Journal article
Adsorption of Organic Acids on TiO2 Nanoparticles: Effects of pH, Nanoparticle Size, and Nanoparticle Aggregation
Langmuir, Vol.24(13), pp.6659-6667
07/01/2008
DOI: 10.1021/la7039916
PMID: 18537279
Abstract
In this study, the adsorption of two organic acids, oxalic acid and adipic acid, on TiO2 nanoparticles was investigated at room temperature, 298 K. Solution-phase measurements were used to quantify the extent and reversibility of oxalic acid and adipic acid adsorption on anatase nanoparticles with primary particle sizes of 5 and 32 nm. At all pH values considered, there were minimal differences in measured Langmuir adsorption constants, K ads, or surface-area-normalized maximum adsorbate−surface coverages, Γmax, between 5 and 32 nm particles. Although macroscopic differences in the reactivity of these organic acids as a function of nanoparticle size were not observed, ATR−FTIR spectroscopy showed some distinct differences in the absorption bands present for oxalic acid adsorbed on 5 nm particles compared to 32 nm particles, suggesting different adsorption sites or a different distribution of adsorption sites for oxalic acid on the 5 nm particles. These results illustrate that molecular-level differences in nanoparticle reactivity can still exist even when macroscopic differences are not observed from solution phase measurements. Our results also allowed the impact of nanoparticle aggregation on acid uptake to be assessed. It is clear that particle aggregation occurs at all pH values and that organic acids can destabilize nanoparticle suspensions. Furthermore, 5 nm particles can form larger aggregates compared to 32 nm particles under the same conditions of pH and solid concentrations. The relative reactivity of 5 and 32 nm particles as determined from Langmuir adsorption parameters did not appear to vary greatly despite differences that occur in nanoparticle aggregation for these two different size nanoparticles. Although this potentially suggests that aggregation does not impact organic acid uptake on anatase particles, these data clearly show that challenges remain in assessing the available surface area for adsorption in nanoparticle aqueous suspensions because of aggregation.
Details
- Title: Subtitle
- Adsorption of Organic Acids on TiO2 Nanoparticles: Effects of pH, Nanoparticle Size, and Nanoparticle Aggregation
- Creators
- John M PettiboneDavid M CwiertnyMichelle SchererVicki H Grassian
- Resource Type
- Journal article
- Publication Details
- Langmuir, Vol.24(13), pp.6659-6667
- Publisher
- American Chemical Society
- DOI
- 10.1021/la7039916
- PMID
- 18537279
- ISSN
- 0743-7463
- eISSN
- 1520-5827
- Alternative title
- Organic Acids on TiO2 Nanoparticles
- Language
- English
- Date published
- 07/01/2008
- Academic Unit
- Center for Health Effects of Environmental Contamination; Civil and Environmental Engineering; Occupational and Environmental Health; Public Policy Center (Archive); Chemistry; Chemical and Biochemical Engineering
- Record Identifier
- 9983992076902771
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