In this study, a two-step alkaline hydrothermal method was used to prepare SBA-15 mesoporous molecular sieves from fly ash obtained from a thermal power plant in Inner Mongolia, China. CH₃O-SBA-15 was prepared using trimethoxychlorosilane as a modifier and toluene as the solvent. The silylated SBA-15 was characterized using X-ray diffraction, IR spectroscopy, N₂ adsorption–desorption, and scanning and transmission electron microscopies. The adsorption of nitrobenzene (NB), a persistent organic hydrophobic pollutant, by silylated SBA-15 and improvements in its hydrophobicity were studied. The effects of adsorbent dosage, time, temperature, and pH on the NB adsorption rate were investigated. The results show that CH₃O-SBA-15 has the same two-dimensional hexagonal pore structure as SBA-15 but that its specific surface area, average pore size, and pore volume are lower. The NB removal rate gradually increased with increasing adsorbent dosage and time. The NB removal rate gradually decreased with increasing temperature and pH; an alkaline environment is not conducive to NB removal. The NB removal rate achieved with CH₃O-SBA-15 was higher than that with SBA-15. At 25 °C and pH 5 with 5.5 g of adsorbent/L in an 8 μmol/L NB solution, SBA-15 and CH₃O-SBA-15 both rapidly adsorbed NB. After 60 min, the adsorption rate became constant. The maximum values were 77.5% and 89.06% with SBA-15 and CH₃O-SBA-15, respectively. Langmuir and Freundlich adsorption isotherms were obtained for NB solutions with various initial concentrations. The results show that adsorption of NB on both SBA-15 and CH₃O-SBA-15 is basically consistent with the Langmuir equation and that the adsorption process is mainly physical adsorption, accompanied by chemical adsorption. The adsorption capacity of silylated SBA-15 reached 10.42 μmol/g. A pseudo-second-order kinetic model described the adsorption of NB on CH₃O-SBA-15 well. The coefficient of determination was greater than 0.99. The thermodynamic data show that adsorption of NB on CH₃O-SBA-15 is a spontaneous, exothermic process accompanied by a decrease in entropy. The developed fly-ash-derived SBA-15 molecular sieves provide an effective technique for the treatment of industrial organic wastewater and a new method for the efficient use of fly ash.

中文翻译：

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表面硅烷化的粉煤灰衍生的SBA-15增强了硝基苯在水溶液中的吸附

在这项研究中，采用了两步碱性水热法，由从内蒙古热电厂获得的粉煤灰制备SBA-15中孔分子筛。使用三甲氧基氯硅烷作为改性剂和甲苯作为溶剂制备CH ₃ O-SBA-15。使用X射线衍射，红外光谱，N ₂吸附-解吸以及扫描和透射电子显微镜对甲硅烷基化的SBA-15进行了表征。研究了甲硅烷基化SBA-15吸附持久性有机疏水污染物硝基苯（NB）及其疏水性的改善。研究了吸附剂用量，时间，温度和pH值对NB吸附速率的影响。结果表明CH ₃O-SBA-15具有与SBA-15相同的二维六边形孔结构，但是其比表面积，平均孔径和孔体积较低。NB去除率随着吸附剂量和时间的增加而逐渐增加。随着温度和pH值的升高，NB的去除率逐渐降低。碱性环境不利于NB的去除。CH ₃ O-SBA-15达到的NB去除率高于SBA-15。在25°C和pH为5且在8μmol/ L NB溶液中含5.5 g吸附剂/ L的情况下，SBA-15和CH ₃ O-SBA-15都迅速吸附NB。60分钟后，吸附速率变为恒定。SBA-15和CH ₃的最大值分别为77.5％和89.06％O-SBA-15。对于具有各种初始浓度的NB溶液，获得了Langmuir和Freundlich的吸附等温线。结果表明，NB在SBA-15和CH ₃ O-SBA-15上的吸附基本符合Langmuir方程，并且吸附过程主要是物理吸附，伴随化学吸附。甲硅烷基化的SBA-15的吸附容量达到10.42μmol/ g。拟二级动力学模型描述了NB在CH ₃ O-SBA-15孔中的吸附。测定系数大于0.99。热力学数据表明，NB在CH ₃上的吸附O-SBA-15是一个自发的放热过程，伴随着熵的降低。研制出的粉煤灰衍生的SBA-15分子筛为工业有机废水的处理提供了有效的技术，也是有效利用粉煤灰的新方法。