Industrial ecotoxicology in focus. The unexplored environmental impacts of pilot-scale advanced filtration in Sc recovery

Abstract

The demand within the European Union (EU) for the crucial raw material Scandium (Sc), coupled with the lack of sufficient recovery strategies, has gravitated research into exploiting alternative secondary sources. Utilizing residues from ore-production processes has proven to be a successful attempt for advanced Sc recovery. Despite the emergence of new technologies for Sc recovery from such residues, the potential environmental impacts of byproducts and technology wastes are often disregarded. Our study aimed to ssess the environmental efficiency of a pilot-scale Sc recovery technology that relies solely on filtration. We employed a problem-specific ecotoxicity toolkit based on the approach of Direct Toxicity Assessment (DTA). The results of DTA provide an indication of the scale of the adverse effect of (contaminated) samples without the necessity of translating the results into chemical concentration. Standardized test methods (Aliivibrio fischeri bioluminescence inhibition, Daphnia magna lethality and Sinapis alba root and shoot elongation inhibition) were applied, supplemented by a bioconcentration assessment with the D. magna bioaccumulation test method to gain insight on the bioaccumulation potential of different metals in the case of all samples from the filtration technology. Comprehensive genotoxicity evaluations were also implemented using three distinct test methods (Ames test, Ames MPF test, SOS Chro-motest). We conducted a comparative direct toxicity assessment to anticipate the potential environmental impacts of residues generated at each filtration step on the aquatic ecosystem. Our findings indicate that the environmental impact of the generated intermediate and final residues was alleviated by the consecutive filtration steps employed. The pilot-scale application of the Sc recovery technology hieved a high and statistically significant reduction in toxicity according to each test organism during the filtration processes. Specifically, toxicity decreased by 73 %, 86 % and 87 % according to the Aliivibrio fischeri bioluminescence inhibition assay, the Sinapis alba shoot longation inhibition test, and the Daphnia magna lethality test, respectively. The toolbox of industrial ecotoxicology is recommended to predict the environmental performance of metal recovery technologies related to potential ecosystem effects.