Activated carbon for multicomponent heavy-metal removal: bridging macroscopic adsorption performance and microscopic...

Area of Science:

• Environmental Chemistry
• Materials Science
• Physical Chemistry

Background:

• Heavy metal contamination poses significant risks to aquatic ecosystems and human health.
• Developing efficient and sustainable adsorbents for simultaneous removal of multiple heavy metals is crucial for environmental remediation.

Purpose of the Study:

• To synthesize and evaluate banana peel-derived activated carbon (BPAC) for ternary adsorption of Ni(ii), Cd(ii), and In(iii).
• To investigate the adsorption mechanism using an extended statistical physics model and thermodynamic analysis.
• To assess the reusability and performance of BPAC compared to commercial activated carbon (CAC).

Main Methods:

• Synthesis of BPAC from banana peels.
• Ternary adsorption experiments at varying temperatures (30-50 °C).
• Isotherm and kinetic modeling using an extended statistical physics model and pseudo-second-order kinetics.
• Microscopic analysis (SEM, BET) and adsorption energy distribution (AED) analysis.
• Adsorption-desorption cycling for reusability assessment.

Main Results:

• BPAC demonstrated high adsorption capacity for Ni(ii), Cd(ii), and In(iii).
• Adsorption followed pseudo-second-order kinetics and was well-described by the extended statistical physics model.
• BPAC exhibited excellent reusability, retaining 89% capacity after five cycles.
• AED analysis indicated heterogeneous, high-affinity sites for Ni(ii) and Cd(ii), and physisorption for In(iii).
• Thermodynamic analysis confirmed spontaneous adsorption with negative Gibbs free energies.

Conclusions:

• BPAC is a highly efficient and sustainable adsorbent for multicomponent heavy metal removal.
• The extended statistical physics model provides a physically consistent description of non-ideal multicomponent adsorption.
• BPAC's superior performance is attributed to its high density of accessible sites and favorable interaction parameters.
• Temperature influences the adsorption of different heavy metals differently, highlighting the complexity of multicomponent systems.