Abstract
The degradation of imazapyr (C13H15N3O3), an active element in the aqueous solution of commercial herbicide, was investigated. This study was the first to evaluate in a comprehensive manner the efficiency of advanced oxidation processes for imazapyr degradation. Results showed that Imazapyr degradation is significantly affected by operational conditions such as TiO2 concentration, ozone concentration, initial concentration of imazapyr and pH. The kinetics of Imazapyr consumption was the first order with respect to Imazapyr concentration and zero order with respect to ozone concentration with a constant rate of 0.247 min−1 and 0.128 min−1 for photocatalytic ozonation and heterogeneous photocatalysis, while it was the first order with respect to Imazapyr and the first order with respect to ozone concentrations when only ozone was used with a constant rate of 0.053 mol L−1 min−1 at pH 7. The results revealed that more than 90 percent of the removal efficiency representing the elimination of imazapyr was held up to 7 μM. Further increase in the concentration of imazapyr leads to a drop in the removal efficiency, however the total imazapyr degradation was reached in 20 min utilizing photocatalytic ozonation for 5 μM of Imazapyr in the presence of 100 mg L−1 of TiO2, 10 mg L−1 of ozone at pH 7. Photocatalytic ozonation and heterogeneous photocatalysis utilizing TiO2 as a semiconductor process appeared possible and well suited for the treatment of organic contaminants such as imazapyr herbicides, although at certain dosages of pH and common time for wastewater treatment, imazapyr was not degraded with ozonation on its own. The association of two oxidation processes, ozonation and photocatalysis, has improved oxidation efficiencies for water treatment under optimal conditions, leading to the development of non-selective hydroxyl and more reactive radicals in the oxidation medium, as well as the resulting synergistic effects between photocatalysis and ozonation that react more rapidly with imazapyr herbicide.
Highlights
Increasing industrial activity has become a significant issue leading to increased contamination of air, soil and water
In order catalyst traces.to compare the efficiency of photolysis (UV), heterogeneous photocatalysis (TiO2/UV), ozonation (O3/UV) and photocatalytic ozonation (O3/TiO2/UV), experiments were performed by the Experiment usage of the initial concentration of pesticide and the same amount of TiO2 at pH 7 (Figure 3)
The high-performance liquid chromatography (HPLC) imazapyr degradation chromatograms after 10 min of irradiation with
Summary
Increasing industrial activity has become a significant issue leading to increased contamination of air, soil and water. The AOPs are focused on developing very reactive and non-selective substances such as hydroxyl radical (OH.), ozonide (O3 ̄), superoxide (O2 ̄), photo-produced electron-hole pairs with a higher oxidizing potential than standard oxidants (O2 , O3 , Cl2 , H2 O2 , ClO2 , etc.) leading to the mineralization and decomposition of water contaminants [5,6] These oxidative species have been widely investigated to eliminate pollutants or oxidize them gradually to less harmful substances from different wastewater types, most researches are centered on single compounds, generally at concentrations higher than these observed in wastewater [7,8]
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