Crystal violet removal using magnetic composite based on biochar and Fe nanoparticles

Abstract

The presence of synthetic dyes in aquatic systems constitutes a significant environmental problem, especially in the current context of water scarcity. These compounds generate adverse impacts on both aquatic ecosystems, by inhibiting processes such as photosynthesis, and on human health, due to their persistence and potential toxicity. This study evaluated a composite obtained through green synthesis, based on biochar and iron nanoparticles, for the removal of the dye gentian violet, with the aim of contributing to the mitigation of its environmental impact in aquatic environments. The composite was synthesized using an extract of Peumus boldus and characterized by infrared spectroscopy, scanning electron microscopy, X-ray diffraction, and potentiometric titration. The removal of gentian violet was evaluated as a function of pH, composite dosage (2–32 mg), and contact time, in order to determine the optimal operating conditions and elucidate the dye removal mechanism. The composite synthesis yielded 42.6%. Under optimal conditions (pH 10, 4 mg dose, and 24 h contact time), a removal efficiency of 95.2% and an adsorption capacity of 9.5 mg/g were achieved. However, considering operational criteria, a contact time of 4 h was established, resulting in a removal efficiency of 88%. Kinetic analysis indicated that the experimental data fit the pseudo-second-order model well (R2 = 0.9995), suggesting that the removal process is primarily governed by a chemical adsorption mechanism.