Solubility-normalized combined adsorption-partitioning sorption isotherms for organic pollutants

Area of Science:

• Environmental Chemistry
• Soil Science
• Adsorption Science

Background:

• Understanding organic compound sorption is crucial for environmental remediation and risk assessment.
• Sorption behavior varies significantly with sorbent properties like organic matter content and surface area.

Purpose of the Study:

• To investigate and model equilibrium sorption isotherms for low-polarity organic compounds across diverse sorbent types.
• To evaluate the applicability of the Polanyi-Dubinin-Manes (PDM) model and linear partitioning for different sorbent classes.

Main Methods:

• Equilibrium sorption isotherms were measured for five organic compounds (benzene, trichloroethene, dichlorobenzenes, phenanthrene).
• Sorbents were categorized into humic soil organic matter, carbon materials, and engineered microporous materials.
• The Polanyi-Dubinin-Manes (PDM) model was applied, combined with linear partitioning where appropriate.

Main Results:

• Humic soil organic matter exhibited linear sorption (partitioning), while carbon materials and microporous materials showed nonlinear isotherms.
• The PDM model accurately fitted sorption data for all compounds and sorbent classes.
• A solubility-normalized concentration successfully predicted unique sorption isotherms for similar compounds.

Conclusions:

• The PDM model, integrated with linear partitioning, provides a unified framework for predicting organic compound sorption across various environmental matrices.
• An inverse linear relationship between the distribution coefficient (Kd) and water solubility was confirmed, explaining correlations between sorption capacity and nonlinearity.