Abstract
BackgroundThis work studied the performance of UV/PS/TiO2NPs and UV/PI/TiO2NPs as hybrid advanced oxidation processes for degradation of paraquat in aqueous solution, because this very toxic herbicide is used third most widely.ResultsThe effects of several factors such as UV irradiation, initial oxidant concentration, TiO2 nanoparticles dosage, and pH on the degradation efficiency were investigated. The process optimization was performed by the central composite design as a tool of response surface methodology for 30 mgL−1 of the herbicide initial concentration at 25 ℃ and 40 min of degradation process. Based on the results, a degradation efficiency of 77% and 90% were obtained for the UV/PS/TiO2NPs and UV/PI/TiO2NPs processes, respectively, in the optimum conditions. The mineralization efficiency of the paraquat solution using UV/PS/TiO2NPs and UV/PI/TiO2NPs processes are about 32% and 55%, respectively, after 40 min. The kinetic studies show that both processes follow a pseudo-first-order kinetic model, and the kinetic constants are 0.0299 min−1 for the PS process and 0.0604 min−1 for the PI process. The electrical energy consumption was estimated to be about 481.60 kWhm−3 for the PS process and 238.41 kWhm−3 for the PI process.ConclusionsThe degradation and mineralization efficiency of the paraquat solution using the UV/PI/TiO2NPs process was more than that of the UV/PS/TiO2NPs process at the optimum conditions after 40 min.
Highlights
This work studied the performance of UV/PS/Nanoparticles of TiO2 (TiO2NPs) and UV/PI/TiO2NPs as hybrid advanced oxidation processes for degradation of paraquat in aqueous solution, because this very toxic herbicide is used third most widely
The results indicated that at optimum pH 5.8, maximum decomposition of 84.39% in 5 h occurred under visible irradiation with initial concentration of 10 m gL−1 and the amount of photocatalyst of 30.8 g [33] such that both time and used catalyst amount were high
The range of the variables companion with the designed experiments for the UV/PS/TiO2NPs and UV/PI/TiO2NPs processes are shown in Tables 1 and 2, respectively
Summary
This work studied the performance of UV/PS/TiO2NPs and UV/PI/TiO2NPs as hybrid advanced oxidation processes for degradation of paraquat in aqueous solution, because this very toxic herbicide is used third most widely. In the recent years, advanced oxidation processes (AOPs) have been intensively studied as the most environmentally friendly and promising techniques for the degradation of recalcitrant organic pollutants in water by powerful oxidants, especially hydroxyl radicals and superoxide radicals [4,5,6,7,8,9,10]. In the photocatalytic activity process, the photoelectrons in the conduction band and highly oxidative holes in the valence band are produced, where a reaction occurs with the adsorbed water to form the highly reactive hydroxyl radicals according to Eqs. 1– 8 [19].
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