Abstract:

The pitch-based spherical activated carbon was used as support to load different amounts of citric acid into its pores by equivalent-volume impregnation method. The effect of citric acid modification on the activated carbon's ammonia adsorption was evaluated by a fixed bed dynamic adsorption device. The physicochemical properties of activated carbon before and after modification were characterized by SEM, XRD, FTIR, nitrogen adsorption and desorption. The results showed that the modified activated carbon had the best ammonia adsorption performance when the load of citric acid was 60%. The ammonia protection time was 194min, and the ammonia adsorption capacity was 42.8mg/mL (66.8mg/g), which was 24 times that of unmodified activated carbon. The total specific surface area, pore volume and pH of the adsorbent decreased with the increase of citric acid loading, and the correlation coefficients R² between the specific surface area and pore volume of the adsorbent, and citric acid loading were 0.9944 and 0.9842, respectively. As the loading capacity increased, the utilization rate of citric acid decreased. Ammonia reacted with citric acid to produce ammonium citrate. The products were mainly deposited in micropores, which were crucial for ammonia adsorption.

Key words: activated carbon, citric acid, composites, fixed-bed, adsorption, ammonia

摘要：

以沥青基球形活性炭为载体，采用等体积浸渍法将不同浓度的柠檬酸负载到活性炭孔隙内。通过固定床动态吸附装置评价柠檬酸改性活性炭对氨气吸附性能的影响。采用扫描电子显微镜、X射线衍射仪、傅里叶变换红外光谱和氮气吸脱附对改性前后活性炭的理化特性进行表征分析。结果表明，当柠檬酸负载量为60%（质量分数）时，改性活性炭对氨气的吸附性能最佳，氨气防护时间为194min，单位活性炭的氨气吸附容量为42.8mg/mL（66.8mg/g），是未改性活性炭吸附容量的24倍；吸附剂的总比表面积和孔体积以及pH都随着柠檬酸负载量的增加不断减小，其中微孔的比表面积和孔体积与柠檬酸负载量的相关系数R²分别为0.9944和0.9842；柠檬酸的利用率随着负载量的增加不断减少，氨气与柠檬酸反应生成柠檬酸铵，产物主要沉积在微孔内，微孔对氨气吸附至关重要。

关键词: 活性炭, 柠檬酸, 复合材料, 固定床, 吸附, 氨气