High Efficiency and Facile Butanol Recovery with Magnetically Responsive Micro/Mesoporous Carbon Adsorbents

The in situ recovery of n-butanol from conventional batch fermentation is an effective strategy to overcome cytotoxic titer limitations. Here, we demonstrate efficient butanol recovery using magnetically responsive micro/mesoporous carbon adsorbents. Although large surface areas (>1400 m²/g) promote adsorption, inclusion of magnetic Ni nanoparticles enables direct and facile magnetic retrieval of spent adsorbents, bypassing the need for column configurations (e.g., packed or expanded bed). Butanol loading capacities of a family of mesoporous powders (4-10 wt %Ni content) are not significantly impacted by Ni content, performing comparably to commercial resins and activated carbons (e.g., up to 0.26 g/g at 12.5 g/L equilibrated butanol). Magnetic recovery of the mesoporous powder is dependent on the Ni content, with up to 89 wt % recovery achieved in 6 min with 10 wt % Ni. Desorption studies using retrieved adsorbents demonstrated an average of 93% recovery of the total adsorbed butanol. Biocompatibility studies using an Escherichia coli model showed no discernible toxicity, even at high Ni content and levels of adsorbent addition. Kinetic studies indicate that neither the effective adsorption or desorption rates should constitute a bottleneck with respect to the future development of a semicontinuous butanol fermentation process using these novel, magnetically responsive adsorbents.