Nitrogen‑containing species evolution during co-pyrolysis of gentamicin residue and biomass

Abstract

In the present study, the nitrogen‑containing species evolution in gas-liquid-solid three phases during co-pyrolysis of gentamicin residue and typical biomass was thoroughly investigated. A series of methods for qualitative and quantitative analysis of nitrogen‑containing products were applied. Quaternary-N, pyrrolic-N and pyridinic-N in pyrolysis char, amides, N-heterocyclic chemicals and nitriles in bio-oils, as well as NH3 and HCN in gaseous products were identified. Obviously, the pyrolysis temperature was found to play a crucial role in nitrogen-containing species distribution, where high temperature contributed to the formation of nitrogen-containing species in gas and liquid phases. The plausible evolution avenue for nitrogen-containing species in three phases was also proposed. Furthermore, it is observed that the introduction of biomass (corn cob, corn straw and wheat straw) significantly facilitated the nitrogen transformation into the char from liquid products. In the case of gentamicin residue-to-corn cob mass ratio of 7:3, the nitrogen yield in co-pyrolysis char achieved 43.96 wt% at a temperature of 450 °C, demonstrating the effective fixation of nitrogen-containing species in the presence of biomass. This crucial finding supplies a feasible method for realizing the clean disposal of antibiotic residues and rational construction of nitrogen-containing carbon materials from solid wastes.