The two-species phosphate adsorption kinetics on goethite
Jeison Manuel Arroyave1, Marcelo Avena1, Wenfeng Tan2
1INQUISUR, Departamento de Química, Universidad Nacional Del Sur (UNS)-CONICET, Av. Alem 1253, 8000 Bahía Blanca, Argentina.
Chemosphere
|July 23, 2022
Summary
This study reveals how phosphate binds and releases from goethite using ATR-FTIR spectroscopy. Phosphate desorbs faster from goethite at lower pH, offering practical environmental insights.
Area of Science:
- Environmental Science
- Geochemistry
- Surface Chemistry
Background:
- Understanding ion and molecule adsorption-desorption is key to environmental nutrient and pollutant mobility.
- The phosphate-goethite system serves as a model for studying pollutants like glyphosate.
- Accurate kinetic analysis requires robust calibration methods for spectroscopic data.
Purpose of the Study:
- To investigate the adsorption-desorption kinetics of phosphate on goethite.
- To demonstrate a methodology for calibrating ATR-FTIR spectroscopic data with adsorption isotherms.
- To monitor the time evolution of surface species during adsorption-desorption at various pH levels.
Main Methods:
- Attenuated Total Reflectance Fourier-Transform Infrared (ATR-FTIR) spectroscopy was employed.
- Experiments were conducted at three distinct pH values: 4.5, 7.0, and 9.5.
- Adsorption-desorption kinetics were analyzed using a model incorporating transport, attachment, detachment, and surface transformation.
Main Results:
- A clear methodology for converting absorbance data to adsorption data using spectroscopic and isotherm information was established.
- Simultaneous monitoring of surface species revealed advantages over traditional total adsorption methods.
- Identical rate parameters at a given pH successfully predicted kinetics and isotherms for two surface species.
Conclusions:
- The study provides new insights into the dynamics of phosphate on goethite surfaces.
- Phosphate desorption from goethite was observed to be faster at low pH than at high pH, contrary to initial expectations.
- These findings have significant practical and environmental implications for managing phosphate mobility.
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