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.
Nickel is one of the toxic heavy metals, it is widely used in our daily lives, so there is a lot of risk of being released into the water to poison the human, flora, and fauna. In this study, we investigated the adsorption of Ni(II) on calcium alginate beads (CA), a natural polysaccharide with many outstanding advantages. The effects of initial pH, adsorptive times, and initial concentration of Ni(II) on the adsorption process were investigated. The results showed that the pH value of 3‐7.5 was favorable for the adsorption of Ni(II) on CA, the equilibrium adsorption started 60 minutes. The pseudo‐second order kinetic equation, both Langmuir and Freundlich isothermal models were fit to describe the experimental data. The maximum adsorption capacity reached 6.48 mg/g with wet alginate calcium beads, corresponding to 144 mg/g dry beads. Materials after adsorption were also studied desorption for reuse.
In this study, waste rubber powder (WRP) was devulcanized by ultrasonic in alkaline medium and blended with the different ratios of ethylene‐propylene‐diene copolymer EPDM/PP (polypropylene) and the coupling agent of dicumyl peroxide (DCP) to produce WRD/EPDM/PP polymer blends. With the concentration of 10 wt.% WRP gived the mechanical properties of blends before and after accelerated weathering testing were approxiated with those of EPDM/PP 30/70 blends. The presence of DCP improved the tensile at strength and thermal resistance, caused by interaction between EPDM and PP. Result of thermogravimetric analysis showed that the presence of 0.5 % DCP gaved the maximum thermal resistance of polymer blends up to 380°C.
In this study, waste rubber powder (WRP) was devulcanized by ultrasonic in alkaline medium and blended with the different ratios of EPDM/PP and the coupling agent of dicumyl peroxide (DCP) to produce WRD/EPDM/PP polymer blends. With the concentration of 10 wt.% (by weight) WRP gived the mechanical properties of blends before and after accelerated weathering testing were approxiated with those of EPDM/PP 30/70 blends. The presence of DCP improved the tensile at strength and thermal resistance, caused by interaction beetwen EPDM and PP. The results of thermogravimetric analysis showed that the presence of 0.5 %DCP gaved the maximum thermal resistance of polymer blends up to 380°C.
The antioxidant capacity of polyphenols have been widely used in food and pharmaceutical industries. Quercetin (Quer) is a polyphenolic flavonoid that shows several biological effects such as antioxidant, antitumor, antibacterial and antiproliferative effects both in-vitro and in-vivo. However, the solubility of quercetin in water is poor. Thus, it is essential to improve solubility of quercetin in pharmaceuticals by making its complexation with other compounds. In this study, the synthesis of the 2-hydroxypropyl-β-cyclodextrin complex with quercetin (Quer-HPβCD) in the form of nanoparticles in water-ethanol solvents has been carried out. The results showed that the obtained yield of (Quer-HPβCD) complexation in binary solvent was greater than that in pure water. The highest Y value was 80% in a binary solvent with 20% v/v of ethanol. The composition, morphology, structural and thermodynamic properties of the nanoparticles Quer-HPβCD have been determined. This study demonstrated that using mixed water- ethanol solvent and lyophilization technique was able to produce quercetin nanoparticles with significantly smaller particle size. The nanoparticles have a spherical shape with an average size of about 40-60 nm. The results of the phase solubility diagram showed that in water the solubility of quercetin increased and linearly depended on the concentration of host’s molecule while Quer and HP-βCD obtained a 1:1 stoichiometric complex. The stability constant of (Quer-HPβCD) complex was found to be logK = 2.56. The Gibbs energy change of the complexation reaction was found to be -14.60 kJ/mol.
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