Diazinon and MCPA photo-reduction with sulfite excitation under UV irradiation and reducing agents' generation.

Diazinon (DIZ) and 4-Chloro-2-methylphenoxyacetic acid (MCPA) herbicide and widely used in agricultural lands. Present study investigates diazinon and 4-chloro-2-methylphenoxyacetic acid photo-reduction via UV/Sulfite (US) in as Advanced Reduction Processes (ARP). The ideal pH was Molar ratio of sulfite: DIZ or MCPA 1:1 and, 20 min reaction time, and pH 9, in which about 100 % reduction of DIZ and MCPA with a concentration of 10 mg L-1 was achieved and the optimal conditions were considered. Kinetic investigation increasing DIZ and MCPA concentration from 5 to 20 mgL-1, kobs increase about from 0.151 to 0.234 for DIZ and from 0.231 to 0.589 min-1. Also, reaction rate (robs) increases about from 0.755 to 4.68 for DIZ and from 1.155 to 11.78 mg L-1.min. The amount of energy consumption in DIZ solution increased from 5 to 20, respectively, from 0.73 to 2.37, and in the reduction of MCPA from 0.47 to 1.49 kWh per cubic meter. According to experiments performed in 30 min with the US process, COD levels were reduced by about 46 % of both pollutants. It is important to note that the BOD/COD ratio rose from about 0.20 to 0.48 after 30 min. Since the index of biodegradability has grown high, it can be concluded that non-biodegradable COD (NBDCOD) convert to biodegradable COD (BDCOD) and toxicity is lower than of before of treatment. This study has been very suggesting that the UV/sulfite method produces effluent with a non-toxic and ecologically beneficial manner by biological treatment or discharge directly in environment.

Simultaneous Cr (VI) reduction and diazinon oxidation with organometallic sludge formation under photolysis: kinetics, degradation pathways, and mechanism.

In this study, simultaneous removal of an organic matter (diazinon, DIZ) and an inorganic substance (chromium, Cr) was used. Breaking down of organic matter by UV irradiation produces various radicals, including sulfides, carboxyl, hydroxyl, hydrated electrons, and various organic radicals that are highly reactive and help us to precipitation inorganic substance (Cr). The optimal condition was 30:1 DIZ:Cr molar ratio, pH 9, and about 100% and 82.3% of DIZ and Cr were obtained in 30 min. Cr deposition was very slow at first. After the destruction of the DIZ structure, Cr deposition began, and various types of sludge with disturbed properties were formed. These sledges were analyzed by FTIR analysis and showed that green sludge could be chromium (III) hydroxide; brown sludge due to chromium (III) hydroxide, tiny green crystals from chromium (III) oxide, red brick from chromium (II) acetate chromium trioxide, as well as black sludge caused by chromium oxide were identified. In UV/DIZ/Cr process, kobs and robs range obtained 0.33-0.15 and 16.8-23.4 $ with both Cr and DIZ concentration increased from 50 to 150 mg L-1. Also, EEO for Cr precipitation was 24.65 to 5.74 and for DIZ 12.54 to 4.73 (kwh m-3). Depending on the amount of energy consumption, TCS was 37.19 to 10.47 for Cr precipitation and 4.46 to 1.25 $. It is important to note that when both pollutants are exposed to ultraviolet light, more energy and cost are generally required from UV/DIZ process and less than of UV/Cr process. But it should be noted that in fact 50 mg L-1 of chromium and 50 mg L-1 of DIZ are being removed at the same time. In UV/DIZ and UV/Cr processes that are exposed to ultraviolet radiation alone, only one of them is removed. Also, when these two pollutants are being removed at the same time, the total amount of energy is much less than the total energy consumption of the pollutants one by one.

Comparative study of energy consumption, kinetic, and performance between conventional and baffled photocatalytic reactor (BPCR) to ofloxacin photo-degradation.

Regarding the cost-effective photo-degradation of ofloxacin (OFL), present study investigates UV/sulfite /ZnO (USZ) in reactor conventional (without baffles) and baffled photocatalytic reactor (BPCR). The optimal condition was 0.77:2:50 sulfite/ZnO/OFL molar ratio, pH 7, and 30 min reaction time for 100% degradation of 200 mg L-1 concentration of OFL. As information obtained, the UZI process reduces the BOD and COD level about 66% to 86.29% within 80 min reaction, respectively. Also, BOD/COD ratio initial from 0.26 reaches 0.6 after 30 min of reaction time. Kinetic investigation increasing OFL concentration, kobs and robs increase, and, secondly, in the conventional and BPCR reactor, kobs increase is about 17% and 50% with increasing OFL concentration from 50 to 200 mgL-1. Also, figure-of-merit EEo varies from 12.66 to 17.41 and 7.26 to 10.15 kWhm3 for conventional reactor and 8.66-13.61 to 5.24-8.12 kWhm3, respectively. Also, kinetic model EEo declines from 15.23 to 8.61 and from 13.31 to 5.37 kWh m-3 in conventional and BPCR, respectively. Total cost of the system (TCS) decreases from 7.31 to 2.16 $ in conventional reactor and 4.57 to 0.55 $ in PCBR reactor. Total cost of the system (TCS) was investigated at different concentrations.

Diazinon pesticide photocatalytic degradation in aqueous matrices based on reductive agent release in iodide exciting under UV Irradiation.

Regarding the cost-effective degradation of diazinon (DIZ), the present study was conducted to develop and UV/iodide process in a photo catalyst reactor. CCD modeling applied and the results shows that the highest R-squared value (adjusted R-squared: 0.9987), the lowest P-value (2.842 e - 10), the lowest AIC (14.54), and the most insignificant lack-of-fit (0.73) belonged to the second-order model. Based on second-order model, the stationary points for time, iodide: DIZ (molar ratio %), DIZ concentration, and pH were 6.99 min, 80.15% iodide: DIZ (molar ratio %), 3.34, mg L-1, and pH 7.34 (- log10[H+]), respectively. The maximum reduction efficiency of 97.22% was obtained at the experimental conditions. The LC-MS analyses from optimal condition implied that all the DIZ molecules and its intermediates breaking to simple compounds during 15 min of processing. The data shown UI process reduced the BOD and COD levels by about 66% and 86.29% within 80 min of photoreaction, respectively. Furthermore, in kinetic investigation, with the increase in DIZ concentration, kobs and robs increased and secondly, the conventional and PCBR reactor kobs increased by about respectively 17% and 50% with an increase in DIZ concentration from 5 to 15 mgL-1. Additionally, when the DIZ concentration increase from 5 to 15 mg L-1, robs increased in the conventional and PCBR reactors respectively about 4.9 and 6 times. Figure-of-merit EEo changed from 12.66-17.41 to 7.26-10.15 kWhm3 for the conventional reactor, and 8.66-13.61 to 5.24-8.12 kWhm3 in PCBR, when the DIZ concentration increasing from 5 to 15 mg L-1. Consequently, in the PCBR reactor, the energy consumption reduced by 14% at 5 mg L-1 DIZ concentration and by 60% at 15 mg L-1 DIZ concentration. Also, total cost of the system (TCS) decreases from 4.52 to 1.46 $ in conventional reactor and 1.47 to 0.42 $ in PCBR reactor when the DIZ concentration increase from 5 to 15 mg L-1.