Novel ultrasonic technology for advanced oxidation processes of water treatment.

Textile wastewater accounts for a significant proportion of industrial wastewater worldwide. In particular, dye wastewater accounts for a large proportion and consists of non-degradable dyes, which are substances resistant to biodegradation. Methylene blue is a representative example of such non-degradable dyes. It is not biologically degraded and exhibits toxicity. Various methods for their decomposition are currently being studied. Advanced oxidation processes (AOPs), which generate highly reactive hydroxyl radicals that oxidize and degrade pollutants, have been actively studied. Particularly, the photocatalytic degradation method using TiO2 nanoparticles is one of the most actively studied fields; however, there are still concerns regarding the toxicity of nanoparticles. Research is currently being conducted on AOPs using the cavitation phenomenon of ultrasonic waves. However, achieving high efficiency using existing ultrasonic equipment is difficult. Therefore, in this study, we evaluated a new water treatment technology through AOPs using a focused ultrasonic system with a cylindrical piezoelectric ceramic structure. After determining the optimal conditions for degradation, the degradation process was evaluated as a useful tool for mitigating the toxicity of methylene blue. We found that, under the optimal conditions of 100 W intensity at a frequency of 400 kHz, this system is a helpful instrument for degradation and a new water treatment technology suitable for removing ecotoxicity and genotoxicity.

Preparation of Uniform Nano Liposomes Using Focused Ultrasonic Technology.

Liposomes are microspheres produced by placing phospholipids in aqueous solutions. Liposomes have the advantage of being able to encapsulate both hydrophilic and hydrophobic functional substances and are thus important mediators used in cosmetics and pharmaceuticals. It is important for liposomes to have small sizes, uniform particle size distribution, and long-term stability. Previously, liposomes have been prepared using a homo mixer, microfluidizer, and horn and bath types of sonicators. However, it is difficult to produce liposomes with small sizes and uniform particle size distribution using these methods. Therefore, we have developed a focused ultrasound method to produce nano-sized liposomes with better size control. In this study, the liposome solutions were prepared using the focused ultrasound method and conventional methods. The liposome solutions were characterized for their size distribution, stability, and morphology. Results showed that the liposome solution prepared using focused ultrasonic equipment had a uniform particle size distribution with an average size of 113.6 nm and a polydispersity index value of 0.124. Furthermore, the solution showed good stability in dynamic light scattering measurements for 4 d and Turbiscan measurements for 1 week.

Effect of the TiO2 Colloidal Size Distribution on the Degradation of Methylene Blue.

TiO2 is the most commonly used photocatalyst in water treatment. The particle size of TiO2 is an important factor that significantly influences its activity during photocatalytic degradation. In the presence of liquid, the properties of nanopowders composed of exactly the same product clearly differ according to their aggregation size. In this study, TiO2 nanoparticles with a controlled size were fabricated by focused ultrasound dispersion. The high energy generated by this system was used to control the size of TiO2 particles in the suspension. The constant high energy released by cavitation enabled the dispersion of the particles without a surfactant. The activities of the prepared TiO2 photocatalysts for methylene blue (MB) degradation were then compared. The dye degradation effect of the photocatalyst was as high as 61.7% after 10 min when the size of the powder was controlled in the solution, but it was only as high as 41.0% when the aggregation size was not controlled. Furthermore, when the TiO2 concentration exceeded a certain level, the photocatalytic activity of TiO2 decreased. Controlling the size of the aggregated photocatalyst particles is, therefore, essential in water-treatment technologies utilizing TiO2 photocatalytic properties, and adjusting the TiO2 concentration is an important economic factor in this photocatalytic technology. This study contributes to the development of processes for degrading dyes, such as MB, released from wastewater into aquatic environments.

Preparation of Surfactant-Free Nano Oil Particles in Water Using Ultrasonic System and the Mechanism of Emulsion Stability.

Emulsion technology is widely used in the preparation of cosmetics, pharmaceuticals, drug delivery, and other daily necessities, and surfactants are frequently used to prepare these emulsions because of the lack of reliable surfactant-free emulsification techniques. This is disadvantageous because some surfactants pose health hazards, cause environmental pollution, have costly components, and place limitations on process development. In this paper, an efficient method for surfactant-free nano-emulsification is presented. In addition, we discuss the effects of different operating parameters on the oil particle size, as well as the effect of the particle size on the emulsion stability. Specifically, we compared three surfactant-free ultrasonic emulsification technologies (horn, bath, and focused ultrasonic systems). The focused ultrasonic system, which concentrates sound energy at the center of the dispersion system, showed the best performance, producing emulsions with a particle size distribution of 60-400 nm at 400 kHz. In addition, phase separation did not occur despite the lack of surfactants and thickeners, and the emulsion remained stable for seven days. It is expected to be widely used in eco-friendly emulsification processes.

Effect of Particle Size on the Mechanical Properties of TiO2-Epoxy Nanocomposites.

This study investigated the effects of the packing density and particle size distribution of TiO2 nanoparticles on the mechanical properties of TiO2-epoxy nanocomposites (NCs). The uniform dispersion and good interfacial bonding of TiO2 in the epoxy resin resulted in improved mechanical properties with the addition of nanoparticles. Reinforcement nano-TiO2 particles dispersed in deionized water produced by three different ultrasonic dispersion methods were used; the ultrasonication effects were then compared. The nano-TiO2 suspension was added at 0.5-5.0 wt.%, and the mechanical and thermal properties of TiO2-epoxy NCs were compared using a universal testing machine, scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), and differential scanning calorimetry (DSC). The tensile strength of the NCs was improved by the dispersion strengthening effect of the TiO2 nanoparticles, and focused sonication improved the tensile strength the most when nano-TiO2 suspensions with a particle size of 100 nm or smaller were used. Thus, the reinforcing effect of TiO2 nanoparticles on the epoxy resin was observed, and the nano-TiO2 suspension produced by focused sonication showed a more distinct reinforcing effect.