Novel catalytic degradation of Diazinon with ozonation/mg-Al layered double hydroxides: optimization, modeling, and dispersive liquid-liquid microextraction

Degradation of cefixime antibiotic by heterogeneous catalytic ozonation process using novel LDH/zeolite nano-composite: modeling and optimization process

In recent decades, the indiscriminate use of antibiotics and their discharge into the environment have caused serious consequences for aquatic and terrestrial organisms. The present study investigates the optimization of cefixime antibiotic decomposition by a powerful catalytic ozonation process. In this study, the MgAl-LDH /zeolite nanocomposite was synthesized and used as an ozonation-adsorption catalyst to degrade Cefixime antibiotic from an aqueous solution. XRD, FE-SEM, and FTIR analyses were scrutinized to reveal the main characteristics of the as-prepared nanocomposite, showing that it was well-synthesized. The investigated variables in the catalytic ozonation of Cefixime by the mentioned nanocomposite included solution pH level (5-9), nanocatalyst dose (0.5-2.5 g/L), Cefixime concentration (5-25 mg/L) and reaction time (5-60 min) which they were optimized by adopting RSM-CCD. The results showed that all variables positively affected the efficiency of the catalytic ozonation process. Nonetheless, the lowest effect of operational factor pH, the degradation of Cefixime was subjected to the initial content of Cefixime in this treatment system. The optimal conditions for cefixime removal by catalytic ozonation process were determined at pH of 7.72, nanocatalyst dosage of 1 g/L, cefixime concentration of 23 mg/L, and reaction time of 55 min. In the optimized operating conditions, the removal efficiency of Cefixime by MgAl-LDH /zeolite nanocomposite was high, up to 98.37%, and It is suggested that due to the high efficiency of this process, it can be used in the treatment of pharmaceutical wastewater.

Graphical Abstract

Design and modeling of diazinon degradation in hydrous matrix by Ni-doped ZnO nanorods under ultrasonic irradiation: process optimization using RSM (CCD), kinetic study, reaction pathway, mineralization, and toxicity assessment

In first, the Ni-doped ZnO nanorods used as an appeal sonocatalyst was synthesized through co-precipitation method. Afterwards, the crystalline structure, functional groups, surface morphology, and elemental composition were characterized by a set of analysis. Removal of diazinon ((DZ) as a renowned pesticide) was investigated using sonocatalytic performance of US/Ni-doped ZnO system. In this empirical study, response surface methodology (RSM) based central composite design (CCD) was applied for optimization of operational factors. Under the optimum conditions such as initial pH = 5, initial DZ concentration = 15 mg L^-1, sonocatalyst dosage = 1 g L^-1, and in the presence of organic compounds (oxalic acid, humic acid, and folic acid) = 3 mg L^-1, the sonocatalytic degradation of DZ after 15 min was 82.29%. The F-value (6.64) and P-value (< 0.0001) for DZ degradation in the quadratic model imply the proposed model was significant. A-factor (pH) considers as a prominent factor owing to having the highest F-value. In addition, the sonocatalytic data in this study exhibited valid fitting for the first order kinetic model (R² > 0.98). After six consecutive cycles, the Ni-doped ZnO nanorods could be recyclable for sonocatalytic degradation of DZ. The five main compounds produced during the US/Ni-doped ZnO embracing 2-isopropyl-6-methyl-4-pyrimidinol (IMP), diethyl phosphonate, diazoxon, hydroxyldiazinon, and diazinon methyl ketone are formed in the path of DZ degradation. OFAT style also revealed 99.99% of DZ degradation with 73.26% of mineralization rate in optimum status. The Ni-doped ZnO presented agreeable sonocatalytic facility in the refinement of real water and wastewater matrix. Finally, the results of toxicity evaluation (Daphnia magna) in the sonocatalytic degradation of DZ (by US/Ni-doped ZnO system) showed that the toxicity of the DZ solution lessened under US waves (LC₅₀ and TU 48 h equal to 36.472 and 2.741 volume percent, respectively).