9/23/2023 0 Comments White carbon blackLater, Kalapathy, Proctor, and Shultz ( 2002) improved the method mentioned above. Kalapathy, Proctor, and Shultz ( 2000a, 2000b) found that, before alkali treatment, washing RH ash with hydrochloric acid solution can effectively remove Ca 2+ and metal impurities from RH, and washing silicate precipitation with distilled water can effectively remove Na +, K +, and Cl − from white carbon black products. While white carbon black prepared by alkali fusion method usually contains Ca 2+, Na + (or K +), SO 4 2− (or Cl −), and other metal impurities. It was found that it was possible to recover over 90% of the silica contained in RHA. Shelke, Bhagade, and Mandavgane ( 2011) produced sodium silicate by reacting rice hull ash (RHA) with aqueous NaOH and precipitated silica from the sodium silicate by acidification. Compared with acid precipitation method, alkali fusion method (involved dissolution of silica in NaOH solution followed by precipitation using acid solutions) was widely used. The results showed that the purity of white carbon black could reach to 98.48% when the NaOH solution with the RH ash was heated for 2 hr at 90☌ and then finished its acid reaction at pH of 3 for 2 hr. ( 2014 prepared white carbon black from nano‐husk ash by analkali dissolving‐acid reaction method and investigated the effects of the pH and reaction time on the purity of the white carbon black. The results showed that the quality of SiO 2 in the product was increased from 84.43% to 91.32% after hydrochloric acid was used. Gao, Song, Yang, and Wu ( 2016) studied the preparation of white carbon black from water‐quenching blast furnace slag based on acid precipitation. Recently, white carbon black from RH is mainly prepared by chemical precipitation synthesis method in China because it is easy to control size, shape, and purity of the material (Fan, Xu et al., 2014 Yuvakkumar, Elango, Rajendran, & Kannan, 2014). White carbon black, as a kind of white, innocuous and amorphous powders, can be used in rubber, pesticide, feedstuff, catalyst carrier, and other fields (Jacobsen et al., 2010 Jiang, Wang, & Zhang, 2013 Shu, Shu, Zhi, & Li, 2010 Zhang, Tang, Xu, & He, 2011). Due to high content of natural silica, producing white carbon black from RH is both economically beneficial and environmentally friendly (An, Guo, Bo, Zhu, & Wang, 2011). Therefore, the utilization of RH has been drawn widespread attentions. Usually, RH is burned to generate energy or stacked on farmland, which will cause environmental pollution and occupancy of landfill space (Shan et al., 2015). The rice production in China was approximately 228 million tons in 2011, which was resulted in approximately 45.6 million tons of RH (Xu, Sun, Guo, Zhang, & Dong, 2014). During the process of multistage processing of rice, a great amount of rice husk (RH) was produced (Rafiee, Shahebrahimi, Feyzi, & Shaterzadeh, 2012).
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