Developing a bifunctional adsorption-photocatalysis system in a S-scheme SiO2/MOF-808(Zr)/Bi2O3 heterojunction 3D-MOF-based photocatalyst for enhanced petroleum refinery produced water treatment

Abstract

The increasing discharge of produced water from oil and gas operations poses a critical environmental challenge due to its complex composition, high salinity, and mixed organic-inorganic pollutant load. This study reports the application of a ternary SiO2/MOF-808(Zr)/Bi2O3 composite as a bifunctional material integrating adsorption and visible light driven photocatalysis for the treatment of actual petroleum refinery produced water collected from PT. Pertamina, Indonesia. The composite exhibited a hierarchical mesoporous structure with a high pore volume (1.16 cm3/g) and a specific surface area of 170.57 m2/g, ensuring effective pollutant accessibility under highly saline conditions (23,450 mg/L). Incorporation of Bi2O3 narrowed the optical bandgap to 2.72 eV, enabling visible light activation, while interfacial coupling with MOF-808(Zr) promoted an S-scheme heterojunction that suppressed charge recombination. Under visible light irradiation, the composite achieved simultaneous removal efficiencies of 84.4% for chemical oxygen demand (COD) and 77.15% for ammonia-nitrogen (NH3-N) within 120 min. Kinetic and mechanistic analyses revealed distinct removal pathways, where COD degradation followed pseudo second order kinetics governed by chemisorption and reactive oxygen species-mediated oxidation, whereas NH3-N removal proceeded via pseudo first order kinetics dominated by electrostatic physisorption and intraframework diffusion. The composite retained over 91% of its initial activity after five consecutive cycles, indicating high operational stability. This work establishes mechanistic principles for MOF-based adsorption-photocatalysis systems under extreme-salinity industrial wastewater and demonstrates their viability as a sustainable technology for petroleum refinery produced water management.