Cu sorption on Phragmites australis leaf and stem litter: a kinetic study

Area of Science:

• Environmental Science
• Biogeochemistry
• Ecotoxicology

Background:

• Decaying organic matter in wetlands is crucial for metal cycling.
• Phragmites australis litter is a significant component of wetland ecosystems.
• Understanding metal sorption kinetics on plant litter is vital for wetland management.

Purpose of the Study:

• To investigate the sorption kinetics of copper (Cu(II)) on Phragmites australis leaf and stem litter.
• To evaluate the influence of litter decomposition stage on Cu sorption.
• To determine the best kinetic models describing Cu sorption on wetland plant litter.

Main Methods:

• Sampling of fresh and 5-month decomposed Phragmites australis leaf and stem litter from a surface flow wetland.
• Experimental study of Cu(II) sorption kinetics at various initial Cu concentrations.
• Fitting experimental data to Lagergren pseudo-first-order, pseudo-second-order, Elovich, and intra-particle diffusion models.

Main Results:

• Sorption capacity was significantly affected by the decomposition stage of the litter.
• The pseudo-second-order kinetic model provided the best fit (R(2) ≈ 0.99) for the sorption process.
• Intra-particle diffusion models also showed a good fit (R(2) > 0.95), and theoretical analysis suggested it could explain the pseudo-second-order kinetics.
• Sorption exhibited a fast initial phase followed by a slower phase, dependent on initial Cu concentration.

Conclusions:

• Litter decomposition critically influences copper sorption dynamics in wetlands.
• Pseudo-second-order kinetics, likely driven by intra-particle diffusion, accurately models copper sorption on Phragmites australis litter.
• These findings enhance our understanding of metal fate and transport in wetland environments.