Kinetics of arsenate adsorption-desorption in soils

Area of Science:

• Environmental Science
• Soil Science
• Geochemistry

Background:

• Arsenic adsorption-desorption in soils critically influences its bioavailability and mobility.
• Understanding these processes is vital for environmental risk assessment and soil remediation.

Purpose of the Study:

• To investigate the adsorption-desorption characteristics of arsenate [As(V)] in soils with varying properties.
• To analyze the kinetic aspects and reversibility of As(V) interactions with soil components.

Main Methods:

• Kinetic batch experiments were conducted on Olivier loam, Sharkey clay, and Windsor sand.
• Arsenic release was studied using successive dilutions and sequential extraction procedures.
• Adsorption kinetics were modeled using a multireaction model (MRM).

Main Results:

• As(V) adsorption was nonlinear and strongly kinetic, showing initial rapid retention followed by slower processes.
• Freundlich and Langmuir parameters increased with reaction time, indicating ongoing sorption.
• Desorption exhibited hysteresis, suggesting irreversible or slowly reversible As(V) binding.
• Sequential extraction confirmed significant irreversible As(V) adsorption across all soils.

Conclusions:

• The multireaction model (MRM) effectively described As(V) adsorption and desorption kinetics for Olivier loam and Windsor sand.
• Sharkey clay, with its high arsenic affinity, required an additional irreversible reaction phase in the model.
• Soil properties significantly influence the kinetics and reversibility of arsenate sorption.