Efficient Catalytic Removal of Polycyclic Aromatic Hydrocarbons from Produced Water Using Fe ²⁺ -Terpyridine-Modified Superparamagnetic Nanoparticles

This study presents the development and application of a novel Fe²⁺-supported terpyridine-modified superparamagnetic iron oxide nanoparticle catalyst (Fe²⁺-Tpy@SPIONs) for the efficient removal of polycyclic aromatic hydrocarbons (PAHs) from produced water. The catalyst was synthesized through the coprecipitation of iron oxides, followed by surface functionalization with a terpyridine ligand to immobilize Fe²⁺, thereby enhancing its catalytic activity. Catalytic performance was optimized by adjusting pH, temperature, and catalyst dosage. Under the optimized conditions, the catalyst demonstrated superior efficiency in degrading PAHs, reducing total organic carbon (TOC) levels in real produced water samples, achieving an 82% reduction. Reusability tests indicated that the Fe²⁺-Tpy@SPIONs catalyst retained its catalytic activity and structural integrity over five consecutive cycles, with minimal performance loss, as confirmed by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) analyses. Control experiments further established that the catalytic activity required the presence of both Fe²⁺ and terpyridine on the SPIONs surface, as neither unmodified SPIONs nor Tpy@SPIONs alone resulted in significant PAH removal. This work underscores the potential of Fe²⁺-Tpy@SPIONs as an effective, reusable, and magnetically recoverable catalyst for large-scale environmental remediation, particularly for treating organic pollutants in wastewater produced by the oil and gas industry.