Fusinato Mirian Dosolina, da Silva Amaral Maria Alice Farias, de Irigon Paula Irigon, Calgaro Camila Ottonelli, de Los Santos Diego Gil, Filho Pedro José Sanches
Grupo de Pesquisa de Contaminantes Ambientais (GPCA), Instituto Federal de Educação, Ciência E Tecnologia Sul-Rio-Grandense (IFSul), Campus Pelotas, Endereço postal: Praça 20 de Setembro, 455, Centro, Pelotas, RS, 96015360, Brasil.
Environ Sci Pollut Res Int. 2023 Feb;30(8):21494-21511. doi: 10.1007/s11356-022-23687-1. Epub 2022 Oct 22.
Rice is among the main foods produced in the world and is part of the daily diet of most families. The main waste from rice processing is rice husk (RH), which has been used as biomass for energy generation through combustion. In this process, rice husk ash (RHA) is generated as a residue, and its silica (SiO) content varies from 85 to 98%. The present work describes the study of the extraction of silica from RHA by the ultrasound-assisted sol-gel method. An experimental design based on the response surface methodology (RSM) with the symmetrical, second-order rotational central composite design (RCCD) was applied to determine the best extraction conditions considering extraction time and molar ratio (n) as variables = n/n). These optimal conditions were then applied to three ash samples, two obtained by the combustion process in a boiler furnace, with a mobile grate system (RHAC and RHAC), and one obtained by the pyrolysis process (RHAP) carried out in a fixed bed reactor. Results showed that a molar ratio of 4.4, and an extraction time of 107 min were the best extraction conditions, leading to a yield of 73.3% for RHAP, 43.9% for RHAC, and 31.1% for RHAC. It was found that the extraction yield and textural properties of the silica obtained depend on the characteristics of the ash used. The silica extracted from RHAC presented a surface area of 465 m.g, mesopores of 4.69 nm, purity greater than 95%, and an ultra-fine granulometric distribution, reaching nanoparticle dimensions, characteristics comparable to commercially available silicas.
大米是世界主要粮食作物之一，也是大多数家庭日常饮食的一部分。大米加工产生的主要废料是稻壳（RH），它已被用作通过燃烧产生能源的生物质。在此过程中，会产生稻壳灰（RHA）作为残渣，其二氧化硅（SiO）含量在85%至98%之间变化。本工作描述了通过超声辅助溶胶-凝胶法从稻壳灰中提取二氧化硅的研究。采用基于响应面法（RSM）的对称二阶旋转中心复合设计（RCCD）进行实验设计，以提取时间和摩尔比（n）=n/n）为变量来确定最佳提取条件。然后将这些最佳条件应用于三个灰分样品，其中两个是通过带有移动炉排系统的锅炉炉燃烧过程获得的（RHAC和RHAC），另一个是通过在固定床反应器中进行的热解过程获得的（RHAP）。结果表明，摩尔比为4.4，提取时间为107分钟是最佳提取条件，RHAP的产率为73.3%，RHAC为43.9%，RHAC为31.1%。研究发现，所获得的二氧化硅的提取产率和织构性质取决于所用灰分的特性。从RHAC中提取的二氧化硅表面积为465 m.g，中孔为4.69 nm，纯度大于95%，粒度分布超细，达到纳米颗粒尺寸，其特性与市售二氧化硅相当。
