Nanobubbles in environmental remediation and sustainable technologies: A comprehensive overview of mechanisms, applications, and future prospects

Nanobubbles (NBs) are unique gas-filled colloidal systems with significant potential for environmental remediation and sustainable resource management applications. Unlike conventional aeration or solid nanomaterials, NBs provide a high interfacial area, extended residence time, enhanced gas transfer efficiency, and mobility in complex media, thereby intensifying the oxidation, reduction, and biological treatment processes. This review critically evaluates NBs generation methods, their physicochemical behavior, mechanistic pathways, and environmental applications in groundwater remediation, soil systems, aquaculture, and ecological restoration. Studies have indicated that NB-assisted systems can improve oxygen delivery, oxidant utilization, and contaminant removal under controlled conditions; however, the treatment performance depends on the gas type, pollutant class, pH, reaction time, matrix composition, and reactor design. In addition to conventional oxygen-, ozone-, and air-based systems, hydrogen nanobubbles (H₂-NBs) have emerged as a promising area of research owing to their potential to support reductive treatment pathways and mitigate metal-induced oxidative stress in the biological systems. This review is distinguished by its thorough comparison of gas-specific functions, engineering parameters, mechanistic uncertainties, and sustainability implications. It also underscores significant deficiencies in standardized reporting, validation of reactive oxygen species (ROS), pilot-scale evidence, and techno-economic assessments of these technologies. Overall, this review positions NBs technology as a promising low-chemical and potentially low-carbon platform for pollution control, ecological protection and sustainable water management.