Removal of catechol from aqueous solutions using catalytic ozonation by magnetic nanoparticles of iron oxide doped with silica and titanium dioxide: A kinetic study

Background and purpose: Catechol is a ring form organic compound with high toxicity that is used in petrochemical, pharmaceutical and manufacturing of pesticide. It has adverse effects on human and environmental health if discharged into the environment. The purpose of this study was removal of catechol using catalytic ozonation using core-shell magnetic nanoparticles of iron oxide doped with silica and titanium dioxide from aqueous solution. Materials and methods: We conducted a basic-applied study in which magnetic nanoparticle Fe3O4@SiO2@TiO2 was synthesized using sol-gel method. To determine the characteristics of nanoparticle, XRD, SEM and EDX tests were used. Then effect of different parameters on removal efficiency were investigated. These included solution pH (2-10), reaction time (0-60 min), dose of catalyst (0.2-3 gr/L), initial concentration of catechol (50-1000 mg/L), recycled test (7 times), and determining the mineralization and scavenger effect. The residual concentration of catechol was measured using high-performance liquid chromatography at 275 nm. Results: The optimal pH for the catalytic ozonation process was 8. The maximum efficiency of the process in optimal conditions (catechol concentration 1000 mg/l, pH=8, catalyst dosage 3 gr/L and dose of ozone 0.38 gr/hr) was 100 after 60 minutes of contact time. Kinetics of degradation of catechol followed first degree model. After reaction time the amount of mineralization was 91.5. Reusability of catalyst was done 7 times and its efficiency decreased by about 4. Scavenger (1 gr/l tert-butanol) decreased removal of catechol by 4.16. Conclusion: The catalytic ozonation process using Fe3O4@SiO2@TiO2 nanoparticles in an alkaline pH was found to be capable of eliminating high concentrations of catechol effectively. © 2016, Mazandaran University of Medical Sciences. All rights reserved

Performance evaluation of magnetized multiwall carbon nanotubes by iron oxide nanoparticles in removing fluoride from aqueous solution

Background and purpose: Contamination of drinking water with fluoride due to natural and human activities is a serious problem that threatens human health. Long-term and excessive consumption of water containing fluoride could lead to endocrine glands diseases and Alzheimer's disease. Adsorption process is an effective and popular method for removal of fluoride, so the purpose of this research was magnetizing multiwall carbon nanotubes with nano iron oxide and using it as an adsorbent for fluoride removal from aqueous solution. Materials and methods: Co-precipitation method used for synthesized magnetic nano composite and its characteristics were investigated by SEM, TEM, XRD and VSM techniques. The effect of independent variables such as contact time, pH, temperature, adsorbent dose and initial concentration on fluoride removal was analyzed by response surface methodology (box-Behnken design method) and ANOVA. Results: The optimum condition was obtained at pH= 3, 2g/L sorbent dosage in 2h contact time and 45oC temperature. Isotherms and kinetics results showed that the Langmuir model and pseudo-second order were correlated by data with R2>٠.٩٨ and R2>0.941, respectively. Thermodynamic values revealed that fluoride adsorption process was endothermic and spontaneous. Conclusion: In this study synthesized adsorbent was found efficient in fluoride removal (98.5 adsorption in optimal condition) and due to magnetic ability it can be easily separated from the samples by an external magnet. Therefore, it can be applied in removal of fluoride from drinking water. ©, 2015, Mazandaran University of Medical Sciences. All rights reserved

Removal of diethyl phthalate from aqueous solution using persulfate-based (UV / Na2S2O8 / Fe2+) advanced oxidation process

Background and purpose: Phthalate esters (PEs) are a large family of industrial chemicals widely used as plasticizers. Phthalates can cause endocrine disruption and cancers. Nowadays, phthalate esters are commonly used in cosmetics, adhesives and toy industries and simply get into the surface water and groundwater. The aim of this study was to evaluate the performance of UV / Na2S2O8 / Fe2+ in DEP removal from aqueous solution. Materials and methods: In this study the effect of pH, concentration of persulfate, Fe2+ concentration and contact time on removal of diethyl phthalate were studied in laboratory scale using a cylindrical-shaped reactor containing a UV-C lamp (16 watts) by batch method. The residual concentrations of Diethyl phthalate (DEP) were determined by HPL. The effects of independent parameters on DEP removal were evaluated by Multi simplex and the response surface method (box Behnken method). Results: In this study the optimum condition was obtained at pH = 11, persulfate concentration of 0.4 Mmol/L, 0.07 Mmol/L Fe2+ and 90 minutes contact time. The results showed that the DEP removal by UV / Na2S2O8 / Fe2+ process followed a first-order reaction kinetic. Conclusion: The results indicated high efficiency of UV / Na2S2O8 / Fe2+ process (95 removal under optimal condition) in removal of DEP from aqueous solutions. This efficiency demonstrates that this method is acceptable in DEP removal on industrial scale. © 2016, Mazandaran University of Medical Sciences. All rights reserved

Performance, kinetic, and biodegradation pathway evaluation of anaerobic fixed film fixed bed reactor in removing phthalic acid esters from wastewater

Emerging and hazardous environmental pollutants like phthalic acid esters (PAEs) are one of the recent concerns worldwide. PAEs are considered to have diverse endocrine disrupting effects on human health. Industrial wastewater has been reported as an important environment with high concentrations of PAEs. In the present study, four short-chain PAEs including diallyl phthalate (DAP), diethyl phthalate (DEP), dimethyl phthalate (DMP), and phthalic acid (PA) were selected as a substrate for anaerobic fixed film fixed bed reactor (AnFFFBR). The process performances of AnFFFBR, and also its kinetic behavior, were evaluated to find the best eco-friendly phthalate from the biodegradability point of view. According to the results and kinetic coefficients, removing and mineralizing of DMP occurred at a higher rate than other phthalates. In optimum conditions 92.5, 84.41, and 80.39% of DMP, COD, and TOC were removed. DAP was found as the most bio-refractory phthalate. The second-order (Grau) model was selected as the best model for describing phthalates removal

Ozone-Assisted photocatalytic degradation of benzene using nano-zinc oxide impregnated granular activated carbon (ZnO–GAC) in a continuous fluidized bed reactor

Benzene is one of the volatile organic compounds, exposure to which causes different complications including coughs, headache, dizziness, and even cancer. Therefore, methods are required to remove benzene from polluted air. In this study, for the first time, benzene degradation was examined using photocatalytic ozonation process in the presence of nano-zinc oxide impregnated granular activated carbon (ZnO–GAC) in a continuous fluidized bed reactor. The experiments were performed with the aim of investigating the effect of factors including the ratio of superficial gas velocity to the minimum fluidization velocity ((Formula presented.)), initial benzene concentration, relative humidity, catalyst dosage, bed temperature, ozone dosage, and intensity of UV lamp in removing benzene from the air. The results of this study indicated that the minimum fluidization velocity (Umf) was obtained as 0.47 L/min, while benzene removal efficiency reached its maximum at (Formula presented.) = 2.5. Addition of ozone to the ZnO-UV/GAC process enhanced the process efficiency considerably. With elevation of benzene concentration from 50 to 300 ppm, removal efficiency by UV/ZnO–GAC process declined from 84.14 to 45.12%, while with O3/ZnO–GAC/UV, it decreased from 93.8 to 68.78%. The range of the optimal humidity for benzene removal in both processes was obtained as 30–35%. With elevation of ZnO–GAC dosage from 0 to 10 mg, benzene removal efficiency increased from 42.07 to 70.24 and from 60.9 to 89.57% using UV/ZnO–GAC and O3/ZnO–GAC/UV processes, respectively. Furthermore, the efficiency of O3/ZnO–GAC was directly related to bed temperature, while UV/ZnO–GAC and UV/O3/ZnO–GAC processes were inversely related. Eventually, the removal efficiency of the processes had a direct relation with the ozone dosage and UV intensity

Application of a new N,S-containing silica-coated nanomagnetic sorbent for the trace quantification of Hg(II) ions in aquatic samples: evaluation of adsorption mechanism

Herein, an effective µ-dispersive solid-phase extraction (µ-dSPE) for the adsorption of Hg(II) ions from various water samples was implemented using a N,S-containing silica-coated nanomagnetic sorbent (Fe3O4@SiO2-N/S). Initially, the sorbent was synthesized via N-substituted amide reaction followed by the characterization by several analytical techniques such as scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), vibrating sample magnetometer (VSM) and X-ray diffraction (XRD). After that, Hg(II) ions interacted with the dentate (N,S) of the dispersed sorbent, which seems to be the cornerstone of the extraction concept. Then, Hg(II) ions were desorbed off the sorbent and quantified by a cold vapor atomic absorption spectrometer (CV-AAS). A number of influential factors impacting the analyte extraction/desorption efficiency were fully investigated, and subsequently, the optimal conditions were established. Under the optimal conditions, the calibration curve was linear over the concentration range of 0.1�5.0 µg L�1, and based on a signal-to-noise ratio of 3 (S/N = 3), the method detection limit was determined to be 0.05 µg L�1 for the analyte of interest. The µ-dSPE method was applied for the determination of Hg(II) in various fortified real aquatic samples to test its performance. The average relative recoveries obtained from the fortified water samples varied in the range of 93�107 with the relative standard deviations of 2.8�6.4. In addition, an investigatory approach regarding the equilibrium adsorption isotherms of the target ion was performed which fitted best to the Langmuir isotherm model. Finally, the method is assumed to have a great potential to be implemented in environmental/other laboratories for the monitoring trace level of Hg(II) ions. © 2020, Iranian Chemical Society

Application of a photocatalytic ozonation process using TiO2 magnetic nanoparticles for the removal of Ceftazide from aqueous solutions: Evaluation of performance, comparative study and mechanism

The presence of antibiotics in the environment leads to microbial resistance in humans and pathogenic microbes. Given the resistance of antibiotics even after conventional wastewater treatments, the present study is centered on the removal of ceftazide (CFT) from aqueous solutions by the photocatalytic ozonation process using TiO2 magnetic nanoparticles (T-MNPs). The effects of a number of operational parameters such as pH, initial CFT concentration, ozone concentration, reaction time on the degradation of CFT was thoroughly studied by the photocatalytic process. Under the optimum conditions (CFT concentration of 10 mg/L, pH 11, catalyst dosage of 1.0 g/L and ozone flow of 0.22 g/h), the removal efficiency and mineralization of 100 was 75.5 were obtained for CFT after a 15-min treatment. Following on, the reusability of the photocatalyst was evaluated indicating a 5.8 drop in the removal performance after six consecutive cycles of use. The mechanism for the degradation of CFT was predominantly governed by the formation of radOH radicals. In conclusion, the photocatalytic ozonation process can significantly remove CFT and seems to be a suitable alternative to the others methods used for removal of antibiotics from aqueous solutions. © 2020 Elsevier Gmb

Pesticide decontamination using UV/ferrous-activated persulfate with the aid neuro-fuzzy modeling: A case study of Malathion

In the current study, the Malathion decontamination by the aid of the UV/ferrous-activated persulfate (PS) was investigated and the effects of pH, persulfate (PS) concentration, ferrous concentration, Malathion concentration, and different inorganic ions were evaluated. Also, the Adaptive Neuro-Fuzzy Inference System (ANFIS) was applied to model Malathion degradation data. The maximum degradation efficiency was associated with pH = 3, PS concentration of 1.2 mM, the ferrous concentration of 0.6 mM, Malathion concentration of 20 mg/L for 60 min. The degradation efficiency was decreased in the presence of Cl� (23), NO3� (13.5), HCO3� (35.4) and H2PO4� (48.7) ions. Results revealed that persulfate radical (52) plays a more important role in Malathion degradation while compared with hydroxyl radical (15). The low root mean square error (RMSE = 6.451), mean absolute error (MAE = 3.8306), absolute-average-deviation (AAD = 0.1005) and high coefficient of determination (R2 = 0.972) correlated with the proposed ANFIS models confirmed the model accuracy. Besides, the process optimization was conducted by using ANFIS to predict the best operating circumstances, which resulted in the maximum Malathion degradation (95.54). © 2020 Elsevier Lt

Pesticide decontamination using UV/ferrous-activated persulfate with the aid neuro-fuzzy modeling: A case study of Malathion

In the current study, the Malathion decontamination by the aid of the UV/ferrous-activated persulfate (PS) was investigated and the effects of pH, persulfate (PS) concentration, ferrous concentration, Malathion concentration, and different inorganic ions were evaluated. Also, the Adaptive Neuro-Fuzzy Inference System (ANFIS) was applied to model Malathion degradation data. The maximum degradation efficiency was associated with pH = 3, PS concentration of 1.2 mM, the ferrous concentration of 0.6 mM, Malathion concentration of 20 mg/L for 60 min. The degradation efficiency was decreased in the presence of Cl� (23), NO3� (13.5), HCO3� (35.4) and H2PO4� (48.7) ions. Results revealed that persulfate radical (52) plays a more important role in Malathion degradation while compared with hydroxyl radical (15). The low root mean square error (RMSE = 6.451), mean absolute error (MAE = 3.8306), absolute-average-deviation (AAD = 0.1005) and high coefficient of determination (R2 = 0.972) correlated with the proposed ANFIS models confirmed the model accuracy. Besides, the process optimization was conducted by using ANFIS to predict the best operating circumstances, which resulted in the maximum Malathion degradation (95.54). © 2020 Elsevier Lt

Kinetic study and performance evaluation of an integrated two-phase fixed-film baffled bioreactor for bioenergy recovery from wastewater and bio-wasted sludge

The present study evaluated the performance of an integrated two-phase fixed-film baffled bioreactor for wastewater treatment with regard to its energy consumption and production. The total potential of the bioenergy recovery of the bioreactor was evaluated not only from the anaerobic wastewater treatment but also from the produced bio-wasted sludge of both phases. Statistical correlations between bio-methane production and kinetic coefficients were uncovered. Methane yields between 0.15 and 0.30 L CH4.g sCODremoved−1 were obtained during anaerobic wastewater treatment. The maximum energy recoveries from the digestion of bio-wasted sludge (sloughed biofilm) equaled 0.28 and 0.3 L CH4. g TS−1 for aerobic and anaerobic units, respectively. The Grau model was appropriate for predicting the performance of the bioreactor and the potential of bio-methane production. It was demonstrated that substrate utilization rate (Rsu) and Grau coefficient (KG) can be applied to predict the rate of methane production. Regarding the volume of treated wastewater, the energy production was in the range of 2.8–12 kWh.m−3. Moreover, the overall energy consumption of wastewater treatment was in the range of 0.32–0.79 kWh/kg sCODremoved, while the total energy production was 3.7–5.1 kWh/kg sCODremoved. Therefore, the designed bioreactor was energy positive with net energy production of 3.39–4.5 kWh/kg sCODremoved−1. The total energy requirement for both wastewater treatment and bio-wasted sludge digestion was 7–15.5% of the total energy production, and, therefore, the bioreactor is a sustainable energy process. The contribution of anaerobic wastewater treatment and anaerobic digestion of bio-wasted sludge of aerobic and anaerobic units for energy recovery as bio-methane was 53, 26, and 21%, respectively. As the bioreactor achieved more than 95% of sCOD removal and have a high bioenergy production, and since kinetic coefficients demonstrated the considerably high performance of the bioreactor, it can be of interest as an appropriate treatment process