预处理方法对活性炭结构及吸附性能的影响

Effects of different pretreatment methods on structure and adsorption properties of activated carbon

分别采用水洗、酸洗、酸洗+碱洗等方法对活性炭进行预处理,通过扫描电镜(SEM)、低温液氮吸附及傅立叶红外光谱(FTIR),研究活性炭组织与结构的变化,并以灰分、亚甲基蓝脱色能力、碘值以及苯酚值分析活性炭吸附性能的变化,对比评价不同预处理方法对活性炭结构及吸附性能的影响。结果表明,水洗对活性炭的结构和吸附性能影响不大;HCl酸洗以及HCl酸洗+NaOH碱洗使活性炭的比表面积增大以及微孔与中孔比例增加,从而改变活性炭的表面性质,提高其吸附性能;经过HNO3酸洗或HNO3酸洗+NaOH碱洗后,活性炭的中孔和大孔比例增加,比表面积略有下降,吸附性能不及HCl酸洗以及HCl酸洗+NaOH碱洗的结果。用HCl酸洗能更好地提高活性炭对小分子物质的吸附能力;NaOH碱洗能增加活性炭对较大分子的吸附。

Activated carbons were pretreated by water washing, pickling and pickling＋alkali washing, respectively. Structure changes were characterized by scanning electron microscopy（SEM）, low temperature liquid nitrogen adsorption and Fourier transform infrared spectroscopy（FTIR）. Adsorption properties changes were tested by ash content, methylene blue decolorizing ability, iodine adsorption value and phenol adsorption value. The effects of five different pretreatment methods on the structure and adsorption properties of activated carbon were compared and investigated. The results show that little effects on the structure and adsorption properties are caused by water washing method. HCl washing and HCl washing＋NaOH washing methods can increase the specific area, micropores and mesopores ratio of activated carbon, modify the surface properties and improve the adsorption properties. HNO3 washing and HNO3washing＋NaOH washing methods can increase mesopores and macropores ratio of activated carbon, decrease the specific area slightly and the adsorption properties are worse than those of HCl washing＋NaOH washing treatment. HCl pretreatment method is better for enhancing the adsorption ability of small molecules. NaOH washing method can improve adsorption ability of large molecules.