Selective Removal Of Nitroaromatic Compounds From Wastewater In An Integrated Zero Valent Iron （ZVI） Reduction And ZVI/H₂O₂ Oxidation Process

2,4-Dinitrophenyl ether (DNAN) is an important chemical raw material and the waste water containing DNAN generated in the production process has insensitive properties, high toxicity and bioaccumulative characteristic, which resulted in the unbiodegradable feature of DNAN wastewater. In order to improve the biodegradability of the DNAN wastewater, an integrated system comprised of zero-valent iron (ZVI) reduction and ZVI-based Fenton oxidation process (ZVI-ZVI/H2O2) was applied for the selective removal of nitroaromatic compounds (NACs) from DNAN wastewater in this study. In addition, a novel method for the reuse of iron-containing sludge derived from the ZVI/H2O2 process was explored.In the research of the ZVI-ZVI/H2O2 process, the reaction parameters of ZVI reduction process and ZVI/H2O2 oxidation process were analyzed and optimized respectively. For the ZVI reduction process, the optimal pH and hydraulic retention time (HRT) were found to be 7.2 and 6 h; For the ZVI/H2O2 oxidation process:the optimal pH, HRT and H2O2 dosage were found to be 3.0,8 h and 100 mmol/L, respectively. After pretreatment by the ZVI-ZVI/H2O2 process under the optimal conditions, the removal efficiencies DNAN, 2,4-dinitrophenol (DNP) and 2,4-dinitrochlorobenzene (DNCB) were 95.8 ± 0.2%,100 ± 0.0% and 99.9 ± 0.1%, respectively. The NACs contained by the DNAN wastewater, i.e., DNAN, DNP, DNCB, were removed selectively and completely, as was indicated by the low UV254 value of 0.104 ± 0.003 and the low TOC removal efficiency of 32.4 ± 0.7% in the effluent of ZVI/H2O2 oxidation process. The BOD5/COD value of the effluen was promoted to be 0.337 eventually, which indicated that the biodegradability of wastewater was improved. Compared to the combined ZVI-Fenton process (ZVI-Fe-/H2O2), the ZVI-ZVI/H2O2 process had obvious advantages. Firstly, the utilization efficiencies of H2O2 and catalyst were higher. Secondly, the dosage of H2O2 and the yield of ferric sludge were lower. Comprehensively, the ZVI-ZVI/H2O2 process was economical for the treatment of NACs-containing wastewater.In the following research, a novel method for the reuse of iron-containing sludge which generated in the ZVI/H2O2 oxidation process was proposed. Firstly, a kind of material was successfully synthesized in the source of the iron-contained sludge through co-precipitation method. The synthesized material was confirmed to be NiFe2O4 by various characterization methods. Secondly, the obtained NiFe2O4 exhibited a heterogeneous Fenton catalytic feature for the degradation of phenol in the presence of H2O2. In addition, the magnetic catalyst was stable and recoverable, indicating a potential applications in organic pollutant removal.In conclusion, the NACs contained by the DNAN wastewater were removed selectively and completely in the coupled ZVI reduction and ZVI/H2O2 oxidation process. This research provide technical reference for the engineering application for the wastewater treatment.