Rapid removal of phenol from aqueous solutions by AC_Fe3O4 nano-composite: Kinetics and equilibrium studies

Background and purpose: Phenol and its derivatives are used as raw material in many chemical, pharmaceutical and petrochemical industries. It is classified as priority pollutant, due to its high toxicity. In this study, the magnetic activated carbon nano-composite was used for quick removal of phenol. Materials and methods: The activated carbon was modified by magnetic nano-particles. Then physical properties of the adsorbent were investigated using BET, XRD and SEM. Afterwards, adsorption behavior of phenol onto the adsorbent was studied considering various parameters such as: pH, phenol concentration, contact time and adsorbent dosage. Also, the isotherms and adsorption kinetics model was studied. Results: BET analysis showed 10.25% decrease in the specific area of activated carbon after being amended by the Fe3O4 nano-particles. SEM and XRD confirmed the presence of Fe3O4 nanoparticles on the activated carbon. Optimum absorption points in this process were pH=8, contact time of 15 min and adsorbent dose 2 g/L. The Longmuir isotherm and pseudo-second-order kinetics were fitted to the data. The maximum adsorption capacity of phenol on AC_Fe3O4 was 84.033 mg/g. Conclusion: Creating magnetic properties on the activated carbon which has a high adsorption capacity of phenol could result in quick separation of phenol from aqueous solutions. Also, this adsorbent could be widely applied since it is inexpensive and simple to use. © 2015, Mazandaran University of Medical Sciences. All rights reserved

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

Carbon fibers modified with polypyrrole for headspace solid phase microextraction of trace amounts of 2-pentyl furan from breath samples

This study introduces micrometric carbon strands as a suitable fiber for headspace solid phase microextraction. Compared to previous supports, carbon fibers have mechanical flexibility, wide thermal expansion, and a large surface area, which is an important factor in headspace solid phase microextraction. The electrophoretic technique was applied to modify the surface of stainless steel and carbon fibers with polypyrrole. Modified carbon fibers were used for extraction of 2-pentylfuran (2-PF) as a model analyte from patients� breath and coffee samples. 2-PF belongs to the furan family, which was suggested as a biomarker for Aspergillus fumigatus and was classified as a possible carcinogen. 2-PF can be found in many heat-processed foods and drinks. The separation and detection of the analyte was performed by gas chromatography coupled to mass spectrometry. The effective factors in the extraction performance of the analyte by carbon fiber supports were investigated and optimized. Under optimized extraction conditions (temperature, 20 °C; time, 15 min; desorption temperature, 200 °C; desorption time, 2 min; salt concentration, 10 w/v; and stirring rate, 700 rpm), the limit of detection was calculated as 0.05 ng mL�1, whereas repeatability and fiber-to-fiber reproducibility (RSD ) was found to be in the range of 3.2�4.1. The experimental results showed that the proposed fiber had greater extraction performance for 2-pentylfuran. © 201

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

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

Analysis of paraben preservatives in cosmetic samples: Comparison of three different dynamic hollow fiber liquid-phase microextraction methods

This study focused on a comparison of three different dynamic hollow fiber-based liquid-phase microextraction (DHF-LPME) methods for extraction and preconcentration of parabens from wastewater, toothpaste, cream, and shampoo samples. The first method is two-phase DHF-LPME, in which n-octanol was used as the extraction solvent. The second is three-phase DHF-LPME, in which n-octanol and basic aqueous solution were used as the extraction solvent and acceptor phase, respectively. High-performance liquid chromatography with UV detection (HPLC-UV) was applied for determination of the parabens in both methods. The third method is a recently introduced method; three-phase DHF-LPME based on two immiscible organic solvents (n-dodecane as organic solvent and acetonitrile as an acceptor phase). The quantitative analyses were performed by the use of gas chromatography-mass spectrometry (GC-MS) after injection port derivatization. The effect of different extraction conditions (i.e., extraction solvent, pH, ionic strength, stirring rate, and dynamic and extraction times) on the extraction efficiency of the parabens was investigated and optimized. All the three procedures provide similar working parameters characterized by high repeatability (3.9-6.3 %) and good linearity (correlation coefficient ranging from 0.989 to 0.998). Results of real sample analyses obtained by these three methods were highly correlated. Although all methods provide compatible alternatives for paraben analysis, the three-phase DHF-LPME based on two immiscible organic solvents may be a more appropriate technique due to its higher extraction efficiency and thus lower limits of detection (LODs). LODs for all the parabens ranged from 0.2 to 5.0 μg L-1 using the two first methods combined with HPLC-UV. An improvement in sensitivity of several orders of magnitude was achieved using three-phase DHF-LPME based on two immiscible organic solvents followed by single-ion monitoring GC-MS analyses (0.01-0.2 μg L-1) due to compatibility of this technique with GC instrument. © 2013 Springer-Verlag

Mercury level in biological samples of dentists in Iran: a systematic review and meta-analysis

Exposure to mercury is an important risk to dentists health. The aim of the present study was to assess the pooled mean mercury level (MML) in the urine, blood, nail, and hair of Iranian dentists (IDs) through the meta-analysis technique. Comprehensive and systematic searches were performed in main local databases including SID, Magiran, Iran medex, and ISC as well as internationally available databases including Embase, PubMed and Scopus for all the relevant studies up to 2018. In order to prevent bias in this study and identify eligible studies, various steps of the study was performed independently by two researchers. Out of 13 studies in the meta-analysis process which included 1499 IDs, the mean of the mercury level in the urine, nail, and blood was estimated to be 6.29 (95 CI: 2.61�9.97, I-square: 62.7, P: 0.006), 3.54 (95 CI: 2.81�4.28, I-square: 0.0, P: 0.968), 11.20 (95 CI: 2.28�20.13, I-square: 59.9, P: 0.082), respectively. The mean mercury level (MML) in the biological samples of IDs was higher than the standard of World Health Organization (WHO). So, in accordance with Article 10 of the European Union Regulations (EUR), in the context of the Minamata Convention (MC) on Dental Amalgam (DA), in order to avoid the dangers of mercury exposure in dentists, it is necessary for Iran and other countries to approve laws and to implement a national plan to reduce mercury levels and replace the appropriate materials. © 2020, Springer Nature Switzerland AG

Synthesis of magnetic multiwalled carbon nano tubes and investigation of isotherm and kinetic models for cleanup of carbaryl pesticide

Water is the main factor of movement and transport of pesticides and contamination of water by these pollutants is one of the most important challenges due to their widespread use and increased concentrations. Moreover, these compounds are on the U.S.EPA Priority Pollutant list because of the potential of accumulation and the property of damaging effects. In this study, multiwalled carbon nanotube-based magnetic nanoparticles were synthesized and used as an affective adsorbent for carbaryl pesticide. The properties of the synthesized Fe3O4@MWCNTs were characterized by TEM images and XRD analysis. The obtained data were studied by isotherm and kinetic models. Carbaryl adsorbed onto the synthesized adsorbent was compatible with the Langmuir isotherm (R2 = 0.993). The maximum adsorption capacity (qmax) of the pesticide onto the Fe3O4-MWCNTs was obtained at 68.2 mg/g. The kinetic studies of the reactions showed that the adsorption process followed the pseudo-second order model with R2 � 0.99 for all initial carbaryl concentrations. The adsorbent was extracted by magnet reused several times (six rounds) with a reasonable efficiency. The Fe3O4MWCNTs have great potential for adsorption of carbaryl from water and wastewater due to high efficiency, easy separation and reusability. © 2020 Global NEST

Bioremediation of soils contaminated with diesel using biostimulation method in the bioreactors of vermicompost and activated sludge

Background and purpose: There are several methods for removing oil contaminations from the polluted environments. Bioremediation could be considered as one of the best and most practical methods in the removal of oil contaminations. The aim of this research was to determine the bioremediation efficiency for soils contaminated with diesel by the biological stimulation of bioreactors containing vermicompost and activated sludge. Materials and methods: In an experimental study, the soil samples were collected from an area which was free of any oil pollution and 5 reactors containing one kilogram of soil were contaminated with diesel at the mass concentration of 1. Two reactors were mixed with vermicompost at 15 and 20 mass concentrations and two reactors were mixed with activated sludge at 5 and 10 mass concentrations. Additionally, one control reactor was used to control the process. The pH of the reactors was between 7.5 and 8 and the C:N:P ratio was 100:5:1. The amount of TPH was measured at seven retention times within three months with two repetitions. The total removal of petroleum hydrocarbons (TPHs) was evaluated by GC-FID device. Results: The highest removal efficiency of TPH (40.24) was observed in bioreactors containing vermicompost at a 20 mass concentration. In this reactor, the highest percentage of removal was observed in lighter hydrocarbons (50.49). In reactors containing activated sludge, the average percentage of TPH removal was 32 which was observed in the reactor containing the 10 concentration of sludge. In this reactor, the highest percentage of removal (44.86) was also observed in lighter hydrocarbons. Conclusion: Vermicompost and activated sludge can be used in the bioremediation of soils contaminated with diesel. In current study, the performance of vermicompost was found to be more efficient. Also, the results showed that by increasing the concentration of biological modifiers, the removal rate would increase. © 2018, Mazandaran University of Medical Sciences. All rights reserved

Bioremediation of soils contaminated with diesel using biostimulation method in the bioreactors of vermicompost and activated sludge

Background and purpose: There are several methods for removing oil contaminations from the polluted environments. Bioremediation could be considered as one of the best and most practical methods in the removal of oil contaminations. The aim of this research was to determine the bioremediation efficiency for soils contaminated with diesel by the biological stimulation of bioreactors containing vermicompost and activated sludge. Materials and methods: In an experimental study, the soil samples were collected from an area which was free of any oil pollution and 5 reactors containing one kilogram of soil were contaminated with diesel at the mass concentration of 1. Two reactors were mixed with vermicompost at 15 and 20 mass concentrations and two reactors were mixed with activated sludge at 5 and 10 mass concentrations. Additionally, one control reactor was used to control the process. The pH of the reactors was between 7.5 and 8 and the C:N:P ratio was 100:5:1. The amount of TPH was measured at seven retention times within three months with two repetitions. The total removal of petroleum hydrocarbons (TPHs) was evaluated by GC-FID device. Results: The highest removal efficiency of TPH (40.24) was observed in bioreactors containing vermicompost at a 20 mass concentration. In this reactor, the highest percentage of removal was observed in lighter hydrocarbons (50.49). In reactors containing activated sludge, the average percentage of TPH removal was 32 which was observed in the reactor containing the 10 concentration of sludge. In this reactor, the highest percentage of removal (44.86) was also observed in lighter hydrocarbons. Conclusion: Vermicompost and activated sludge can be used in the bioremediation of soils contaminated with diesel. In current study, the performance of vermicompost was found to be more efficient. Also, the results showed that by increasing the concentration of biological modifiers, the removal rate would increase. © 2018, Mazandaran University of Medical Sciences. All rights reserved