Innovative Nanostructured Activated Carbon - Silica Composite Adsorbent Based On High Ash Biochar

Biochar is the solid byproduct of the thermochemical bioenergy conversion processes. In general, biochar from native grasses, agricultural crop residues including switch grass, corn stover and rice hulls contains from 25% to 85% ash, which mainly composed of SiO2. Therefore, biochar generated in thermochemical conversion has only been used as a soil amendment or low grade fuel until now.

Nanostructured carbon–silica composites were prepared from biochar containing high silicon ash. After activation of biochar using alkali metal carbonates and alkali metal hydroxide as catalysts, nanometer silica particles were uniformly precipitation and distributed on the surface of activated carbon with CO2 bubbling under ultrasonic radiation and high shear strength mechanic stirring. Internal and surface structures of nanostructured carbon–silica composites were characterized with FTIR, XRD, DSC, TGA, SEM and AFM. Adsorption and desorption properties of nanostructured carbon–silica composites were quantified with methylene blue value, iodine value, N2 BET and metal ions (Cu2+ and Ni2+) adsorption. Nanostructured carbon–silica composites prepared in this project shown unique dynamic and equilibrium adsorption properties. Optimal parameters of preparation methods such as catalysts loading, activation temperature, CO2 flow rate and mixing conditions were determined. The prepared nanostructured carbon–silica composites can be applied in multiple adsorption separation processes such as pressure/temperature swing adsorption, drinking water purification, waste water treatment and volatile organic compounds removal. .

Nanostructured carbon–silica composites, developed in this project, as a value added co-product of cellulosic biofuel or bioenergy will significantly improve economic viability of regional bioenergy systems, help speed commercialization of biofuels and bioenergy, increase employment opportunities and achieve sustainable economic growth in rural area as well as thereby reduce our dependence on foreign oil.