abstract
The exponential increase in electronic waste (e-waste) from end-of-life electrical and electronic equipment presents a growing environmental challenge. E-waste contains high concentrations of rare earth elements (REEs), which are classified as critical raw materials (CRMs). Their removal and recovery from contaminated systems not only mitigate pollution but also support resource sustainability within a circular economy framework. The present study proposed the use of hazelnut shells as a biosorbent to reduce water contamination and recover REEs. The sorption capabilities of this lignocellulosic material were assessed and optimized using the response surface methodology (RSM) combined with a Box-Behnken Design (three factors, three levels). Factors such as pH (4 to 8), salinity (0 to 30), and biosorbent dose (0.25 to 0.75 g/L) were evaluated in a complex mixture containing 9 REEs (Y, La, Ce, Pr, Nd, Eu, Gd, Tb and Dy; equimolar concentration of 1 mu mol/L). Salinity was found to be the factor with greater significance for REEs sorption efficiency, followed by water pH and biosorbent dose. At a pH of 7, salinity of 0, biosorbent dose of 0.75 g/L, and a contact time of 48 h, optimal conditions were observed, achieving removals of 100% for Gd and Eu and between 81 and 99% for other REEs. Optimized conditions were also predicted to maximize the REEs concentration in the biosorbent, which allowed us to obtain values (total REEs content of 2.69 mg/g) higher than those in some ores. These results underscore the high potential of this agricultural waste with no relevant commercial value to improve water quality while providing an alternative source of elements of interest for reuse (circular economy).
keywords
RESPONSE-SURFACE METHODOLOGY; AQUEOUS-SOLUTIONS; HAZELNUT SHELL; BIOSORPTION; OPTIMIZATION; VALORIZATION; ISOTHERM; REMOVAL
subject category
Materials Science; Metallurgy & Metallurgical Engineering
authors
Ferreira, N; Tavares, DS; Baptista, I; Viana, T; Jacinto, J; Silva, TSC; Pereira, E; Henriques, B
our authors
Daniela Soraia dos Santos Tavares
PhD Student
Nicole Viana Ferreira
PhD Studentacknowledgements
This work received financial support from the European Union (FEDER funds through the Operational Competitiveness Program (COMPETE2020) and from PT national funds (FCT/MCTES, Fundacao para a Ciencia e Tecnologia and Ministerio da Ciencia, Tecnologia e Ensino Superior) through the projects UID/50006-Laboratorio Associado para a Quimica Verde-Tecnologias e Processos Limpos.