Caracterização e avaliação da sílica lixiviada da casca de arroz como material adsorvente para remoção de micropoluentes de águas residuais

Abstract

Brazil stands out in the world economy as an important supplier of commodities in the agricultural sector, ranking fourth in world food production. The expansion of agribusiness accompanies the concern with the environmental protection of Brazilian fauna, flora, rivers and soil. Therefore, research focused on sustainability stands out in academia in search of agri-environmental solutions. The misuse of water resources is a global concern, as water scarcity is a reality all year round. Reusing water has become the way to reduce waste, which is why water purification studies are even more important in the race for a more sustainable world. New riverbeds continue to be contaminated due to inadequate disposal of waste, especially of organic and anthropogenic origin, such as pharmaceutical waste, pesticides, dyes and micropollutants. In this work, silica was used after acid leaching of rice husk ash, na abundant residue in the southern region of the country, and mainly in the western border, to evaluate the adsorption potential of these biosorbents in relation to the compounds 2-nitrophenol and dichlorophenoxyacetic acid 2 ,4D. The materials were characterized using scanning electron microscopy (SEM), specific area analysis using Brunauer, Emmett and Taller (BET) isotherms, spectrophotometry in the Ultraviolet/Visible region – UV/Vis, X-ray fluorescence spectroscopy – FRX, infrared spectroscopy – FTIR, point of zero charge (pHPCZ) and hydrophobicity index. The results obtained showed a material with a surface area of 175.81 m2. g-1, mesoporous with a flocculated and irregular surface. The adsorption kinetics showed that the pseudo-second order model was the one that best described the results with R2 = > 1. The Langmuir isotherm was the mathematical model that best fit. The highest removals for 2,4D were at pH 2, removing 51% at the initial concentration (Ci) of 10 ppm, 45% at Ci of 20 ppm and 31% at Ci of 60 ppm. The pH of 2 was also the one that obtained the best removals of the 2-nitrophenol molecule 59% at Ci of 10 ppm, 65% at Ci of 20 ppm and 50% at Ci of 60 ppm. The maximum adsorption capacities obtained were 3.01 mg. g-1 for 2-nitrophenol and 6.53 mg. g-1 of 2,4D. Based on the results obtained in this research, it is possible to state that silica from rice husks leached with sulfuric acid used as an adsorbent has the potential for significant removal of 2-nitrophenol and 2,4D.