Physicochemical assessment of anionic dye adsorption on bone char using a multilayer statistical physics model

Area of Science:

• Environmental Chemistry
• Materials Science
• Physical Chemistry

Background:

• Anionic dyes pose environmental challenges, necessitating efficient removal methods.
• Bone char is a low-cost, sustainable adsorbent with potential for dye remediation.
• Understanding adsorption mechanisms is crucial for optimizing dye removal processes.

Purpose of the Study:

• To investigate the adsorption mechanism of anionic dyes (RB4, AB74, AB25) on bone char using statistical physics.
• To determine the influence of temperature and pH on dye adsorption.
• To elucidate the nature of dye-adsorbent interactions and dye aggregation.

Main Methods:

• Theoretical study employing a multilayer statistical physics model.
• Fitting equilibrium adsorption data at temperatures ranging from 298 to 313 K and pH 4.
• Analysis of adsorption capacities, layer formation, and adsorption energies.

Main Results:

• Adsorption capacities ranged from 0.08 to 0.12 mmol/g, with 1.62 to 2.24 dye layers formed.
• Dye molecular aggregation (dimers, trimers) was observed, particularly for RB4 and AB74.
• Adsorption was identified as multimolecular, endothermic, with energies between 10.6 and 20.8 kJ/mol.

Conclusions:

• Statistical physics modeling provides insights into the complex adsorption of anionic dyes on bone char.
• The adsorption process is influenced by temperature, leading to multilayer formation and dye aggregation.
• Van der Waals interactions and hydrogen bonding likely contribute to the adsorption mechanism, highlighting bone char's potential in dye wastewater treatment.