Grafeno multicamadas (MLG) na ozonização: um processo oxidativo avançado para degradação de melanoidina e substâncias húmicas

Abstract

This study show how multilayer grapheme (MLG) can be applied in pollutant removal processes to improve water quality. Different chapters represents the stages of the study, being first presented a bibliographical exploration of the works that make up the state of the art on the participation of nanomaterials, such as graphene, in the treatment of water and wastewater, and on the techniques used in the production of this material. Subsequently, one presents a step that compares the catalytic activity of multilayer graphene with two other catalysts (molybdenum oxide and manganese ferrite) in the ozonization process for melanoidin degradation and discoloration. The results show that the reaction rate constant (K) of the melanoidin decolorization process by catalytic ozonation is 1.7 times higher than that of the non-catalytic ozonation process. MLG was the most efficient catalyst in total organic carbon (TOC) removal. The removal efficiency was 32% for the non-catalytic ozonation process and 63% for the catalytic ozonation using MLG. This increase in efficiency is due to a better production of hydroxyl radicals in the presence of MLG, which the use of propanol as a radical scavenger confirms. Finally, the final stage evaluates multilayer graphene as a catalyst for the ozonation reaction of humic substances (SH) at different pHs and after having received different pretreatments. The non-catalytic ozonation reaction of SH at pH 9.5 allowed the removal of 90.9% of color in just 15 min. With the addition of MLG to the process, the removal efficiency jumped to 95.2% (MLG without treatment), 96.7% (ozonated MLG) and 97.3% (ground MLG). The TOC removal rates in 60 min using only ozone were 38.3% in non-catalytic ozonation; 40.9% with untreated FFM; 66.0% with ozonated MLG and 56.7% with ground MLG. The study concludes that the ozonation process using MLG as a catalyst is able to remove melanoidin and SH from aqueous solutions and, consequently, increase the efficiency of water and wastewater treatment systems.