Electrostatic self-assembly of TiO2 nanoparticles onto carbon spheres with enhanced adsorption capability for Cr(VI)

Qian, Huanhuan; Hu, Yong; Liu, Yu; Zhou, Mojiao; Guo, Changfa

doi:10.1016/j.matlet.2011.10.054

Cited by 27 publications

(14 citation statements)

References 21 publications

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“…In general, the predominant Cr(VI) species in the solution would gradually change from monovalent HCrO 4 − to divalent CrO 4 2− and Cr 2 O 7 2− as the pH increases . At lower pH values, the Cr(VI) removal efficiency is high because the dominant Cr(VI) species is monovalent HCrO 4 − , which is more favorably adsorbed than CrO 4 2− or Cr 2 O 7 2− at the same concentration . Meanwhile, a large quantity of hydrogen and hydronium ions (H + and H 3 O + ) changed the functional groups through protonation (OH + H + ↔ OH + at low pH), which made the GFMO surface positively charged and increased the attractive force for the negatively charged Cr(VI) species.…”

Section: Resultsmentioning

confidence: 99%

Cr(VI) adsorption from aqueous solution and its reactions behavior on the surfaces of granular Fe–Mn binary oxides

Zhu

2018

Env Prog and Sustain Energy

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A granular Fe–Mn binary oxide (GFMO) was prepared for Cr(VI) removal and characterized by its Brunauer–Emmett–Teller surface area, scanning electron microscopy, X‐ray photoelectron spectroscopy, X‐ray diffraction, and Fourier transform infrared spectroscopy. Scanning electron microscopy images of the GFMO showed it had a rough surface and heterogeneous porous structure. The Brunauer–Emmett–Teller surface area was 57.64 m2/g. X‐ray photoelectron spectra showed that manganese and iron existed mainly in the +IV and + III oxidation states, respectively. Adsorption of Cr(VI) by the GFMO was investigated. Kinetic data showed that the Cr(VI) adsorption onto the GFMO followed a pseudo‐second‐order model, indicating that the adsorption process was chemisorption. Equilibrium data were analyzed by both the Freundlich and Langmuir models, and the Langmuir isotherm model fitted better with the maximum adsorption capacity of 16.79 mg/g at 318 K. The Cr(VI) adsorption on GFMO was endothermic and nonspontaneous in nature. It was also strongly pH dependent, with higher Cr(VI) removal efficiency occurring under acidic conditions and a sharp decrease in adsorption as the pH increased. Coexisting anions competed with Cr(VI) for adsorption on the GFMO in the order silicate > sulfate > nitrate. Cr(VI) adsorption on the GFMO mainly occurred via anion exchange, surface complexation, and electrostatic attraction. Novelty or Significance: Combined adsorbent with iron oxides and manganese oxides was usually synthesized for heavy metal removal and showed an excellent adsorption capacity. However, the Fe–Mn binary oxide adsorbent mentioned above were mostly exhibited in particles, limiting its engineering application due to the dispersion state in aqueous solutions. Therefore, novel granular Fe–Mn oxide adsorbents, with good stability and high adsorption capacity, are highly desired. A novel granular Fe–Mn oxide (GFMO) adsorbent with the polyvinyl alcohol (PVA) as the adhesive was synthesized to investigate its adsorption behaviors for Cr(VI) for further used as filler in most water treatment equipment. © 2018 American Institute of Chemical Engineers Environ Prog, 38: S176–S184, 2019

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Section: Resultsmentioning

confidence: 99%

Cr(VI) adsorption from aqueous solution and its reactions behavior on the surfaces of granular Fe–Mn binary oxides

Zhu

2018

Env Prog and Sustain Energy

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“…In order to determine the optimal pH, the adsorption experiments were performed with the varying pH of 1-11. 44 Meanwhile, at lower pH, abundance of hydronium ions (H + and H 3 O + ) in the solution can conjugate with the amino groups which made the surface of HDA-RGO-ZnFe 2 O 4 to be more positively charged. 8, the adsorption capacity first increases with the increase in pH from 1 to 2 and then decreases with the increase in pH from 2 to 11 4 2is predominant at pH > 6.…”

Section: Effect Of Solution Phmentioning

confidence: 99%

One-step synthesis of magnetic 1,6-hexanediamine-functionalized reduced graphene oxide–zinc ferrite for fast adsorption of Cr(vi)

Zhang

Sun

et al. 2015

RSC Adv.

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A one-step solvothermal method was developed to prepare nearly cubic ZnFe 2 O 4 nanoparticles loaded on 1, 6-hexanediamine-functionalized reduced graphene oxide (HDA-RGO-ZnFe 2 O 4 ) for fast removing Cr (VI). The materials were characterized by transmission electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, Raman, and vibrating sample magnetometry. Experimental results indicated that Cr (VI) adsorption by HDA-RGO-ZnFe 2 O 4 is strongly pH dependent and the adsorption equilibrium could be reached within 12 min. The kinetic adsorption of different initial concentrations can be accurately described by the pseudo-second-order model. The overall rate process was apparently influenced by external mass transfer and intraparticle diffusion. The Langmuir isotherm model is consistent with the experimental data at different temperatures and the maximum adsorption capacity was determined to be 172.4 mg g -1 . Moreover, the thermodynamic parameters indicated that the adsorption process was spontaneous and endothermic. The adsorption mechanism and desorption experiments were also studied. After adsorption, the HDA-RGO-ZnFe 2 O 4 could be quickly separated from the media by an external magnetic and the adsorption capacity can remain up to 82% after five times of usage. The results implied that HDA-RGO-ZnFe 2 O 4 is a promising adsorbent for the removal of Cr (VI).

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“…The adsorption free energy change for HCrO 4 -ion is lower than those of CrO 4 2-and Cr 2 O 7 2-ions. Therefore, HCrO 4 -is more easily adsorbed at acidic pH values resulting in a higher removal of Cr(VI) (Qian et al, 2012). It is also postulated that Cr(VI) can be reduced to Cr(III) at low pH values in the presence of a carbonaceous material such as bio-char.…”

Section: Chromium Sorption Characteristicsmentioning

confidence: 99%

Investigating Bio-Char as Flow Modifier and Water Treatment Agent for Sustainable Pavement Design

Walters¹,

Begum²,

Fini³

et al. 2015

American Journal of Engineering and Applied Sciences

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The life expectancy of Asphalt Binder (AB) has been negatively impacted by the harsh bombardment of Ultraviolet (UV) rays. UV rays cause asphalt to oxidize faster, which results in the deterioration of asphalt's rheological characteristics that can lead to pavement distresses. This paper investigates merits of bio-char to improve asphalt aging susceptibility by blending one control binder (PG 64-22) and two bio-modified binder at concentrations of 3 and 6% individually; the specimens were then analyzed in terms of their rheological characterization before and after aging. Rolling Thin Film Oven (RTFO) method was used to age all specimens, aged and un-aged samples were then tested using a Rotational Viscometer (RV) to evaluate the changes in their rheological behavior before and after aging as a result of aforementioned modifications. This paper also looks at the chemical composition and elemental analysis of bio-char along with biochars' ability to absorb chromium. A sorption procedure was used to determine whether or not bio-char can be used to absorb chromium. The highest chromium removal occurred at a pH value of 5.5. Bio-char was used to improve dispersion and liquid retention, while enhancing oxidation resistance.

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Electrostatic self-assembly of TiO2 nanoparticles onto carbon spheres with enhanced adsorption capability for Cr(VI)

Cited by 27 publications

References 21 publications

Cr(VI) adsorption from aqueous solution and its reactions behavior on the surfaces of granular Fe–Mn binary oxides

Cr(VI) adsorption from aqueous solution and its reactions behavior on the surfaces of granular Fe–Mn binary oxides

One-step synthesis of magnetic 1,6-hexanediamine-functionalized reduced graphene oxide–zinc ferrite for fast adsorption of Cr(vi)

Investigating Bio-Char as Flow Modifier and Water Treatment Agent for Sustainable Pavement Design

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