Characterization of Silica Produced from Rice Husk Ash: Comparison of Purification and Processing Methods

As a byproduct of the combustion of rice husk to generate energy, rice husk ash (RHA) is formed by silica and carbon, apart from small amounts of other constituents. Several treatments can be used to increase the purity of the silica obtained, or even produce pure silica. The present study tested the efficiency of different techniques to obtain silica, characterizing and comparing the silicas obtained from RHA. A literature review was conducted, and then selected techniques were used to produce silica, which was characterized by XRF, XRD, particle sizing, specific weight, specific surface area, total carbon, and SEM. The literature review showed that most techniques include a pretreatment like acid or alkaline leaching followed by thermal treatment to increase the amount of silica produced by reduction of carbonaceous materials. The results showed that it is possible to produce silica from RHA using simple methods, and that these produced silica with purity above 98%. The treatments that afforded the best results were acid leaching followed by thermal treatment at 800ºC, and alkaline extraction at low temperature, with silica purity of 99.3% and 99.6%, respectively.

稻壳燃烧发电的副产物为稻壳灰（Rice Husk Ash, RHA），其主要成分为二氧化硅与碳，另含少量其他组分。可通过多种处理工艺提升所得二氧化硅的纯度，甚至制备纯二氧化硅。本研究对多种从稻壳灰中提取二氧化硅的工艺效能进行了测试，并对所得二氧化硅开展表征与对比分析。研究首先完成文献调研，随后选取部分工艺制备二氧化硅，并通过X射线荧光光谱法（XRF）、X射线衍射法（XRD）、粒径分析、比重测试、比表面积测试、总碳含量分析以及扫描电子显微镜（SEM）对产物进行表征。文献调研结果显示，多数工艺均包含酸浸或碱浸预处理步骤，后续辅以热处理以还原含碳组分，从而提升二氧化硅产率。研究结果表明，采用简易工艺即可从稻壳灰中制备二氧化硅，且所得产品纯度可达98%以上。其中效果最优的两种工艺分别为：酸浸辅以800℃热处理，以及低温碱提取，所得二氧化硅纯度分别为99.3%与99.6%。