Due to the toxic effects of chromium, its high environmental persistence, and potential for bioaccumulation, it is imperative to develop sustainable strategies for managing its contamination. In the present study, the synthesis time of supported biogenic iron-based microparticles (BioFe-MMT) and their performance in the Cr(VI) removal process were analyzed. Its lethal and sublethal ecotoxicological effects were subsequently evaluated through standardized bioassays using amphibian Rhinella arenarum larvae exposed to BioFe-MMT and Cr(VI) before and after the removal treatment. Results demonstrated that BioFe-MMT biosynthesized for 3 weeks had smaller particle size and better Cr(VI) and total Cr removal efficiency (>
99% and >
91%, respectively) compared to longer synthesis times. Ecotoxicological bioassays showed that Cr(VI) caused a significant increment of lethal toxicity to larvae with 50% Lethal Concentration (LC 50) at 96 and 504 h of 25.1 and 0.04 mg L