Mehdi Shirzad-Siboni

This study investigates the efficiency of a photocatalytic process utilizing a cobalt ferrite nanocomposite coated on recycled cigarette butts for the removal of hexavalent chromium Cr(VI) from aqueous environments under visible light. The variables under investigation were optimized using a entral composite design (CCD) within the framework of the response surface methodology (RSM). XRD, FTIR, SEM, and EDX mapping were employed to determine the structural, functional groups, morphology and compositional attributes of the synthesized nanocomposite. At the established optimal parameters (pH 2, 20 mg/L Cr(VI), 1.5 g/L catalyst dosage, and a reaction time of 120 min) the synthesized nanocomposite achieved a 95.49% photocatalytic reduction. Furthermore, the influence of environmental parameters, including purging gases, H₂O₂, organic compound types, various anions, radical scavengers, and catalyst recyclability, on the photocatalytic reduction of Cr(VI) was examined under optimal conditions. The value and accuracy of the proposed model were statistically evaluated based on the coefficient of determination (R²) and analysis of variance (ANOVA). The Visible/CoFe₂O₄-RCBs system demonstrated superior performance in Cr(VI) removal and optimal electrical energy consumption compared to other visible-light processes, achieving an energy efficiency of 6.89 × 10⁻^⁵ mg/J. The operational cost of this system was calculated at US$33.50 per kilogram, indicating its practical and economic viability compared to other visible-light systems. Furthermore, toxicity analysis using Daphnia magna confirmed a significant reduction in toxicity after treatment. Overall, the findings of this research indicate that the CoFe₂O₄-RCBs nanocomposite can serve as an effective, environmentally friendly, and promising catalyst for the removal of hexavalent chromium from contaminated water.

The photocatalytic removal of Reactive Black 5 (RB5) was investigated using a titanium dioxide-polyethylene terephthalate (TiO₂-PET) catalyst under visible (VIS) light. The sol-gel method was employed for the fabrication of the TiO₂-coated PET catalyst, which was then characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and elemental mapping (MAP) analysis. This study examined the reaction kinetics using the one-factor-at-a-time (OFAT) approach and evaluates the effects of various parameters, including pH (3–11), catalyst dosage (0.1–1 g L^− 1), contact time (15–120 min), RB5 concentration (10–50 mg L^− 1), hydrogen peroxide (H₂O₂) content (2–100 mM), purging gases, organic compound types, and ionic strength, on the photocatalytic removal of RB5. Under optimal conditions (pH= 3, [RB5]_°= 20 mg L^− 1, nanocatalyst dosage= 0.5 g L^− 1), 99.99% of the dye was removed after 120 min. Increasing the RB5 concentration (10–50 mg L^− 1) resulted in a decrease in the observed reaction rate constant (k_obs) from 0.052 to 0.0017 min^− 1, while the calculated electrical energy per order (EEO) increased from 11.08 to 338.82 kWh m^− 3. Furthermore, the total operating cost of the light emitting diode (LED)/TiO₂-PET process (3 USD kg^− 1) was lower than that of other photocatalytic processes, including LED/TiO₂ (4.73 USD kg^− 1), LED/PET (40 USD kg^− 1), and LED (63.16 USD kg^− 1). The removal of RB5 was negatively affected by the presence of H₂O₂, O₂ and N₂ gases, organic compounds, and ionic species. Radical quenching experiments confirmed that hydroxyl radicals (^·OH) were the dominant reactive species responsible for RB5 degradation. The RB5 removal efficiency using the LED/TiO₂-PET method (99.99%) was significantly higher than that of the LED/TiO₂ method (63.42%). Desorption experiments demonstrated excellent catalyst stability, maintaining catalytic activity for up to five sequential cycles. GC-MS analysis identified several intermediate degradation products, including 1,2-benzenedicarboxylic acid, benzoic acid (2-amino-, methyl ester), benzene [(methylsulfonyl) methyl], phenol, 4-naphthalenedione, acetic acid, and propionic acid. Moreover, the removal efficiency in drinking water samples was approximately 63.31%, whereas for real textile wastewater samples, it reached 96.66%. Toxicity tests conducted on the final treated solutions confirmed no toxicity toward Daphnia magna, demonstrating the effectiveness of the LED/TiO₂-PET method in degrading both RB5 dye and its toxic by-products.

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).

At this present investigation, sugarcane bagasse magnetic graphene oxide (SCBMGO) was synthesised in several stages and used to remove Acid Red 14 dye under LED visible light. XRD, FT-IR, SEM, EDX, VSM and pH_PZC analyses demonstrated the structural characteristics. The effect of variables like the pH, catalyst dose, dye concentration, hydrogen peroxide, purging gases, organic compounds, ionic strength, and comparison of different processes, radical scavengers, and reusability on AR14 removal efficiency were investigated. The most removal efficiency occurred under ideal situation: [AR14]₀ = 10 mgL⁻¹, SCBMGO dosage = 0.5 gL⁻¹, pH = 3, hydrogen peroxide = 5 mM, and contact time equal to 120 minutes. Except for the dose, the efficiency of photocatalytic removal of AR14 decreased with the addition of other variables. AR14 photocatalytic removal obeyed the pseudo-second-order reaction kinetic. The E_EO value for LED/SCBMGO (59.62 kWh/m³) process, as a function of removal proficiency, illustrated that this process was elevated productivity and diminished the cost of electrical energy consumed by the system. The highest removal efficiency of AR14 occurred in the LED/SCBMGO process (89.85%). In addition, recycling test efficiency was the same at the beginning, and the 6th stage. The removal efficiency of AR14 in drinking water was (71.45%). SCBMGO, as an effective and environmentally friendly catalyst, can be used in removing AR14 dye and organic pollutants of aqueous environments under the LED visible light.