Activating peroxymonosulfate using carbon from cyanobacteria as support for zero-valent iron

Area of Science:

• Environmental Chemistry
• Materials Science
• Nanotechnology

Background:

• Wastewater contamination by persistent organic dyes like orange II (OII) poses significant environmental challenges.
• Developing efficient and stable catalysts for dye degradation is crucial for environmental remediation.
• Nanoscale zero-valent iron (NZVI) is effective for pollutant degradation but often suffers from aggregation and instability.

Purpose of the Study:

• To synthesize and characterize a novel composite material, cyanobacterial char-supported nanoscale zero-valent iron (NZVI@ACC).
• To evaluate the efficiency of the NZVI@ACC/peroxymonosulfate (PMS) system for degrading orange II (OII) dye.
• To elucidate the degradation mechanism and identify the active species involved.

Main Methods:

• Preparation of NZVI@ACC composite using cyanobacterial char as a nanoscale carrier for NZVI.
• Characterization of the composite using XRD, XPS, SEM, and TEM.
• Degradation experiments of OII using the NZVI@ACC/PMS system under varying conditions.
• Identification of active radicals via quenching and EPR experiments.
• Kinetic analysis and theoretical calculations to understand the degradation pathway.

Main Results:

• The NZVI@ACC composite exhibited a stable structure with high surface area (42.249 m²/g) and magnetism for easy separation.
• The NZVI@ACC/PMS system achieved 98.32% OII degradation within 14 minutes.
• The degradation followed first-order kinetics with an activation energy of 17.34 kJ/(mol·K).
• Sulfate radicals (SO₄·⁻) were identified as the primary active species, attacking the azo and hydrogenated azo structures of OII.
• Halogen ions (I⁻, Br⁻, Cl⁻) showed inhibitory effects on OII degradation, with inhibition increasing in the order Cl⁻ < Br⁻ < I⁻.

Conclusions:

• NZVI@ACC is a highly efficient and magnetically separable catalyst for PMS activation.
• The NZVI@ACC/PMS system offers a promising approach for the effective degradation of orange II dye in wastewater.
• Understanding the role of active species and the impact of co-existing ions is vital for practical applications.