Subsurface Transport Behavior of Micro-Nano Bubbles and Potential Applications for Groundwater Remediation

Hengzhen Li,Liming Hu,Dejun Song,Abir Al-Tabbaa

doi:10.3390/ijerph110100473

Abstract

Micro-nano bubbles (MNBs) are tiny bubbles with diameters on the order of micrometers and nanometers, showing great potential in environmental remediation. However, the application is only in the beginning stages and remains to be intensively studied. In order to explore the possible use of MNBs in groundwater contaminant removal, this study focuses on the transport of MNBs in porous media and dissolution processes. The bubble diameter distribution was obtained under different conditions by a laser particle analyzer. The permeability of MNB water through sand was compared with that of air-free water. Moreover, the mass transfer features of dissolved oxygen in water with MNBs were studied. The results show that the bubble diameter distribution is influenced by the surfactant concentration in the water. The existence of MNBs in pore water has no impact on the hydraulic conductivity of sand. Furthermore, the dissolved oxygen (DO) in water is greatly increased by the MNBs, which will predictably improve the aerobic bioremediation of groundwater. The results are meaningful and instructive in the further study of MNB research and applications in groundwater bioremediation.

Highlights

Microbubbles and nanobubbles, known as micro-nano bubbles (MNBs) for short, are tiny bubbles with diameters of several tens of micrometers and nanometers, respectively [1,2]
The Micro-nano bubbles (MNBs) generated by the spiral liquid flow type apparatus made the water milky-like and it remained so for minutes
The main conclusions are as follows: (1) Two peaks were found in the size distribution of MNBs generated by the spiral liquid flow type generator, one was 10 μm and the other was 50 μm

Summary

Introduction

Microbubbles and nanobubbles, known as micro-nano bubbles (MNBs) for short, are tiny bubbles with diameters of several tens of micrometers and nanometers, respectively [1,2]. In the past few years, the potential applications of these MNBs in many fields of science and technology have drawn more and more attention, especially in environmental engineering such as surface water remediation because of their special characteristics of large specific surface area, negatively charged surface and high oxygen mass transfer efficiency [2,3,4,5,6,7,8,9,10]. Nanobubbles with a 720 nm diameter are observed to significantly enhance the rate of decomposition of sodium dodecylbenzenesulfonate due to their large surface area that facilitates the reaction [17]

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Conclusion