Enhanced aqueous phosphate removal using chitosan-modified zirconium-loaded cork biochar

Area of Science:

• Environmental Chemistry
• Materials Science
• Water Treatment

Background:

• Eutrophication, driven by excess phosphate (PO4-P), is a major environmental concern.
• Effective phosphate removal is crucial for mitigating water body degradation.
• Development of efficient and selective adsorbents is needed for phosphate remediation.

Purpose of the Study:

• To synthesize and evaluate a novel Zr(IV)-loaded chitosan-modified used cork stopper biochar composite (CS-CBC-Zr) for phosphate removal.
• To investigate the adsorption performance and influencing parameters of the CS-CBC-Zr beads.
• To understand the adsorption mechanism and kinetics for phosphate removal.

Main Methods:

• Synthesis of CS-CBC-Zr composite beads from cork stopper biochar and chitosan.
• Batch adsorption experiments to assess PO4-P removal efficiency.
• Investigation of parameters: Zr loading, adsorbent dosage, pH, co-anions, contact time, and initial PO4-P concentration.
• Adsorption kinetics and isotherm modeling (pseudo-second-order, Sips model).
• Characterization of adsorbents using FTIR, SEM, and XPS.

Main Results:

• CS-CBC-Zr beads demonstrated superior PO4-P adsorption compared to unmodified biochar.
• Maximum adsorption capacity reached 33.89 mg/g, predicted by the Sips model.
• 95% PO4-P removal efficiency achieved at 50 mg/L initial concentration within 120 minutes.
• Effective performance across a wide pH range (4-10) and high selectivity for PO4-P over co-anions.
• Adsorption followed pseudo-second-order kinetics, indicating chemisorption.

Conclusions:

• CS-CBC-Zr composite beads are highly effective and selective adsorbents for phosphate removal.
• The material shows potential for practical application in controlling eutrophication.
• The adsorption process is primarily governed by chemisorption, with a high capacity and broad applicability.