Fe/Cs are composite materials effective for Cr(VI) removal due to synergistic adsorption and reduction effects. However, conventional Fe/C preparation involves multiple discrete steps to impregnate iron particles onto the surface of porous carbon supports, decreasing scalability and reusability. Ultrasonic spray pyrolysis (USP) is a continuous and scalable materials synthesis technique used to prepare spherical, uniformly sized particles. In this study, Fe/C composites are prepared from glycerol, a by-product of the biodiesel industry, making this study of great practical importance to apply a waste precursor for USP carbon generation. Precursor solutions containing glycerol, sulfuric acid, sodium salts, and iron salts were ultrasonically aerosolized by a nebulizer. Prepared materials were fully characterized and applied in Cr(VI) removal and regeneration tests. Carbon microspheres were developed through acid induced glycerol dehydration, polymerization, and carbonization. Variable surface morphologies and hierarchical porous structures achieved for Fe/C composites depend on selected iron and sodium salt combinations. Porosity results from iron-catalyzed carbon gasification and solid salt templating, generating carbonaceous materials dominated by meso- and macropores. Iron impregnation into carbon microspheres reaches 6.6 wt%, and the oxidation state of the iron species is tailored by changing iron and sodium salts. Fe0 was generated in situ and impregnated into microspheres when using ferric ammonium citrate as both iron precursor and reducing agent. Potential for simultaneous nitrogen (up to 3.3 wt %) and sulfur (up to 6.3 wt%) doping is also reported. Hexavalent chromium removal efficiency of 95% at C0 ≤ 20 mg/L is achieved within 2 h, attributed to meso/macropore volume that aids adsorbate diffusion and reductive iron species. Magnetic properties (up to 20 emu/g) from iron nanoparticles facilitate Fe/C separation and reuse, highlighting the performance potential of the porous Fe/C materials for heavy metal remediation.

Cr (VI) removal with porous Fe/C microspheres prepared from glycerol via ultrasonic spray pyrolysis

2019 Spring National Meeting

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