Zero-Valent Iron Technology For The Remediation Of Ground Water Contaminated By Nitrobenzene And Poly Chlorinated Aromatic Hydrocarbons

In this paper, we investigated the reduction of nitrobenzene （NB）, pentachlorophenol（PCP） and hexachlorobenzene （HCB） in ground water using zero-valent iron technology.The main contents and results are summarized as follows:（1） The prepared iron nanoparticles （NPs） immobilized in nylon membrane weresynthesized and characterized, and the reduction of NB in groundwater by the NPs wasinvestigated. Characterization results showed that the NPs distributed homogeneously on themembrane surface without heavy agglomeration, and they were mainly composed ofFe-oxides rather than Fe⁰. Using these NPs, NB in groundwater was rapidly decreased by68.9%just in the first20min, the adsorbed Fe²⁺on NPs were mainly responsible for thereduction. The reaction rate constants increased upon decreasing the pH value and decreasedin the presence of ground water ions. The samples we prepared exhibited good corrosionresistance for humic acid （HA） but had a short-term performance for NB degradation.（2） We prepared nylon membrane immobilized Pd/Fe NPs in air by two differentprocedures, Pd deposition and co-reduction. The two kinds of NPs were both composed ofFe⁰and Fe-oxide. The NPs prepared from co-reduction had much smaller particle size andhigher Fe⁰content, they could dechlorinate85%of PCP to phenol within45min, whichproved the possibility of synthesizing highly reactive immobilized bimetallic NPs in air.However, the efficiency of PCP dechlorination by NPs immobilized by Pd deposition wasrather low. Immersion by H2SO4could recover membrane, Pd and Fe after treatment. ThePd/Fe NPs prpared using recovered materials could dechlorinate PCP despite thedechlorination efficiency declined for the porous structure of membrane was broken by acid.（3） Pd/Fe-PRB and TX-100enhanced washing technology was combined to study theremediation of ground water contaminated by HCB source in subsurface. The HCB waseffectively dechlorinated to PCB and1,2,3,4-TeCB when the modeling contaminatedground water passed through Pd/Fe-PRB, and the efficiency increased with timeprolonging, which proved the feasibility of Pd/Fe-PRB for the remediation of HCBcontaminated ground water.