Dye adsorption on autohydrolyzed pine sawdust in batch and fixed-bed systems

Batch and column kinetics of three basic dyes, methylene blue (MB), bismarck brown (BB) and acridine orange (AO), adsorption on autohydrolyzed (160–240 °C, 0–50 min) Scots pine (Pinus sylvestris L.) sawdust were studied, using untreated pine sawdust as control, in order to explore the potential use of these low-cost industrial byproducts (untreated autohydrolyzed sawdust) for wastewater cleaning. The effect of the autohydrolysis time and temperature on the microstructure and the crystallinity of pine sawdust was investigated be means of: SEM, FTIR, XRD and BET, in order to obtain information at a higher granularity level, in comparison with previous studies. The BET surface area increased from 0.89 to 19.3 m2 g−1. In the case of MB, the Freundlich's adsorption capacity KF increased from 5.60 to 15.7 (mg g−1)(L mg−1)1/n, the amount of dye adsorbed when saturation is attained (Langmuir constant qm) increased from 38.7 to 88.0 mg g−1, and the Bohart-Adams adsorption capacity coefficient N increased from 8046 to 14157 mg L−1, indicating the extent that the severity of the autohydrolysis treatment enhanced the adsorption behavior of the material.

► Pretreatment enhances sawdust adsorptivity.
► Optimal conditions of sawdust autohydrolysis are determined.
► The possibility of using recyclable water is supported.
► Waste biomass exploitation in an industrial ecology framework is suggested.