TY  - JOUR
AU  - Ahribesh, Aysha Ali
AU  - Lazarevic, Slavica
AU  - Jankovic-Častvan, Ivona
AU  - Jokić, Bojan M.
AU  - Spasojević, Vojislav
AU  - Radetić, Tamara
AU  - Janaćković, Đorđe T.
AU  - Petrović, Rada
PY  - 2017
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/1349
AB  - The magnetic nanocomposites (MNCs), used as adsorbents for Cd2+ ions, were prepared by a co-precipitation method using both the untreated natural (SEP) and the partially acid-activated (ASEP) sepiolites as supports for magnetite. The synthesis conditions differed as follows: NaOH or NH3 was added in the SEP or the ASEP suspension before or after the addition of Fe3 and Fe2+. The SEP-based MNCs prepared using NaOH had a lower magnetization, but higher adsorption capacities than the MNCs synthesized using NH3. The order of the mixing of the reagents had a small influence on the properties of SEP-based MNCs, especially when NaOH was used for the synthesis. Due to acidity of the surface functional groups of the ASEP, the magnetic composite could be synthesized only when NH3 was added in the suspension of ASEP having Fe3+ and Fe2+ ions. Despite of the worse dispersibility of the magnetic particles, the adsorption capacityof the ASEP-based composite was higher than of the MNC with SEP prepared by the same procedure. All the MNCs showed a superparamagnetic behavior at room temperature and the adsorption capacities were higher than of pure compounds. The adsorption of Cd2+ on the composites was best fitted with the Sips model, which suggested the chemisorption on the heterogeneous surface at energetically non-uniform sites until a monolayer was formed. (C) 2016 Elsevier B.V. All rights reserved.
T2  - Powder Technology
T1  - Influence of the synthesis parameters on the properties of the sepiolite-based magnetic adsorbents
VL  - 305
SP  - 260
EP  - 269
DO  - 10.1016/j.powtec.2016.09.086
ER  - 

@article{
author = "Ahribesh, Aysha Ali and Lazarevic, Slavica and Jankovic-Častvan, Ivona and Jokić, Bojan M. and Spasojević, Vojislav and Radetić, Tamara and Janaćković, Đorđe T. and Petrović, Rada",
year = "2017",
abstract = "The magnetic nanocomposites (MNCs), used as adsorbents for Cd2+ ions, were prepared by a co-precipitation method using both the untreated natural (SEP) and the partially acid-activated (ASEP) sepiolites as supports for magnetite. The synthesis conditions differed as follows: NaOH or NH3 was added in the SEP or the ASEP suspension before or after the addition of Fe3 and Fe2+. The SEP-based MNCs prepared using NaOH had a lower magnetization, but higher adsorption capacities than the MNCs synthesized using NH3. The order of the mixing of the reagents had a small influence on the properties of SEP-based MNCs, especially when NaOH was used for the synthesis. Due to acidity of the surface functional groups of the ASEP, the magnetic composite could be synthesized only when NH3 was added in the suspension of ASEP having Fe3+ and Fe2+ ions. Despite of the worse dispersibility of the magnetic particles, the adsorption capacityof the ASEP-based composite was higher than of the MNC with SEP prepared by the same procedure. All the MNCs showed a superparamagnetic behavior at room temperature and the adsorption capacities were higher than of pure compounds. The adsorption of Cd2+ on the composites was best fitted with the Sips model, which suggested the chemisorption on the heterogeneous surface at energetically non-uniform sites until a monolayer was formed. (C) 2016 Elsevier B.V. All rights reserved.",
journal = "Powder Technology",
title = "Influence of the synthesis parameters on the properties of the sepiolite-based magnetic adsorbents",
volume = "305",
pages = "260-269",
doi = "10.1016/j.powtec.2016.09.086"
}

Ahribesh, A. A., Lazarevic, S., Jankovic-Častvan, I., Jokić, B. M., Spasojević, V., Radetić, T., Janaćković, Đ. T.,& Petrović, R.. (2017). Influence of the synthesis parameters on the properties of the sepiolite-based magnetic adsorbents. in Powder Technology, 305, 260-269.
https://doi.org/10.1016/j.powtec.2016.09.086

Ahribesh AA, Lazarevic S, Jankovic-Častvan I, Jokić BM, Spasojević V, Radetić T, Janaćković ĐT, Petrović R. Influence of the synthesis parameters on the properties of the sepiolite-based magnetic adsorbents. in Powder Technology. 2017;305:260-269.
doi:10.1016/j.powtec.2016.09.086 .

Ahribesh, Aysha Ali, Lazarevic, Slavica, Jankovic-Častvan, Ivona, Jokić, Bojan M., Spasojević, Vojislav, Radetić, Tamara, Janaćković, Đorđe T., Petrović, Rada, "Influence of the synthesis parameters on the properties of the sepiolite-based magnetic adsorbents" in Powder Technology, 305 (2017):260-269,
https://doi.org/10.1016/j.powtec.2016.09.086 . .

TY  - JOUR
AU  - Savić, Andrija B.
AU  - Čokeša, Đuro
AU  - Lazarevic, Slavica
AU  - Jokić, Bojan M.
AU  - Janaćković, Đorđe T.
AU  - Petrović, Rada
AU  - Živković, Ljiljana
PY  - 2016
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/1262
AB  - This study demonstrates that PEG-assisted hydrothermal synthesis provides a convenient and eco-friendly route to fabrication of mesoporous magnetite with enhanced capacity for phosphate removal, excellent potential for magnetic separation and good reusability. Adsorption of phosphate onto 4 laboratory prepared magnetite powders was investigated in a systematic manner. Powders were synthesized in poly(ethylene) glycol-free or assisted conditions (PEGs 400 and 20,000 at varied PEG/water ratio), and characterized in terms of crystalline structure, and magnetic, morphological, textural, and acid-base properties. PEG acted as a powerful pore forming agent, the PEG/water ratio being the key factor in developing the surface area and mesoporosity of magnetite. Uptake capacity for phosphates increased with an increase in surface area and pore volume. PEG 20,000 at a ratio of 3:1 gave the best result. This mesoporous (D-max = 11 nm), nano-scale ( LT 10 nm) magnetite was ca. 9 times more efficient than nonporous micrometric powder derived from PEG-free synthesis (Langmuir maximum capacity, q(m) = 26.2 vs. 3.0 mg g(-1)). The adsorption was pH-dependent, in accord with variations in zeta potential of magnetite. Opposite shifts of isoelectric point and point of zero charge confirmed specific adsorption of phosphates at water/magnetite interface which proceeded via replacement of surface hydroxyls and sulfates. (C) 2016 Elsevier B.V. All rights reserved.
T2  - Powder Technology
T1  - Tailoring of magnetite powder properties for enhanced phosphate removal: Effect of PEG addition in the synthesis process
VL  - 301
SP  - 511
EP  - 519
DO  - 10.1016/j.powtec.2016.06.028
ER  - 

@article{
author = "Savić, Andrija B. and Čokeša, Đuro and Lazarevic, Slavica and Jokić, Bojan M. and Janaćković, Đorđe T. and Petrović, Rada and Živković, Ljiljana",
year = "2016",
abstract = "This study demonstrates that PEG-assisted hydrothermal synthesis provides a convenient and eco-friendly route to fabrication of mesoporous magnetite with enhanced capacity for phosphate removal, excellent potential for magnetic separation and good reusability. Adsorption of phosphate onto 4 laboratory prepared magnetite powders was investigated in a systematic manner. Powders were synthesized in poly(ethylene) glycol-free or assisted conditions (PEGs 400 and 20,000 at varied PEG/water ratio), and characterized in terms of crystalline structure, and magnetic, morphological, textural, and acid-base properties. PEG acted as a powerful pore forming agent, the PEG/water ratio being the key factor in developing the surface area and mesoporosity of magnetite. Uptake capacity for phosphates increased with an increase in surface area and pore volume. PEG 20,000 at a ratio of 3:1 gave the best result. This mesoporous (D-max = 11 nm), nano-scale ( LT 10 nm) magnetite was ca. 9 times more efficient than nonporous micrometric powder derived from PEG-free synthesis (Langmuir maximum capacity, q(m) = 26.2 vs. 3.0 mg g(-1)). The adsorption was pH-dependent, in accord with variations in zeta potential of magnetite. Opposite shifts of isoelectric point and point of zero charge confirmed specific adsorption of phosphates at water/magnetite interface which proceeded via replacement of surface hydroxyls and sulfates. (C) 2016 Elsevier B.V. All rights reserved.",
journal = "Powder Technology",
title = "Tailoring of magnetite powder properties for enhanced phosphate removal: Effect of PEG addition in the synthesis process",
volume = "301",
pages = "511-519",
doi = "10.1016/j.powtec.2016.06.028"
}

Savić, A. B., Čokeša, Đ., Lazarevic, S., Jokić, B. M., Janaćković, Đ. T., Petrović, R.,& Živković, L.. (2016). Tailoring of magnetite powder properties for enhanced phosphate removal: Effect of PEG addition in the synthesis process. in Powder Technology, 301, 511-519.
https://doi.org/10.1016/j.powtec.2016.06.028

Savić AB, Čokeša Đ, Lazarevic S, Jokić BM, Janaćković ĐT, Petrović R, Živković L. Tailoring of magnetite powder properties for enhanced phosphate removal: Effect of PEG addition in the synthesis process. in Powder Technology. 2016;301:511-519.
doi:10.1016/j.powtec.2016.06.028 .

Savić, Andrija B., Čokeša, Đuro, Lazarevic, Slavica, Jokić, Bojan M., Janaćković, Đorđe T., Petrović, Rada, Živković, Ljiljana, "Tailoring of magnetite powder properties for enhanced phosphate removal: Effect of PEG addition in the synthesis process" in Powder Technology, 301 (2016):511-519,
https://doi.org/10.1016/j.powtec.2016.06.028 . .

TY  - JOUR
AU  - Lazarevic, Slavica
AU  - Jankovic-Častvan, Ivona
AU  - Onjia, Antonije E.
AU  - Krstić, Jugoslav B.
AU  - Janaćković, Đorđe T.
AU  - Petrović, Rada
PY  - 2011
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/4517
AB  - Inverse gas chromatography at infinite and finite surface coverages was applied to evaluate the surface properties of an iron-modified sepiolite sorbent, Fe-sepiolite. The adsorptions of different nonpolar and polar probes were measured in the infinite-dilution regime, in the temperature range 483-513 K. For the organic probes used, the thermodynamic parameters (free energy, enthalpy, and entropy) of adsorption and the dispersive and specific components of the free energy of adsorption were determined and are discussed in terms of specific reactions that can occur on the adsorbent surface. Following the approach of Gutmann (The Donor Acceptor Approach to Molecular Interactions; Plenum Press: New York, 1978), acid/base surface characteristics were determined. The adsorption isotherms of n-hexane, benzene, chloroform, and tetrahydrofuran were used to estimate the specific surface areas, isosteric heats of adsorption, and adsorption energy distributions for the adsorption of organic molecules.
T2  - Industrial and Engineering Chemistry Research
T1  - Surface Characterization of Iron-Modified Sepiolite by Inverse Gas Chromatography
VL  - 50
IS  - 20
SP  - 11467
EP  - 11475
DO  - 10.1021/ie200595n
ER  - 

@article{
author = "Lazarevic, Slavica and Jankovic-Častvan, Ivona and Onjia, Antonije E. and Krstić, Jugoslav B. and Janaćković, Đorđe T. and Petrović, Rada",
year = "2011",
abstract = "Inverse gas chromatography at infinite and finite surface coverages was applied to evaluate the surface properties of an iron-modified sepiolite sorbent, Fe-sepiolite. The adsorptions of different nonpolar and polar probes were measured in the infinite-dilution regime, in the temperature range 483-513 K. For the organic probes used, the thermodynamic parameters (free energy, enthalpy, and entropy) of adsorption and the dispersive and specific components of the free energy of adsorption were determined and are discussed in terms of specific reactions that can occur on the adsorbent surface. Following the approach of Gutmann (The Donor Acceptor Approach to Molecular Interactions; Plenum Press: New York, 1978), acid/base surface characteristics were determined. The adsorption isotherms of n-hexane, benzene, chloroform, and tetrahydrofuran were used to estimate the specific surface areas, isosteric heats of adsorption, and adsorption energy distributions for the adsorption of organic molecules.",
journal = "Industrial and Engineering Chemistry Research",
title = "Surface Characterization of Iron-Modified Sepiolite by Inverse Gas Chromatography",
volume = "50",
number = "20",
pages = "11467-11475",
doi = "10.1021/ie200595n"
}

Lazarevic, S., Jankovic-Častvan, I., Onjia, A. E., Krstić, J. B., Janaćković, Đ. T.,& Petrović, R.. (2011). Surface Characterization of Iron-Modified Sepiolite by Inverse Gas Chromatography. in Industrial and Engineering Chemistry Research, 50(20), 11467-11475.
https://doi.org/10.1021/ie200595n

Lazarevic S, Jankovic-Častvan I, Onjia AE, Krstić JB, Janaćković ĐT, Petrović R. Surface Characterization of Iron-Modified Sepiolite by Inverse Gas Chromatography. in Industrial and Engineering Chemistry Research. 2011;50(20):11467-11475.
doi:10.1021/ie200595n .

Lazarevic, Slavica, Jankovic-Častvan, Ivona, Onjia, Antonije E., Krstić, Jugoslav B., Janaćković, Đorđe T., Petrović, Rada, "Surface Characterization of Iron-Modified Sepiolite by Inverse Gas Chromatography" in Industrial and Engineering Chemistry Research, 50, no. 20 (2011):11467-11475,
https://doi.org/10.1021/ie200595n . .

TY  - JOUR
AU  - Lazarevic, S.
AU  - Radovanović, Željko
AU  - Veljović, Đorđe N.
AU  - Onjia, Antonije E.
AU  - Janaćković, Đorđe T.
AU  - Petrović, R.
PY  - 2009
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/3619
AB  - The adsorption properties of sepiolite from Andrici, Serbia, were studied by inverse gas chromatography at zero and finite surface coverage between 483 and 513 K. The thermodynamic parameters (free energy, enthalpy, entropy) of adsorption, as well as the dispersive and specific components of the free energy of adsorption and the acid/base of the solid were calculated from the IGC data at zero coverage. The K(D)/K(A) ratio indicated basis character. The adsorption isotherms were used to estimate the specific surface area, isosteric heat of adsorption and the adsorption energy distribution for the adsorption of organic molecules. (C) 2008 Elsevier B.V. All rights reserved.
T2  - Applied Clay Science
T1  - Characterization of sepiolite by inverse gas chromatography at infinite and finite surface coverage
VL  - 43
IS  - 1
SP  - 41
EP  - 48
DO  - 10.1016/j.clay.2008.07.013
ER  - 

@article{
author = "Lazarevic, S. and Radovanović, Željko and Veljović, Đorđe N. and Onjia, Antonije E. and Janaćković, Đorđe T. and Petrović, R.",
year = "2009",
abstract = "The adsorption properties of sepiolite from Andrici, Serbia, were studied by inverse gas chromatography at zero and finite surface coverage between 483 and 513 K. The thermodynamic parameters (free energy, enthalpy, entropy) of adsorption, as well as the dispersive and specific components of the free energy of adsorption and the acid/base of the solid were calculated from the IGC data at zero coverage. The K(D)/K(A) ratio indicated basis character. The adsorption isotherms were used to estimate the specific surface area, isosteric heat of adsorption and the adsorption energy distribution for the adsorption of organic molecules. (C) 2008 Elsevier B.V. All rights reserved.",
journal = "Applied Clay Science",
title = "Characterization of sepiolite by inverse gas chromatography at infinite and finite surface coverage",
volume = "43",
number = "1",
pages = "41-48",
doi = "10.1016/j.clay.2008.07.013"
}

Lazarevic, S., Radovanović, Ž., Veljović, Đ. N., Onjia, A. E., Janaćković, Đ. T.,& Petrović, R.. (2009). Characterization of sepiolite by inverse gas chromatography at infinite and finite surface coverage. in Applied Clay Science, 43(1), 41-48.
https://doi.org/10.1016/j.clay.2008.07.013

Lazarevic S, Radovanović Ž, Veljović ĐN, Onjia AE, Janaćković ĐT, Petrović R. Characterization of sepiolite by inverse gas chromatography at infinite and finite surface coverage. in Applied Clay Science. 2009;43(1):41-48.
doi:10.1016/j.clay.2008.07.013 .

Lazarevic, S., Radovanović, Željko, Veljović, Đorđe N., Onjia, Antonije E., Janaćković, Đorđe T., Petrović, R., "Characterization of sepiolite by inverse gas chromatography at infinite and finite surface coverage" in Applied Clay Science, 43, no. 1 (2009):41-48,
https://doi.org/10.1016/j.clay.2008.07.013 . .

TY  - JOUR
AU  - Lazarevic, Slavica
AU  - Jankovic-Častvan, Ivona
AU  - Jovanovic, Dusan
AU  - Milonjić, Slobodan K.
AU  - Janaćković, Đorđe T.
AU  - Petrović, Rada
PY  - 2007
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/3206
AB  - The adsorption mechanisms of Ph2+, Cd2+ and Sr2+ ions on natural sepiolite and the influence of acid treatment on the adsorption capacity of sepiolite were investigated. The point of zero charge pH(pzc), is 7.4 +/- 0.1 for natural sepiolite and 6.9 +/- 0.1 for partially acid-activated sepiolite. The shift of the pH(pzc) of sepiolites toward lower pH values in solutions of Ph2+ and Cd2+ ions indicates that specific adsorption of these cations on natural and acid-activated sepiolites occurred, which was more pronounced for Pb2+ ions than for Cd2+ ions. There was no shift of the pH(pzc) in Solution containing Sr2+ ions, suggesting that specific adsorption of this cation did not occur. The affinity for ion exchange with the Mg2+ ions from the sepiolite structure was the highest for Pb2+ ions, then Cd2+, whereas the affinity for Sr2+ ions was negligible. The adsorption isotherms suggest that the sequence of the efficiency of the sepiolites adsorption is Ph2+ GT Cd2+ GT Sr2+. The retention of Pb2+ and Cd2+ ions by sepiolite occurs dominantly by specific adsorption and exchange of Mg2+ ions from the sepiolite structure. The concentration in the external outer sphere of the Stem layer by electrostatic forces is the dominant mechanism for the retention of Sr2+ ions on the surface of sepiolites. Despite increases in the surface areas upon acid activation, improvements in the adsorption were not observed, as a result of the decreasing number of Mg-OH groups, as main centers for specific adsorption, and the number of Mg2+ ions available for ion exchange with Pb2+, Cd2+ and Sr2+ ions. The removal of Mg-OH groups from the sepiolite also resulted in a decrease in the point of zero charge and an increase of the relative surface acidity, from 2.6 +/- 0.1 for the natural to 6.4 +/- 0.1 for the acid-activated sepiolite. (C) 2006 Elsevier B.V. All rights reserved.
T2  - Applied Clay Science
T1  - Adsorption of Pb2+, Cd2+ and Sr2+ ions onto natural and acid-activated sepiolites
VL  - 37
IS  - 1-2
SP  - 47
EP  - 57
DO  - 10.1016/j.clay.2006.11.008
ER  - 

@article{
author = "Lazarevic, Slavica and Jankovic-Častvan, Ivona and Jovanovic, Dusan and Milonjić, Slobodan K. and Janaćković, Đorđe T. and Petrović, Rada",
year = "2007",
abstract = "The adsorption mechanisms of Ph2+, Cd2+ and Sr2+ ions on natural sepiolite and the influence of acid treatment on the adsorption capacity of sepiolite were investigated. The point of zero charge pH(pzc), is 7.4 +/- 0.1 for natural sepiolite and 6.9 +/- 0.1 for partially acid-activated sepiolite. The shift of the pH(pzc) of sepiolites toward lower pH values in solutions of Ph2+ and Cd2+ ions indicates that specific adsorption of these cations on natural and acid-activated sepiolites occurred, which was more pronounced for Pb2+ ions than for Cd2+ ions. There was no shift of the pH(pzc) in Solution containing Sr2+ ions, suggesting that specific adsorption of this cation did not occur. The affinity for ion exchange with the Mg2+ ions from the sepiolite structure was the highest for Pb2+ ions, then Cd2+, whereas the affinity for Sr2+ ions was negligible. The adsorption isotherms suggest that the sequence of the efficiency of the sepiolites adsorption is Ph2+ GT Cd2+ GT Sr2+. The retention of Pb2+ and Cd2+ ions by sepiolite occurs dominantly by specific adsorption and exchange of Mg2+ ions from the sepiolite structure. The concentration in the external outer sphere of the Stem layer by electrostatic forces is the dominant mechanism for the retention of Sr2+ ions on the surface of sepiolites. Despite increases in the surface areas upon acid activation, improvements in the adsorption were not observed, as a result of the decreasing number of Mg-OH groups, as main centers for specific adsorption, and the number of Mg2+ ions available for ion exchange with Pb2+, Cd2+ and Sr2+ ions. The removal of Mg-OH groups from the sepiolite also resulted in a decrease in the point of zero charge and an increase of the relative surface acidity, from 2.6 +/- 0.1 for the natural to 6.4 +/- 0.1 for the acid-activated sepiolite. (C) 2006 Elsevier B.V. All rights reserved.",
journal = "Applied Clay Science",
title = "Adsorption of Pb2+, Cd2+ and Sr2+ ions onto natural and acid-activated sepiolites",
volume = "37",
number = "1-2",
pages = "47-57",
doi = "10.1016/j.clay.2006.11.008"
}

Lazarevic, S., Jankovic-Častvan, I., Jovanovic, D., Milonjić, S. K., Janaćković, Đ. T.,& Petrović, R.. (2007). Adsorption of Pb2+, Cd2+ and Sr2+ ions onto natural and acid-activated sepiolites. in Applied Clay Science, 37(1-2), 47-57.
https://doi.org/10.1016/j.clay.2006.11.008

Lazarevic S, Jankovic-Častvan I, Jovanovic D, Milonjić SK, Janaćković ĐT, Petrović R. Adsorption of Pb2+, Cd2+ and Sr2+ ions onto natural and acid-activated sepiolites. in Applied Clay Science. 2007;37(1-2):47-57.
doi:10.1016/j.clay.2006.11.008 .

Lazarevic, Slavica, Jankovic-Častvan, Ivona, Jovanovic, Dusan, Milonjić, Slobodan K., Janaćković, Đorđe T., Petrović, Rada, "Adsorption of Pb2+, Cd2+ and Sr2+ ions onto natural and acid-activated sepiolites" in Applied Clay Science, 37, no. 1-2 (2007):47-57,
https://doi.org/10.1016/j.clay.2006.11.008 . .