Preparation of Porous SiO2 Materials from Tobermorite and Its Adsorption Performance
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摘要: 通过水热合成制备具有良好的结晶形态的托贝莫来石（TOB），用不同温度对TOB进行加热活化（H-TOB），然后对H-TOB进行酸处理成功制备出多孔二氧化硅材料（300AH-TOB），并用XRD、N2吸-脱附、SEM、TEM等测试方法对多孔SiO2材料进行表征，研究了其形成机理。结果表明，制备的多孔SiO2材料比表面积达到了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对碱性红2和结晶紫两种有机染料的吸附性能，在0.4 g的加入量下，TOB的吸附率分别为56.35%、47.69%；300H-TOB的吸附率为25.57%、42.69%；300AH-TOB吸附率为91.46%、88.86%。由托贝莫来石制备的多孔材料对有机染料具有良好的吸附作用，具有作为染料吸附剂的应用潜力。Abstract: Tobermorite (TOB) was major phase of calcium silicate board and autoclaved aerated concrete, which were widely used refractory materials and thermal insulation materials in the building engineering field. However, these materials were easy to wear so that large quantities 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 temperature (H-TOB). Then the porous SiO2 material (300AH-TOB) was successfully prepared by acid treatment of H-TOB, and the porous SiO2 material was characterized by XRD, N2 adsorption-desorption, SEM, TEM and other testing methods to investigated the formation mechanism. The 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 exhibits an eight-membered ring double-chain deformation structure composed of a silicon-oxygen tetrahedron, resulting in an increase in mesopores and micropores. The adsorption performance of TOB, 300H-TOB and 300AH-TOB on two organic dyes, Safranine T and crystal violet, was investigated by static adsorption experiments. The adsorption rates were 56.35% and 47.69% for TOB; 25.57% and 42.69% for 300H-TOB; and 91.46% and 88.86% for 300AH-TOB, respectively, with the addition amount of 0.4 g. 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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图 2 (a) 不同温度热处理TOB的XRD图谱；(b)煅烧托贝莫来石酸处理后的XRD图谱
Figure 2. XRD results of the calcined TOB samples (a) and the insoluble matters of the calcined TOB (b).
图 3 N2吸附-脱附等温线（a）和由2D-NLDFT方法计算的孔径分布曲线（b）
Figure 3. Nitrogen adsorption-desorption isotherms (a) and Pore size distribution curves calculated by 2D-NLDFT method (b)
图 4 TOB, 300H-TOB和300AH-TOB的SEM形貌
Figure 4. SEM morphology of TOB, 300H-TOB and 300AH-TOB
图 5 TOB, 300H-TOB和300AH-TOB的透射电镜形貌及衍射斑点图
Figure 5. TEM morphology and diffraction spectrogram of TOB (a), 300H-TOB (b), and 300AH-TOB (c)
图 6 TOB的多孔形成示意图
Figure 6. Schematic model for the possible formation of porous silica from TOB.
图 10 300AHTOB吸附CV的（a）Langmuir和（b）Freundlich等温吸附模型拟合
Figure 10. Langmuir and Freundlich isotherms for CV adsorption on 300AH-TOB
图 7 TOB、300H-TOB和300AH-TOB对碱性红2（a）和结晶紫（b）的吸附
Figure 7. TOB、300H-TOB and 300AH-TOB adsorption of basic red 2 (a) and crystal violet (b)
图 8 TOB, 300H-TOB和300AH-TOB的Zata电位图
Figure 8. Zeta potential of TOB, 300H-TOB and 300AH-TOB
图 9 300AHTOB吸附ST的（a）Langmuir和（b）Freundlich等温吸附模型拟合
Figure 9. Langmuir and Freundlich isotherms for ST adsorption on 300AH-TOB
表 1 TOB、300H-TOB、300AH-TOB的化学成分
Table 1. Chemical composition of TOB, 300H-TOB, 300AH-TOB
Sample 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 
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表 2 不同温度热活化TOB经过酸处理后的纳米孔道参数
Table 2. Porosity parameters of the HCl acid treatment samples pre-calcined at different temperatures.
Sample SBET/(m2/g) Sexternal/(m2·g−1) Smicro/(m2·g−1) Vmicro/(cm3·g−1) Vmeso/(cm3·g−1) Vt/(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 0.05 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
Vt: Total pore volume;
Vmicro：Microporous volume by t-plot method
Vmeso：Mesopore volume
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表 3 ST等温吸附模型拟合参数
Table 3. Isotherm parameters of ST adsorption on 300AHTOB
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
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表 4 CV等温吸附模型拟合参数
Table 4. Isotherm parameters of CV adsorption on 300AHTOB.
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 0.951 0.13 27.73 0.968 318 7.13 0.34 0.797 0.08 38.41 0.986
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