Produção e caracterização de nano sílica modificada obtida de casca de arroz para a utilização como adsorvente de corantes

Abstract

The large generation of agro-industrial wastes around the world requires the search for alternatives to use these materials. Among the materials, rice husks are used in large scale in the industrial sector for energy generation. The husk burning generates solid residues, being this one of the main problems faced, the treatment of the inorganic residue produced. Many papers published in recent years have used purification routes to produce silica obtained from rice husks, but in most of the works, there is no later use and few routes to improve the material produced. In this sense, the change in the leaching route for the purification and subsequent production of nanoparticles is shown as a means of valorizing the rice husk residue. This work proposes to investigate the use of sonication and microwaves in the leaching process for the production of silica (nSiO2) nanoparticles from the rice husk and subsequent use in the adsorption of terxtile dyes. For this, three different types of silica nanoparticles were produced: using conventional methods for leaching (nSiO2), using ultrasound (UM-nSiO2) and using microwaves (MW-nSiO2). At first, the nanoparticles were characterized according to the functional groups (FT-IR), pore size (BET), crystallinity (XRD), calorimetric properties (DSC), particle size (SEM) and specific mass. After that, tests were carried out for the adsorption of crystal violet using the standard and ultrasonic-modified samples. The following parameters were analyzed: adsorbent dosage (ranging from 0.1 to 1 g L-1), pH (ranging from 2 to 10), the adsorption time (ranging from 0 to 240 min) and the temperature (ranging from 25 to 55 °C). By means of the obtained data, the adjustments were made to kinetic and isothermal models for both adsorbents. The ultrasound-modified sample (UM-nSiO2) showed superior adsorption capacity (495 mg g -1) and greater dye removal (98%) compared to the standard sample ( 424 mg g-1) (nSiO2) to remove Crystal violet. For the second article, the standard sample (nSIO2) and sample modified with microwaves (MW-nSiO2) were used for adsorption of methylene blue. The same variations of the first article were performed, obtaining a greater adsorption capacity for MW-nSiO2 (679 mg g-1) compared to nSiO2 (547 mg g-1) for the methylene blue dye. Both modifications of the nanoparticles show promise due to the increased surface area of the particles produced, leading to better adsorption characteristics.