Physico-chemical characteristics and the adsorption of ammonium of biochar pyrolyzed from distilled spirit lees, tobacco fine and Chinese medicine residues

Abstract

This paper investigates the physico-chemical characteristics of biochar from three specific waste materials including distilled spirit lees (DSL), tobacco fine (TF) and Chinese medicine residue (CMR) prepared by pyrolysis at 450℃, 550℃ and 650℃. All produced biochars were further analyzed for their ability to adsorb ammonium with initial concentrations of 0−500 mg·L−1. Results showed that all biochars mainly consist of C and O, and possess highly-porous morphology features with pore size of 2.029–6.731 nm. With same feedstock, carbonized DSL, TF and CMR at 650℃ has largest specific surface area of 6.293 m² g−1, 57.485 m² g−1 and 14.668 m² g−1 respectively. The positions of the infrared peaks of biochar derived from same feedstock are similar, but the intensity of some peaks has changed. With same feedstock, DSL450/550, TF650, and CMR450 biochar showed the best performance for ammonium removal with an adsorption capacity of 10.3199–11.8906, 10.4603–13.3511 and 23.2558-24.1546 mg g−1 respectively. The adsorption progress of ammonium by DSL biochar could be well described by both Freundlich and Langmuir adsorption isotherm, while the progress of TF biochar and CMR biochar was best described by Langmuir and Freundlich adsorption isotherm respectively. The fitted results indicate that the adsorption process of NH4+-N by both DSL biochar and TF biochar are uniform monolayer adsorption on the surface, but the adsorption of CMR biochar is mainly in the heterogeneous adsorption mode of multi-molecular layers. In sum, the experiment that was performed as well as the parameters used proved to be feasible for DSL biochar, TF biochar and CMR biochar production as adsorbing medium.