Highly dispersed La on biochar-based self-support framework for rapid and selective phosphate removal: Performance...

Area of Science:

• Environmental Chemistry
• Materials Science
• Nanotechnology

Background:

• Phosphate-driven eutrophication is a major environmental concern.
• Metal-doped biochar shows potential for phosphate adsorption but requires structural optimization.
• Biochar-carbon nanofiber frameworks offer a stable and adaptable platform for adsorbent development.

Purpose of the Study:

• To develop a highly efficient and selective phosphate adsorbent using a biochar-carbon nanofiber framework.
• To investigate the structural influence of dispersed lanthanum (La) species on adsorption performance.
• To evaluate the adsorbent's efficacy in fixed-bed operations and its reusability.

Main Methods:

• Fabrication of a self-supporting biochar-carbon nanofiber framework (C-ACF).
• Functionalization with an amine-rich polymer (HCCP-PEI) to create PCP@C-ACF.
• Anchoring of highly dispersed La species onto PCP@C-ACF to yield PCP-La@C-ACF.
• Phosphate adsorption experiments, including kinetics, isotherms, selectivity tests, and fixed-bed column studies.
• Molecular dynamics simulations to elucidate adsorption mechanisms.

Main Results:

• PCP-La@C-ACF achieved a phosphate uptake of 63.5 mg P·g^-1 within 1 minute and an equilibrium capacity of 93.9 mg P·g^-1.
• The adsorbent demonstrated broad pH tolerance and excellent reusability over multiple cycles.
• Fixed-bed operation maintained effluent phosphate concentration below 0.2 mg P·L^-1 (removal rate > 99.4%).
• Significantly enhanced selectivity against common anions (Cl^-, NO₃^-, SO₄^2-) compared to La-free counterparts.
• Molecular dynamics simulations confirmed enhanced phosphate dehydration and interfacial diffusion due to dispersed La species.

Conclusions:

• The developed PCP-La@C-ACF is a highly performant adsorbent for phosphate removal.
• Dispersed La species are crucial for enhancing adsorption rate, capacity, and selectivity.
• The biochar-carbon nanofiber framework provides a stable and effective platform for advanced adsorbent design.
• This material holds significant promise for mitigating eutrophication and water purification applications.