Mechanistic Studies in Ultrasound-Assisted Adsorption for Removal of Aromatic Pollutants
Mechanistic Studies in Ultrasound-Assisted Adsorption for Removal of Aromatic Pollutants
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DOI：
10.1021/ie900049e
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发表时间：
2009-08-05
影响因子：
4.2
通讯作者：
Moholkar, Vijayanand S.
中科院分区：
文献类型：
--
作者：
Midathana, Venkata Rao;Moholkar, Vijayanand S.
本文试图揭示超声波强化有机污染物吸附的物理机制。试图区分超声和空化的各种物理效应所作的贡献，即，微流、微湍流和声波（或冲击波），它们可以在介质中产生对流并增强吸附过程。采用了将实验结果与气泡动力学模型的模拟相耦合的双重方法。吸附三种芳香族污染物（即，硝基苯、苯酚和对硝基苯酚）在活性炭上的吸附被选择作为模型方法。实验和模拟结果的相关性表明，在超声波的存在下，吸附的程度与空化气泡在介质中产生的对流的强度显示出最佳。空化气泡产生的微湍流对吸附的强化有重要作用。这是由于具有中等液体速度的微湍流的连续性质。另一方面，由空化气泡发射的声波对该过程产生不利影响。这归因于波的离散性质和高压振幅，其在介质中产生过高的对流，导致污染物的解吸。污染物的化学性质也被发现影响超声的增强效果。对于疏水性污染物，超声波增强比亲水性污染物在其他类似条件下更明显。
In this paper we try to discern the physical mechanism of enhancement of adsorption of organic pollutants with application of ultrasound. An attempt is made to discriminate between the contribution made by various physical effects of ultrasound and cavitation, viz., microstreaming, microturbulence, and acoustic (or shock) waves, which could generate convection in the medium and enhance the process of adsorption. A dual approach of coupling experimental results to the simulations of a bubble dynamics model has been adopted. Adsorption of three aromatic pollutants (viz., nitrobenzene, phenol, and p-nitrophenol) onto activated carbon has been chosen as a model process. Correlation of the experimental and simulation results reveals that the extent of adsorption in the presence of ultrasound shows an Optimum with the intensity of convection generated in the medium by the cavitation bubbles. The microturbulence generated by cavitation bubbles makes a useful contribution to the enhancement of adsorption. This is attributed to the continuous nature of microturbulence with moderate liquid velocities. On the other hand, acoustic waves emitted by the cavitation bubbles render an adverse effect on the process. This is attributed to the discrete nature and high pressure amplitude of the waves, which create excessively high convection in the medium, causing desorption of the pollutant. The chemical nature of the Pollutant is also found to influence the enhancement effect of ultrasound. For hydrophobic pollutants, the ultrasonic enhancement is more pronounced than for hydrophilic pollutants under otherwise similar conditions.