Rapid removal of p-chloronitrobenzene from aqueous solution by a combination of ozone with zero-valent zinc

The degradation of p -chloronitrobenzene ( p CNB) in different systems including ozone alone, ozone together with zero-valent zinc (Zn(0)) and Zn(0) bubbled with air instead of ozone was investigated. The results demonstrated that the degradation of p CNB by ozone alone was weak. However, the coexistence of Zn(0) and ozone exhibited a significantly synergistic role in p CNB degradation and approximately 98% of the initial p CNB (10   mg/L) was removed within 18   min. The degradation efficiency of p CNB was related to Zn(0) dosage and ozone flow amount, and the optimum conditions were 0.5   g/L and 4.8   mg/min, respectively. p CNB could be effectively degraded in the initial pH range of 4–10, but a higher or a lower pH was not beneficial to the removal of p CNB. Accompanying anions also affected p CNB degradation. Chloride and sulfate slightly improved p CNB degradation, whereas bicarbonate and phosphate markedly suppressed the degradation of p CNB. The reuse of Zn(0) (4 cycles) for p CNB ozonation indicated that the catalytic activity of Zn(0) maintained high and stable. The experiments of free radical scavengers ( tert -butyl alcohol and p -benzoquinone) corroborated the dominant active species responsible for p CNB degradation by a combination of ozone with Zn(0) was O 2 − rather than OH. Based on the results obtained in this study, it can be concluded that ozone activated by Zn(0) is an effective and promising approach to degrade organic contaminants.