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Surface Functionalization of Metal-Organic Frameworks for Improved Moisture Resistance
Published on: September 5, 2018
Surface complexes of phthalic acid at the hematite/water interface.
Yu Sik Hwang1, Jin Liu, John J Lenhart
1Department of Civil and Environmental Engineering and Geodetic Science, The Ohio State University, Columbus, OH 43210, USA.
Journal of Colloid and Interface Science
|December 26, 2006
Summary
O-phthalic acid adsorption on hematite shows anionic behavior, with adsorption decreasing at higher pH. Three phthalate surface complexes form, including outer-sphere and inner-sphere types, influenced by pH and surface coverage.
Area of Science:
- Environmental chemistry
- Surface science
- Mineralogy
Background:
- Hematite is a key iron oxide mineral in various environmental systems.
- Understanding organic acid adsorption is crucial for contaminant transport and fate.
- O-phthalic acid is a common organic pollutant.
Purpose of the Study:
- Investigate o-phthalic acid adsorption mechanisms at the hematite/water interface.
- Characterize the types and structures of surface complexes formed.
- Determine the influence of pH, ionic strength, and surface loading on adsorption.
Main Methods:
- Batch adsorption experiments were conducted under varying conditions.
- Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy was used for surface complex identification.
- Molecular orbital calculations aided in assigning atomistic structures to spectral features.
Main Results:
- Adsorption exhibited typical anionic characteristics, decreasing with increasing pH.
- Adsorption was strongly dependent on ionic strength, indicating outer-sphere complex formation.
- ATR-FTIR and calculations identified three deprotonated phthalate surface complexes: one outer-sphere and two inner-sphere (mononuclear bidentate and binuclear bidentate).
Conclusions:
- Outer-sphere complex dominates adsorption near neutral pH.
- Inner-sphere complexes become more important at low pH and high surface coverage.
- Adsorption mechanisms involve both outer-sphere and inner-sphere complexation, with specific structures dependent on chemical conditions.
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