Development of a diffusion-limited shrinking particle model of cellulose dissolution in a carbon dioxide switchable system Phawinee Nanta a , Wanwisa Skolpap a,⇑ , Kittiwut Kasemwong b , Yusuke Shimoyama c a Department of Chemical Engineering, Faculty of Engineering, Thammasat University, Pathumthani 12120, Thailand b NANOTEC Research Unit, National Nanotechnology Center, National Science and Technology Development Agency, 130 Thailand Science Park, Phaholyothin Rd., Khlong Luang, Pathumthani 12120, Thailand c Department of Chemical Science and Engineering, Tokyo Institute of Technology, 2-12-1 S1-33, Ookayama, Meguro-ku, Tokyo 152-8550, Japan highlights  We develop a diffusion-limited model of cellulose dissolved in CO 2 switchable system.  The shrinking particle model estimates diffusion coefficients at various conditions.  The shrinking particle model accurately predicts cellulose conversion.  Spearman’s rho correlation gives strength relationship among the model variables. graphical abstract article info Article history: Received 27 September 2017 Received in revised form 1 December 2017 Accepted 14 January 2018 Keywords: Carbon dioxide switchable system Cellulose dissolution Diffusion coefficient Diffusion-limited Shrinking particle model SPM abstract A diffusion-limited shrinking spherical particle model was developed to describe cellulose dissolution in carbon dioxide switchable system (CO 2 -SWS) by assuming an instantaneous reaction of the CO 2 -SWS on the cellulose surface. CO 2 , the main precursor of the SWS, was mixed with 1,8-diazabicyclo [5.4.0] undec- 7-ene, ethylene glycol and dimethyl sulfoxide under various operating pressures (P) and temperatures (T) to yield a CO 2 switchable ionic liquid for cellulose dissolution. As dissolution proceeded, the cellulose par- ticle radius decreased because of the disappearance of cellulose. The model–predicted diffusion coefficient (D), completed dissolution time (s), and dissolution conversion (X C ) were determined under various CO 2 -SWS operating conditions. The predicted s and X C values were in good agreement with the observed results. The influence of the CO 2 -SWS operating conditions on the predicted numerical D, s, and X C values were investigated using Spearman’s rho correlation. The results showed that the D values ranged from 10 20 to 10 17 m 2 s 1 for the CO 2 -SWS–cellulose system depending on the system conditions. Ó 2018 Elsevier Ltd. All rights reserved. 1. Introduction The heterogeneous dissolution process that occurs on a solid– liquid phase boundary involves two main steps: (i) transfer of solute molecules from the solid surface and (ii) diffusion of these molecules toward the bulk aqueous phase. The slower of these steps dominates the rate of dissolution. A film theory proposed by Sherwood et al. (1975) describes the diffusion of solute particles to the bulk liquid phase under the dilute-solution assumption. Hsu et al. (2009) derived analytical expressions for radius variations of the undissolved portion of a solid particle and for https://doi.org/10.1016/j.ces.2018.01.019 0009-2509/Ó 2018 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: swanwisa@engr.tu.ac.th (W. Skolpap). Chemical Engineering Science 179 (2018) 214–220 Contents lists available at ScienceDirect Chemical Engineering Science journal homepage: www.elsevier.com/locate/ces