ABSTRACT
Abstract Dicksonia sellowiana Hook., Dicksoniaceae, is a tree-fern which is being recently used in medicine mainly for its phytotherapic activities. While several other studies have focused on D. sellowiana extract characterization in terms of its biological and antioxidant activity, the novelty of this work aims to understand the fate of this extract during thermal disposal through thermogravimetry/differential thermal analysis, thermogravimetry/mass spectrometry, Fourier transform infrared spectroscopy and elemental analysis, to further characterize this plant's extract. Thermal analysis revealed mass loss within three well-defined steps, with the respective mass signals represented generated during heating. Light-volatiles were released during the first step, with release of NO2, CO2, and ethanol in the following, as a result of extract pyrolytic decomposition. Furthermore, mass signals variation during heating indicated the release of harmless by products in contrast to other pharmaceutical and personal care products. Finally, chemical characterization confirmed the observed under thermal analysis suggesting a highly polar structure within extract's composition.
ABSTRACT
Thermal treatment is one of the most promising disposal techniques for heavy metal- (HM)-enriched hyperaccumulators. However, the thermal characteristics and fate of HMs during thermal treatment of hyperaccumulator biomass need to be known in detail. A horizontal tube furnace was used to analyze the disposal process of hyperaccumulator biomass derived from a phyto-extracted field in which the soil was moderately contaminated with heavy metals. Different operational conditions regarding temperature and gas composition were tested. A thermo-dynamic analysis by advanced system for process engineering was performed to predict HM speciation during thermal disposal and SEM-EDS, XRD and sequential chemical extraction were used to characterize the heavy metals. The recovery of Zn, Pb and Cd in bottom ash decreased with increasing temperature but recovery increased in the fly ash. Recovery of Zn, Pb and Cd fluctuated with increasing air flow rate and the metal recovery rates were higher in the fly ash than the bottom ash. Most Cl, S, Fe, Al and SiO2 were found as alkali oxides, SO2, Fe2(SO4)3, iron oxide, Ca3Al2O6, K2SiO3 and SiO2 instead of reacting with HMs. Thus, the HMs were found to occur as the pure metals and their oxides during the combustion process and as the sulfides during the reducing process.
