Comprehensive analysis of water vapor sorption kinetics and mechanisms using biosorbent pellets from canola meal and oat hull

Abstract

Agricultural residues, specifically canola meal (CM) and oat hull (OH), have been innovatively utilized to develop biosorbents for sorbing water vapor from the air. These biomaterials are comprised of hydrophilic functional groups that effectively perform air dehydration. Air, being non-polar, was used as a model gas in this study to simulate gas dehydration. In the current research, these materials were formed into pellets to produce high-quality biosorbents with controlled size, shape, and enhanced moisture uptake capacity. CM (309.48 mg/g) and OH (233.07 mg/g) pellets had higher or comparable water sorption capacities than commercialized adsorbents used for drying gases. The mixed-order kinetic model described the sorption process well and identified both mass transfer and sorption on active site steps (R² > 0.991 and χ² < 16.0). Regarding the OH pellet, sorption on active sites was the predominant kinetic mechanism at the beginning, followed by intraparticle diffusion until equilibrium. However, sorption on CM pellets was delayed at 4.2 min at the initial stage, owing to the external mass transfer resistance; then, intraparticle diffusion controlled the process until equilibrium. Adding sodium lignosulfonate (LS_Na) lowered the initial sorption rate but enhanced the water uptake and strength of pellets. The addition of LS_Na resulted in a 25% and 14% increase in the water uptake capacity of oat hull and canola meal pellets, respectively; conversely, it also caused an increase in the delay time for sorption on CM pellets at the beginning of the process, extending it to 9.50 min.

Keywords:

• Biosorbent
• Sorption kinetics
• Sorption mechanisms
• Mass transfer
• Surface properties
• Adsorption

Acknowledgments

The technical assistance of Obiora Samuel Agu in the pelletizing of biomass is acknowledged. The authors also appreciate Richardson Milling, Martensville, SK and Federated Co-Op, Saskatoon, SK for providing free raw biomass for this research.

Disclosure statement

The authors declare no competing financial interest.

Additional information

Funding

Special thanks are given to Natural Sciences and Engineering Research Council of Canada (No. RGPIN-2019-4813) and Canada Foundation for Innovation (No. 11357) for financial support to this research.