interaction energy between urea and cellulose, dispersion interactions were revealed to be the key driving force for the accumulation of urea around cellulose. The preferred orientation of urea and water molecules in the first solvation shell varied depending on the nature of the cellulose surface, but urea molecules were systematically oriented parallel to the hydrophobic plane of cellulose. The translational entropies of urea and water molecules, calculated from the velocity spectrum of the trajectory, are lower near the cellulose surface than in bulk. As urea molecules adsorb on cellulose and expel surface water into the bulk, the increase in the translational entropy of the water compensated for the decrease in the entropy of urea, resulting in a total entropy gain of the solvent system. Therefore, the cellulose-urea dispersion energy and the translational entropy gain of water are the main factors that drive the adsorption of urea on cellulose.
authors.affiliation: Aachener Verfahrenstechnik, RWTH Aachen University , Turmstrasse 46, D-52064 Aachen, Germany.|Wallenberg Wood Science Center, and the Department of Fibre and Polymer Technology, KTH Royal Institute of Technology , SE-10044 Stockholm, Sweden.
authors.forename: Pan
authors.initials: P
authors.lastname: Chen
authors.affiliation: CERMAV, Univ. Grenoble Alpes , F-38000 Grenoble, France.|CERMAV, CNRS , F-38000 Grenoble, France.
authors.forename: Yoshiharu
authors.identifier: 0000-0003-4069-2307
authors.initials: Y
authors.lastname: Nishiyama
authors.affiliation: Wallenberg Wood Science Center, and the Department of Fibre and Polymer Technology, KTH Royal Institute of Technology , SE-10044 Stockholm, Sweden.
authors.forename: Jakob
authors.initials: J
authors.lastname: Wohlert
authors.affiliation: College of Chemistry and Molecular Science, Wuhan University , Wuhan 430072, China.
authors.forename: Ang
authors.initials: A
authors.lastname: Lu
authors.affiliation: CERMAV, Univ. Grenoble Alpes , F-38000 Grenoble, France.|CERMAV, CNRS , F-38000 Grenoble, France.
authors.forename: Karim
authors.initials: K
authors.lastname: Mazeau
authors.affiliation: Department of Chemical and Biomedical Engineering, West Virginia University , Morgantown, West Virginia 26505, United States.
authors.forename: Ahmed E
authors.initials: AE
authors.lastname: Ismail