Materiais avançados para adsorção de herbicidas: uma abordagem inovadora combinando resíduos agroindustrial e eletroeletrônico

Abstract

The extensive use of herbicides and plant growth regulators, such as picloram and 4-CPA, has contributed to the contamination of water and soil. Biochars produced from agro-industrial waste emerge as sustainable alternatives for the removal of these compounds, especially after chemical modifications. However, the high cost of some modifying agents, such as deep eutectic solvents (DES), motivates the search for more economical solutions, such as mixtures derived from green leaching processes. The objective of this work is to remove picloram and 4-CPA from aqueous media using biochars obtained from passion fruit peels modified with DES and mixtures derived from the green leaching process of metals from different electronic waste (e-waste). The biochars were synthesized in a muffle furnace at a temperature of 400 °C and characterized by different techniques: fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), thermogravimetric analysis (TGA), and X-ray diffraction (XRD). Chemical analyses for determining the point of zero charge (pHPZC) and studies evaluating the effect of pH, adsorption kinetics, and equilibrium of picloram and 4-CPA were performed for the materials with the best removal performance: BC-M1 (unmodified), BC-D2 (derived from biomass modification with methanesulfonic acid and choline chloride), and BC-LD2 (derived from biomass modification with lithium-ion battery leachate using methanesulfonic acid and choline chloride). The different types of biomass pretreatment affected the structure of the materials, the functional groups present on the surface, and the pHPZC values. Maximum adsorption capacity values were observed for the BC-M1, BC-D2, and BC-LD2 materials, respectively, of 49.68 mg g⁻¹, 149.22 mg g⁻¹, 129.33 mg g⁻¹ for picloram and 83.31 mg g⁻¹, 151.54 mg g⁻¹, and 147.27 mg g⁻¹ for 4-CPA. The adsorption kinetics of BC-D2 and BC-LD2 were very fast, reaching equilibrium in approximately 30 min, while BC-M1 exhibited slower kinetics. The adsorption isotherms revealed the Redlich-Peterson (R-P) model as the best fit for BC-M1 and BC-D2, and the Sips model for BC-LD2, in picloram adsorption. In 4-CPA adsorption, the Sips model showed a better fit for BC-M1 and BC-D2, and the Freundlich model for BC-LD2. The produced biochars demonstrate a sustainable and economical solution for the treatment of contaminants in water.