紫外辐照改性生物炭对VOCs的动态吸附

采用365 nm紫外光辐照改性椰壳生物炭,以提升对挥发性有机污染物(VOCs)的吸附性能.选取苯和甲苯两种典型的VOCs为吸附质,考察了改性前后生物炭的吸附穿透曲线.结果表明,紫外辐照改性后的生物炭其吸附性能显著增加,对苯和甲苯的饱和吸附量分别由7.27 mg·g~(-1)和7.98 mg·g~(-1)提升至122.80 mg·g~(-1)和236.36 mg·g~(-1),吸附穿透时间也由1 min和2 min大大延长至390 min和620 min.生物炭表面理化特征分析表明,紫外辐照增大了生物炭表面含氧官能团的含量和外比表面积,这可能是改性生物炭吸附性能提升的关键因素.Yoon-Nelson、Thomas和BDST模型均能很好地模拟改性生物炭对不同浓度苯和甲苯的吸附过程,其相关系数大于0.992.热重分析结果表明,紫外辐射对生物炭的热稳定性影响甚微.改性生物炭吸附饱和后,可经热再生后重复利用,对甲苯的吸附重复利用5次后仍有较高的吸附能力.

Studies of Dynamic Adsorption Behavior of VOCs on Biochar Modified by Ultraviolet Irradiation

Coconut shell based biochar was modified by ultraviolet irradiation with UV light at a wavelength of 365 nm in order to enhance the adsorption capacity for volatile organic compounds (VOCs). The breakthrough curves of biochars for adsorbing two typical VOCs (benzene and toluene) were examined. The results showed that the adsorption capacity of modified biochar was greatly increased. The saturation adsorption capacity of modified biochar for benzene and toluene was increased to 122.80 mg·g^-1 and 236.36 mg·g^-1, comparing to that of the pristine biochar (7.27 mg·g^-1 and 7.98 mg·g^-1, respectively). The breakthrough time of modified biochar for benzene and toluene (390 min and 620 min) was also drastically prolonged as compared to the raw biochar (1 min and 2 min). The characterization analysis of biochars suggested that the carboxylic groups and external surface area were largely enriched, which might be the main factor responsible for the enhanced adsorption of the two VOCs on the modified biochar. The processes of adsorbing benzene and toluene at different concentrations on modified biochar were fitted by Yoon-Nelson, Thomas and BDST models. The result demonstrated that these three models could provide good fitting and the correlation coefficients were all above 0.992. The TG-DTG result proved that ultraviolet irradiation had little effect on the thermal stability of biochar. The modified biochar after adsorption saturation could be reused after thermal regeneration and the regenerated char also had high adsorption capacity after five times of repeated utilization.