Density functional theory simulation for Cr(VI) removal from wastewater using bacterial cellulose/polyaniline

Area of Science:

• Materials Science
• Environmental Chemistry
• Computational Chemistry

Background:

• Hexavalent chromium (Cr(VI)) poses significant environmental and health risks.
• Bacterial cellulose (BC) and polyaniline (PANI) are promising materials for pollutant remediation.
• Understanding adsorption mechanisms is crucial for developing effective Cr(VI) removal strategies.

Purpose of the Study:

• To elucidate the adsorption mechanism of HCrO4- and CrO42- (Cr(VI) models) onto BC, PANI, and BC/PANI composites.
• To investigate the influence of pH on the adsorption process.
• To explore the role of protonation states of PANI in adsorption.

Main Methods:

• Density Functional Theory (DFT) calculations were employed.
• Simulations were conducted under both acidic and neutral pH conditions.
• Three protonation states of PANI (neutral, partially protonated, fully protonated) were analyzed.

Main Results:

• Hydrogen bonding is the primary mechanism for Cr(VI) adsorption onto BC and PANI.
• PANI exhibits approximately three times higher adsorption energy compared to BC.
• The BC/PANI composite enhances PANI stability, indicated by an increased HOMO-LUMO energy gap.
• Adsorption is more favorable in acidic pH due to stronger and more diverse hydrogen bonding interactions (O⋯H and N⋯H).
• Physisorption governs the interfacial interaction, evidenced by minimal charge transfer.

Conclusions:

• BC/PANI composites demonstrate superior performance for Cr(VI) adsorption compared to individual components.
• Acidic pH significantly promotes the adsorption of Cr(VI) by BC/PANI systems.
• DFT calculations provide valuable insights into the adsorption mechanisms and material design for Cr(VI) remediation.