Selective adsorption of water from aqueous butanol solution using canola-meal-based biosorbents

Abstract

In the present paper, the capabilities of canola meal (CM)-based biosorbents for the selective water removal from aqueous solution of butanol were investigated for purifying butanol. The raw canola meal (RCM) after protein extraction was pretreated using 5% (v/v) sulfuric acid to enhance the water adsorption characteristics of CM. This pretreated canola meal (PCM) was used as an adsorbent along with the RCM adsorbent for selective water removal. Biosorbents were characterized by Fourier transform infrared, carbon hydrogen nitrogen sulfur (CHNS), Brunauer, Emmett, and Teller surface area, and X-ray diffraction. The surface area and micropore volume were increased in PCM. In addition, crystallinity index and CHNS content in PCM were also increased. Both the adsorbents were able to selectively adsorb water from the aqueous solutions of butanol. PCM demonstrated a higher water uptake and a higher final butanol concentration than RCM. The adsorption diffusion model better fits the kinetic data of water adsorption by PCM in a butanol solution containing 95.3 wt% water. The adsorption isotherm was also investigated. The mean free energy per molecule of adsorbate () based on Dubinin–Radushkevich theory indicated that water adsorption is favorable and water or butanol adsorption was physical in nature.

KEYWORDS:

• Adsorption
• adsorption isotherm
• butanol
• canola meal
• Dubinin–Radushkevich theory
• selective water removal

Abbreviations::

• ABE: acetone–butanol–ethanol
• BET: Brunauer, Emmett, and Teller
• CHNS: carbon hydrogen nitrogen sulfur analysis
• CM: canola meal
• C_rI: crystallinity index
• FTIR: Fourier transform infrared spectroscopy
• GC: gas chromatography
• IPD: intra-particle diffusion
• PCM: pretreated canola meal
• RCM: raw canola meal
• XRD: X-ray diffraction

Acknowledgments

Financial assistance from the Saskatchewan Ministry of Agriculture, Mitacs, Saskatchewan Canola Development Commission, University of Saskatchewan, and Western Grains Research Foundation is sincerely acknowledged. Authors also thank Richard Blondin and Heli Eunike for their technical guidance.

Competing financial interest

The authors declare no competing financial interest.

Additional information

Funding

This work was supported by the Mitacs [Grant Number IT04850], Saskatchewan Ministry of Agriculture [Grant Number 20130220], Saskatchewan Canola Development Commission [Grant Number 20130220], and Western Grains Research Foundation [Grant Number 20130220].