随着纳米碳管(CNTs)的广泛应用,其不可避免地进入环境中,天然有机质与CNTs的相互作用增大了CNTs的分散性,可能带来更大的环境风险.本研究系统考察了溶解胡敏酸(HA)对CNTs的悬浮效果,发现随着悬浮次数的增加,HA的累积吸附量不断增大,而CNTs的悬浮量先增加后减少,表明CNTs确实存在分级悬浮的现象.通过透射电子显微镜和热重分析对高悬浮量和低悬浮量的CNTs进行表征发现,高悬浮量的CNTs相比低悬浮量的CNTs短且碎,说明具有较多缺陷的CNTs可能是易悬浮的部分;尽管高悬浮量的CNTs对HA的累积吸附量较低,但其较早的出现了明显的失重平台,具有较差的热稳定性.两方面的证据可以证实CNTs自身性质的差异是其分级悬浮的控制性因素.
The widespread use of carbon nanotubes (CNTs) may cause them to be released into the environment.Their interaction with natural organic matter enhances their dispersion in water, leading to a severe environmental threat.In this study, the effect of dissolved humic acid (HA) on the dispersion of graphitized or hydroxylated CNTs in water was investigated by repeated dispersion of both CNTs in HA water with a concentration of 100 mg/L for 19 times.Results showed that the cumulative adsorption amounts of HA on the graphitized CNTs increased and leveled off, but those on the hydroxylated ones increased continually with the number of dispersions.The amounts of graphitized CNTs suspended in HA water were always lower than those of the hydroxylated ones, which reached a maximum after 4 of 5 dispersions.TEM images showed that hydroxylated CNTs were shorter than the graphitized ones and the suspended CNTs were shorter than the un-suspended ones for both types of CNTs, indicating that CNTs with more defects are easily suspended.
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