Solid waste to biofuels and heterogeneous sorbents via pyrolysis of wheat straw in the presence of fly ash as an in situ catalyst

Abstract

Solid waste disposal imposes worldwide environmental and economic hardships. To alleviate such issues, the present work uses coal fly ash to in situ catalyze the pyrolysis of wheat straw, an abundant agricultural biomass, and to simultaneously produce heterogeneous sorbents for water treatment. Coal fly ash mixed in varying proportions with wheat straw shows a catalytic effect by lowering the temperature at which many noncondensable gaseous species are released. As the weight fraction of fly ash in the wheat straw increased from 1 to 10 wt%, the overall conversion of biomass increased. 1–5 wt% fly ash favored conversion to the gas phase (especially CO2, CH4 and C2H4), whereas the 10 wt% mixture produced more condensable species with fewer detectable oxygenated components and increased furan concentration. For a more complete waste-to-byproduct transformation, the resulting heterogeneous wheat straw-fly ash biochars were used to removed methylene blue, a model organic pollutant, from water, at higher capacities and faster rates than biochar alone. Overall, the coal fly ash may be a potential inexpensive catalyst for in situ upgrading biomass pyrolysis, simultaneously producing heterogeneous sorbents with enhanced adsorption capacities for organic pollutants.