Ozone Microbubble synergy effect with activated carbon

https://www.sciencedirect.com/science/article/abs/pii/S1383586617325753?via%3Dihub

• Much better performance in catalytic microbubble ozonation with activated carbon.

• Synergistic effect of ozone microbubble and catalyst enhanced OH oxidation.

• More efficient TOC removal in catalytic microbubble ozonation even at low pH.

• Proposed degradation pathway of acid red 3R in catalytic microbubble ozonation.

The performance of catalytic microbubble (MB) ozonation using a commercial granular

activated carbon (AC) as catalyst in synthetic acid red 3R wastewater treatment was

more efficient than that of coarse bubble (CB) and MB ozonation alone. The ozone

mass transfer coefficient, ozone decomposition coefficient, decolorization rate

constant, TOC removal rate constant, and ozone reaction efficiency achieved

in catalytic MB ozonation were 0.253 min⁻¹, 0.093 min⁻¹, 0.342 min⁻¹, 0.0242 min⁻¹ 

and 0.128 mg_{(TOC removed)}/mg_{(ozone consumed)}, respectively. The average ozone

utilization efficiency in catalytic MB ozonation was as high as 98.3%. The synergistic

effect of collapsing ozone MBs and catalytic activity of AC enhanced hydroxyl

radicals (OH) oxidation in catalytic MB ozonation which provided about 75% of

oxidative capacity for TOC removal, even at a low pH. The enhanced OH

oxidation was crucial for the mineralization of acid red 3R in catalytic MB ozonation

where some OH scavengers could make TOC removal less efficient, especially

Na₂CO₃. In addition, the catalytic activity of this commercial AC seemed stable

after five recycling cycles. UV–Vis spectra and GC–MS analyses indicated that

acid red 3R was oxidized-degraded by a pathway of azo bond cleavage, formation

of naphthalene- and benzene-type compounds, further generation and final

mineralization of small organic acids, which initially reduced the pH and increased

the value again during catalytic MB ozonation. Therefore, the catalytic MB ozonation

with commercial granular AC was a promising solution for wastewater treatment

by ozonation process.