Degradation of Nitrobenzene-Containing Wastewater with O_3 and H_2O_2 by High Gravity Technology

Nitrobenzene-containing industrial wastewater was degraded in the presence of ozone coupled with H2O2 by high gravity technology. The effect of high gravity factor, H2O2 concentration, pH value, liquid flow-rate, and reaction time on the efficiency for removal of nitrobenzene was investigated. The experimental results show that the high gravity technology enhances the ozone utilization efficiency with O3/H202 showing synergistic effect. The degradation efficiency in terms of the COD removal rate and nitrobenzene removal rate reached 45.8% and 50.4%, respectively, under the following reaction conditions, viz.： a high gravity factor of 66.54, a pH value of 9, a H2O2/O3 molar ratio of 1：1, a liquid flow rate of 140 L/h, an ozone concentration of 40 rag/L, a H2O2 multiple dosing mode of 6 mL/h, and a reaction time of 4 h. Compared with the performance of conventional stirred aeration mixers, the high gravity technology could increase the COD and nitrobenzene removal rate related with the nitrobenzene-containing wastewater by 22.9% and 23.3%, respectively.

Effects of Coexisting Substances on Nitrobenzene Degradation with O_3/H_2O_2 Process in High-Gravity Fields

This study used nitrobenzene as the simulated pollutant to study the effects of common inorganic sodium salts and organics on nitrobenzene degradation by O_3/H_2O_2 in high-gravity fields. The experiment results showed that the highgravity technology could increase the nitrobenzene removal rate by improving the ozone transfer efficiency and ozone dissolution. Coexisting substances had different effects on the degradation kinetics of nitrobenzene in high-gravity fields. Among such substances, Na_2CO_3, NaOH, Na_3PO_4, and NaNO_3 accelerated the removal of nitrobenzene. The main action principle of nitrobenzene degradation by O_3/H_2O_2 is that the additives can increase the pH value of the solution, stimulate ozonolysis, generate hydroxyl radicals(·OH), and improve oxidation efficiency. By contrast, NaCl, NaHCO_3, NaHSO_4, ethanol(C_2H_5OH), acetic acid(CH_3COOH), formic acid(HCOOH), and tert-butyl alcohol(TBA) inhibited nitrobenzene removal. When NaHCO_3, CH_3COOH, or HCOOH were added, the pH value of the solution decreased and free radical chain reactions were hindered. However, NaCl, NaHCO_3, C_2H_5OH, and TBA consumed ·OH radicals and inhibited nitrobenzene removal.