Nitrobenzene Wastewater Treatment By Hybrid Zero-Valent Iron-Hydrogen Peroxide System

As a kind of toxic organic compounds, nitrobenzene is difficultly biodegradable. Industrial scrap iron is often used in industry for the degradation of nitrobenzene. However, nitrobenzene can not be mineralized by iron powder. Ferrous ions can form strong oxidation system combined with hydrogen peroxide under acid conditions, in which difficult bio-degraded organic compounds can be oxidation. The degradation of wastewater containing nitrobenzene by hybrid iron reduction-hydrogen peroxide oxidation technology was studied in this article, and nitrobenzene was hoped to be completely mineralized.The experiments were carried out from three aspects in this research: nitrobenzene reduction by micron iron, aniline oxidation by Fenton reagent and nitrobenzene degradation by hybrid iron reduction-hydrogen peroxide oxidation technology. The influence of technical parameters on the reaction process and its mechanism were discussed preliminary.The study of nitrobenzene reduction by micron iron indicated that nitrobenzene removal rate increased with the increase of rotational speed. The smaller the particle size of Zero-valent iron (ZVI), the greater the removal rate of nitrobenzene can be. The process of nitrobenzene reduction by micron iron was in line with the pseudo first-order kinetics model. The reaction rate constant Kobs decreased with the loss of the pH, and reached the maximum0.616min-1at pH3, and nitrobenzene removal rate reached100%respectively. Increasing the temperature from10℃to40℃increased the rate constant by6.8times. The reaction activation energy and pre-exponential factor were50.7KJ/mol and1.27×10min-1, respectively. The rate constant correlated positively to ZVI dosage. It reached0.609min-1when ZVI dosage selected to be14.3mmol/L.Fenton regent was added in aniline containing wastewater to discusse the oxidation performance. The result showed that the removal rate of aniline increased with increasing time. It found out to be99.7%at10min, the removal rate of TOC reached29.0%, respectively. The removal rate of aniline increased first and then decreased with the increase of H2O2concentration. With the increase of Fe2+concentration, both of the removal rate of aniline and TOC showed a trend of increase before decrease. With the increase of initial concentration of aniline, the removal rate of aniline were found to be slightly lower, but still kept more than97%, the TOC removal rate showed a tendency of increase. Aniline and TOC removal rate increased at first, and then decreased with the increase of pH. The maximum removal rate appeared at pH4. The research of nitrobenzene degradation by hybrid iron reduction-hydrogen peroxide oxidation technology showed that there were4.11mmol/L Fe2+generated after15min (initial concentration of nitrobenzene was0.813mmol/L). Iron powder was avoided by precipitation separation. Adding7.20mmol/L H2O2into the supernatant for further reaction. After15min, nitrobenzene removal rate was detected to be100%finally, and corresponding TOC removal rate reached70.1%.