Pyrolysis of waste materials: Characterization and prediction of sorption potential across a wide range of mineral contents and pyrolysis temperatures.

Sewage sludge (50% mineral), manure (29%) and wood (<1%) were pyrolyzed at 200, 350 and 500°C with the aim to study the characteristics and sorption potential of materials undergoing pyrolysis across a wide range of mineral contents. A commercial plant-derived biochar (41% mineral) was also considered. The materials were extensively characterized and tested for their sorption towards the model sorbates benzene, naphthalene and pyrene. Plant-derived materials, regardless of their mineral content, developed micropores causing size exclusion of pyrene. Changes in properties and sorption behavior upon pyrolysis were generally consistent for the manure and wood series. A single regression equation developed on our data (including the sorbate hydrophobicity and sorbent polarity) provided excellent prediction of previously reported changes in sorption upon pyrolysis across a wide range of mineral content (up to 500°C). The sewage sludge series, however, followed a particular behavior, possibly due to very high mineral content (up to 67%).