Liao Wei, Li Wenqing, Fang Zhenggang, Lu Chunhua, Xu Zhongzi
State Key Laboratory of Materials-Oriented Chemical Engineering, College of Materials Science and Engineering, Nanjing Tech University, Nanjing 210009, China.
Materials (Basel). 2019 Nov 15;12(22):3765. doi: 10.3390/ma12223765.
Tobermorite and Al-substituted tobermorite with varying Al/(Si + Al) molar ratios were synthesized via the static hydrothermal method. The effect of different Al substitution ratios on the structure of tobermorite was investigated by XRD, SEM-EDS, TG-DSC, FT-IR, Si, and Al MAS-NMR. The interplanar crystal spacing of (002) increased with the increment of the Al substitution ratio. The maximum ratio of the Al substitution for Si in the structure of tobermorite was about 15 at %, which was limited by the compositions of tobermorite and the electrostatic repulsive forces caused by Al substitution. The DSC curve of the tobermorite with an Al/(Al + Si) molar ratio of 0.15 showed a larger exothermic peak area at 850 °C, indicating that the Al-O-Si bond was formed in the structure of tobermorite and the Al participated in the recrystallization. The Si and Al MAS-NMR results confirmed that tetrahedral Al was introduced into the structure of the tobermorite. New silicon sites, Q(1Al) and Q(1Al), formed by the Al substitution for Si in bridging and non-bridging sites, were detected. Compared to the tobermorite without Al substitution, the adsorption capacity of Al-substituted tobermorite with Al/(Al + Si) = 0.15 to Na was improved by 44%.
采用静态水热法合成了具有不同Al/(Si + Al)摩尔比的雪硅钙石和Al取代雪硅钙石。通过XRD、SEM-EDS、TG-DSC、FT-IR、Si和Al MAS-NMR研究了不同Al取代比例对雪硅钙石结构的影响。(002)晶面间距随Al取代比例的增加而增大。雪硅钙石结构中Al取代Si的最大比例约为15 at%，这受到雪硅钙石的组成以及Al取代引起的静电排斥力的限制。Al/(Al + Si)摩尔比为0.15的雪硅钙石的DSC曲线在850℃时显示出更大的放热峰面积，表明在雪硅钙石结构中形成了Al-O-Si键，且Al参与了重结晶过程。Si和Al MAS-NMR结果证实四面体Al被引入到雪硅钙石结构中。检测到在桥连和非桥连位点上Al取代Si形成的新硅位点Q(1Al)和Q(1Al)。与未Al取代的雪硅钙石相比，Al/(Al + Si)=0.15的Al取代雪硅钙石对Na的吸附容量提高了44%。
