Micro-/nano- bubbles ozonation for effective industrial wastewater remediation: From lab to pilot-scale application

Herein, micro-nano bubbles (MNBs) assisted ozonation process (O-3/MNBs) was developed to enhance interfacial reactions for pollutant degradation. Notably, the removal of organic contaminants in O-3/MNBs system was ultrafast over a wide pH range, much faster than that of macrobubbles ozonation process (O-3/MaBs). Experimental observations suggested that MNBs can effectively accelerate O-3 interfacial mass transfer and enrich abundant OH- from a bulk solution, thus inducing high concentrations of O-3 and hyperaccumulation of OH- ions at gas-liquid interface. These interfacial characteristics of MNBs resulted in formation of a special interfacial reaction field, in which high concentration of O-3 can be quickly activated by hyperaccumulated OH- ions along with assistance of energy released by MNBs collapse, ultimately boosting center dot OOH generation significantly. In addition, center dot OOH/center dot O-2(-) performed as critical intermediates for the formation of center dot OH in O-3/MNBs process. O-3/MNBs system demonstrated favorable and steady performance during long-term advanced treatment of industrial wastewater (similar to 7 m(3)/h) with significantly lower Delta O-3/Delta COD (1.41) than O-3/MaBs system (2.69). The pilot-scale demonstration of O-3/MNBs efficiently degraded all four categories of organic contaminants according to EEM fluorescence spectra. The study demonstrated an environmentally-benign technology for effective treatment of industrial wastewater.