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149 results on '"Humelnicu, Doina"'

20. Adsorption Capacity of Silica SBA-15 and Titanosilicate ETS-10 toward Indium Ions.

Author

Zinicovscaia, Inga, Yushin, Nikita, Humelnicu, Doina, Grozdov, Dmitrii, Ignat, Maria, and Humelnicu, Ionel

Subjects
ADSORPTION capacity, INDIUM, FREUNDLICH isotherm equation, QUANTUM chemistry, SORPTION, SILICA, INDIUM gallium zinc oxide
Abstract

Indium is an extremely important element for industry that is distributed in the Earth's crust at very low concentrations. The recovery of indium by silica SBA-15 and titanosilicate ETS-10 was investigated at different pH levels, temperatures, times of contact and indium concentrations. A maximum removal of indium by ETS-10 was achieved at pH 3.0, while by SBA-15 it was within the pH range of 5.0–6.0. By studying kinetics, the applicability of the Elovich model for the description of indium adsorption on silica SBA-15 was shown, while its sorption on titanosilicate ETS-10 fitted well with the pseudo-first-order model. Langmuir and Freundlich adsorption isotherms were used to explain the equanimity of the sorption process. The Langmuir model showed its applicability for the explanation of the equilibrium data obtained for both sorbents, the maximum sorption capacity obtained using the model constituted 366 mg/g for titanosilicate ETS-10 at pH 3.0, temperature 22 °C and contact time 60 min, and 2036 mg/g for silica SBA-15 at pH 6.0, temperature 22 °C and contact time 60 min. Indium recovery was not dependent on the temperature and the sorption process was spontaneous in nature. The interactions between the indium sulfate structure and surfaces of adsorbents were investigated theoretically using the ORCA quantum chemistry program package. The spent SBA-15 and ETS-10 could be easily regenerated by using 0.01 M HCl and reused with up to 6 cycles of adsorption/desorption with a decrease in the removal efficiency between 4% and 10% for SBA-15 and 5% and 10% for ETS-10, respectively. [ABSTRACT FROM AUTHOR]

Published
2023
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46. Removal of chromium(III) ions from aqueous solutions using different types of hydroxyapatites.

Author

Zinicovscai, Inga, Yushin, Nikita, Grozdov, Dmitrii, Humelnicu, Ionel, Humelnicu, Doina, and Mitina, Tatiana

Abstract

This study explored the possibility of using hydroxyapatite and its two modifications as sorbents to remove Cr(III) ions under different experimental conditions. The effect of pH (3-7), chromium concentration (10-100 mg L-1) and time (5-60 min) on adsorption was investigated. The Langmuir, Freundlich and Temkin adsorption models were applied to describe experimental data. Maximum adsorption capacity constituted 78.1 mg g-1 for hydroxyapatite treated with pluronic P123, 79.7 mg g-1 for hydroxyapatite and 134 mg g-1 for hydroxyapatite treated with pluronic F127 surfactant. The pseudo-first-order, pseudo-second-order, Elovich and intraparticle diffusion models were used to describe the kinetics of the process. For all sorbents, the experimental data fitted very well the pseudo-second-order and intraparticle diffusion models. The obtained results showed the potential of synthesized sorbents to be used for Cr(III) removal from wastewater. [ABSTRACT FROM AUTHOR]

Published
2020
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48. Removal of chromium(III) ions from aqueous solutions using different types of hydroxyapatites

Author

Zinicovscaia, Inga, Yushin, Nikita, Grozdov, Dmitrii, Humelnicu, Ionel, Humelnicu, Doina, and Mitina, Tatiana

Abstract

This study explored the possibility of using hydroxyapatite and its two modifications as sorbents to remove Cr(III) ions under different experimental conditions. The effect of pH (3–7), chromium concentration (10–100 mg L–1) and time (5–60 min) on adsorption was investigated. The Langmuir, Freundlich and Temkin adsorption models were applied to describe experimental data. Maximum adsorption capacity constituted 78.1 mg g–1for hydroxyapatite treated with pluronic P123, 79.7 mg g–1for hydroxyapatite and 134 mg g–1for hydroxyapatite treated with pluronic F127 surfactant. The pseudo-first-order, pseudo-second-order, Elovich and intraparticle diffusion models were used to describe the kinetics of the process. For all sorbents, the experimental data fitted very well the pseudo-second-order and intraparticle diffusion models. The obtained results showed the potential of synthesized sorbents to be used for Cr(III) removal from wastewater.

Published
2020
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