Real-Time Characterization of Sodium Bicarbonate Crystallization in PVDF Membrane Modules Using FBRM.

Real-Time Characterization of Sodium Bicarbonate Crystallization in PVDF Membrane Modules Using FBRM. Syeda Laraib¹, Patricia Luis Alconero¹ ¹UCLouvain, Place Sainte Barbe 2,1348 Louvain la Neuve, Belgium, * syeda.laraib@uclouvain.be Introduction: Sodium bicarbonate (NaHCO₃) crystallization is pivotal in various industrial processes, including water treatment and resource recovery1. Osmotic Membrane Distillation Crystallization (OMDC) has emerged as an innovative technique that leverages osmotic gradients to induce supersaturation, facilitating controlled crystallization.While traditional crystallization methods have been extensively studied, real-time monitoring within membrane modules remains underexplored.2.This study introduces the direct insertion of a Focused Beam Reflectance Measurement (FBRM) probe into the membrane module, enabling in situ monitoring of crystal size distribution (CSD) and growth kinetics. This novel approach aims to enhance our understanding of the effects of feed concentration and flow rate on NaHCO₃ crystallization within an OMDC system. Experimental Methodology: Commercial polyvinylidene fluoride (PVDF) flat-sheet membranes were utilized in the OMDC setup. A sodium bicarbonate feed solution, with concentrations ranging from 10 to 96 g/L, and a sodium chloride (NaCl) osmotic solution concentration 200 g/L were employed to drive water transport across the membrane, inducing supersaturation and subsequent crystallization. The system operated at differnt feed flow rates to assess their impact on crystallization behavior while the osmotic side constant. For the first time, an FBRM probe was directly inserted into the membrane module, facilitating real-time monitoring of CSD dynamics and providing insights into nucleation, and growth phenomena. Data indicated that higher flow rates enhanced shear forces, leading to the formation of smaller, more uniform crystals. Conversely, increased feed concentrations elevated supersaturation levels, promoting rapid nucleation and the growth of larger crystals. This study successfully demonstrated the feasibility of using an FBRM probe for in situ monitoring of NaHCO₃ crystallization within an OMDC system. The findings highlight the significant roles of feed concentration and flow rate in determining crystal characteristics, offering valuable insights for optimizing membrane-based crystallization processes in industrial applications. Acknowledgements I would like to acknowledge that the project has been funded by the French Community of Belgium. References 1 M. G. Alvarez, V. S. Sefidi, M. Beguin, A. Collet, R. B. Soria, and P.Luis, “Osmotic Membrane Distillation Crystallization of NaHCO3,” Energies (Basel), vol. 15, no. 7, Apr. 2022. 2 J. Gómez et al., “Crystal growth analysis in a membrane crystallization process using focused beam reflectance measurements (FBRM),” Desalination, vol. 573, Mar. 2024.