Agricultural byproducts-based biosorbents for purification of bioalcohols: a review

For the purification of alcohols derived from microbial fermentations, extensive processing is required. Adsorption is described as one of the most cost-effective and efficient techniques for the separation of water and purification of alcohols. Biobased sorbents (called biosorbents) are advantageous for dehydration of alcohols as they can be developed from cost-effective feedstocks such as waste agricultural biomass or byproducts, have adsorption capacities at par with chemical adsorbents, and can be safely disposed. Alternatively, the spent adsorbents can be reused for fuel or energy production. Agricultural byproducts are low cost and abundantly available materials containing cellulose, hemicellulose, proteins, and lignin as their constituents. Biosorbents have the capability to adsorb water by the polar interaction of their hydroxyl, carboxyl, carbonyl, and amine groups with water molecules. The pore size distribution and thermal stability of biosorbents are also industrially relevant features. They are a promising option to be used in industries for dehydration of alcohols. This paper reviews adsorptive purification of bioalcohols with a focus on using biosorbents, and describes their structure, global availability, water adsorption mechanism, and the use of biosorbents in liquid phase and vapor phase adsorption systems for the purification of ethanol, butanol, and other higher alcohols.