Micro-nano Bubble Research Articles

Recyclable cellulose nanofibrils composite film derived from bamboo fiber tableware waste

The world faces a serious environmental pollution from petrochemical plastic. Sustainable green cellulose films can be employed as an alternative to plastic films, thus providing a solution to the pollution caused by the latter. In this study, cellulose nanofibrils (CNF) with low food content were extracted from food solutions of discarded bamboo fiber tableware using micro-nano bubble technology. The CNF were then stabilized in oil-water emulsions to form a biobased CNF-food solution composite film using the solvent casting method. The composite film treated with micro-nano bubbles called post-cleaning bamboo fiber tableware(PS-BFT) exhibited a significantly better mechanical strength, transparency, and thermal performance than those of stained bamboo fiber tableware(S-BFT), and even better transparency and thermal performance than those of clean bamboo fiber tableware(C-BFT). Furthermore, microscopic observations revealed that the films with a high food content exhibited a clear multilayer structure, while those with a lower food content presented only a few agglomerations of food solution-fiber. This confirms the cleaning effect of micro-nano bubbles on the residual food solution in discarded tableware and demonstrates their potential in the high-value utilization of secondary fibers.

Micro-nano bubble water with potassium fertigation improves strawberry yield and quality by changing soil bacterial community

Aerated drip irrigation can increase the soil oxygen content and improve the utilization efficiency of fertilizer. However, limited information is available on how soluble potassium fertilizer with different aeration levels affects plant yield and quality. Specifically, the underlying mechanism associated with microbial community level has not been reported so far. In this study, a micro-nano bubble water (MNBW) drip irrigation experiment was conducted in a strawberry plantation greenhouse, with three ratios of MNBW and two potassium application amounts and a control treatment (without MNBW). The results showed that compared with the CK (no aeration, 100% traditional potassium fertilizer application, 144 kg hm−2 of potassium sulfate), MNBW irrigation improved the soil oxygen content and changed the structure and functionality of the soil microbial community in the strawberry rhizosphere. The bacterial diversity was reduced, and the microbial co-occurrence patterns were altered. The soil respiration intensity increased by 1.32%–14.22%. The soil temperature increased, and the decomposition of organic matter was enhanced. It was indicated that the increase of soil oxygen had a positive impact on soil fertility, strawberry yield, and quality under the condition of reducing potassium application. The yield and quality of strawberries in MNBW treatments were significantly higher than those treated with CK (p < 0.05), but the carbon dioxide emissions significantly increased. High potassium fertilizer application amount and MNBW ratio did not mean high yield and quality of strawberries. Thus, O20K70 (20% of irrigation water with micro-nano bubbles, 70% of traditional drip irrigation potassium fertilizer level, 101 kg hm−2 of potassium sulfate) and O60K70 (60% of irrigation water with micro-nano bubbles, 70% of traditional drip irrigation potassium fertilizer level, 101 kg hm−2 of potassium sulfate) could be chosen for strawberry plantations with MNBW.

Hydrodynamic cavitation degradation of hydroquinone using swirl-type micro-nano bubble reactor

ABSTRACT This study reports the degradation of hydroquinone using lab-scale hydrodynamic cavitation approach (aswirl-type micro-nano bubble reactor), which is considered a green and effective method. The effects of inlet pressure, gas flow rate, pH and initial hydroquinone concentration on hydroquinone degradation were analysed based on experimental research. After experiments investigation, it was concluded that with pH 7.38, hydroquinone concentration of 50 mg/L, and int pressure of 0.2 MPa, the degradation efficiency of hydroquinone reached 91.25% in wastewater. Furthermore, this study also investigated the degradation effect of hydroquinone wastewater by hydrodynamic cavitation combined with persulfate oxidation (HC + PS). The kinetics of hydroquinone degradation by HC or PS oxidation alone and HC + PS oxidation were also examined. Compared with the degradation method alone, the degradation of hydroquinone by HC + PS was more pronounced, and the enhancement factor was 4.55, which indicates that HC greatly enhances the oxidation capacity of PS. In additon, from viewpoint of energy consumption and operating cost, the synergy of HC + PS (1.05 mM) is also the most promising combination. Based on the detection results of the Gas chromatography-mass spectrometry (GC-MS) the possible degradation pathways of hydroquinone were analysed: under the action of ·OH and the high temperature and pressure by cavitation process, the hydroquinone molecule undergoes dehydrogenation and ring-opening reaction, demethylation and decarboxylation reaction to produce intermediate products, which are finally converted into CO2 and H2O in micro-nano bubble cavitation process.

Numerical Simulation and Structural Optimization of Swirl Flow Micro-Nano Bubble Generator

The development of the bubble generator that can efficiently generate micro-nano bubbles has always been recognized as a challenge. Swirling flow is considered to be an efficient method to enhance hydrodynamic cavitation. The vortex supply chamber and the variable-diameter accelerated vortex cavitation reaction chamber were combined to obtain a stable high-speed tangential liquid flow and improve the cavitation effect inside the generator in this study. The central air intake column was innovatively installed above the cavitation reaction chamber, which prolonged the shear fracture time of bubbles under high shear force and improved the gas–liquid contact and mixing efficiency. The influence of geometric parameters on the internal and external flow fields of the generator was analyzed through the numerical simulation. The optimized central air intake column was located 10 mm above the inlet of the cavitation reaction chamber. The optimized variable diameter contraction angle was 16°, and the optimized generator outlet diameter was 15 mm. Through the bubble performance test, it was verified that the micro-nano bubbles with the minimum size and average size of 0.31 μm and 3.42 μm could be generated by the manufactured generator. The enforcement of the research provided theoretical guidance and data support for the development of efficient micro-nano bubble generators.

Enhanced treatment of azo dyes in wastewater using heat-activated persulfate with micro-nano bubble aeration

Azo dyes-containing wastewater can lead to environmental issues and pose threats to public health. The efficient degradation of azo dyes with novel and potent techniques, remains a challenge. This study presented an innovative utilization of micro-nano bubble aeration technology to improve the treatment of Rhodamine B through heat-activated persulfate oxidation. Through single factor experiments, the impacts of persulfate concentration, temperature, initial Rhodamine B concentration, and pH values were systematically explored on the degradation of Rhodamine B in heat-activated persulfate oxidation. The removal rate of Rhodamine B was 94.53% optimized by Response surface optimization method. The reaction rate was in the range of 0.0109–0.0528 min−1, governed by pseudo-first-order kinetics. By applying the Arrhenius equation, the activation energy was determined to be 14.06 KJmol−1. Furthermore, properties of micro-nano bubbles and their synergistic coefficient were investigated in heat-activated persulfate oxidation. Quenching tests revealed the predominance of sulfate radicals, and full wavelength scanning facilitated an in-depth investigation of the reaction mechanism. Additionally, a proposed electron shell structure elucidated the decomposition process of Rhodamine B. Therefore, the implementation of micro-nano bubble aeration technology based on heat-activated persulfate oxidation, held the promise as an efficient and effective approach for the treatment of printing and dyeing wastewater.

Effect of Micro-Nano Bubble Water and Silica Fume on Properties of C60 Concrete.

Micro-nano bubble water (WNBW) in concrete is relatively uncommon due to its newness as a technology. This paper presents the preparation of C60 concrete with 35% fly ash (FA) through WNBW and varying amounts of silica fume (0%, 4%, 7%, and 10% SF). The study examines the impact of WNBW and SF on the working performance, compressive strength, and durability of concrete. The findings indicate that applying WNBW and SF independently or jointly deteriorates the working performance of fresh concrete. However, compared to regular mixing water, WNBW reduces the concrete passing time through the V-funnel, decreasing by 40%, 39.1%, 42.9%, and 50.5% for the four varying SF contents. Furthermore, using WNBW, SF, or both resulted in the increased compressive strength of concrete at 7 days and 28 days, with 7% SF content yielding a 12.2% and 6.6% increase, respectively. Using a combination of WNBW and SF has been shown to decrease the impermeability of concrete effectively. The addition of 4% SF results in the lowest electric flux when using regular mixing water, with a discernible decrease of 30.1% compared to the control group. Conversely, using WNBW as mixing water yields a decrease in electric flux at each SF content, with the maximum decrease being 39.7%. Furthermore, both the single and combined use of these materials can contribute to the reduction in the carbonation resistance of the concrete. C60 concrete mixed with 7% SF and 100% WNBW boasts enhanced frost resistance, as indicated by the mass loss and dynamic elastic modulus loss being the least following freeze-thaw under the same SF content. According to the findings of the tests, there is evidence that the incorporation of 7% SF and 100% WNBW into C60 concrete results in lowered viscosity, a highly advantageous attribute for actual construction. Additionally, this mixture displays impressive compressive strength and durability properties. These results provide technical support regarding the integration of WNBW and SF in C60 concrete.

Micro-nano bubble water process: Effect of micro-nano bubble water as mixing water on volume stability of shotcrete

As a kind of active water, micro-nano bubble water (MBW) can promote the early hydration of cement paste and improve the early mechanical strength of shotcrete. However, accelerating the hydration process of cement-based materials will increase their shrinkage deformation to a certain extent at early age. Therefore, this paper mainly studies the effect of MBW combined with aluminum sulfate alkali-free accelerator (AL) on the volume stability of cement-based materials within 180d. The results show that MBW as mixing water can reduce the autogenous and drying shrinkage of cement-based materials with AL, and also has a certain mitigation effect on water loss rate and internal humidity (IH) drop under dry conditions. It can also reduce the ring constraint shrinkage cracking time and crack width. MBW can reduce the cement paste pore size distribution of 10–50 nm, and reduce the surface tension of the aqueous solution, thereby reducing the capillary tensile stress. This paper provides some theoretical guidance for micro-nano bubble water in practical engineering applications.

Enhanced oxidation of aromatic hydrocarbons by ozone micro-nano bubble water: Mechanism and influencing factors

Aromatic hydrocarbons are common contaminants in groundwater, which could threat human health through multiple ways and have low degradation rates. Micro-nano bubble ozonation has been developed as a novel technology to oxidize organic contaminants effectively. Since most technologies such as dissolved air flotation (DAF) could only produce ozone micro-nano bubble water (OMBW) instead of independent ozone micro-nano bubbles, the comparison between OMBW and ozonated water (OW) had more significant implications. This study investigated the oxidation rate of four aromatic hydrocarbons (AHs) including toluene, ethylbenzene, o-xylene and p-xylene by both OW and OMBW at the same dissolved ozone concentration through a series of batch experiments. Results showed that the oxidation rate of AHs by OMBW was 13.6–22.6% higher than that by OW when solution pH was 8, which was mainly caused by the promoted contact between AHs and OH·at the micro-nano bubble interface. This conclusion was also validated by the faster increase of reaction rate between OH·and AHs for OMBW when solution pH increased from 5 to 9, leading to the increase of OH·utilization rate in alkaline environment. The inhibition effect by anions (Cl-, SO42- and HCO3-) as well as dissolved organic matter, and the promotion effect by Mg2+ were both magnified in OMBW, which was also caused by the interfacial effect of micro-nano bubble. This study was critical to our understanding of the removal behavior of organic contaminants by OMBW, and it would also guide the design of more efficient oxidation technologies based on micro-nano bubbles.

Ozone micro-nano bubble water preserves the quality of postharvest parsley

The production and use of ozone micro-nano bubble water (O3-MNBW) is an innovative technology that prolongs the reactivity of aqueous-phase ozone and maintains the freshness and quality of fruits and vegetables by removing pesticides, mycotoxins, and other contaminants. The quality of parsley treated with different concentrations of O3-MNBW was investigated during storage at 20 ℃ for 5 d, and found that a ten-minute exposure of parsley to 2.5 mg·L−1 O3-MNBW effectively preserved the sensory quality of parsley, and resulted in lower weight loss, respiration rate, ethylene production, MDA levels, and a higher level of firmness, vitamin C, and chlorophyll content, relative to untreated parsley. The O3-MNBW treatment also increased the level of total phenolics and flavonoids, enhanced peroxidase and ascorbate peroxidase activity, and inhibited polyphenol oxidase activity in stored parsley. Five volatile signatures identified using an electronic nose (W1W, sulfur-compounds; W2S, ethanol; W2W, aromatic- and organic- sulfur compounds; W5S, oxynitride; W1S, methane) exhibited a significant decrease in response to the O3-MNBW treatment. A total of 24 major volatiles were identified. A metabolomic analysis identified 365 differentially abundant metabolites (DMs). Among them, 30 and 19 DMs were associated with characteristic volatile flavor substance metabolism in O3-MNBW and control groups, respectively. The O3-MNBW treatment increased the abundance of most DMs related to flavor metabolism and reduced the level of naringin and apigenin. Our results provide insight into the mechanisms that are regulated in response to the exposure of parsley to O3-MNBW, and confirmed the potential use of O3-MNBW as a preservation technology.

Develop an optimal washing and care mode for knapsack

In order to develop a suitable washing mode for knapsack, mechanical agitation (1), water bath vibration (2), ultrasonic (3), micro-nano bubble (4) and complex washing mode of the two were systematically investigated. Results showed that regardless of fabric, the washing efficiency of composite washing mode {mechanical agitation + ultrasonic (1 + 3), mechanical agitation + micro-nano bubble (1 + 4)}, was highest among all washing modes. Moreover, the decrease of stiffness, tensile strength, smoothness and micro-morphology of knapsack by using complex washing mode {mechanical agitation + ultrasonic (1 + 3), mechanical agitation + micro-nano bubble (1 + 4)} significantly lower than that of mechanical agitation. This indicated that mechanical agitation was the key to remove stain, micro-nano bubbles and ultrasound only assisted its removal. But the addition of micro-nano bubbles and ultrasound was helpful to improve the washing efficiency and reduce the performance degradation caused by washing mode of mechanical agitation. Complex washing mode {mechanical agitation + ultrasonic (1 + 3), mechanical agitation + micro-nano bubble (1 + 4)} was optimal washing combination for knapsack, especially the composite mode of mechanical agitation + ultrasonic (1 + 3), due to its ability to remove residual stains in the inner layer and slit. Moreover, the complex washing mode was also more environmental-friendly and sustainable, compared to other washing mode, because of washing time and detergent dosage reducing occurred by its high washing efficiency. The results were not only helpful to guide manufacturers of washing machine to develop a program dedicated to the daily washing and care knapsack, but also provided scientific care guidance and optimization ideas for subsequent research and applications.

Chemically-induced active micro-nano bubbles assisting chemical mechanical polishing: Modeling and experiments

The material loss caused by bubble collapse during the micro-nano bubbles auxiliary chemical mechanical polishing (CMP) process cannot be ignored. In this study, the material removal mechanism of cavitation in the polishing process was investigated in detail. Based on the mixed lubrication or thin film lubrication, bubble-wafer plastic deformation, spherical indentation theory, Johnson-Cook (J-C) constitutive model, and the assumption of periodic distribution of pad asperities, a new model suitable for micro-nano bubble auxiliary material removal in CMP was developed. The model integrates many parameters, including the reactant concentration, wafer hardness, polishing pad roughness, strain hardening, strain rate, micro-jet radius, and bubble radius. The model reflects the influence of active bubbles on material removal. A new and simple chemical reaction method was used to form a controllable number of micro-nano bubbles during the polishing process to assist in polishing silicon oxide wafers. The experimental results show that micro-nano bubbles can greatly increase the material removal rate (MRR) by about 400% and result in a lower surface roughness of 0.17 nm. The experimental results are consistent with the established model. In the process of verifying the model, a better understanding of the material removal mechanism involved in micro-nano bubbles in CMP was obtained.

Effect of dissolved organic matter on selective oxidation of toluene by ozone micro-nano bubble water

The oxidation capacity of ozone micro-nano bubble water (OMBW) was always higher than ozonated water due to enhanced contact by bubble interface, while the effect of coexisted dissolved organic matter (DOM) on the oxidation efficiency was still unclear. In this paper, batch experiments were carried out to investigate the selective oxidation of toluene by both OMBW and ozonated water (OW) with coexisted DOM in water. Five types of background solutions were applied in this study, including humic acid solution, fulvic acid solution and three types of diluted landfill leachates at the same content of total organic carbon. Results showed that coexisted DOM had a greater inhibition effect on toluene oxidation rate by OMBW, and the oxidation rate of toluene by OMBW and OW became close. It was mainly caused by the decreased reaction rate between toluene and hydroxyl radical (kT-OH·) in OMBW after the introduction of DOM, which competed for the adsorption sites on micro-nano bubble interface. The fraction of ozone to oxidize toluene as well as kT-OH· was in positive correlations with SUVA254 and the content of humic acid-like substances, but negatively correlated with E2/E3, content of tryptophan-like proteins and content of fulvic acid-like substances. In addition, increasing the ozone dose was not effective in increasing the utilization rate of ozone in OMBW due to limited adsorption sites on micro-nano bubble interface. The paper was conductive to the application of ozone micro-nano bubble water in groundwater remediation with complex water matrices.

Study on Treatment of Basic Yellow 28 dye Wastewater by Micro-nano Bubble Ozone Catalytic Oxidation

Mn loaded AC (Mn/AC), Cu loaded AC (Cu/AC), and Fe loaded AC (Fe/AC) catalysts were prepared by the impregnation-calcination method, which can be used to degrade Basic Yellow 28 dyes in simulated printing and dyeing wastewater for catalytic ozonation. The catalyst preparation and reaction conditions were optimized with the degradation efficiency of chemical oxygen demand (COD) and the absorbance of some organic compounds under 254 nm UV light (UV254) as indicators. The surface structure, specific surface area, and active component distribution of the catalysts were analyzed by scanning electron microscopy (SEM), nitrogen adsorption, and X-ray diffraction (XRD) characterization. Results indicated that Mn was the best active component, and a catalyst dosage of 3.5 g/L, an initial pH of 9.4, and an initial temperature of 31.7°C were the best reaction parameters to degrade Basic Yellow 28 dyes. After five recycling experiments, the catalysts could retain a relatively stable catalytic effect. Furthermore, this study can be informative for the sustainable development of future catalysts.

Comparison of Ozone Production by Difference DBD Configuration Reactor and Dissolved Ozone in Waterwith Micro-Nano Bubble Technology

Comparison of Ozone Production by Difference DBD Configuration Reactor and Dissolved Ozone in Waterwith Micro-Nano Bubble Technology

Experimental Study on Properties of Cement Mortar with Micro-Nano Bubble Water

Experimental Study on Properties of Cement Mortar with Micro-Nano Bubble Water

Study on frost resistance of shotcrete by micro-nano bubble water and admixture

Shotcrete was prepared by using micro-nano bubble water as mixing concrete water in cooperation with air-entraining agent (AOS-R) and superabsorbent polymer (SAP), and its frost resistance performance was experimentally studied. The results show that the incorporation of AOS-R and SAP will reduce the 28-day strength of concrete, but MNBW can compensate for the strength loss to a certain extent. The frost resistance of concrete mixed with alkali accelerators is inferior to that of concrete mixed with the alkali-free accelerator. The incorporation of AOS-R or SAP into shotcrete can improve its frost resistance to in some degree as well. Given the frost resistance of concrete mixed with SAP is not as effective as AOS-R, MNBW can play a synergistic effect to improve the frost resistance of concrete. The main reason why the AOS-R improves the frost resistance of concrete is that it generates a large number of small bubbles to isolate the water transmission channel which manage to relieve the crystallization pressure of water. MNBW improves the frost resistance of concrete, because it refines the pore structure and increases the density of concrete.

Effects of aerated brackish water irrigation on growth of Lycium barbarum seedlings

The management of Lycium barbarum seedling has an important influence on its fruit yield and quality at mature stage. Pot experiments were conducted to investigate the effects of four water salinity levels (0.6 (fresh water), 1.5, 3.0 and 4.5 g/L) under non-aeration (O2 content of 8.5 mg/L) and aeration (15.0 mg/L) irrigation on soil enzyme activity and the physiological parameters and growth status of Lycium barbarum seedlings. The results showed that brackish water irrigation increased soil electrical conductivity by 1.8 – 5.8 times, inhibited soil enzyme activities by 12.1% – 52.0%, and decreased the net photosynthetic rate by 10.7% – 24.8%, transpiration rate by 24.3% – 27.3%, and plant water consumption by 0.9% – 18.0% compared with fresh water irrigation. Brackish water irrigation also significantly inhibited the growth of leaves, base stem, roots and biomass of Lycium barbarum seedlings. Compared with non-aeration irrigation, the micro-nano bubble aerated brackish water irrigation promoted the activities of urease and alkaline phosphatase by 0.5% – 33.0% and 4.4% – 9.0%, respectively, and increased net photosynthetic rate by 3.3% – 8.0%, plant transpiration rate by 0.1% – 25.3%, and water consumption by 0.7% – 5.0% under brackish water irrigation. It also promoted the growth of leaves, branches, base stem and roots, and increased the biomass accumulation of Lycium barbarum seedlings by 7.4% – 9.3%. The aerated water irrigation with micro-nano bubbles can alleviate the negative effects of salt stress on the growth of Lycium barbarum seedlings to varying degrees, so the salinity of irrigation water less than 3.0 g/L combining with the aerated disposal is suggested to be as an optional solution to the planting of Lycium barbarum seedlings in arid oasis regions.

Microalgae removal technology for the cold source of nuclear power plant: A review.

In the past three decades, nuclear energy has gained much attention as carbon-free electricity. Due to the supply of cooling water in nuclear power plant, large amount of waste heat will increase the water temperature, promote the microalgae and cyanobacteria propagation and increase the chance of red tide. Excess phytoplankton of cool source will result in abnormal operation of cooling system, even core overheating and nuclear leakage. Consequently, it is very important to remove microalgae and cyanobacteria from cold source of nuclear power plants. This review summarizes the formation mechanism and monitoring methods of red tide, compares the advantages and disadvantages of traditional microalgae removal technology including physical, chemical and biological methods. Furthermore, the improved electrochemical method and micro-nano bubble method are introduced in detail. Their combination is considered to be a low-cost, efficient and environmentally-friendly technology to prevent and control red tides for cold source of nuclear power plant.

Effects of Different Concentrations of Micro-Nano Bubbles on Grain Yield and Nitrogen Absorption and Utilization of Double Cropping Rice in South China

Micro-nano bubble (MNB) irrigation can effectively improve the hypoxia stress caused by conventional irrigation and shows great potential in plant development, yield improvement, and saving of water and fertilizer, and has been recognized as a new and high-efficiency technology in crop planting. However, former research on MNB concentration had no clear segmentation, and other MNB concentrations can achieve better or worse effects. This remains to be further explored in order to explore the optimal concentration of MNBs for the yield and nitrogen absorption and utilization of the double cropping rice. With early rice Ganxin203 and late rice WufengyouT025 as the experimental cultivars, the effects of MNBs on growth, yield, and nitrogen absorption and utilization of the potted double cropping rice were analyzed by setting three concentrations of MNBs (LM, low concentration; MM, middle concentration; HM, high concentration), compared with the ordinary running water (CK). Compared with CK, grain yield of the early rice under the MNB treatment increased by 4.84~10.95% and the late rice increased by 6.10~14.31%. It was found that the higher the concentration of the MNBs, the higher the yield of the rice. This is due to that the MNBs improved the tiller-bearing rate, increased the SPAD and Pn values of the flag leaves in the whole growth period, slowed down the drop of the leaf SPAD and Pn from heading stage to maturity, increased the number of the adventitious roots, improved the α-NA oxidation of the root, and simultaneously promoted the nitrogen accumulation, absorption, and utilization. The HM treatment obtained the best benefits, and the effect of the MNBs on the late rice was better than the early rice.

Generation of micro-nano bubbles by self-developed swirl-type micro-nano bubble generator

The fabrication of bubble generator with high micro-nano bubble generation efficiency has always been challenging. Strong turbulence is considered to be beneficial. Herein, we developed a swirl-type micro-nano bubble generator by equipping a variable-pitch spiral cavitation reactor to enhance the shear breakage effect of bubbles. The variable-pitch spiral guide vanes and central column were innovatively installed into the cavitation reactor to generate swirling liquid flow so as to intensify gas-liquid contacting and mixing. The effect of geometric parameters on the flow field structure was investigated through numerical simulations and the optimum structure was obtained. Then the lab-scale swirl-type micro-nano bubble generator was manufactured to conduct flow tests. The bubbles with size down to 0.301 μm were generated. In addition, the bubble generator displayed superior oxygen enrichment capacity, which was higher than that of the traditional venturi tube. The insights from this study provide a guideline for the development of efficient micro-nano bubble generators.