Domestic wastewaters and industrial wastewaters from food processing industry, pulp industry, pharmaceutical and organic synthesis industries, coalmines and mines contain various inorganic and organic substances in the form of fine suspension, emulsions, colloids, etc. In particular, the microplastics contained in wastewater pose a potential threat to the environment and human health due to their small particle size, high hydrophobicity and easy adsorption of toxic substances.

There are several methods for treating wastewater containing microplastics, among which the dissolved air flotation (DAF) process using microbubbles has attracted special attention. DAF process is one of the wastewater treatment methods for accelerating gravity separation by adhering microbubbles to solid particles in wastewater and increasing the density difference between continuous and dispersed phases.

Most of the previous studies have paid a great deal of attention to the structure of DAF tanks and fluid flow characteristics, and little effort has been directed to the effect of liquid properties on flotation efficiency.

Since the objective of the DAF process is to increase the efficiency of impurity removal under constant hydraulic surface loads, it is also important to have a correct understanding of the interaction characteristics between particles to be removed, bubbles and liquid phases.

Kim Kwang Jun, a researcher at the Institute of Nano Science and Technology, has simulated the process of dissolved air flotation (DAF) to remove microplastics from various wastewaters by the computational fluid dynamics (CFD) method.

First, he injected a solution with a resin particle concentration of 0.2 g/L at a flow rate of 20 mL/min. Then, he injected a solution with a water-to-microbubble volume ratio of 4:1 at a flow rate of 300 mL/min. The simulation results showed that the kinematic and distribution characteristics of the resin particles and microbubbles were in good agreement with the experimental results.

Based on the simulation system to analyze the behavior of particles in flotation solutions, he evaluated the flotation performance by varying the concentration of NaCl solution and the pH value of 10-2 M salt solution. The calculation results showed that the flotation performance improved with increasing NaCl concentration and pH, and the concentration of NaCl had a greater effect.

These results provide some basic information for designing industrial wastewater treatment processes for removing microplastics from wastewater of different properties.

For further details, you can refer to his paper “CFD Simulation of DAF processing for removal microplastic in different flotation solution” in “Water Science & Technology” (SCI).

Quick-freezing is an essential process for long-term storage and long-range transport of fish. With the development of fish processing, it is very important to realize automatic line of fish quick-freezing processes and increase quick-freezing capacity.

Therefore, wheeled mobile loaders (WMLs) are important for automatic line of fish processing.

Pak Myong Nam, a researcher at the Institute of Robotics, evaluated the static stability of a newly designed WML in consideration of its structure, working principle and overturning moment. Then, he analyzed the effect of parameters on its dynamic stability by using ADAMS and conducted an analysis of variance (ANOVA) to optimize its design parameters.

The results show that dynamic analysis of collision force acting on the wheels can be effectively used to improve the vibration characteristics of WMLs, and that dynamic stability simulations and design optimization for all the working processes can reduce vibration and eliminate overturning tendency.

If more information is needed, please refer to his paper “Dynamic Stability Simulation and Design Optimization of the Wheeled Mobile Loaders for Automatic Line of Fish Processing” in “Journal of Vibration Engineering & Technologies” (SCI).

Scandium has been widely used as alloy material in the fields of aerospace, optics, transport, etc. Scandium is an effective grain refiner and it increases the recrystallization temperature in different alloys with its unique property.

The amount of Sc in the earth’s crust is 22ppm on average. Scandium is found in small amounts in other metal ores. Minerals containing Sc include monazite, bastnasite, ilmenite, rutile, bauxite, uraninite, etc.

Several researchers have employed different methods for determining the amount of scandium. These methods have several disadvantages like complex pretreatment procedure and long pretreatment time.

An Hyo Song, a researcher at the Institute of Analysis, has proposed a new method for determining scandium content in the sedimentary rock based apatite on the continental shelf using Ti as an internal standard element by wavelength dispersive X-ray fluorescence spectrometry (WDXRFS) technique, and established a sample preparation procedure and the parameters of equipment.

RSD of the proposed method was less than 5%. The average scandium content in the total survey area was 25ppm.

The proposed WDXRF technique can be applied to the studies of different geological materials containing less than 1% of scandium.

For more information, you can refer to his paper “Analytical Method for Determination of Scandium Distribution Characteristics in Sedimentary stratum on the Continental shelf by Wavelength Dispersive X-ray Fluorescence Spectrometry” in “Journal of X-ray science and technology” (SCI).