Study On Mechanism And Influencing Factors Of The Degradation Of Recalcitrant Organic Compounds By Metallic Iron And Electrolytic Reduction

The recalcitrant organic compounds will pollute the ecological environment over a long period of time once released into the surroundings. They are of great health concern because of their toxicity and nonbiodegradability. Recently, it was proposed that reductive methods could be applied to Wastewater treatment to enhance the degradation of recalcitrant organic compounds. In this dissertation, zero-valent iron, catalytic iron and electrolytic reduction were studied to degrade model organic pollutants such as 2,4-dinitrotoluene (DNT). The influencing factors, treatment effects, reaction mechanisms and pathways were investigated deeply to search after efficient abiotic treatment techniques.Zero-valent iron is moderately strong reducing agent that is capable of reducing many common environmental contaminants including DNT. The influencing factors, reaction pathway and reaction productions of reducing degradation were studied systematically to evaluate the performance and discuss reaction mechanism. The main influencing factors include: the surface character of zero-valent iron, dissolved oxygen, pH value, solution original concentration and the structure of nitroaromatic compounds (NACs). The results showed that acid wash activation of iron surface affected its reactivity greatly. The dissolved oxygen competed with organics for electrons and affected adversely the degradation of DNT. The degradation of DNT was enhanced at low pH values. There were limited number of reactive surface sites on the surface of zero-valent iron, and competition effects were observed at high initial DNT concentrations. In term of degradation rate by zero-valent iron the NACs ranked as followed nitrobenzene (NB) > dinitrobenzene (DNB) > dinitrotoluene (DNT).The ions coexisted in solutions significantly affected the degradation of DNT by zero-valent iron. The addition of electrolyte (Na₂SO₄) increased the conductance, intensified the electron transfer, and accelerated the rate of reaction of DNT. The presence of chloride in solution significantly accelerated the degradation of DNT by zero-valent iron, and pitting corrosion mechanism was proposed to explain the chloride effect. CO₃^2-, SiO₃^2- and PO₄^3- could inhibit the corrosion of iron, reacting...