RSM-optimized Mg/Al-LDH biochar composite for enhanced phosphorus removal: Insights into interlayer structure...

Area of Science:

• Environmental Chemistry
• Materials Science
• Water Treatment Technologies

Background:

• High phosphorus concentrations in agricultural wastewater pose significant ecological risks due to toxicity and persistence.
• Layered double hydroxides (LDH)-modified biomass shows promise for anion adsorption, but optimizing LDH structures for phosphate removal and understanding mechanisms is crucial.

Purpose of the Study:

• To optimize the synthesis of Mg/Al-LDH modified biochar (MABC) for enhanced phosphate adsorption using Response Surface Methodology (RSM).
• To investigate the microscopic mechanisms responsible for efficient phosphorus adsorption by the optimized MABC.
• To evaluate the potential of phosphorus-enriched MABC as a slow-release fertilizer.

Main Methods:

• Batch adsorption experiments were conducted to test MABC performance.
• Response Surface Methodology (RSM) was employed to optimize MABC synthesis conditions (Mg/Al ratio, biochar dosage, roasting temperature).
• Material characterization utilized XRD, XPS, FTIR, and SEM to elucidate adsorption mechanisms.
• Soil column experiments assessed the phosphorus release rate from MABC-P.

Main Results:

• The optimized MABC (MABC₆) achieved a maximum adsorption capacity of 54.932 mg·g^-1.
• MABC₆ exhibited high crystallinity, large surface area, abundant functional groups, and expanded layer spacing.
• Adsorption mechanisms include chemical adsorption, multilayer adsorption, electrostatic attraction, ion exchange, surface complexation, and ligand exchange.
• MABC₆-P demonstrated a controlled phosphorus release rate (17.59% over 30 days), indicating slow-release fertilizer potential.

Conclusions:

• RSM optimization successfully enhanced MABC's crystalline structure, expanding layer spacing and significantly improving phosphate adsorption capacity.
• The optimized MABC is effective for aquatic environmental remediation.
• MABC shows promise as a viable material for slow-release fertilizer applications, reducing phosphorus runoff.