In order to elucidate the patterns of vacuum desorption of volatile organic compounds( VOCs) from activated carbons, the vacuum desorption curves of the VOCs as a function of the temperature were investigated in a fixed bed by choosing 11 types of VOCs (including alkanes, aromatics, alcohols and ketones, and so on) of different chemical structures and molecular sizes. The results showed that vacuum desorption was a highly potential technology for recovering VOCs. Compared with conventional thermal desorption methods, vacuum desorption significantly reduced VOCs desorption temperatures, and allowed high desorption efficiency of greater than 99% and more reuse of activated carbons. The polar surfaces of activated carbon significantly weakened the desorption of alcohols while the non-polar surface was conducive. The surface property of activated carbons barely affected the desorption of the non-polar VOCs. Further, adsorbed alcohols molecules such as methanol and ethanol were arranged perpendicular to the surface of activated carbon in a way that hydroxyls of alcohols directly contacted with the carbon surface. This arrangement led to carboxyl groups of activated carbons prone to be removed or be changed into lactone in the vacuum thermal desorption process.%以椰壳活性炭(AC)和硝酸氧化改性的活性炭(AC-O)作为吸附剂,选择了具有不同极性和分子大小的烷烃、芳烃、醇和酮等11种挥发性有机化合物(VOCs)作为吸附质,分析了这些VOCs在活性炭固定床上随脱附温度升高的脱附曲线,研究了挥发性有机化合物在活性炭上的真空脱附规律.结果表明:与其它的脱附方法相比,VOCs在活性炭上的真空脱附具有脱附温度低、脱附率高(能达到99％以上)、活性炭的重复利用次数多等优点,是一种具有很好发展潜力的VOCs回收方法.同时,对于化学结构类似的VOCs吸附质,沸点越低则越易于在活性炭上脱附;活性炭的表面化学性质对甲醇和乙醇的脱附影响显著,但对其它VOCs吸附质的脱附影响较小.活性炭的非极性表面非常有利于醇类有机蒸气分子的脱附,硝酸氧化改性则显著降低了醇类分子的脱附率.此外,在活性炭的重复利用过程中,甲醇和乙醇的羟基能与活性炭表面的羧基相互作用,导致活性炭表面羧基在较高温度脱附时发生脱除或转变成内酯基形式,有利于活性炭的重复使用.
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