Preparation of Porous SiO2 Materials from Tobermorite and Their Adsorption Performances
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摘要: 通过水热合成法制备具有良好结晶形态的托贝莫来石(TOB),采用不同温度(300、500、700 ℃)对TOB进行加热活化(产物分别表示为300H-TOB、500H-TOB、800H-TOB),然后对热活化后的TOB进行酸处理(产物分别表示为300AH-TOB、500AH-TOB、800AH-TOB),成功制备出多孔二氧化硅材料。采用X射线多晶衍射(XRD)、N2吸附-脱附、扫描电子显微镜(SEM)、透射电子显微镜(TEM)等测试方法对多孔SiO2材料进行表征,结果表明,300AH-TOB样品的比表面积为570.25 m2/g,总孔容为0.747 m3/g。TOB经过热活化和酸处理后,钙离子选择性溶出,TOB的SiO2骨架保留下来,在TOB的链状八元环结构上原位形成大量的纳米尺度的孔结构。通过静态吸附实验探讨了TOB、300H-TOB、300AH-TOB 3种样品对碱性红2和结晶紫2种有机染料的吸附性能,结果表明在碱性红2和结晶紫中在分别加入0.4 g 3种样品时,TOB的吸附率分别为56.35%、47.69%,300H-TOB的吸附率分别为25.57%、42.69%,300AH-TOB的吸附率分别为91.46%、88.86%。Abstract: Tobermorite (TOB) was a major phase of calcium silicate board and autoclaved aerated concrete, which was widely used refractory materials and thermal insulation materials in the field of civil engineering . However, these materials were easy to wear so that a large number of solid wastes have been produced. The problem of functionalized utilization of TOB needed to be resolved urgently. In the present paper, TOB samples with good crystal morphology were prepared by hydrothermal synthesis and were calcined at different temperatures (H-TOB). Then the porous SiO2 material (AH-TOB) was successfully prepared by acid treatment of H-TOB, and AH-TOB material was characterized by XRD, N2 adsorption-desorption, SEM, TEM and other testing methods to investigate the formation mechanism. The results of BET and pore size distribution test analysis showed that the specific surface area of 300AH-TOB after thermal activation at 300 ℃ and hydrochloric acid modification was 570.25 m2/g, and the total pore volume was 0.747 m3/g. After heat treatment and hydrochloric acid treatment, the calcium ions in TOB were selectively dissolved, and the main component of the acid-insoluble material was silica. Therefore, it was inferred that the silicon oxide exhibited an eight-membered ring double-chain deformation structure composed of a silicon-oxygen tetrahedron, resulting in an increase in mesopores and micropores. The adsorption performances of TOB, 300H-TOB and 300AH-TOB on two organic dyes, Safranine T (ST) and crystal violet (CV), were investigated by static adsorption experiments. When the mass of adsorbent was added at 0.4 g, the adsorption rates of ST and CV were 56.35% and 47.69% on TOB; 25.57% and 42.69% on 300H-TOB; and 91.46% and 88.86% on 300AH-TOB, respectively. The porous material prepared from TOB had favorable adsorption of organic dyes, indicating its promising potential in adsorption application.
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Key words:
- tobermorite /
- selective acid leaching /
- porous silica /
- adsorption
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表 1 TOB、300H-TOB、300AH-TOB的化学成分
Table 1. Chemical composition of TOB, 300H-TOB, 300AH-TOB
Samples w/% SiO2 CaO Others TOB 49.31 38.36 12.33 300H-TOB 54.71 42.56 2.73 300AH-TOB 90.11 0 9.89 表 2 不同温度热活化TOB经过盐酸处理后的纳米孔道参数
Table 2. Porosity parameters of HCl acid treatment samples thermally activated at different temperatures
Sample SBET/(m2·g−1) SExternal/(m2·g−1) SMicro/(m2·g−1) VMicro/(cm3·g−1) VMeso/(cm3·g−1) VTotal/(cm3·g−1) TOB 152.14 123.81 28.33 0.011 0.607 0.611 300AH-TOB 570.25 437.76 132.49 0.057 0.652 0.747 500AH-TOB 539.15 421.21 117.94 0.050 0.651 0.734 700AH-TOB 440.18 337.93 102.25 0.043 0.514 0.576 SBET—Specific surface area; SMicro—Micropores specific surface area by t-plot method; SExternal—External surface area by t-plot method; VTotal—Total pore volume;
VMicro—Microporous volume by t-plot method;VMeso— Mesopore volume表 3 300AH-TOB吸附碱性红2的等温吸附模型拟合参数
Table 3. Isothermal adsorption model fitting parameters for ST adsorption on 300AH-TOB
T/K Freundlich Langmuir Kf 1/n R2 b/(L·mg−1) qm/(mg·g−1) R2 298 3.85 0.41 0.953 0.14 22.57 0.970 308 3.03 0.42 0.949 0.09 20.53 0.989 318 2.94 0.31 0.765 0.08 14.82 0.978 表 4 300AH-TOB吸附结晶紫的等温吸附模型拟合参数
Table 4. Isothermal adsorption model fitting parameters for CV adsorption on 300AH-TOB
T/K Freundlich Langmuir Kf 1/n R2 b/(L·mg−1) qm/(mg·g−1) R2 298 7.52 0.19 0.821 0.26 18.66 0.902 308 6.02 0.33 0.952 0.13 27.73 0.968 318 7.13 0.34 0.798 0.08 38.41 0.986 -
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