Pyrolysis Characteristics of Biomass Impregnated with Cadmium, Copper and Lead: Influence and Distribution

Abstract

It is critical to dispose and reuse metal-contaminated biomass. In this study, pyrolysis technology was used for processing metal contaminated biomass from Arundo donax and Broussonetia papyrifera impregnated with cadmium (Cd), copper (Cu) and lead (Pb). The results showed that metal-impregnated biomass can be pyrolyzed completely, as confirmed by a thermal gravimetric analyzer analysis. From the start to 200 °C, a dehydration reaction occurred. The decomposition of biomass reacted extensively from 200 to 450 °C, and more than 60% of the mass was lost. The mass of solid residue of the biomass loaded with Cd, Cu and Pb was 4.7% (A. donax ) and 7.5% (B. papyrifera) respectively lower than that of the unloaded biomass, which could have contributed to the lowering of the activation energy of the pyrolyzed biomass. The activation energy of A. donax pyrolyzed was reduced by approximately 1.85–3.84 kJ/mol, while that of B. papyrifera was 0.93–13.28 kJ/mol. More than 67.76% of the heavy metals in the biomass were retained in the solid phase, and uniformly distributed in the pore structure. However, the cellulose crystallinity of the biochar was decreased, therefore causing the disordering of the amorphous carbon phase of the carbon structure. The results suggested that heavy metals in biomass can lower the difficulty of the reaction, and most of the heavy metals remained in the solid phase, indicating that pyrolysis is an interesting technology to process metal-contaminated biomass.