Performance of two biochar-MnII-catalysts on tebuthiuron and hexazinone degradation

• Grant number: 16/16140-4
• Support type: Scholarships abroad - Research Internship - Doctorate
• Effective date (Start): November 01, 2016
• Effective date (End): October 31, 2017
• Field of knowledge: Agronomical Sciences - Agronomy - Soil Science
• Principal researcher: Jussara Borges Regitano
• Grantee: Letícia de Pierri
• Supervisor abroad: Maria Louloudi
• Home Institution: Escola Superior de Agricultura Luiz de Queiroz (ESALQ). Universidade de São Paulo (USP). Piracicaba , SP, Brazil
• Research place: University of Ioannina, Greece
• Associated to the scholarship: 14/18293-7 - Tebuthiuron and hexazinone dynamics in soils under biochar application, BP.DR

Abstract

Biochar is amended to soils in order to improve their chemical, physical, and biological properties. This waste is a residue of bioenergy production, and therefore could be inserted into energy sustainability context, besides promoting carbon sequestration and greenhouse gases mitigation. However, biochar can sorb pre-emergent herbicides intentionally applied to soils, requiring higher application rates. Tebuthiuron and hexazinone are two pre-emergent herbicides widely used in Brazilian sugarcane fields that present high soil mobility and persistency and, thus, both have the potential to contaminate groundwater. Although biochar may mitigate leaching due to sorption, herbicides persistence may be enhanced by its application. Pesticides are mainly degraded biotically in soils, but abiotic degradation such as metallic catalysis can be equally important, becoming a management tool for pesticides remediation in soils. MnII-based catalysts are proven to be effective in oxidative degradation of some organic contaminants. These catalysts, when attached covalently to a support matrix, can promote faster degradation, besides easier recycling which facilitates its recovery and reuse. Biochar may work as a cheap matrix and be very useful as a catalyst support material. Therefore, the aim of this research is to evaluate the performance of biochars as supports for MnII-based catalysts, assessing this technology on the oxidative degradation of tebuthiuron and hexazinone. For that purpose, two biochars (one from sugarcane straw and one from poultry manure, both pyrolyzed at 550°C) will be tested. After development and characterization of the catalysts, the catalytic studies will be performed under environmental friendly conditions in which the progress of the degradation will be monitored by High Performance Liquid Chromatography (HPLC). The recyclability of the new heterogeneous catalytic systems will be also evaluated. Mechanistic studies will be performed by monitoring the redox potentials (Eh) and oxidation states of the MnII centers using Electron Paramagnetic Resonance Spectroscopy (EPR). (AU)