Zn/Fe-Layered Double Hydroxide Composites with Kelp-Derived Biochar for Phosphate Recovery and Reutilization as a...

Area of Science:

• Environmental Chemistry
• Materials Science
• Agricultural Science

Background:

• Phosphorus scarcity necessitates sustainable recovery and reuse strategies.
• Inefficient fertilizer use exacerbates phosphorus loss.
• Developing integrated adsorbent-fertilizer systems is crucial for circular phosphorus management.

Purpose of the Study:

• To synthesize a Zn/Fe-layered double hydroxide (Zn/Fe-LDH)-kelp-derived biochar (KBC) composite for phosphate capture and slow-release fertilizer application.
• To investigate the phosphate adsorption capacity and mechanisms of the synthesized composite.
• To evaluate the performance of the P-loaded composite as a fertilizer in enhancing plant growth.

Main Methods:

• Co-precipitation synthesis of Zn/Fe-LDH@0.5KBC composite.
• Phosphate adsorption experiments, including kinetic and isotherm studies.
• Characterization using SEM, XRD, FTIR, and XPS.
• Plant growth experiments using pak choi to assess fertilizer efficacy.

Main Results:

• The Zn/Fe-LDH@0.5KBC composite exhibited a high phosphate adsorption capacity (132.52 mg P/g) and fast adsorption equilibrium (240 min).
• Phosphate adsorption was primarily chemisorption, following the Sips model, via synergistic mechanisms including electrostatic attraction, anion exchange, surface complexation, and precipitation.
• The P-loaded composite demonstrated diffusion-controlled phosphorus release and significantly enhanced pak choi growth, increasing labile and moderately labile phosphorus availability.

Conclusions:

• The developed Zn/Fe-LDH@0.5KBC composite is effective for phosphate recovery from wastewater.
• The composite serves as a viable slow-release fertilizer, improving phosphorus availability and plant growth.
• This study presents a promising strategy for integrated phosphate recovery and agricultural reuse, contributing to circular phosphorus management.