Insight into the application of supercritical water oxidation for dichlorvos degradation: experimental and simulation aspects.

Dichlorvos or 2,2-dichlorovinyl dimethyl phosphate (DDVP) (C4H7Cl2O4P) is a chlorinated organophosphorus pesticide, which is frequently detected in agricultural wastewater. Herein, a batch reactor was used to carry out the supercritical water oxidation (SCWO) of a synthetic wastewater containing dichlorvos as a very hazardous agricultural pollutant. To do so, the impact of four operating parameters including dichlorvos concentration (100-500 ppm), oxidant coefficient (0.7-2), temperature (300-500°C) and time (0-100 s) on dichlorvos removal was optimized by the response surface method (RSM). According to the obtained results, at optimal conditions (i.e. initial concentration of dichlorvos 107.5 ppm, oxidation ratio 1.9234, temperature 419.9°C and time 79.94 s), as an index for dichlorvos removal, the chemical oxygen demand (COD) was found to be about 96.34%. Also, the results of high-performance liquid chromatography test showed that dichloroacetaldehyde (C2CL2H2O) and dichloroacetic acid (C2CL2H2O2) were created as intermediate substances during the dichlorvos degradation. Further, the molecular dynamics simulation was performed using ReaxFF force field to show the reaction path and products obtained in each step of the dichlorvos removal. Finally, as an indication, the simulation results indicated a good coordination with the experimental results.

Distribution and transport of microplastics in groundwater (Shiraz aquifer, southwest Iran).

Despite the significance of groundwater to the hydrological cycle and as a source of potable water, very little information exists on microplastics (MPs) in this environment. In the present study, MPs have been determined in ten well samples obtained from an alluvial aquifer in a semi-arid region (Shiraz, Iran) following filtration, digestion and inspection under a binocular microscope. A total of 96 MPs were identified, and concentrations ranged from 0.1 to 1.3 MP L-1 (mean and median = 0.48 and 0.43 MP L-1, respectively) and exhibited a complex distribution across the area that reflected differences in land use and local hydrology and geology. The majority of MPs (about 70%) were fibres of ≤ 500 µm in length, but fragments and films were present at some sites, and the dominant polymers were polystyrene, polyethylene and polyethylene terephthalate. Coupling meteorological and water table monitoring data from the regional water organization and published information on aquifer hydrology, we estimate a lag time from precipitation to water table intrusion of between one and five months and groundwater velocity flows of between 0.01 and 0.07 m d-1. Although the extent of retardation of MPs within the pores of groundwater is unknown, by considering empirical data and theoretical predictions on particle flow through porous media in the literature we surmise that MP residence times in the aquifer are likely to range from years to decades, thereby impeding any clear means of source identification. Nevertheless, and more generally, the consumption of potable groundwater may make to a contribution to MP exposure through ingestion.

Treatment of methyldiethanolamine wastewater using subcritical and supercritical water oxidation: parameters study, process optimization and degradation mechanism.

In this examination, sub/supercritical water oxidation (SCWO) in a batch reactor was employed to degrade methyldiethanolamine (MDEA). To do so, the impact of different operating parameters including temperature (300-500 °C), time (0-100 s), initial MDEA concentration (1000-4000 ppm), oxidant coefficient (0.7-2), and pH (7.3-9.5) on MDEA degradation was separately and together investigated. Subsequently, the response surface method (RSM) was applied to optimize the operating condition of MDEA degradation. Based on the obtained results, a maximum amount of 97.4% MDEA degradation was achieved at the initial MDEA concentration of 1095 ppm in optimal condition (i.e., oxidant coefficient: 1.913, temperature: 472 °C and residence time: about 17 s). Furthermore, according to the HPLC analysis, there was a negligible amounts of formic acid (CH2O2) and nitrous acid (HNO2) in the solution at the end of MDEA removal experiment. Eventually, the mechanism of MDEA degradation was acquired using molecular dynamics simulation (MDS), which had an acceptable coordination with the experimental results. In this way, the MDS results revealed that the presence of CH2O2 and HNO2 compounds in the products was related to the degradation of MDEA and their production as by-products during the SCWO experiments.

Determination of Swelling Behavior and Mechanical and Thermal Resistance of Acrylamide-Acrylic Acid Copolymers under High Pressures and Temperatures.

Unwanted water production is a serious problem accompanying oil extraction especially in oil-fractured reservoirs. An effective approach to tackle this issue is to utilize gels as a blockage agent. In this paper, an effective series of preformed particle gels (PPGs) was synthesized by a free radical copolymerization of acrylamide and acrylic acid [poly(AAm-co-AA)] copolymers. The key factors of synthesis experiments, gelation time, drying behavior, swelling capacity (in CaCl2·2H2O, MgCl2·6H2O, BaCl2·2H2O, KCl, NaCl, and LiCl saline solutions with 200,000 ppm concentration and pH from 3 to 8), and mechanical and thermal resistance of the synthesized PPGs (with a homemade apparatus) were elucidated. Laboratory results revealed that the prepared PPG sample 1 (9.65 mole ratio of AAm/AA and 6 mol % of MBA) would be a good candidate for controlling water in oil and gas reservoirs with a salinity, pressure, and temperature of up to 200,000 ppm, 300 bar, and 170 °C, respectively, and pH values ranging from 3 up to 8.

Fabrication of CuWO4/Bi2S3/ZIF67 MOF: A novel double Z-scheme ternary heterostructure for boosting visible-light photodegradation of antibiotics.

A novel double Z-scheme CuWO4/Bi2S3/ZIF67 ternary heterostructure was synthesized through hydrothermal method. The catalysts were characterized by XRD, FTIR, SEM, EDX, BET, TEM, PL, and UV-vis DRS analyses. The degradations of Metronidazole (MTZ) and Cephalexin (CFX) antibiotics by ternary catalyst were investigated in the batch and continuous slurry photoreactor under LED illumination. The ternary heterostructure exhibited a remarkable improvement in photoactivity compared with CuWO4/Bi2S3, and pristine ZIF67. Indeed, higher surface area, photo-stability, bandgap suppressing as well as better charge separation based on the dual Z-scheme structure caused the enhancement. The optimum values of operating parameters were obtained by the central composite design as: catalyst dose = 0.3 g/L, pH = 7, illumination time = 80 min, and 20 ppm initial concentration of antibiotic. The maximum degradation efficiencies by the new ternary heterostructure were 95.6% and 90.1%, respectively for MTZ and CFX at optimum conditions in the continuous flow mode. Maximum total organic carbon (TOC) removal rates were 83.2% and 74% for MTZ and CFX, respectively. The degradations by ternary composite followed the first-order kinetic, by reaction rate of 9 times, 5.5 times, and 4 times higher than that obtained by Bi2S3, ZIF67, and the binary CuWO4/Bi2S3, respectively. The influences of temperature and light intensity were explored, revealing 25 °C and 400 W/m2 as the optimum values. The new ternary heterostructure demonstrated excellent reusability and chemical stability after six cycles. The dominant active species were explored by trapping tests, indicating OH. free radicals as the most primary oxidant.

Improved waste-sourced biocomposite for simultaneous removal of crude oil and heavy metals from synthetic and real oilfield-produced water.

Oil- and gas-produced water (PW) which contains various pollutants is an enormous threat to the environment. In this study, a novel low-cost bio-adsorbent was prepared from shrimp shell and acid-activated montmorillonite. The results of FT-IR spectroscopy, energy dispersive X-ray (EDX) analysis, and SEM-EDX technique indicated that the chitosan-activated montmorillonite (CTS-A-MMT) was prepared successfully. The synthesized CTS-A-MMT was applied to remove simultaneously five cationic and anionic metal species and crude oil from synthetic and real oilfield PW. The adsorption data indicated that crude oil and all studied metals (except As) were adsorbed to CTS-A-MMT in a monolayer model (best fitted by Langmuir model), while As adsorption fits well with Freundlich model. Kinetic models' evaluation demonstrated that the adsorption kinetics of metals on CTS-A-MMT are initially controlled by the chemical reaction (film diffusion) followed by intra-particle diffusion. Application of the prepared CTS-A-MMT in real oilfield PW indicated removal efficiency of 65 to 93% for metals and 87% for crude oil in simultaneous removal experiments. Presence of additional ions in PW decreased the removal of studied metals and crude oil considerably; however, the concentration of the investigated pollutants in treated PW is less than the ocean discharge criteria. It is concluded that the prepared CTS-A-MMT composite is a low-cost and effective adsorbent for treating wastewater contaminated with crude oil and heavy metals (i.e., PW).

Comparison of the effects of poultry manure and its biochar on barley growth in petroleum-contaminated soils.

This study was conducted to evaluate and compare the effectiveness of two organic amendments [poultry manure (PM) and poultry manure biochar (PMB)] for the degradation of petroleum hydrocarbons in contaminated soils by barley plant at three levels of total petroleum hydrocarbons (TPHs) during 5 months under greenhouse conditions. TPHs removal efficiency and microbial respiration were shown to be higher at soil-cultivated plant than at uncultivated soil and in lowest level of contamination rather than other levels of contamination and at organic amendment treatment than unamended soil. Soil microbial respiration and TPHs degradation in the rhizosphere of barley increased by 15.64 and 12.74% for PM-amended treatment and 28.07 and 26.83% for PMB-amended treatment, respectively, in the 4% TPHs level compared with unamended treatment. Comparison of two amendments showed that in PMB treatment soil, highest dry weight, microbial respiration, and TPHs degradation potential were observed.

Biological removal of methanethiol from gas and water streams by using Thiobacillus thioparus: investigation of biodegradability and optimization of sulphur production.

The present work mainly deals with biological oxidation, which was tested using the bacterium Thiobacillus thioparus in semi-batch bioreactor systems to evaluate the removal efficiencies and optimal conditions for the biodegradation of methanethiol (MT) in order to treat the natural gas and refinery output streams. The efficiency of this method is analysed by evaluating the concentration of MT in a bioreactor. The effect of operational parameters, such as initial concentration of MT, pH, temperature, dissolved oxygen (DO), initial concentration of bacteria and reaction time on the degradation of MT, were studied. In this process, MT is converted into elemental sulphur particles as an intermediate in the oxidation process of MT to sulphate. The obtained results showed that the highest degradation rate occurred during the first 300 minutes of reaction time. The optimal conditions of the different initial MT concentrations with 0.3-0.6 bacteria OD, DO of 0.5 ppm, acidic pH value of 6.2 and temperature of 300C are obtained. Acidic pH and oxygen-limiting conditions were applied to obtain 80-85% selectivity for elemental sulphur formation in products. Under the optimal conditions, and for the highest (8.51 mM) and the lowest (0.53 mM) concentration of MT, the biological removal was about 89% and 94%, respectively.

Theoretical and experimental investigation of desalting and dehydration of crude oil by assistance of ultrasonic irradiation.

In this paper desalting/dehydration process of crude oil by ultrasonic irradiation in a novel batch standing-wave resonator reactor is studied both theoretically and experimentally. The effect of main parameters including ultrasonic irradiation parameters, namely irradiation input power and irradiation time, and also operating parameters, such as temperature and injected water, on the removal efficiencies of salt and water is examined. The obtained results demonstrate that finding the optimum values of the above mentioned parameters is important to prevent a significant decrease in the removal efficiencies of water and especially salt. Thus, crude oil was subjected to optimal ultrasonic irradiation with an input power of 57.7 W, and irradiation time of 6.2 min at temperature of 100 °C. The injected water to dissolve the salt of crude oil was 7 vol.%. Also, the applied settling time and dosage of chemical demulsifier were 60 min and 2 ppm, respectively. Under these optimum conditions the removal efficiencies of the desalting/dehydration process were 84% and 99.8%, respectively, which are suitable for refineries. Also, based on the optimal experimental data, two inferential estimators are developed to obtain the relationships between the salt and water removal efficiencies, and input energy density. These empirical relationships can offer a proper estimation for the salt and water removal efficiencies with irradiation input energy.

Optimization of biological sulfide removal in a CSTR bioreactor.

In this study, biological sulfide removal from natural gas in a continuous bioreactor is investigated for estimation of the optimal operational parameters. According to the carried out reactions, sulfide can be converted to elemental sulfur, sulfate, thiosulfate, and polysulfide, of which elemental sulfur is the desired product. A mathematical model is developed and was used for investigation of the effect of various parameters on elemental sulfur selectivity. The results of the simulation show that elemental sulfur selectivity is a function of dissolved oxygen, sulfide load, pH, and concentration of bacteria. Optimal parameter values are calculated for maximum elemental sulfur selectivity by using genetic algorithm as an adaptive heuristic search. In the optimal conditions, 87.76% of sulfide loaded to the bioreactor is converted to elemental sulfur.

Biosurfactant production under extreme environmental conditions by an efficient microbial consortium, ERCPPI-2.

The biosurfactant production potential of a new microbial consortium of Enterobacter cloacae and Pseudomonas sp. (ERCPPI-2) which was isolated from heavy crude oil-contaminated soil in the south of Iran, has been investigated under extreme environmental conditions. The isolated consortium produces a biosurfactant mixture with excessive oil spreading and emulsification properties. This consortium was able to grow and produce biosurfactant at temperatures up to 70 °C, pressures up to 6000 psia, salinities up to 15% (w/v), and in the pH range 4-10. Besides, the optimum biosurfactant production conditions were found to be 40 °C and 7.0 for the temperature and pH value, respectively. These conditions gave the best biosurfactant production of 1.74 g/1 when the cells were grown on a minimal salt medium containing 1.0% (w/v) olive oil, 1.0% (w/v) sodium nitrate supplemented with 1.39% (w/v) K(2)HPO(4) at 40 °C and 150 rpm after 48 h of incubation. The ERCPPI-2 could reduce surface and interfacial tensions to 31.7 and 0.65 mN/m from the original values of 58.3 and 16.9 mN/m, respectively. The isolated consortium produced biosurfactant using heavy crude oil as the sole source of carbon and emulsified the available heavy crude oil up to E(24)=83.4%. The results of the core holder flooding tests at simulated reservoir conditions demonstrated that the oil recovery efficiency due to the injection of the cell-free biosurfactant solution was 27.2%, and the bacterium injection reduced the final residual oil saturations to below 3% at optimum conditions.