Nacre-inspired hydroxyapatite/chitosan layered composites effectively remove lead ions in continuous-flow wastewater

Area of Science:

• Materials Science
• Environmental Science
• Nanotechnology

Background:

• Heavy metal contamination in wastewater poses significant environmental and health risks.
• Developing efficient adsorbents for continuous-flow systems remains a challenge.
• Biomimetic approaches offer promising strategies for novel material design.

Purpose of the Study:

• To design and fabricate nacre-inspired hydroxyapatite/chitosan (HA/CH) layered composites.
• To evaluate the mechanical properties and adsorption capabilities of these composites for heavy metal removal.
• To investigate the adsorption mechanism and kinetics for lead (Pb(II)), cadmium (Cd(II)), and mercury (Hg(II)) ions.

Main Methods:

• Layered HA/CH composites were constructed mimicking nacre's hierarchical structure.
• Mechanical properties (flexure strength) were tested under high-pressure drop conditions.
• Adsorption experiments were conducted for Pb(II), Cd(II), and Hg(II) in continuous-flow simulations.
• Adsorption kinetics were analyzed using Elovich and pseudo-order models.

Main Results:

• HA/CH composites exhibited enhanced flexure strength (3.08 MPa) and hierarchical microstructures suitable for continuous flow.
• High adsorption capacities were achieved: 295.96 mg/g for Pb(II), 192.37 mg/g for Cd(II), and 127.38 mg/g for Hg(II).
• Pb(II) removal was most effective due to specific interactions and complex formation.
• Adsorption followed heterogeneous chemisorption, as indicated by kinetic model fitting.

Conclusions:

• Nacre-like HA/CH layered composites demonstrate superior mechanical stability and high adsorption capacity for heavy metals.
• These materials present a novel and effective platform for heavy metal remediation in continuous-flow wastewater treatment.
• The biomimetic design successfully addresses challenges in adsorbent durability and efficiency.