Biosorption optimization of classic and emerging contaminants of water using Ulva lactuca

• Autor(a) principal: Moleiro, Pedro Daniel Ribeiro da Silva
• Data de Publicação: 2021
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/33253
• topic: Living macroalgae; Biosorption; Trace metals; Rare-earth elements; Experi-mental design of Box-Behnken; Water

Water is a scarcer resource nowadays due to the stress applied to water systems, by the increase of the human population, which leads to a wastage of water manly due to agriculture and to anthropogenic activi-ties that contrite to the contamination of hydric resources. Examples of relevant water environmental contaminants are mercury (Hg) (a highly dangerous element that is very toxic to human health), gadolinium (Gd), and lanthanum (La) (rare-earth elements, present in most electric equipment and electronics). The presence of Gd and La in aquatic eco-systems is more and more frequent, without being well known their impacts on organisms. In this work, the biosorption and its optimization using the living macroalgae Ulva lactuca, was studied to evaluate if it is a promising alternative to deal with the problem of water contamina-tion. In the assays carried out (before optimization), the removal of the mentioned elements in a mono and multi-elementar scenario, achieved removals between 77 and 88 % for mercury, 37 and 53 % for lantha-num, and 38 and 65 % for gadolinium after 72 h. In the optimization test, algae mass (1.5 – 4.5 g/L), initial element concentration (5 – 50 μg/L for mercury and 100 μg/L – 1000 μg/L for lanthanum e gadolin-ium), and salinity (15 – 35) were the conditions chosen to evaluate the removal using Response Surface Methodology with the experimental design of Box-Behnken. The optimal conditions of the operation that lead to the maximum removal of the elements (until 100 % of removal for mercury and lanthanum, and 94 % for gadolinium) were deter-mined, and the results allow to conclude that the extension of time of the process further than 72 h is not justified. This work fills some gaps of the literature, namely the removal of potential toxic elements from waters in multi-elementar scenarios and in concentrations that are en-vironmentally realistic.