Photocatalytic degradation and mineralization of diazinon in aqueous solution using nano-TiO2(Degussa, P25): kinetic and statistical analysis

Abstract: In this study, photocatalytic degradation of diazinon was investigated using nano-TiO2, Degussa P25, as a photocatalyst and the effects of some operational parameters such as aeration, pH, photocatalyst concentration, and the irradiation time were also examined. Dispersive liquid-liquid microextraction technique was used to extract and pre-concentration of residual diazinon from the liquid samples and all experiments were carried out by gas chromatography. Amount of degradation and mineralization were determined by gas chromatograph with flame ionization detector (GC/FID) and COD measurements, respectively. The optimum condition for degradation of diazinon has been obtained in the pH 6, [nano-TiO2] = 0.2 g/L, and [time] = 120 min. In the optimal condition the removal efficiency of diazinon and COD were 99.64 and 65%, respectively. The results have shown that the nano-TiO2, aeration and time of reaction have a positive effect on photocatalytic degradation of diazinon and COD removal. Statistical analysis showed that the maximum removal of diazinon and COD were due to UV irradiation (71%, 41%), exposure time (16%, 39%), aeration (7%, 4%), and increased concentration of nano-TiO2 (0.4%, 2%), respectively; and the kinetics of photodegradation were found to follow a first-order kinetic model and the constant rate, at optimal condition, was 0.038 (min−1). © 2014 Balaban Desalination Publications. All rights reserved

Data on modeling of UV/Na2S2O8/FeS2 process in amoxicillin removal using Box-Behnken methodology

Among the pharmaceutical compounds, antibiotics have been paid specific consideration, due to their acute and chronic toxic effects on organisms. Amoxicillin (AMX) is used widely for treatment of bacterial infections. About 80 of amoxicillin excreted unchanged and enters the aquatic environment through different routes including disposal of municipal wastewaters, hospital wastewaters and farm wastewaters. In this study degradation of amoxicillin by UV/Na2S2O8/FeS2 process was evaluated. According to the results, the R-squared and adjusted R-squared were 0.9877 and 0.9828, respectively. The AMX removal efficiency was 93 at optimum conditions. Thus, UV/Na2S2O8/FeS2 process is a useful process for amoxicillin removal. © 2018 The Author

Adsorption and magnetic separation of lead from synthetic wastewater using carbon/iron oxide nanoparticles composite

Background and purpose: Removal of lead as a toxic metal from contaminated water resources is necessary due to the dangerous effect of lead. One of the most effective methods of removal is the adsorption process. The aim of this study was adsorption and magnetic separation of lead from synthetic wastewater using iron oxide nanoparticles and carbon (ION/C) composite Material and Methods: In this study nanoparticles of iron oxide (ION) were used as a source of iron for magnetic separation of powder activated carbon from solution samples. The physical and surface properties of the adsorbent were studied along with influencing factors (pH, contact time, adsorbent dosage, initial lead concentration, and temperature) on the adsorption process. Kinetic equations and equilibrium isotherms studies were also conducted. Results: The size of ION and specific surface area of ION/C were found to be 30-80 nm and 671.2 m2/g, respectively. We observed that the adsorption process reached equilibrium at 60 min and pH=6and adsorption efficiency increased by increasing the amount of adsorbent and temperature. Maximum adsorption capacity based on Langmuir isotherms was obtained 67.1mg/g at 50 °C. Conclusion: According to this study it is believed that magnetized active carbon by keeping its physical and surface properties could be a suitable method to solve some related problems including separation and filtration

Iron-silver oxide nanoadsorbent synthesized by co-precipitation process for fluoride removal from aqueous solution and its adsorption mechanism

Fe-Ag magnetic binary oxide nanoparticles (Fe-Ag MBON) are prepared with co-precipitation of ferric and ferrous chloride solutions, and used for the adsorption of fluoride from aqueous solution. The surface morphology of the adsorbent was characterized by XRD, SEM, TEM, FTIR, XPS, EDX, BET, DLS and VSM techniques. Batch method was followed to optimize the conditions for the removal of fluoride. The results showed maximum removal occurred at pH 3.0 and adsorption equilibrium was achieved within 20 min. Chemical kinetics of the adsorption were well fitted by pseudo-second order models (R2 > 0.968) and the adsorption process followed the Langmuir isotherm model well (R2 > 0.976). The fluoride adsorption capacity of Fe-Ag MBON was 22.883 mg g-1, and decreased with increasing the temperature. Thermodynamic values revealed that the fluoride adsorption process was spontaneous and exothermic. Regeneration experiments were carried out for six cycles and the results indicate a removal efficiency loss of <22. © 2015 The Royal Society of Chemistry

Powder activated carbon/Fe3O4 hybrid composite as a highly efficient heterogeneous catalyst for Fenton oxidation of tetracycline: Degradation mechanism and kinetic

In this work, we prepared and used a composite of powder activate carbon/Fe3O4 magnetic nanoparticles (PAC/Fe3O4 MNPs) as a heterogeneous catalyst to remove tetracycline (TC) from aqueous solution. By using XRD, BET, VSM, SEM, TEM and EDX techniques, also, we tried to characterize the catalyst. The effects of pH, H2O2, catalyst dosages and also initial TC concentration on the degradation process were assessed. Based on the results, it was indicated that at low pH values and initial TC concentrations, the efficiency of the process is higher than the other values and concentrations studied in this work. Under the ambient conditions and setting the initial pH value and TC concentration at respectively 3.0 ± 0.2 and 10 mg L-1, the optimal dosage of reagents were recorded to be 0.3 g L-1 catalyst and 80.0 mM H2O2. The values of observed rate constants, kobs, increased by increasing the catalyst loading in the system; however, these values decreases when the initial TC concentration was increased. Our findings indicated that all of TC concentration was nearly degraded during the 180 min reaction. Regarding the reusability of PAC/Fe3O4 MNPs, the results showed that TC and TOC removal efficiencies of 94.5 and 32.3, respectively, can be achieved after four consecutive runs. By conducting the stability experiments, it was confirmed that PAC/Fe3O4 MNPs is a promising and effective catalyst in Fenton reactions and can be used to treat TC-contaminated water with very low loss of catalytic activity. © 2015 The Royal Society of Chemistry

Performance evaluation of nanocomposit magnetic graphene sheet- iron oxide in removal of nitrate from water using Taguchi experimental design

Background and purpose: Nitrate is one of the chemical water contaminants which can be eliminated through physical, chemical and biological techniques. In this study we aimed for optimization of nitrate adsorption from water onto Magnetic Graphene sheet Nano Particles (G-Fe3O4 MNPs) via Taguchi experimental design. Materials and methods: Batch reactor was used for optimizing of the five parameters (pH, contact time, temperature, adsorbent dosage, and nitrate concentration) at four levels by Minitab software, based on Taguchi experimental design. Signal to noise ratio was used with �the highest is better� approach for optimization of experimental conditions and the highest nitrate removal efficiency. Results: The results revealed that in optimized status (pH=3, contact time= 60 min, initial concentration= 50 mg/L, adsorbent dose= 2g/L, temperature= 50°C) nitrate removal efficiency and adsorption capacity reached 86.4 and 39.37 mg/g, respectively. Contribution percentage of each variable implied that pH and initial concentration of nitrate with 40.20 and 7.49 had the highest and lowest influences on nitrate removal, respectively. Isotherm and kinetic studies illustrated that, nitrate adsorption complied with Langmuir isotherm model (R2>0.993) and pseudo second-order kinetics models (R2> 0.94). Conclusion: G-Fe3O4 MNPs can be used as an effective sorbent for nitrate removal from water or wastewater due to several advantages including easy and rapid separation from solution and high removal efficiency. © 2015, Mazandaran University of Medical Sciences. All rights reserved

Experimental design approach to the optimization of PAHs bioremediation from artificially contaminated soil: Application of variables screening development

Background: The effectiveness of bioremediation systems for PAH-contaminated soil may be constrained by physicochemical properties of contaminants and environmental factors. Information on what is the most effective factor in bioremediation process is essential in the decision of what stimulations can be taken to assist the biodegradation efficacy. Methods: In this study, four factors of surfactant (Tween 80), humic acid (HA), salinity and nutrients in a 24 full factorial design were screened in bioremediation of phenanthrene contaminated soil by using a consortium of bacteria. Results: Between the employed levels of the factors only salinity had not significant effect. Optimal concentrations of surfactant, HA and nutrient were obtained by a response surface design. For phenanthrene biodegradation, a central composite face centred design (CCFD) showed that nutrient, surfactant and HA concentrations had highly significant, significant and insignificant effects, respectively. The best conditions with 87.1 phenanthrene biodegradation were 150 mg HA/Kg soil, 12.68 μg/L surfactant, and nutrients as K2HPO4, 0.8; KH2PO4, 0.2 and KNO3, 1 g/L. A high similarity was between the model prediction and experimental results. Conclusions: This study showed that nutrient with 81.27 efficiency could be considered as the most effective factor for practical implications of bioremediation process for PAHs contaminated soil cleanup strategies. © 2015 Ravanipour et al.; licensee BioMed Central

Ozone-assisted photocatalytic degradation of gaseous toluene from waste air stream using silica-functionalized graphene oxide/ZnO coated on fiberglass: performance, intermediates, and mechanistic pathways

The present study focused on the potential of an ozone-assisted photocatalytic process using the catalyst silica-functionalized graphene oxide/ZnO coated on fiberglass (Si-GO/ZnO-FG) in the removal of toluene from waste air stream. Here, a comparative examination was performed in terms of toluene removal efficiency in the photocatalytic process (UV/Si-GO/ZnO-FG) and photocatalytic ozonation (O3/UV/Si-GO/ZnO-FG). The gaseous intermediates resulting from degradation of toluene by different processes were analyzed using GC-MS. The results of this study indicated that with the addition of ozone to the UV/Si-GO/ZnO-FG process, toluene removal increased significantly from 76.18 to 87.8%. The reason for this incremental efficiency can be explained by the fact that with the addition of ozone, the production rate and the extent of hydroxyl radical (OH•) production grow significantly; thereby, more pathways are developed for toluene degradation. The major byproducts in toluene oxidation by photocatalytic and photocatalytic ozonation processes include formic acid, acetic acid, benzyl alcohol, benzaldehyde, p-cresol, hydroquinone, and benzoic acid. Given the intermediates and the dominant oxidants detected in the aforementioned process, the possible toluene degradation pathway by the utilized process was suggested

Effectiveness of biostimulation through nutrient content on the bioremediation of phenanthrene contaminated soil

Bioremediation has shown its applicability for removal of polycyclic aromatic hydrocarbons (PAHs) from soil and sediments. In the present study, the effect of biostimulation on phenanthrene removal from contaminated soil via adding macro and/or micronutrients and trace elements was investigated. For these purposes three macro nutrients (as N, P and K), eight micronutrients (as Mg, S, Fe, Cl, Zn, Mn, Cu and Na) and four trace elements (as B, Mo, Co and Ni) in 11 mineral salts (MS) as variables were used. Placket-Burman statistical design was used to evaluate significance of variables (MS) in two levels of high and low. A consortium of adapted microorganisms with PAHs was used for inoculation to the soil slurry which was spiked with phenanthrene in concentration of 500 mg/kg soil. The optimal reduction resulted when a high level of macro nutrient in the range of 67-87 and low level of micro nutrient in the range of 12-32 were used with the nitrogen as the dominant macronutrient. The Pareto chart showed that NH4NO3 was the most effective variable in this experiment. The effect of elements on phenanthrene biodegradation showed following sequence as N > K > P > Cl > Na > Mg. Effectiveness of the other elements in all runs was less than 1. The type and concentration of nutrient can play an important role in biodegradation of phenanthrene. Biostimulation with suitable combination of nutrient can enhance bioremediation of PAHs contaminated soils. ©2014 Kalantary et al

Modeling and optimization of adsorption process of reactive dyes on powder activated carbon modified by magnetite nanocrystals

Background and purpose: Some problems such as filtration, centrifugation, and turbidity in effluent has limited the application of activated carbon and many nano-sized adsorbents. The magnetization of adsorbents using magnetic nano-crystals (MNCs) is a useful approach to overcome these problems. In the present study, magnetic activated carbon was synthesized (since it is separated fast and easily from solution) and employed as an adsorbent for removal of reactive dyes (Reactive black 5 (RB5) and Reactive red 120 (RR120)) from aqueous solutions. Materials and methods: Physical, surface and magnetic properties of adsorbent were analyzed using XRD, SEM, TEM, EDX, VSM and BET techniques. The performance of adsorbent in removing dyes was investigated considering the effect of pH, contact time, adsorbent dose, initial dye concentration, and temperature in a batch system. The experimental data was analyzed by Langmuir, Freundlich and Temkin isotherms, pseudo-first and second order kinetic models, and thermodynamic equations. Results: In our study, by increasing temperature and adsorbent dose and decreasing the initial concentration, at pH 3 and equilibrium time of 30 min the adsorption efficiency increased. The optimum dose of the adsorbent was 1 g/L. Based on the Langmuir isotherm model the maximum adsorption capacity of 192.6 and 188.7 mg/g was obtained for RB5 and RR120 dyes, respectively. The adsorption process of both dyes obeyed the Langmuir and pseudo-second order models. The thermodynamic results showed that the adsorption process of dyes was endothermic and spontaneous in nature. Conclusion: The present study showed that the magnetic activated carbon in addition to features such as rapid and easy separation from solution, has a high potential for dye adsorption too. © 2016, Mazandaran University of Medical Sciences. All rights reserved