The work is devoted to the study of adsorption of F- ions on red mud, which is a waste of Vietnam's alumina plant. The red mud was previously activated with a solution of H2SO4 (2M) with a solid / liquid ratio of 1: 2. Investigation of adsorption at pH = 6.8; room temperature and adsorption time of 120 minutes showed that the maximum adsorption capacity of F- ions reached 9.4 mg / g. The kinetic regularities of the process are described by a second-order equation, the isotherm of the adsorption of F- ions is characterized by the equations of Langmuir and Freundlich. The test of the activated red mud on real samples of wastewater containing fluoride ions showed that the quality of the water after treatment satisfies the permissible standard of Vietnam for industrial wastewater.
Protecting the green - clean - beautiful living environment is a matter of concern for the whole world. There are many global or regional conferences held to discuss and find a way to solve that problem. In which, climate change, energy depletion and greenhouse effect are hot issues, this is one of the great challenges for all mankind because they are directly affecting ecology. environment and human life.
Compound reconfigurable antennas have been studied in recent research for modern wireless communication systems due to their advantage of multifunctional capabilities. In this paper, a novel composed structure of frequency and radiation pattern reconfigurable antenna is proposed. The antenna uses four pseudo-Fibonacci curves and the E shape of Defected Ground Structures (DGS) to make the varied directivity radiation. The steering beam along can achieve based on the position of the active PIN diode in different directions. The resonant frequency can also switch from one to other bands depending on the number of active PIN diodes. The antenna gets a compact size of 30mm x 30mm x 1.6mm that can be fit on a small form factor while still being able to scan along with 8 radiation directions of 0°, 90°, 180°, 270°, or 45°, 135°, 225°, 315° and 4 frequencies at 3.5GHz and 5GHz bands. The antenna directivity reaches 2.283dBi and 4.185dBi at 3.5GHz and 5GHz bands, respectively. The simulation, measurement, and experiment results agree well to ensure the proposed reconfigurable antenna can apply for terminals in 5G IoT, 5GHz WLAN, or cognitive radio systems.
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