Nanocompósitos magnéticos à base de zeólita obtida a partir da casca de arroz para adsorção de polifenóis da indústria do vinho

Abstract

In recent years, the wine sector has presented considerable growth, resulting in increased production and, consequently, an increase in the effluents generated during winemaking. Polyphenols stand out among the components present in these effluents due to their analgesic, antimicrobial, and antioxidant properties. However, they can become contaminants in high concentrations. Given this scenario, it is necessary to develop effective methods for recovering these substances and water reuse, emphasizing the adsorption process that permits the reuse of the adsorbed compounds. This project uses rice husks, an agribusiness waste, to obtain zeolite-based magnetic nanocomposites for chlorogenic acid (CGA) adsorption. The synthetic faujasite (FAU) zeolite was initially synthesized and modified with silane agents to optimize the interactions with the polyphenols during the adsorption process with the zeolite nanocomposites obtained from the rice husks. The adsorption tests were carried out using FAU nanostructures silanized with (3-aminopropyl) triethoxysilane (APTES), trimethylchlorosilane (TMCS), and a combination of both under mechanical agitation for 24 h. FAU:APTES:TMCS stood out, showing better performance in the adsorption of ACG (20 mg L-1) compared to FAU without functionalization, achieving removal percentages of 12.78% and 67.80% for FAU and FAU:APTES:TMCS, respectively. The zeolite optimization, using high-purity silica extracted from rice husks, was carried out by investigating the hydrothermal synthesis time to obtain the FAU phase. The FAU phase most evident was in the 18-hour synthesis period (Z18), with a surface area of 217.69 m2 g-1 and a zeta potential of -38.87 mV, indicating stability in aqueous solution. The Z18 zeolite was modified (Z18 M) with the APTES:TMCS silane mixture and used to obtain the magnetic nanocomposites. For immobilizing the zeolites obtained from rice husks, copper ferrite heat-treated at 500ºC (F500) was used due to effective magnetic properties, a lower impurity index, smaller particle sizes, and good stability in aqueous solution. In this respect, the magnetic composites Z18:F500 and Z18 M:F500 showed effective magnetic properties and element distribution along the surface evaluated by energy dispersive X-ray spectroscopy (EDS), achieving GCA adsorption rates of 31.96% and 79.53%, respectively. In this way, it is concluded that silica obtained from rice husks proved an excellent candidate for the sustainable synthesis of zeolites. The zeolite surface modification led to greater efficiency in the recovery of ACG in aqueous media. Finally, the present work presents an alternative for reusing agribusiness waste and recovering polyphenols from wine effluents, contributing to a system capable of magnetic removal in a way that favors the circular economy.