Publicação
Closing the e-cycle: recovery of elements with high economic value from fluorescent lamps
| Resumo: | The increasing use of rare earth elements (REE) in recent years has led to significant progress in the development of “green technologies”. However, these elements are also linked to the environmental degradation caused by ore mining and their contribution to the growing generation of electronic waste. Although they are gradually being replaced by light-emitting diodes, fluorescent lamps (FL) still represent an abundant waste stream with high REE content and have been explored as a possible secondary source. The typical process of recovering REE from FL waste consists of chemical leaching followed by purification through several solvent extraction steps and precipitation, which presents several environmental drawbacks. The present work aims to develop an alternative method to recover Y and Eu from FL waste by studying the reuse of acids during the leaching stage and using live macroalgae Ulva sp. to remove and pre-concentrate the REE from the leachate. The scalability of the methodology and REE purification and separation were also evaluated. The results showed that reuse made it possible to reduce the amount of acid in the first (HNO₃ 0.5 mol/L) and second extraction (HNO₃ 2.0 mol/L) steps by 66 % and 50 %, respectively, and also to obtain a leachate richer in REE. However, residual amounts of Hg (an element present in FL) were also extracted. Regular renewal of the biosorbent (Ulva sp.) during the pre-concentration stage considerably increased the removal efficiency, up to 68 % for Y and 50 % for Eu. The pre-concentration stage was also found to be scalable, achieving a removal efficiency of 69 % for Y and 52 % for Eu, at a volume of 100 L. After pre-concentration, REE-enriched macroalgae had Y and Eu concentrations much higher than apatite ore (primary source of REE). It was then possible to selectively extract 97 % of Y and 89 % of Eu from the surface of the macroalgae using EDTA while maintaining 80% of the Hg that had also been accumulated on the inside of the macroalgae cells. Finally, most of the Y was separated by chemical reduction and precipitation of Eu, yielding an 80 % Eu precipitate. |
|---|---|
| Autores principais: | Barros, Daniel Costa Quental de |
| Assunto: | Rare earth elements Fluorescent lamps Electronic waste Extraction Extraction Pre-concentration Scale-up Purification Separation Macroalgae |
| Ano: | 2023 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso embargado |
| Instituição associada: | Universidade de Aveiro |
| Idioma: | inglês |
| Origem: | RIA - Repositório Institucional da Universidade de Aveiro |
| Resumo: | The increasing use of rare earth elements (REE) in recent years has led to significant progress in the development of “green technologies”. However, these elements are also linked to the environmental degradation caused by ore mining and their contribution to the growing generation of electronic waste. Although they are gradually being replaced by light-emitting diodes, fluorescent lamps (FL) still represent an abundant waste stream with high REE content and have been explored as a possible secondary source. The typical process of recovering REE from FL waste consists of chemical leaching followed by purification through several solvent extraction steps and precipitation, which presents several environmental drawbacks. The present work aims to develop an alternative method to recover Y and Eu from FL waste by studying the reuse of acids during the leaching stage and using live macroalgae Ulva sp. to remove and pre-concentrate the REE from the leachate. The scalability of the methodology and REE purification and separation were also evaluated. The results showed that reuse made it possible to reduce the amount of acid in the first (HNO₃ 0.5 mol/L) and second extraction (HNO₃ 2.0 mol/L) steps by 66 % and 50 %, respectively, and also to obtain a leachate richer in REE. However, residual amounts of Hg (an element present in FL) were also extracted. Regular renewal of the biosorbent (Ulva sp.) during the pre-concentration stage considerably increased the removal efficiency, up to 68 % for Y and 50 % for Eu. The pre-concentration stage was also found to be scalable, achieving a removal efficiency of 69 % for Y and 52 % for Eu, at a volume of 100 L. After pre-concentration, REE-enriched macroalgae had Y and Eu concentrations much higher than apatite ore (primary source of REE). It was then possible to selectively extract 97 % of Y and 89 % of Eu from the surface of the macroalgae using EDTA while maintaining 80% of the Hg that had also been accumulated on the inside of the macroalgae cells. Finally, most of the Y was separated by chemical reduction and precipitation of Eu, yielding an 80 % Eu precipitate. |
|---|
Atividades financiadas
Não foram encontrados projetos financiados.