Combustion of phytoremediation biomass for recycling utilization: Thermal behavior, kinetic analysis, and release of heavy metal

Soil contamination is a very important concern and has received extensive attention worldwide. Especially in mining, the remaining soil after exploitation contains high concentrations of heavy metals and will result in secondary pollution without remediation. Although bioremediation technology is used in many countries, the harvested phytoremediation plants are not recovered and utilized effectively. In this study, the combustion behaviors and kinetics of four special native phytoremediation plants as well as the release characteristics of heavy metals were investigated. The results showed that the combustion process could be divided into four stages, and the main stages of volatiles and char combustion occurred at 180–400℃ and 400–500℃, respectively. Populus showed the best combustion behaviors, followed by Robinia pseudoacacia , Sapium sebiferum , and Dendrocalamus latiflorus . The major heavy metals of Zn, Pb, and Cd were all above the emission limits of EU standard and the combustion process concentrated them in the bottom ash. The release rates of heavy metals in bottom residual increased by 10 %-70 % with the combustion temperature increasing and the volatilization intensity in turn is Cd>Pb>Zn. HSC analysis results suggested that Ca with high content in plants did have a positive effect on the solidification of heavy metals, and Ca(OH) 2 generally showed a higher reactivity with heavy metal chlorides compared with CaCO 3 . These findings illuminated the combustion behaviors and dynamics of phytoremediation plants, and provided insights for developing potential application for metal-containing biomass and remediation strategies for metal-contaminated soil system. • Poplar shows the best combustion performance followed by sophora, tallow tree and bamboo. • The release rates of heavy metals increase by 10 %-70 % with the increased temperature. • The volatilization intensity of heavy metals in turn is Cd>Pb>Zn. • Ca(OH) 2 shows a higher reactivity with heavy metal compounds compared to CaCO 3 .