Catalisador Fenton a base de biochar de fibra de coco verde aplicado na degradação de corante

Abstract

Advanced Oxidative Processes (AOPs), such as heterogeneous Fenton, are a promising alternative for wastewater treatment due to their effectiveness, reuse of catalysts, wide pH operating range and low cost, with wide application potential, especially when using support material to incorporate iron-containing catalysts. Biochar, derived from the pyrolysis of agro- industrial waste biomass, has emerged as an adsorbent and support material for the production of heterogeneous catalysts. This study aims to synthesize a solid catalyst based on green coconut fibre biochar for the degradation of methylene blue (AM) dye by the heterogeneous Fenton process. The green coconut obtained in Catalão was pyrolyzed at temperatures of 300, 500 and 700 oC. The pyrolyzed materials and the raw material were treated with a solution of ferric chloride hexahydrate and ferrous chloride tetrahydrate under agitation for the synthesis of catalysts. The materials were filtered, dried and pyrolyzed again at 600 oC. For the catalysts obtained, in natura (IN@Fe), biochar at 300 oC (BC300@Fe), biochar at 500 oC (BC500@Fe) and biochar at 700 oC (BC700@Fe), the efficiency of AM degradation was evaluated using UV-Vis molecular absorption spectrometry at 665 nm, with BC300@Fe showing the highest degradation rate (97.6%). The catalysis was optimized for the variables pH, catalyst concentration and hydrogen peroxide, using factorial design. Adsorption and degradation kinetics studies were carried out under the optimized conditions. The catalyst was characterized by SEM-EDS, infrared spectroscopy and X-ray diffractometry. BC300@Fe showed 94.9% adsorption of AM, and its zero charge point pH was 3.79. The IR spectrum showed peaks corresponding to the precursor materials (in natura and BC300), which may have favored the adsorption and consequently the degradation of the AM dye. BC300@Fe showed a predominantly amorphous character, as observed by the X-ray diffractogram. The micrographs obtained by SEM showed greater irregularity for the BC300@Fe material and EDS showed a higher percentage of C, O and the presence of Fe. The results of AM degradation by BC300@Fe fitted the BMG model. The bioassay with the test organism Lactuca sativa L. showed the catalytic efficiency of BC300@Fe and the absence of phytotoxic substances. The catalyst showed 94.9% degradation for the 1st and 2nd cycles and 44.75% efficiency up to the 7th reuse cycle. Biochar as a support material for an iron-based catalyst showed properties that guaranteed catalytic efficiency for the degradation of methylene blue dye in wastewater.