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

Herein, micro-nano bubbles (MNBs) assisted ozonation process (O3/MNBs) was developed to enhance interfacial reactions for pollutant degradation. Notably, the removal of organic contaminants in O3/MNBs system was ultrafast over a wide pH range, much faster than that of macrobubbles ozonation process (O3/MaBs). Experimental observations suggested that MNBs can effectively accelerate O3 interfacial mass transfer and enrich abundant OH− from a bulk solution, thus inducing high concentrations of O3 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 O3 can be quickly activated by hyperaccumulated OH− ions along with assistance of energy released by MNBs collapse, ultimately boosting •OOH generation significantly. In addition, •OOH/•O2- performed as critical intermediates for the formation of •OH in O3/MNBs process. O3/MNBs system demonstrated favorable and steady performance during long-term advanced treatment of industrial wastewater (∼7 m3/h) with significantly lower ΔO3/ΔCOD (1.41) than O3/MaBs system (2.69). The pilot-scale demonstration of O3/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.