Multi element removal and recovery using living macroalgae: data treatment influence on results interpretation

• Autor(a) principal: Amaral, Joana Bastos
• Data de Publicação: 2020
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/29212
• topic: Rare earth elements; Living macroalgae; Multi element removal; Potentially toxic elements; Design of experiments; Surface response methodology

Water contamination is not a new problem today, as the presence of potentially toxic elements in waters is a known reality throughout the world. However, technological development and the widespread use of electrical and electronic equipment, which have been increasing each year, have contributed to the emergence of new contamination sources, such as electronic waste, and new contaminants, such as rare earth elements. The discharge of these economically valuable and technology critical elements in aquatic ecosystems is increasingly frequent, requiring actions that reduce or eliminate risks to ecosystems and to humans. This study evaluates the potential use of living macroalgae for the removal of rare earth elements (La, Dy, Eu, Nd and Gd) and potentially toxic elements (Hg and Pb) from waters in environmentally relevant concentrations. It is also assessed the influence that different approaches can have on results interpretation, which are based on statistical foundations, and on physical, chemical, and biological aspects, inherent to multidisciplinary studies like the present one. Macroalgae are already known to be efficient in removing potentially toxic elements from water; however, can living macroalgae be the new future to solve both the water crisis as well as the crisis of rare earth elements as a raw material scarcity? With the present study, it was possible to determine, using both a cluster analysis and a linear discriminant analysis, that the rare earths elements in study had similar removal behaviours, however different from the other two potentially toxic elements in study, Pb and Hg. The latter being the most well removed element having possible predicted removal percentages of 97 % with only 24 hours of exposure. Nevertheless, through a surface response methodology, it was possible to determine the optimal conditions for these elements’ removal from multi contaminated waters, using a living macroalgae (Ulva lactuca). Hence, after 72 hours it would be possible to obtain predicted removals above 70 % for all elements in study at a salinity of 21 ± 9, an initial contaminant concentration of 1.6 ± 0.9 μmol/L and a macroalgae dosage of 3.6 ± 2.0 g/L.