Points of Zero Charge and Intrinsic Equilibrium Constants of Silica–Magnetite Composite Oxides

Shen, Jun; Ebner, Armin D.; Ritter, James A.

doi:10.1006/jcis.1999.6206

Cited by 23 publications

(16 citation statements)

References 25 publications

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“…1 as a function of pH and ionic strength. This plot shows that side reactions are only significant for pH < 4 and pH > 9, in agreement with the results reported by Shen et al (1999). At 60°C, the results are acceptable in the pH range 4-8.…”

Section: Blank Experimentssupporting

confidence: 93%

Surface chemistry of kaolinite and Na-montmorillonite in aqueous electrolyte solutions at 25 and 60°C: Experimental and modeling study

Tertre

Castet

Berger

et al. 2006

Geochimica et Cosmochimica Acta

109

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Section: Blank Experimentssupporting

confidence: 93%

Surface chemistry of kaolinite and Na-montmorillonite in aqueous electrolyte solutions at 25 and 60°C: Experimental and modeling study

Tertre

Castet

Berger

et al. 2006

Geochimica et Cosmochimica Acta

109

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“…This decrease was likely caused by the surface coverage with magnetite or maghemite, since the point of zero charge of magnetite and maghemite is about 6.5 or somewhat higher (Lucas et al, 2007, Milonji c et al, 1983, Shen et al, 1999, while all the pristine a Calculated by the weight ratio of pristine carbon and iron oxides, and their SSA. The BET surface area of iron oxides is 66 m 2 /g, according to Oliveira et al (2002).…”

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confidence: 99%

Magnetite impregnation effects on the sorbent properties of activated carbons and biochars

et al. 2015

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This paper discusses the sorbent properties of magnetic activated carbons and biochars produced by wet impregnation with iron oxides. The sorbents had magnetic susceptibilities consistent with theoretical predictions for carbon-magnetite composites. The high BET surface areas of the activated carbons were preserved in the synthesis, and enhanced for one low surface area biochar by dissolving carbonates. Magnetization decreased the point of zero charge. Organic compound sorption correlated strongly with BET surface areas for the pristine and magnetized materials, while metal cation sorption did not show such a correlation. Strong sorption of the hydrophobic organic contaminant phenanthrene to the activated carbon or biochar surfaces was maintained following magnetite impregnation, while phenol sorption was diminished, probably due to enhanced carbon oxidation. Copper, zinc and lead sorption to the activated carbons and biochars was unchanged or slightly enhanced by the magnetization, and iron oxides also contributed to the composite metal sorption capacity. While a magnetic biochar with 219 ± 3.7 m(2)/g surface area nearly reached the very strong organic pollutant binding capacity of the two magnetic activated carbons, a magnetic biochar with 68 ± 2.8 m(2)/g surface area was the best metal sorbent. Magnetic biochars thus hold promise as more sustainable alternatives to coal-derived magnetic activated carbons.

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“…Due to the presence of NH 2 groups, the surface of Fe 3 O 4 /SiO 2 -NH 2 composite was more basic (Fe 3 O 4 /SiO 2 -NH 2 + H + → Fe 3 O 4 /SiO 2 -NH 3 + ) and shifted to higher values of Pzc. The surface charge of Fe 3 O 4 /SiO 2 -NH 2 -DTPA decreased because of amino group deprotonation by DTPA residues (Fe 3 O 4 /SiO 2 -NH 2 -DTPA 4− + Fe 3 O 4 /SiO 2 -NH 3 + → Fe 3 O 4 /SiO 2 -NH 2 -DTPA 3− + Fe 3 O 4 /SiO 2 -NH 2 ) [ 30 , 31 , 32 ].…”

Section: Resultsmentioning

confidence: 99%

Sol-Gel Derived Adsorbents with Enzymatic and Complexonate Functions for Complex Water Remediation

et al. 2017

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Sol-gel technology is a versatile tool for preparation of complex silica-based materials with targeting functions for use as adsorbents in water purification. Most efficient removal of organic pollutants is achieved by using enzymatic reagents grafted on nano-carriers. However, enzymes are easily deactivated in the presence of heavy metal cations. In this work, we avoided inactivation of immobilized urease by Cu (II) and Cd (II) ions using magnetic nanoparticles provided with additional complexonate (diethylene triamine pentaacetic acid or DTPA) functions. Obtained nanomaterials were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). According to TGA, the obtained Fe3O4/SiO2-NH2-DTPA nanoadsorbents contained up to 0.401 mmol/g of DTPA groups. In the concentration range Ceq = 0–50 mmol/L, maximum adsorption capacities towards Cu (II) and Cd (II) ions were 1.1 mmol/g and 1.7 mmol/g, respectively. Langmuir adsorption model fits experimental data in concentration range Ceq = 0–10 mmol/L. The adsorption mechanisms have been evaluated for both of cations. Crosslinking of 5 wt % of immobilized urease with glutaraldehyde prevented the loss of the enzyme in repeated use of the adsorbent and improved the stability of the enzymatic function leading to unchanged activity in at least 18 cycles. Crosslinking of 10 wt % urease on the surface of the particles allowed a decrease in urea concentration in 20 mmol/L model solutions to 2 mmol/L in up to 10 consequent decomposition cycles. Due to the presence of DTPA groups, Cu2+ ions in concentration 1 µmol/L did not significantly affect the urease activity. Obtained magnetic Fe3O4/SiO2-NH2-DTPA-Urease nanocomposite sorbents revealed a high potential for urease decomposition, even in presence of heavy metal ions.

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Points of Zero Charge and Intrinsic Equilibrium Constants of Silica–Magnetite Composite Oxides

Cited by 23 publications

References 25 publications

Surface chemistry of kaolinite and Na-montmorillonite in aqueous electrolyte solutions at 25 and 60°C: Experimental and modeling study

Surface chemistry of kaolinite and Na-montmorillonite in aqueous electrolyte solutions at 25 and 60°C: Experimental and modeling study

Magnetite impregnation effects on the sorbent properties of activated carbons and biochars

Sol-Gel Derived Adsorbents with Enzymatic and Complexonate Functions for Complex Water Remediation

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