Visible-light Z-scheme MoS2/CdS heterostructure for photocatalytic degradation of organics and surfactants in produc

Produced water from oil and gas operations contains persistent organic compounds and surfactants that are difficult to remove using conventional treatment. In this study, novel MoS₂/CdS Z-scheme heterostructures were synthesized and systematically characterized. Characterizations confirmed the intimate interfacial integration of ultrathin MoS₂ nanosheets on CdS nanorods, leading to enhanced surface area (68.5 m²/g for 5%-MC vs. 42.1 m²/g for CdS) and broadened visible-light absorption. The optimal composite, containing 5 wt% MoS₂, exhibited superior photocatalytic activity toward phenol and sodium dodecyl sulfate (SDS) degradation under visible light. Phenol degradation reached 95.2% with a pseudo-first-order rate constant of 0.0245 min⁻¹, approximately 4.9 and 8.2 times higher than pure CdS (0.0050 min⁻¹) and MoS₂ (0.0030 min⁻¹), respectively. For SDS, the same composite achieved 81.5% total organic carbon removal within 120 minutes. Photoelectrochemical analyses showed a 5-fold higher photocurrent density and significantly reduced charge transfer resistance compared with pristine materials, while photoluminescence quenching confirmed efficient suppression of electron–hole recombination. Radical scavenging experiments identified superoxide radicals and holes as the dominant species, consistent with a direct Z-scheme charge transfer pathway that preserves strong redox potentials. Reusability tests over five cycles demonstrated only a minor decline in phenol degradation efficiency (from 95.2% to 88.7%), and post-reaction XRD confirmed structural stability. These results highlight the MoS₂/CdS heterostructure as a robust, highperformance photocatalyst for treating complex industrial wastewater and provide insights into rationally designing advanced Z-scheme systems for environmental remediation.