摘要
以粉煤灰为原料,通过碱熔-水热法合成沸石吸附剂.首先将粉煤灰与氢氧化钠以1∶1.2的质量比混合,然后在850 ℃下焙烧2 h得到碱熔灰,随后通过单因素实验探究水热反应过程中前驱体硅/铝摩尔比、反应时间、温度和液/固比对粉煤灰基沸石吸附剂结构的影响.利用X射线衍射仪(XRD)、扫描电镜(SEM)和比表面积及孔径分析仪(BET)等手段对合成的粉煤灰基沸石进行表征.在水热反应前驱体硅/铝摩尔比为1.5、反应时间16h、反应温度70 ℃、液/固比为8mL/g的最佳条件下,合成的产物中X型沸石相对质量分数为96.3％,比表面积达到489.9 m2/g,孔体积达到0.28 cm3/g.在此基础上,还探究了粉煤灰基沸石吸附剂对典型挥发性有机物苯的气体吸附效果,并与商业活性炭进行了对比.结果表明,在污染物初始浓度为800 μg/L、吸附温度为100℃、气体流量为200 mL/min、吸附剂装填量为0.1 g的条件下,粉煤灰基沸石对苯的饱和吸附量为41.5 mg/g,优于商业活性炭(31.3 mg/g),可为粉煤灰资源化利用提供参考.
Abstract
Zeolite adsorbents were synthesized through an alkali fusion-hydrothermal process,using coal fly ash as a raw material.Firstly,the coal fly ash was mixed with sodium hydroxide at a mass ratio of 1∶1.2 and then roasted at 850 ℃ for 2 h to obtain the alkali-fused ash.The effects of the Si/Al molar ratio of the precursor,reaction time,temperature,and liquid/solid ratio on the structure of the zeolite adsorbents derived from coal fly ash were investigated through single-factor experiments conducted during the hydrothermal reaction.The synthesized zeolite adsorbents derived from coal fly ash were systematically characterized using X-ray diffractometer(XRD),scanning electron microscope(SEM)and specific surface area and pore size analyzer(BET).Under the optimized conditions of a Si/Al molar ratio of the precursor set at 1.5,a reaction time of 16 h,a reaction temperature of 70 ℃,and a liquid/solid ratio of 8 mL/g in hydrothermal reaction,the relative mass fraction of type X zeolite in the synthesized product was 96.3％,the specific surface area was 489.9 m2/g,and the pore volume was 0.28 cm3/g.Subsequently,the gas adsorption performance of benzene,a typical volatile organic compound,by zeolite adsorbent derived from coal fly ash was investigated and compared with commercial activated carbon.The results showed that at an initial pollutant concentration of 800 μg/L,an adsorption temperature of 100 ℃,a gas flow rate of 200 mL/min,and an adsorbent loading of 0.1 g,the zeolite adsorbents derived from coal fly ash exhibited a saturated adsorption capacity of benzene at 41.5 mg/g,which was higher compared to commercial activated carbon(31.3 mg/g).This study provides a reference for the resource utilization of coal fly ash.
万方数据