Study on the pore surface fractal dimension and surface acid–base properties of natural particles around Guanting reservoir
Study on the pore surface fractal dimension and surface acid–base properties of natural particles around Guanting reservoir
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DOI：
10.1016/j.colsurfa.2007.04.055
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发表时间：
2007-10
期刊：
影响因子：
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通讯作者：
Yili Wang;Baiyu Du;Xiaomin Dou;Jie Liu;Baoyou Shi;Dongsheng Wang;Hong-xiao Tang
中科院分区：
文献类型：
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作者：
Yili Wang;Baiyu Du;Xiaomin Dou;Jie Liu;Baoyou Shi;Dongsheng Wang;Hong-xiao Tang
通过对官厅水库周边不同天然颗粒的氮吸附-解吸等温线的测定，分析了其孔隙结构和分形特征。这些颗粒的其他微观结构参数如下：BET比表面积9.5669- 4.5605m2 g-1，BJH累积吸附体积0.01784- 0.06656cm3 g-1，BJH解吸平均孔径7.20-7.74nm。样品2、3和4的孔径分布（PSD）曲线的峰值在3.74nm附近，样品1的峰值在3.25nm附近，样品5的峰值在5.17nm附近。平均孔径大于孔径分布（PSD）峰值对应的孔径。这些颗粒的孔隙面积很小，但其孔隙体积可占总孔隙体积的15%以上。用分形FHH方程计算得到的吸附分支和解吸分支的孔表面分形维数D_s在2.69 ~ 2.80之间，两者相差不大，对应的分形尺度也不同。这可能是由于Ds值计算和孔结构性质的p/p0范围不同所致。否则，通过热力学模型计算的Ds值不能给出颗粒表面不规则性的有意义的指示。在这些颗粒表面上每平方纳米约有1-2个比表面位（DOH），并且在大多数pH范围内，每个表面位反应的平均质子数（Z）为负值，只有当pH值低于约4时，Z才能为正值。电位滴定实验和两种表面络合模型的模拟结果表明，在离子强度为0.005molL− 1时，CCM模拟结果比DLM更能解释实验数据点。基于CCM的质子化和去质子化反应模型可以较好地描述天然颗粒表面的酸碱行为，并可以得到天然颗粒表面的本征酸性常数和表面活性中心的总浓度。
Nitrogen absorption–desorption isotherms were obtained on different natural particles around Guanting reservoir, and their data points were used to analyze the pore structure and fractal properties of the obtained solids. Other microstructure parameters of these particles are the following: 9.5669–4.5605m2g−1of BET specific surface area, 0.01784–0.06656cm3g−1of BJH cumulative absorbed volume and 7.20–7.74nm of BJH desorption average pore diameter. The peak values of pore size distribution (PSD) curves were found at near 3.74nm for samples 2, 3 and 4, and near 3.25nm for sample 1, and near 5.17nm for sample 5. The average pore diameter was larger than that corresponding to the peak value of pore size distribution (PSD). The micropore areas are very small in these particles, but their micropore volume of them can occupy over 15% of total pore volume. The self-similar and rough surface was observed on these particles, and the pore surface fractal dimensions Dsof them were between 2.69 and 2.80, calculated by fractal FHH equation with the data of the adsorption branch of the isotherm, are a little difference from ones with the isotherm data of desorption branch, and also their corresponding fractal scales are different. It may be attributed to the different p/p0range for Dsvalues calculation and pore structure property. Otherwise, the computing Dsvalues by thermodynamic model do not give meaningful indication for particle surface irregularity. There are about 1–2 specific surface sites (DOH) in each square nanometers on these particles surface, and at most pH range, the average number of protons reacted per surface site (Z) have negative values, and only when pH values are lower than about 4, Z can have positive values. Potentiometric titration experiment and two surface complexation model simulation results indicate that CCM simulation results can better interpret the experiment data points than DLM at 0.005molL−1ion strength. Based on the CCM, the protonation and deprotonation reactions model can successfully depicted the acid–base behavior of natural particles surface, and the surface intrinsic acidic constants and the total concentration of surface sites for these natural particles, could be obtained.