Adsorption as a Technique to Recover Butanol

This chapter reviews adsorption as a promising technique for the recovery of n-butanol from fermentation broths, highlighting its advantages in terms of energy efficiency, selectivity, and biocompatibility compared to solvent-based methods. Adsorption relies on the binding of butanol molecules to solid surfaces, followed by desorption through thermal or chemical treatments, enabling adsorbent regeneration and reuse. Various adsorbent materials have been studied, including activated carbons, zeolites, polymeric resins, lignin, and advanced materials such as metal-organic frameworks (MOFs) and covalent organic frameworks (COFs). Their performance depends on factors such as surface properties, pore size, and hydrophobicity, with reported adsorption capacities ranging from tens to hundreds of mg/g. This chapter discusses the application of Langmuir and Freundlich isotherms to model adsorption equilibria and emphasizes challenges such as competitive adsorption from other metabolites, fouling, and adsorbent stability. In situ product recovery (ISPR) strategies are detailed, covering direct adsorbent addition, fixed-bed, expanded-bed, and simulated moving-bed configurations, all of which enhance butanol titers, yield, and productivity. The integration of adsorption with complementary techniques, such as gas stripping, further improves the process efficiency. Finally, desorption and regeneration techniques, including thermal swing and methanol displacement, are examined as critical steps for sustainable operation. The chapter concludes that continued research into novel, selective, and regenerable adsorbents is essential for scaling adsorption-based butanol recovery for industrial applications.