通过静态吸附实验研究了多壁碳纳米管(MWCNTs)对柴油废水中油的吸附特性,并与活性炭进行了比较。表明MWCNTs和活性炭对柴油的吸附量均在前10 min上升迅速60 min左右可达到吸附平衡,但MWCNTs的吸附能力远大于活性炭。在动力学分析中发现准二级动力学模型能较好地符合研究体系,且随温度的升高,吸附速率增加。根据Arrhenius公式,算得MWCNTs吸附柴油2#的活化能(Ea)的值为14.21 k J·mol-1,可推断吸附应是物理吸附。利用颗粒内扩散模型发现MWCNTs吸附分外表面吸附、碳管间大空隙的内扩散和管间小空隙内扩散3阶段,而活性炭对柴油2#的吸附分为外表面吸附和颗粒内扩散两个阶段,且受边界层的影响较大。MWCNTs对柴油的吸附存在初始吸附行为。在298 K下MWCNTs对3种柴油的吸附及在288、298和308 K下对柴油2#的吸附,都是中等起始吸附,柴油2#的吸附,随温度的升高,起始吸附行为增强,在318 K时吸附过程具有较强烈的起始吸附行为。
The adsorption kinetics of diesel oil by multi-walled carbon nanotubes(MWCNTs) was investigated using static adsorption experiment and compared with activated carbon. The results show that the adsorption quantities on both the MWCNTs and activated carbon increase fast in the first 10 min, and the adsorption equilibrium can be reached in about 60 min, while the adsorption capacity on MWCNTs is far higher than activated carbon. The kinetic analysis shows that the adsorption kinetics can be accurately represented by a pseudo second-order model. The activation energy(Ea) of 14.21 k J·mol-1, determined by the Arrhenius law, suggests that physisorption dominates the adsorption of diesel oil 2# onto MWCNTs. The analyzing results with intraparticle diffusion model show that the adsorption mechanism is complex for MWCNTs, consisting of external surface adsorption, internal diffusion in large interstitial pores and in small interstitial pores between the tubes, while for activated carbon it consists of external surface and intraparticle diffusion stages and is strongly influenced by the boundary layer. Initial adsorption behavior is found in the adsorption process of diesel oil onto MWCNTs. The adsorption of three diesel oils at constant temperature(298 K) and that of diesel oil 2# at different temperatures(288, 298 and 308 K) show intermediately initial adsorption behavior. For diesel oil 2#, with the increase of temperature, the initial adsorption enhances, and at 318 K, intensive initial adsorption occurs.