Clustered nanobubbles, methods of formation and potential applications (2023)

carbon monoxide₂Capture, use and storage technology is one of the most effective ways to reduce CO2 emissions₂.Although this technology is relatively mature, the main problem limiting large-scale application is the safety of geological storage. The advantages of microbubbles and nanobubbles are widely recognized due to their size and stability. Microbubbles and nanobubbles are tiny gas-liquid dispersion systems with unique physical properties. Important features of microbubbles and nanobubbles include their excellent stability, high internal pressure, extremely large surface-to-volume ratio, and high gas dissolution rate, which have wide prospects for application in various fields. This review discusses the research conducted in the field of microbubbles and nanobubbles, with a special emphasis on CO₂-EOR i CO₂Geological storage. The classification and composition of microbubbles and nanobubbles is briefly presented. The method of preparation of micro-nano bubbles and the main factors influencing their properties are studied in detail. Characterization parameters of state-of-the-art measurement and analysis techniques for microbubble and nanobubble technology are summarized. In addition, the main application of CO₂-EOR i CO₂Geological storage is discussed. Based on this review, various potential areas and gaps in MNB research in CO₂– EOR i CO₂A geological repository has been identified for further exploration.

In recent years, nanobubbles have attracted much attention due to their potential applications in various fields such as engineering, environment, biology and medicine. In addition, different types of nanobubbles are used in different fields due to their different properties. However, understanding the growth dynamics of interfacial and aggregated nanobubbles at the nanoscale to meet the demands of various applications remains a challenge. Using liquid-cell transmission electron microscopy, we reveal in real time the quasi-equilibrium growth trajectories of electron beam-induced nanobubbles in aqueous solution. In particular, we successfully distinguished interfacial nanobubbles from aggregated nanobubbles by combining growth kinetics analysis and the Fresnel fringe method. In addition, the methods described above revealed nonequilibrium growth of some nanobubbles from the solution to the interface. These insights into the growth kinetics of nanobubbles at the nanoscale can help in the better design of tailored nanobubbles with specific kinetic behavior for different applications.

Since the classical Epstein-Plesset theory predicted that bubbles cannot spontaneously maintain a stable thermodynamic equilibrium, the unusual stability of a large number of nanobubbles has attracted much attention from academia and industry. The dual nature of ionic surfactants, which simultaneously act as charge carriers and surface tension reducers at the gas-liquid interface, enables them to play a unique role in the stabilization of clustered nanobubbles. In this work, the stability of a large number of nanobubbles in solutions of a wide range of concentrations of anionic, cationic and nonionic surfactants is investigated. Experimental results show that different types of molecules of surfactants participate in different ways in the nucleation and stabilization of collective nanobubbles. We show that the accumulation of net charges carried by the surfactant ions at the interface is primarily responsible for the stabilization of the nanobubbles and not for the reduction of the surface tension. Through theoretical calculations, we additionally quantified the effect of coupling of interfacial tension and surface charge on the steady state equilibrium of clustered nanobubbles. The results show that interfacial tension and gas saturation together determine the upper limit of the bubble size that can exist stably. Our study identifies avenues for investigating the mechanisms underlying the stability of aggregated nanobubbles.

Nanobubble technology is a new solution for solving climate change, environmental challenges, reducing costs and energy in industrial processes, optimizing therapeutic and diagnostic techniques and other applications. Although the production and development of nanobubbles is a recently developed field, there are many reports and studies on their characteristics and promising applications in various fields. This paper aims to provide a summary of the latest (as of 2017) scientific findings on the potential of nanobubbles as a multifunctional and sustainable technology. Applications in the environment, agriculture, medicine/biomedicine and others are reviewed, and the most indicative applications in each domain are listed in detail. Special attention is paid to the implementation of water and wastewater treatment.

The purpose of this research was to evaluate the effect of bulk nanobubble (BNB) incorporation during ultrafiltration (UF). Laboratory and pilot ultrafiltration experiments were conducted to evaluate the effect of BNB incorporation on the ultrafiltration process by evaluating permeate flux, membrane microstructure, fouling resistance, and energy consumption. In addition, control dispersions and dispersions of skimmed milk concentrate (SMC) with incorporated BNB were characterized in terms of physicochemical properties, rheology and microstructure. Running the UF with the installation of BNB enabled a better performance of the membrane as evidenced by a better permeate flow. The permeation flux of the control SMC is 9.27 and 6.89 kg/h∙m²After adding BNB, permeate flow increased significantly (P<0.05) to 14.57 and 9.59 kg/h∙m²For laboratory and pilot UF tests. The incorporation of BNB also resulted in a significant decrease in apparent viscosity (P<0.05) and showed a significant change in the microstructure of the skimmed milk concentrate dispersion obtained. In conclusion, the incorporation of BNB helps to improve the performance of the UF membrane, so this study shows that more efficient UF treatment can be achieved by incorporating BNB.

In this study, four different pond sites were analyzed at different time periods to demonstrate the effect of nanobubble ozonation (NBO). NBO is an environmentally friendly new technology that uses only air, ozone and almost no chemicals. All case studies were conducted in real time during different seasons and locations, demonstrating the importance of NBO for treating water bodies with techniques that are completely natural, environmentally sustainable, cost effective and less time consuming. Three case studies were studiedin place(Locations 1, 2, 4) and the previous one- On the spot(location-3), the effectiveness of NBO in treating pond water was confirmed. The NBO-treated water was found to be within standard limits, odors were removed, and the water was purified enough for the animals to drink. Test results showed that ozone nanobubbles (NBO) achieved 85-99% reduction in total soluble solids (TSS), 80-90% reduction in biochemical oxygen consumption (BOD) and 55% reduction in chemical oxygen consumption (COD) in wastewater treatment The % COD of locations 3 and 4 was reduced by 82%. Improved dissolved oxygen suitable for organisms is achieved. Therefore, this paper highlights the effectiveness of NBO treatment on water regeneration and ecological restoration to achieve the sustainable goals of clean water and environmental sustainability. DO levels in all ponds increased significantly after NBO treatment, and measurements showed a value of 14.5 mg/L even after 50 hours. The Nanobubble gas dissolving system is not only capable of raising dissolved oxygen to supersaturation levels, but also keeps it stable for over 14-15 hours. Various reasons for this consistency are that the size of the nanobubbles is about <0.5 μm and that the NBs do not follow buoyancy and therefore move by Brownian motion in water. NBG systems are the future of rejuvenating and maintaining water quality in our lakes and ponds.

Advances in Colloid and Interface Science, Volume 291, 2021, Article 102403

Traditional foam flotation is the main method for the separation and purification of small minerals. However, small, low-grade minerals are difficult to separate effectively. Bubble miniaturization is generally believed to be of great importance for improving flotation efficiency. Due to their unique physical and chemical properties, nanobubbles (NB), as an important tool to solve the problem of fine particle separation, have been widely studied in areas such as ore flotation. Therefore, a fundamental understanding of the effect of NB on flotation is a prerequisite for its suitability for the separation of fine-grained and low-grade minerals. This article reviews recent advances in the field of nanobubble (NB) generation, preparation, and stabilization. We particularly highlight recent advances in the role of NB in ​​particle flotation, with a particular focus on particle-particle and particle-bubble interactions. Discussion of current knowledge gaps and future directions is provided.

Chemical Engineering and Processing - Process Intensification, Volume 136, 2019, Pages 62-71

This work is focused on testing the stability of gas nanobubbles in water. The generation of nanobubbles was performed in two porous membrane modules for two different liquid flow rates. The gaseous phase is nitrogen or oxygen, and the liquid phase is distilled water. Nanodispersion samples were stored for 10 to 35 days. One half of them is stored open and the other half closed to ensure or prevent contact with the atmosphere. The Sauter diameter and zeta potential of the nanobubbles were measured during storage. Also, in the case of oxygen, the concentration of the dissolved gas is measured. The results showed that the stability and size of nanobubbles does not depend on whether the sample is open or closed. The resulting nanobubbles were stable for more than a month, and their Sauter diameters approached values ​​in the range of 250–350 nm from different initial sizes. Furthermore, the average zeta potential of nanobubbles in stable dispersions is in between$-10\mathrm{rice}V$i$-15\mathrm{rice}V$No foaming agent is added to purified water. In addition, the reasons for bubble stabilization are discussed.

Minerals Engineering, Volume 116, 2018, Pages 32-34

Gas dispersion parameters (air entrapment - yes)._G, air surface velocity-Jg and bubble surface flow-Sb), the concentration of nanobubbles formed in the hydrodynamic cavitation tube was measured separately. The best results obtained at an air/liquid volume ratio of 30%; 49m nautical miles⁻¹Air/liquid interfacial tension results in 16% air entrapment and a Jg of 0.87 cm⁻¹, in the year 85 Sb⁻¹and nanobubbles (230–280nm)The concentration is 6.4×10⁸NBsmL⁻¹.The lower the air/liquid interfacial tension, the higher the air retention rate; this occurs by promoting cavitation and the formation of micro- and nano-sized gas bubbles. The obtained data are discussed in terms of solutions, hydrodynamics and interfacial phenomena. The main mechanisms involved in the action of nanobubbles and their interaction with solids and larger bubbles are predicted. These discoveries are believed to be important because techniques and equipment are needed to produce nanobubbles at low cost and at high speeds. This work shows that the tested cavitation tubes have great potential due to the large size of the formed bubbles and the high flow achieved on the surface of the bubbles, especially due to the high concentration of generated nanobubbles. These gas bubbles are of great importance in the separation of pollutants in modern flotation of small minerals and wastewater treatment, and some examples are presented and discussed.

Journal of Colloid and Interface Science, svezak 596, 2021., stranice 184-198

Mineral Engineering, Volume 94, 2016, Pages 29-37

Nanobubbles (NB) possess interesting and exotic properties, such as high stability, long lifetime, and large surface area per unit volume, leading to important applications in mining, metallurgy, and the environment. NBs are also of great interest for the study of interfacial phenomena involving long-range hydrophobic attraction, microfluidics, and adsorption on hydrophobic surfaces. However, there is little data on the efficient creation of concentrated aqueous dispersions of NB and their physicochemical and surface properties. In this work, air was dissolved in pH 7 water at different pressures, and depressurized using a needle valve to create 150–200 nm (mean diameter) NB and MBs microbubbles (about 70 μm). Micrographs of NB were taken only in the presence of methylene blue dye as a contrast agent. The main results show that high NB concentration (amount per unit volume) can be achieved by reducing saturation pressure and surface tension. Number of NBs at 2.5 bar of 1.0×10⁸NB ml⁻¹at 72.5 mNm⁻¹do 1,6×10⁹NB ml⁻¹na 49mNm⁻¹(100 mg l⁻¹alpha-terpineol). The average diameter and concentration of NBs changed only slightly over 14 days, demonstrating the high stability of these high-concentration aqueous NB dispersions. Finally, after NBs were attached to the surface of pyrite particles (a rather hydrophobic mineral), NBs significantly increased the number of MBs, indicating increased particle hydrophobicity due to NB adhesion. The results are explained by surface phenomena, and it is believed that these tiny air bubbles dispersed in water in high concentrations will lead to cleaner and more sustainable mineral flotation.

Advances in Colloid and Interface Science, svezak 246, 2017., stranice 40-51

This review article compares research conducted in the field of microbubbles and nanobubbles, with a special emphasis on water treatment. Based on the interpretation of different researchers, basic definitions of bubble types and their size ranges have also been proposed. Characterization parameters of state-of-the-art measurement and analysis techniques for microbubble and nanobubble technology are summarized. Some main applications of these technologies in water treatment processes are presented and briefly discussed. Based on the review, various potential research areas and gaps in the application of air bubbles in water and wastewater treatment technologies have been identified for further study. This article has been prepared in such a way as to provide a step-by-step introduction to the topic with the aim of focusing on the application of microbubbles and nanobubbles in water purification technology.