Synergistic dispersion and biodegradation of oil in seawater based on Janus nanosheets and oil-degrading bacteria

Abstract

Marine oil spills cause significant pollution to the global environment. Dispersants are frequently used in such spills to break down the oil slick into smaller droplets, facilitating the biodegradation of the oil. Herein, Janus nanosheets (JNs) were used as a new particulate dispersant, which could act synergistically with bacteria in seawater to remediate marine oil spill pollution efficiently. The JNs not only possessed amphiphilic properties and low toxicity but also demonstrated exceptional emulsification capabilities for oil, synergistically enhancing the remediation process alongside oil-degrading bacteria. Due to the inherent constraints on interfacial rotation and multilayer steric hindrance at the diesel–water interface, the emulsion created by JNs remained highly stable, maintaining a small oil droplet size even after a month. Significantly, the JNs enabled the binding of negatively charged oil-degrading bacteria through electrostatic interactions. Following their combination, the JNs effectively transported bacteria directly to the surface of the oil droplets through the influence of sea waves. This cooperative treatment system not only enhanced the oil's dispersibility but also markedly augmented the biodegradation of the oil when compared to the use of bacteria alone. At a diesel concentration of 6 mL L⁻¹ and a JN concentration of 0.3 g L⁻¹, the bacterial biodegradation of diesel was reduced from 5 days to 3 days, and the diesel biodegradation rate increased from 70% to 85%. These findings underscore the remarkable capacity of JNs to effectively emulsify oil and enhance bacterial oil degradation in seawater.