Banca de DEFESA: BRENDA PALHARES DOS REIS VIEIRA

CARBON DOTS FROM SUGAR CANE BAGASSE WASTE VIA HYDROTHERMAL CARBONIZATION 

FOR PHOTOCATALYTIC REMOVAL OF METHYL ORANGE

Carbon dots; hydrothermal carbonization; biomass, sugarcane bagasse; photocatalysis.

Sugarcane bagasse is an abundant supply, coming from the sugar and alcohol industry, and is mostly used as fuel in plants. However, the conversion of this biomass into products with high added value has become very promising, such as the synthesis of carbon quantum dots (CDs). These can be synthesized by a green process, using hydrothermal carbonization. CDs are nanoparticles that have distinct properties, such as conductivity, large surface area, biocompatibility, low toxicity and fluorescence, properties that are responsible for numerous applications. Due to these characteristics, CDs are good candidates as photocatalysts, which can be used in the manipulation of organic contaminants in aqueous systems for wastewater treatment. Among these contaminants, dyes present complex molecules that are resistant to conventional treatment methods. Such as products from the textile, leather and paper industries, which have high demands. In this context, a synthesis of CDs was carried out from sugarcane bagasse biomass via hydrothermal carbonization. Multivariate optimization was the statistical tool used to improve description conditions; therefore two 23-1 fractional factorial designs were constructed to screen variables and the response surface methodology for refinement. The experimental design allows the study of the interaction of the influencing variables on the response variable, and thus verify the potential of using CDs in the photodegradation of the dye, methyl orange, used as a model molecule. The CD production configurations were optimized with the aim of obtaining the ideal conditions for photodegradation of the azo dye, with less use of experiments. The characteristics of the nanoparticles were initially evaluated by analyzing pH, conductivity, Zeta potential, Fourier transform infrared spectroscopy (FTIR) and molecular absorption spectroscopy (UV-Vis), in addition to quantum yield characterizations, fluorescence spectroscopy, transmission electron microscopy (TEM) and thermogravimetric analysis (TG). The percussion biomass was also characterized using FTIR and TG.