Application of Thermogravimetric analysis on combustion study of biomass for Zn extraction

Forage sorghum (Sorghum spp.), recognized among the world most important cereal crops characterized with high biomass yield. Varieties of sorghum are able to uptake Zn from different types of polluted soils, while exhibiting high biomass production and effectiveness in phytoremediation. Considering increased metal concentrations in the plant biomass it is possible to develop an economically viable method for recovering heavy metals, including Zn. One of the key stages in developing an optimal Zn-recovery method is optimization of combustion temperature, to avoid potential loss of Zn due to volatilization. When investigating the combustion of sweet sorghum researhers found that it is comprised of two different thermal stages, pyrolysis and char oxidation. [1] Comprehensive studies have demonstrated the validity of using TGA in combination with other analytical methods when investigating the combustion of biomass. [2] Three different times were investigated in this study at four different temperatures (400 ºC, 450 ºC, 500 ºC, 600 ºC). This low temperature range and operational conditions of combustion are convinient, since studies that also employ thermal analyisis thehniques have shown what can happen to ash after incineration and how the fusing of ash particles can result in slagging, fouling and corrosion within the furnace. However, other studies have shown that combustion ashes chemical compositions are strongly influenced by the feedstock's plant taxonomy, particularly if the feedstock belongs to woody or herbaceous plants. [3] Forage sorghum's (Sorghum spp.) potential for phytoextractions of contaminated dredged sediment in a real environment and authentic natural conditions was investigated, producing harvested biomass enriched with Zn. Combustion time and temperature were varied to see which combination would yield the highest concentration of Zn in the leftover ash. The starting mass of the plant sample was in the range between 30 and 50g and with the mass loss of around 90% the highest Zn content was found after combustion of 6h at 500 C.