Cadmium and arsenic interactions under different molar ratios during coadsorption processes by excluding pH...

Area of Science:

• Environmental Science
• Geochemistry
• Soil Science

Background:

• Cadmium (Cd) and arsenic (As) are toxic heavy metals frequently found together in soils.
• Their coadsorption on soil minerals is influenced by various factors, with pH being critical.
• Understanding these interactions is vital for soil remediation and environmental safety.

Purpose of the Study:

• To investigate the regulatory mechanisms of As(V)-Cd(II) coadsorption on γ-Al2O3.
• To elucidate these interactions while minimizing pH interference.
• To differentiate the roles of competitive and synergistic effects in heavy metal coadsorption.

Main Methods:

• Co-adsorption experiments were conducted at a stable pH of 6.0.
• Analyzed adsorption behavior by varying concentrations of As(V) and Cd(II).
• Utilized zeta potential, X-ray diffraction, and HRTEM for mechanistic analysis.

Main Results:

• Cd(II) adsorption increased then decreased with rising As(V) concentration (As(V)/Cd(II) ratio ~5).
• As(V) adsorption was stable then increased with rising Cd(II) concentration (Cd(II)/As(V) ratio = 1).
• Electrostatic adsorption and ternary complex formation governed Cd(II) reactivity; ternary complexes and surface precipitation controlled As(V) stability.

Conclusions:

• The coadsorption of Cd(II) and As(V) at stable pH involves both competition and synergy.
• Electrostatic interactions and ternary complex formation are key mechanisms.
• Surface precipitation plays a significant role in As(V) stability during coadsorption.