Adsorção de herbicidas utilizando biochar obtido a partir de resíduos de madeira

Abstract

Residues of sawdust of the forest species Cedrela fissilis were modified, with a part of the sample being only physically modified (BCC), while the other was also chemically activated with zinc chloride (ZnCl2) as an activating agent (BACB). The precursor material to cedar sawdust (CBS), as well as BCC and BACB were characterized by the techniques of X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM) , Energy Dispersive X-ray Spectroscopy (EDS), Point of Zero Charge (pHPZC), N2 Adsorption/Desorption Isotherms (BET and BJH methods); and had their potential evaluated for the removal of atrazine and 2,4-D herbicides from effluents. Initial tests indicated that none of the adsorbents were efficient in removing 2,4-D, however, they showed potential in removing atrazine. Since BCC performed relatively better than BACB. Therefore, BCC was the adsorbent chosen to carry out kinetic, isothermal, and thermodynamic studies, as well as the effect of pH, simulated effluent, and material regeneration for atrazine herbicide adsorption. The pH test indicated that the best adsorption results were obtained at pH 4. The isothermal studies proved that the atrazine adsorption process was favored at higher temperatures. The Langmuir model was the most suitable for experimental equilibrium data, the maximum adsorption capacity was 7.679 mg g-1 at 328 K. The thermodynamic parameters confirmed a spontaneous process, of an endothermic nature, governed by physical interactions. Kinetic studies showed that equilibrium was reached within 180 min, being influenced by the atrazine concentration. The linear driving force (LDF) model showed a good statistical fit to the experimental data, and the diffusion coefficient increased with the adsorbate concentration. As for regeneration, the BCC can be reused in up to three cycles. Finally, the adsorbent showed good removal efficiency in real samples of water from rivers contaminated with atrazine, with the removal of 76.58% and 71.29%. Therefore, the adsorbent has potential and can be used to remove pollutants emerging from aqueous solutions.