Collaborative Research: High Surface Area Mesoporous Carbons for Facile Biofuel Recovery from Dilute Aqueous Solution

1159295/1159200

Vogt/Nielsen

Despite significant developments in producing sustainable liquid transportation fuels from renewable biomass resources, end-product toxicity remains a key, productivity-limiting factor in most conventional bioprocesses. One effective approach to relieve biofuel product toxicity is through its in situ recovery from the culture, which requires low cost, low energy, and biocompatible separation technologies that selectively remove biofuels from dilute aqueous solutions. Low energy separation processes have been proposed, but most prior studies have focused on model, biofuel-water solutions; real processes are challenged by complex biological mixtures prone to cause fouling and poor material biocompatibility, which adversely impact separation performance and overall process viability. Here, we propose to systematically examine magnetic, mesoporous, carbon-based materials to elucidate how fundamental physicochemical properties impact adsorbent performance for biofuel (ethanol and n-butanol) recovery in both idealized solutions and growing cultures. Fundamental and mechanistic characterizations of biofuel-adsorbent interactions, as well as nonideal interactions (fouling phenomena), will provide structure-function relationships in real systems. Ultimately, the productivity enhancements that can be realized through continuous, in situ biofuel recovery will be assessed by integrating these materials with biofuel-producing microbial cultures.

High surface area and pore accessibility of ordered mesoporous materials make them attractive for biofuel separations. We propose to utilize soft templated mesoporous carbons as biofuel adsorbents; synthetic tuning of the pore size, surface area, and pore morphology will provide a fundamental understanding of how these properties impact biofuel adsorption capacity, partition coefficients, and heats of adsorption. We propose a single pot synthesis to include cobalt nanoparticles in the carbon without significantly impacting the mesostructure to enable magnetic separation of the adsorbent from culture. Recovery efficacy will be systematically examined to determine if magnetic separation is a viable mechanism for adsorbent recovery. We will begin with fundamental studies using model solutions for direct comparison with other commonly examined adsorbents for biofuel separations; however, additional considerations will be critical in real applications. In reality, biofuel-producing cultures are complex mixtures wherein fouling and other non-ideal interactions lead to altered separation performance. Meanwhile, the microbial biocompatibility of mesoporous carbons is relatively unknown. Accordingly, we will systematically examine the nature and degree of non-ideal interactions to define and incorporate material properties promoting sustained performance under realistic process conditions. Two different recovery strategies will be developed and examined for comparative analysis: a traditional, externally circulated packed-bed column, and the novel dispersion of magnetic adsorbent particles throughout the culture (followed by their magnetic collection). We anticipate the latter novel approach, which has never been examined in growing, biofuel-producing cultures, will provide improved efficacy as it enables continuous contact between the adsorbent and culture medium without costly and cell-damaging pumping requirements. This end-to-end, this proof-of-concept study will enable evaluation of how adsorbent physical properties impact performance as applied to continuous, in situ removal of ethanol and n-butanol from growing microbial cultures. These capstone experiments uniquely allow direct evaluation of if and how fundamental characterizations performed under idealized conditions can predict performance in real systems.

A fundamental understanding of the property-structure relationships of mesoporous materials for biofuel adsorption would enable more efficient separations of biofuels from culture broths and will aid in reducing the U.S. dependence on foreign fossil fuels. The broader educational impact will involve participation of graduate and undergraduate students in this highly interdisciplinary area of inquiry. Moreover, concepts and results from this research will be incorporated into a new teaching lab module on bioreactors and biofuels. Outreach activities to local underrepresented K-12 students are proposed to discuss the societal importance biofuels and the challenges associated with their separation and production; additionally, these activities will aim to correct common misconceptions regarding nanotechnology. Broader dissemination to P-16 will be enabled through the Akron Global Polymer Academy, which has worldwide reach.