Dicamba Degradation by Fenton-Like Process Using Iron/Biochar Composites

In this work, an iron/biochar composite was evaluated as a catalyst for 3,6-dichloro-2-methoxybenzoic acid (dicamba) herbicide degradation by heterogeneous Fenton-like process. The biochar was produced from pyrolysis of coffee husks. After Fe^II adsorption by biochar, the material was submitted to chemical reduction, via borohydride, producing zero-valent iron nanoparticles (BIO-Fe0). The material was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy and energy dispersive X-ray spectroscopy, Raman scattering spectroscopy, nitrogen adsorption/desorption analysis, among other techniques. The BIO-Fe⁰ is a heterogeneous material, and the main constituent elements are carbon (C), oxygen (O), silicon (Si), sulfur (S) and iron (Fe). The dicamba degradation was monitored by high-performance liquid chromatography and biological assays using beans (Phaseolus vulgaris) as indicator species. The commercial dicamba (500 mL; 250 mg L 1) was submitted to Fenton-like process (initial pH 3.20; BIO-Fe⁰: 3 or 5 g; 1.00 mL H₂O₂ at 3.00 mmol L 1; 1.00 mL Al₂(SO₄)₃ at 1.00 mol L 1; 25 ºC and 5 h of reaction), presenting ca. 100% of degradation. These treated solutions were used in a biological assay. The intoxication levels were less 30%. These results show that BIO-Fe⁰ has the potential to be used in the dicamba degradation by Fenton-like processes.

Keywords:
biomass; advanced oxidative processes; biological assay (Phaseolus vulgaris); herbicides; residual water; adsorption/degradation