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 FeII 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.

Nesse trabalho, a oxidação catalítica do contaminante sulfeto em meio aquoso foi estudada na presença de carvão ativado na forma de briquetes mecanicamente resistentes e versáteis produzidos a partir de resíduos da indústria do vinho, i.e., semente e cachos. Caracterizações por microscopia eletrônica de varredura combinada com espectroscopia de dispersão de raios X (SEM/EDS), área superficial Brunauer-Emmett-Teller (BET), Raman, termogravimetria (TG), difração de raio X (XRD) e titulação potenciométrica indicam materiais com alta área mesoporosa e grande quantidade de grupos superficiais oxigenados. Esses briquetes mostraram alta atividade para a oxidação de sulfetos em meio aquoso, mesmo comparados com um carvão ativado comercial de elevada área superficial. A eficiência na oxidação de sulfeto é discutida em termos de dois efeitos: a elevada concentração de grupos superficiais redox do tipo quinona/hidroquinona formados a partir da decomposição do mosto da uva e a alta macro/mesoporosidade dos materiais que facilita a difusão das diferentes espécies durante a reação.

In this work, the catalytic oxidation of the hazardous and unpleasant aqueous sulfide contaminant was investigated by activated carbon in the form of mechanically resistant and versatile briquettes produced from two different wastes of the wine industry, i.e., lex and stalk. Characterization by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDS), surface area Brunauer-Emmett-Teller (BET), Raman, thermogravimetry (TG), X-ray diffractometry (XRD) and potentiometric titration showed that the materials have high mesoporous area with a large number of surface oxygen functionalities. These briquettes showed high efficiency for the oxidation of sulfides in aqueous medium, which is discussed in terms of two effects: the relatively high concentrations of quinone/hydroquinone surface redox groups formed from the grape must binder and the macro/mesoporosity, which facilitates the diffusion of the different species during the reaction.