Influence of torrefaction intensities on bamboo (Acidosasa longiligula) shoot shell-derived biochar and its application for Tc(VII) reductive immobilization.

• Influence of torrefaction intensity on a hemicellulose-rich biomass characteristics and pyrolysis behaviors was investigated. • The reductive immobilization mechanism of chromate, as a chemical surrogate for pertechnetate, on the torrefaction biochar was discussed. • Torrefaction biochar is a potential immobilization material for repairing Tc(VII) contaminated water. In this study, the torrefaction biochar from bamboo (Acidosasa longiligula) shoot shell under different torrefaction intensities (TI) were prepared and characterized. Nonradioactive Cr(VI), a chemical surrogate for radioactive Tc(VII), was used to evaluate Tc(VII) reductive immobilization of torrefaction biochar. Batch adsorption experiments indicated that torrefaction biochar had strong adsorption ability to Cr(VI) with the best uptake capacity of 63.11 mg/g. The adsorption kinetic was well fitted by pseudo-second-order model and Park model. The adsorption equilibrium was considerably fitted by Freundlich and Temkin isotherm The adsorption-reduction mechanism during the whole Cr(VI) immobilization process was confirmed by the Raman spectrum analysis and the nice fitting of Park model. This study demonstrates that torrefaction biochar deserves to be a low-cost and effective immobilization material for Tc(VII). [ABSTRACT FROM AUTHOR]