改性焦粉对氟离子吸附热力学及机理
Mechanism and thermodynamics of fluor hydronium adsorption on modified coke powder
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摘要: 以废弃焦粉为原料，50%硝酸为改性剂，借助JSM、XRD和XPS现代分析测试方法表征其结构。考察了改性焦粉对氟离子吸附模型、热力学参数、粘附几率和活化能，初步探讨了吸附机理。结果表明，硝酸改性焦粉是硝酸刻蚀焦粉表面增加孔结构，增大表面积，表面氧化形成较为丰富含氧功能组的过程；吸附符合Langmuir和Langmuir吸附等温方程；吸附焓变为3.6596 kJ/mol，自由能变在-1.5004～-2.0107 kJ/mol之间，熵变为0.0173 kJ/(mol?K)；粘附几率和活化能分别为S=1.78×10-5、21.35 kJ/mol，表明该吸附过程是界面上混乱度增加的自发吸热过程；吸附氟离子过程是颗粒内扩散吸附，表面杂质与氟离子之间形成配位化合物、氟化钙胶体及表面含氧基团与氟离子形成氢键三者共同作用的结果，而颗粒内扩散吸附是该吸附的主要过程。Abstract: The structure of waste coke powders modified by 50% HNO3 was characterized by scanning electron microscope (SEM)， X-ray diffraction (XRD)， X-ray photoelectron spectroscopy (XPS)， etc. Adsorption model， the thermodynamics parameters， sticking probability and activation energy of fluor hydronium on modified coke powders were investigated. The adsorption mechanism was also primarily discussed. The result showed that the modified coke powders’ pore structure was enlarged， surface area increased and abundant oxygenous function groups grew on the surface. In addition， the adsorption equation was consistent with the Langmuir and Langmuir absorption model. The enthalpy change was 3.6596 kJ/mol， the free energy changed from -1.5004 to -2.0107 kJ/mol， the entropy change was 0.0173 kJ/（mol?K）， sticking probability was 1.78×10-5 and the activation energy was 21.35 kJ/mol. These results proved that this adsorption was a spontaneous and endothermic process accompanied with the interface chaos increasing. And the adsorption process to fluor hydronium was interacted by internal diffusion of particles， the formation of coordination complex between surface impurity and fluor hydronium， the formation of hydrogen bond among fluridizer of calcium colloid， oxygenous function groups and fluor hydronium， but internal diffusion of particles was the dominant process.
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