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Destruction of dinitroaromatic compounds in aqueous solution by UV-oxidation technologies
Author
Chen, Qianming
Supervisor
Goh, Ngoh Khang
Abstract
Dinitrobenzenes are one of the main contaminants appeared in the discharged wastewater around army ammunition production plants and certain chemical industries. These organic compounds are very stable in nature and are difficult to be treated using conventional technologies. In this work, the advanced oxidation processes (AOPs), in the field of which much attention has been attracted recently for wastewater treatment, were applied to degrade 1,3-dinitrobenzene in aqueous solution.
Direct photolysis of 1,3-dinitrobenzene by polychromatic light was studied. The main detected intermediates were 2,4-dinitrophenol, 3-nitrophenol and resorcinol. The direct photolysis of 1,3-dinitrobenzene followed zero-order kinetics. The degradation rate was around 10-9 M.s-1 under the experimental conditions.
In UV/H2O2 process, the degradation of 1,3-dinitrobenzene followed first-order kinetics and the range of degradation rate was from 10-8 to 10-7 M.s-1. 2,4-dinitrophenol, 3-nitrophenol, nitrohydroquinone, 4-nitrochatechol, resorcinol, catechol, hydroquinone were identified as the major aromatic intermediates. Reaction mechanisms and kinetics were discussed. The effect of initial concentration of H2O2, initial pH value and mixing rate was studied for the degradation of 1,3- dinitrobenzene.
Photocatalytic degradation was carried out for 1,3-dinitrobenzene in aqueous solution with UV/TiO2 and UV/ZnO processes. 2,4-dinitrophenol and 3-nitrophenol were identified as the main organic intermediates. Both processes were proved to be inefficient for 1,3-dinitrobenzene under the experimental conditions. The initial reaction rates were around 10-9 M.s-1.
UV/Fenton and UV/Fenton-like processes were used to degrade 1,3-dinitrobenzene in aqueous solution. It was found that the addition of ferric and ferrous ions enhanced the reaction rate greatly. The initial reaction rates in UV/Fe2+/H2O2, UV/Fe3+/H2O2 processes were around 10-7 M.s-1. The UV/ferrioxalate/H2O2 process with the initial reaction rate around 10-6 M.s-1. A conclusion can be made from the above results that UV/ferrioxalate/H2O2 process is the most efficient technology among all the AOPs used in the experiment.
Photolysis of H2O2 in aqueous solution irradiated by monochromatic light was also studied. A possible reaction mechanism and corresponding reaction rate expressions were proposed. The experimental results also showed that the decomposition of H2O2 in aqueous solution irradiated by both polychromatic and monochromatic light followed zero-order kinetics.
In addition, a detailed literature review related to the degradation of nitroaromatic compounds was also given in the thesis.
Direct photolysis of 1,3-dinitrobenzene by polychromatic light was studied. The main detected intermediates were 2,4-dinitrophenol, 3-nitrophenol and resorcinol. The direct photolysis of 1,3-dinitrobenzene followed zero-order kinetics. The degradation rate was around 10-9 M.s-1 under the experimental conditions.
In UV/H2O2 process, the degradation of 1,3-dinitrobenzene followed first-order kinetics and the range of degradation rate was from 10-8 to 10-7 M.s-1. 2,4-dinitrophenol, 3-nitrophenol, nitrohydroquinone, 4-nitrochatechol, resorcinol, catechol, hydroquinone were identified as the major aromatic intermediates. Reaction mechanisms and kinetics were discussed. The effect of initial concentration of H2O2, initial pH value and mixing rate was studied for the degradation of 1,3- dinitrobenzene.
Photocatalytic degradation was carried out for 1,3-dinitrobenzene in aqueous solution with UV/TiO2 and UV/ZnO processes. 2,4-dinitrophenol and 3-nitrophenol were identified as the main organic intermediates. Both processes were proved to be inefficient for 1,3-dinitrobenzene under the experimental conditions. The initial reaction rates were around 10-9 M.s-1.
UV/Fenton and UV/Fenton-like processes were used to degrade 1,3-dinitrobenzene in aqueous solution. It was found that the addition of ferric and ferrous ions enhanced the reaction rate greatly. The initial reaction rates in UV/Fe2+/H2O2, UV/Fe3+/H2O2 processes were around 10-7 M.s-1. The UV/ferrioxalate/H2O2 process with the initial reaction rate around 10-6 M.s-1. A conclusion can be made from the above results that UV/ferrioxalate/H2O2 process is the most efficient technology among all the AOPs used in the experiment.
Photolysis of H2O2 in aqueous solution irradiated by monochromatic light was also studied. A possible reaction mechanism and corresponding reaction rate expressions were proposed. The experimental results also showed that the decomposition of H2O2 in aqueous solution irradiated by both polychromatic and monochromatic light followed zero-order kinetics.
In addition, a detailed literature review related to the degradation of nitroaromatic compounds was also given in the thesis.
Date Issued
2000
Call Number
TD745 Che
Date Submitted
2000