从粉煤灰中提取白炭黑及其硅烷偶联剂改性工艺研究

摘要/Abstract

摘要： 为了提高粉煤灰综合利用附加值,基于酸碱联合法系统研究从粉煤灰中提取SiO₂最佳条件,并在最佳提取条件下,提出了新型的简化传统改性白炭黑的制备方法。研究表明,粉煤灰经过800 ℃预活化后,在硫酸(固液比(g/mL)为1∶8,3 mol/L)氛围下保持80 ℃反应90 min后成功转化成硅酸凝胶,并在质量分数为30%的NaOH作用下溶解提纯,最后调节溶液pH值得到SiO₂含量大于93%(质量分数)的白炭黑,此时SiO₂的提取率为95.7%。此外,在新型改性白炭黑制备方法研究中,硅烷偶联剂KH560与形成的白炭黑通过Si—O—Si化学键发生键合,成功覆盖在白炭黑表面。当改性剂用量为2 mL/g、改性温度为70 ℃、改性时间为60 min时,获得分散性、疏水性及粒径均匀度较好的改性白炭黑,其SiO₂含量仍达95.97%(质量分数),比表面积(381.97 m²/g)是未改性白炭黑的2.78倍,粉体亨特白度达91.43%,符合A类工业级白炭黑的相关标准。

关键词: 粉煤灰, 改性白炭黑, 二氧化硅, 硅烷偶联剂改性, 酸碱联合法, 活化度

Abstract: In order to improve the added value of comprehensive utilization of fly ash, this paper systematically studied the optimum conditions for extracting SiO₂ from fly ash using the acid base combination method, and a novel method for the preparation of simplified conventional modified silica was proposed based on the optimal extraction conditions. Results show that fly ash is preactivated at 800 ℃ and successfully converted into silicate gel after continuously reacting for 90 min at the temperature of 80 ℃ and the atmosphere of sulfuric acid (solid-liquid ratio (g/mL) of 1∶8, 3 mol/L), and then the silicate gel is dissolved and purified with the action of NaOH with a mass fraction of 30%, and finally, the solution pH value is adjusted to obtain more than 95.7% of SiO₂ extraction and silica with SiO₂ content greater than 93% (mass fraction). In addition, the silane coupling agent KH560 is successfully covered on the surface of the silica after bonding with the formed silica through Si—O—Si chemical bonding in this novel method. The modified silica, which possesses a superior nature in dispersibility, hydrophobicity and particle size, is obtained under the modification conditions of modifier dosage ratio of 2 mL/g, 70 ℃ and 60 min. And SiO₂ content in the resulting product is still above 95.97% (mass fraction), showing a significant improvement in specific surface area (381.97 m²/g, 2.78 times higher than that of unmodified silica), and the Hunter whiteness (91.43%) is close to the standard white board, which meets the relevant standards of Class A industrial grade silica.

Key words: fly ash, modified silica, SiO₂, silane coupling agent modification, combined acid-base method, activation degree

中图分类号:

X752

向杰, 黎建宏, 王桂芳, 薛清远, 何建桥, 刘书均, 胡青艳. 从粉煤灰中提取白炭黑及其硅烷偶联剂改性工艺研究[J]. 硅酸盐通报, 2023, 42(3): 989-1000.

XIANG Jie, LI Jianhong, WANG Guifang, XUE Qingyuan, HE Jianqiao, LIU Shujun, HU Qingyan. Extraction of Silica from Fly Ash and Modification by Silane Coupling Agent[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2023, 42(3): 989-1000.

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