Effect of the injection of pure oxygen into a membrane bioreactor on the elimination of bisphenol A

The effect of the injection of pure oxygen instead of air in a membrane bioreactor for the elimination of bisphenol A is investigated. A dynamic experiment was developed in a pilot plant where the aerobic reactor was continuously spiked with 1 mg L^?1 of bisphenol A. Air was injected for 10 days and then pure oxygen was injected for another 10 days. The bisphenol A concentration was determined in aqueous phases and activated sludge using simple and sensitive analytical methods based on different extraction procedures and liquid chromatography tandem mass spectrometry analysis. Enzymatic activity was also determined and toxicity tests were performed to discard that the spiked bisphenol A concentration could negatively affect the microorganisms in the bioreactor and, thus, the membrane bioreactor performance. The effluent bisphenol A concentration increased up to 0.26 mg L^?1 after 4 days in the air injection treatment, and up to 0.48 mg L^?1 after only 12 h in the oxygen injection treatment. In both cases, this was followed by a decrease in concentration despite the continuous spiking of bisphenol A into the bioreactor. In presence of pure oxygen, bisphenol A concentration reached background levels (below the limit of quantification) after 5 days. In contrast, when using air a total of 10 days were required to reach background levels. The injection of pure oxygen instead of air is an important innovation in wastewater treatment, allowing permanent elimination of organic contaminants, avoiding their return to the environment and ensuring the safety of water.     

Influence of energy efficiency on VOCs decomposition in non-thermal plasma reactor

In order to promote the plasma technology for commercial application and improve the energy efficiency of non-thermal plasma, a series of experiments on energy efficiency of plasma reactor were carried out for volatile organic compounds removal. This research adopts a pipe-line reaction device with plasma generated by dielectric barrier discharge technology to examine the effects of different experimental parameters, including medium packing, electric field strength, the pollutant initial concentration, and gas velocity, on the energy efficiency. In the study, four kinds of packed materials were packed into the plasma reactor: a complex catalyst, Ba_0.8Sr_0.2Zr_0.1Ti_0.9O₃, MnO₂/γ-Al₂O₃, and γ-Al₂O₃. Through optimizing the experimental parameters, the best decomposition efficiency of toluene and the best energy efficiency were achieved. The experimental results show that the energy efficiency has a trend from increasing to decreasing with increasing pollutant gas velocity, and the energy efficiency changes from increasing to decreasing with the increasing of initial concentration of pollutants, and the decomposition efficiency and the energy efficiency have the same order from high to low with different packed materials in the plasma reactors, in turn, packed with complex catalyst, Ba_0.8Sr_0.2Zr_0.1Ti_0.9O₃, MnO₂/γ-Al₂O₃, γ-Al₂O₃ and no padding. The optimized parameters for toluene decomposition are: the gas flow rate of 2 mL/min, the initial concentration range of 1500–2000 mg/m³, the field strength intensity of 9.6 kV/cm, and the plasma reactor packed with a complex catalyst, which results in the best energy efficiency of 10 g/kWh. This research provides not only a new way to develop the plasma technology, but also a reference for the commercial application.     

Applicability of upflow anaerobic sludge blanket (UASB) reactor for typical sewage of a small community: its biomass reactivation after shutdown

In this study, the characteristics of sewage of small community were determined for 6 months to ascertain the type of treatment required in subtropical conditions. The results demarcated sewage of this community as a medium-strength wastewater (chemical oxygen demand: 475 mg/L, biochemical oxygen demand: 240 mg/L and total suspended solids: 434 mg/L). Chemical oxygen demand to sulphate ratio of the sewage (11.6) established that it was amenable to anaerobic digestion. The temperature, strength, biodegradability and components of sewage were suitable for anaerobic digestion, and thus, upflow anaerobic sludge blanket reactor (UASB) was selected for its treatment. These reactors are often shutdown in small communities due to environmental and/or socio-economic factors. The ability of two UASB reactors, seeded with cow dung (UASB_CD) and activated sludge of a dairy treatment plant (UASB_ASDIT) to restart after a long idle period of 12 months, was investigated along with sludge analysis by scanning electron microscope. Biomass in both reactors reactivated rapidly after shutdown period and within 30 days after substrate feeding achieved uniform removal efficiencies for chemical oxygen demand, total suspended solids, total dissolved solids, chloride and oil and grease. Chemical oxygen demand removal efficiency of both reactors became uniform and remained close to 80% after 30 days through reactivation of microbes in sludge bed due to adequate food and temperature conditions. During restart-up, at an average organic loading rate of 0.902 kg COD/m³ per day, methane yields of 0.091 and 0.084 m³/kg COD removed were achieved for UASB_CD and UASB_ASDIT reactors, respectively.     

In situ observations of bubble growth in basaltic,andesitic and rhyodacitic melts

Bubble growth strongly affects the physical properties of degassing magmas and their eruption dynamics. Natural samples and products from quench experiments provide only a snapshot of the final state of volatile exsolution, leaving the processes occurring during its early stages unconstrained. In order to fill this gap, we present in situ high-temperature observations of bubble growth in magmas of different compositions (basalt, andesite and rhyodacite) at 1,100 to 1,240 °C and 0.1 MPa (1 bar), obtained using a moissanite cell apparatus. The data show that nucleation occurs at very small degrees of supersaturaturation (<60 MPa in basalt and andesite, 200 MPa in rhyodacite), probably due to heterogeneous nucleation of bubbles occurring simultaneously with the nucleation of crystals. During the early stages of exsolution, melt degassing is the driving mechanism of bubble growth, with coalescence becoming increasingly important as exsolution progresses. Ostwald ripening occurs only at the end of the process and only in basaltic melt. The average bubble growth rate (G _R) ranges from 3.4 × 10^?6 to 5.2 × 10^?7 mm/s, with basalt and andesite showing faster growth rates than rhyodacite. The bubble number density (N _B) at nucleation ranges from 7.9 × 10⁴ mm^?3 to 1.8 × 10⁵ mm^?3 and decreases exponentially over time. While the rhyodacite melt maintained a well-sorted bubble size distribution (BSD) through time, the BSDs of basalt and andesite are much more inhomogeneous. Our experimental observations demonstrate that bubble growth cannot be ascribed to a single mechanism but is rather a combination of many processes, which depend on the physical properties of the melt. Depending on coalescence rate, annealing of bubbles following a single nucleation event can produce complex bubble size distributions. In natural samples, such BSDs may be misinterpreted as resulting from several separate nucleation events. Incipient crystallization upon cooling of a magma may allow bubble nucleation already at very small degrees of supersaturation and could therefore be an important trigger for volatile release and explosive eruptions.     

A network flow model for the genesis and migration of gas phase

We present a network flow model to compute transport, through a pore network, of a compositional fluid consisting of water with a dissolved hydrocarbon gas. The model captures single-phase flow (below local bubble point conditions) as well as the genesis and migration of the gas phase when bubble point conditions are achieved locally. Constant temperature computational tests were run on simulated 2D and 3D micro-networks near bubble point pressure conditions. In the 2D simulations which employed a homogeneous network, negligible capillary pressure, and linear relative permeability relations, the observed concentration of CO₂ dissolved in the liquid phase throughout the medium was linearly related to the liquid pressure. In the case of no gravity, the saturation of the gas phase throughout the medium was also linearly related to the liquid pressure; under gravity, the relationship became nonlinear in regions where buoyancy forces were significant. The 3D heterogeneous network model had nonnegligible capillary pressure and nonlinear relative permeability functions. While 100 % of the CO₂ entered the 3D network dissolved in the liquid phase, 25 % of the void space was occupied by gas phase and 47 % of the CO₂ exiting the outlet face did so via the gaseous phase after 500 s of simulation time.     

Elimination of natural organic matter by electrocoagulation using bipolar and monopolar arrangements of iron and aluminum electrodes

The aim of this research was to evaluate the efficiency of electrocoagulation (EC) for the removal of natural organic matter (NOM) by using iron (Fe) and aluminum (Al) electrodes. The effects of several operational parameters such as initial pH (3–10), time of electrolysis (5–30 min), initial concentration of organic matter (10–50 mg NOM/L), current density (0.25–1.25 mA/cm²), type of electrode material (n = 4, 2 sides × 11 cm × 10 cm, wall thickness = 2 mm, distance between each electrode = 5 mm), and type of connection of electrodes (bipolar and monopolar configurations) were explored for the removal of NOM from synthetic humic acid solution in a 2 L laboratory-scale EC cells (A _s/V = 0.110 cm^?1). The optimum conditions for the process were identified as pH = 3 and 7, electrolysis time = 20 and 10 min for Fe and Al electrodes, respectively. Using both electrodes at current density = 0.25 mA/cm² and initial concentration of organic matter = 50 mg/L, a NOM removal efficiency of almost 100% could be achieved in the bipolar mode. Based on the optimum conditions, specific reactor electrical energy consumptions were 14.90 kWh/kg Al (or 0.092 kWh/m³) and 2.88 kWh/kg Fe (or 0.11 kWh/m³). Specific electrode consumptions were obtained to be 0.0062 and 0.0382 kg/m³, and operating costs of the EC system were preliminary estimated at 0.057 and 0.119 $/m³ for Al and Fe electrodes, respectively.     

Attachment of individual particles to a stationary air bubble in model systems

A particle–bubble attachment apparatus, similar to that used by Whelan and Brown [Bull. Inst. Min. Met. Trans. 65 (1956) 181] is developed to study free falling glass beads (d_p=131 μm) with different surface treatment attaching to a stationary air bubble (d_b=3 mm). The entire process of the particle–bubble attachment is photographically recorded using a high framing-rate camera and analyzed frame by frame. It is found that the hydrophilic particle slides on the top half of the bubble, and then the particle leaves the bubble, as anticipated. The particle sliding velocity increases with increasing angular position on the bubble surface. For the hydrophobic particle, it was found that the particle slides over the entire bubble surface without detaching from the bubble. The sliding velocity, however, reaches a maximum at an angular position of 90–100°, and then slows down to zero. A smaller sliding velocity is obtained for the hydrophobic particle than that of the hydrophilic particle at a given angular position. The attachment efficiency for the hydrophobic particle reduces with increasing initial angular positions, suggesting that the hydrophobicity alone does not directly guarantee the attachment to a bubble. Adding surfactant (sodium dodecyl sulfate [SDS]) to the test solution makes the hydrophobic particle become less hydrophobic or even hydrophilic, thereby decreasing the attachment efficiency. A much longer induction time is obtained in our present work than that reported in the literature. A simplified particle sliding velocity and attachment model is developed, and a good agreement between the theoretical prediction and experimental measurement is obtained.     

Biodegradation of phthalic acid esters in sewage sludge by composting with pig manure and rice straw

To comparatively study the biodegradation of phthalic acid esters (PAEs) in sewage sludge by composting with pig manure or with rice straw, four composting modes were designed: Mode 1 (sewage sludge + pig manure + intermittent aeration), Mode 2 (sewage sludge + pig manure + continuous aeration), Mode 3 (sewage sludge + rice straw + intermittent aeration) and Mode 4 (sewage sludge + rice straw + continuous aeration). Physicochemical parameters of composts were measured according to standard methods and PAEs were analyzed by gas chromatography coupled with mass spectrometry (GC/MS). The biodegradation of each PAE was also discussed. The results showed that Mode 1 was the best mode to biodegrade PAEs, which might be related to the wide class of indigenous microbial communities in pig manure and high efficiency of intermittent ventilation for providing oxygen. During the biodegradation process, di(2-ethylhexyl) phthalate was the most abundant and decisive for the removal of total PAEs. It showed a first-order kinetic degradation model. In conclusion, composting with pig manure could be suggested as an effective detoxification process for the removal of PAEs from sewage sludge, providing a safe end product.     

Influence of hydraulic retention time on heterotrophic biomass in a wastewater moving bed membrane bioreactor treatment plant

Wastewater treatment using moving bed membrane bioreactor technology was tested with real urban wastewater at a pilot plant, combining moving bed treatment as a biological process with hybrid biomass (suspended and fixed) and the advantages of a membrane separation system. The evolution of the kinetic constants of the hybrid biomass and organic matter removal were studied in a pilot plant under different operational conditions, by varying hydraulic retention time (HRT), mixed liquor suspended solids (MLSS) and temperature, and considering the attached biomass of the carrier and the dispersed biomass of the flocs to reproduce real treatment conditions. The rates of organic matter removal were 97.73 ± 0.81 % of biochemical oxygen demand (BOD₅), 93.44 ± 2.13 % of chemical oxygen demand (COD), 94.41 ± 2.26 % of BOD₅ and 87.62 ± 2.47 % of COD using 24.00 ± 0.39 and 10.00 ± 0.07 h of HRT, respectively. The influence of the environmental variables and operational conditions on kinetic constants was studied; it was determined that the most influential variable for the decay coefficient for heterotrophic biomass was HRT (0.34 ± 0.14 and 0.31 ± 0.10 days^?1 with 10.00 ± 0.07 and 24.00 ± 0.39 h of HRT, respectively), while for heterotrophic biomass yield, this was temperature (0.61 ± 0.04 and 0.52 ± 0.06 with 10.00 ± 0.07 and 24.00 ± 0.39 h of HRT, respectively). The results show that introducing carriers in an MBR system provides similar results for organic matter removal, but with a lower concentration of MLSS.     

Mechanism of efficient nutrient removal and microbial analysis of a combined anaerobic baffled reactor–membrane bioreactor process

A combined ABR–MBR process consisting of an anaerobic baffled reactor (ABR) combined with an aerobic membrane bioreactor (MBR) treating municipal wastewater was investigated at controlled pH range 6.5–8.5 and at constant temperature 25 ± 1 °C. Total nitrogen (TN), ammonia (NH₄ ⁺–N), total phosphorus (TP), and chemical oxygen demand (COD) removal performances were evaluated by analyzing the mechanism for efficient nutrient removal. The results showed that the average removal rates of COD, NH₄ ⁺–N, TN, and TP reached 93, 99, 79, and 92 %, respectively, corresponding with the COD, NH₄ ⁺–N, TN, and TP effluent of 24 (18–31), 0.4 (0–0.8), 10.6 (8.8–12.9), and 0.31 (0.1–0.5) mg/L under the operational condition of hydraulic retention time (HRT) 7.5 h, recycle ratio 200 %, and dissolved oxygen 3 mg/L. The MBR enhanced NH₄ ⁺–N, TN, and TP removal rates of 13, 10, and 18 %, respectively, and the membrane retention reduced TP 0.17 mg/L. The process was able to maintain a stable performance with high-quality effluent. Analysis of the results by fluorescence in situ hybridization showed that the abundance of ammonia-oxidizing bacteria, nitrite-oxidizing bacteria, and phosphorus accumulating organisms as percentages of all bacteria in each compartment was stable. The enriched microorganisms in the system appear to be the main drivers of the process efficient for nutrient removal.     

Assessment of groundwater quality in and around Vedaraniyam,South India

Groundwater from 47 wells were analyzed on the basis of hydrochemical parameters like pH, electric conductivity, total dissolved solids, Ca²⁺, Mg²⁺, Na⁺, K⁺, Cl^?, CO₃ ^2?, HCO₃ ^?, NO₃ ^?, PO₄ ^3? and F^? in the Cauvery delta of Vedaraniyam coast. Further, water quality index (WQI), sodium percentage (Na %), sodium absorption ratio, residual sodium carbonate, permeability index and Kelley’s ratio were evaluated to understand the suitability of water for drinking and irrigation purposes. The result shows significant difference in the quality of water along the coastal stretch. The order of dominance of major ions is as follows: Na⁺ ≥ Mg²⁺ ≥ Ca²⁺ ≥ K⁺ and Cl^? ≥ HCO₃ ^? ≥ CO₃ ^2? ≥ PO₄ ^3? ≥ F^?. Na/Cl, Cl/HCO₃ ratio and Revelle index confirmed that 60–70 % of the samples were affected by saline water intrusion. WQI showed that 36 % of the samples were good for drinking and the remaining were poor and unsuitable for drinking purpose. The degradation of groundwater quality was found to be mainly due to over-exploitation, brackish aquaculture practice, fertilizer input from agriculture and also due to domestic sewage.     

Assessment of pollution sources in the southeastern of the Riyadh and its impact on the population/Saudi Arabia

The rapid growth of Riyadh—capital of Saudi Arabia—is pushing the area to more pollution and incentive for reorganization. The aim of this research is to assess air pollutants in southeast of Riyadh and detect opinion of the population about their environment. The assessment was done by analyzing 405 questionnaires, evaluating thermal band of Landsat 8, and spatial analyzing of particular matter and chemicals in 19 air samples by geostatistical tool in the ArcMap. Most of the inhabitants stated that they are suffering from bad odor, sewage leakage, and dust mainly from a cement factory. The thermal band of Landsat clarified the location of the pollution sources mainly the 1st industrial city, Yammama Cement Factory, and power plant in Farouq area. The ordinary kriging maps showed that the highest concentration of PM₁₀ (>403 μg/m³) lied to the northern and western side of the study area and caused a health issue to most inhabitants.     

Application of the cBΩ model to the calculation of diffusion parameters of He in olivine

The validity of the thermodynamic cBΩ model is tested in terms of the experimentally determined diffusion coefficients of He in a natural Fe-bearing olivine (Fo₉₀) and a synthetic end-member forsterite (Mg₂SiO₄) over a broad temperature range (250–950 °C), as reported recently by Cherniak and Watson (Geochem Cosmochim Acta 84:269–279, 2012). The calculated activation enthalpies for each of the three crystallographic axes were found to be (134 ± 5), (137 ± 13) and (158 ± 4) kJ mol^?1 for the [100], [010] and [001] directions in forsterite, and (141 ± 9) kJ mol^?1 for the [010] direction in olivine, exhibiting a deviation of <1 % with the corresponding reported experimental values. Additional point defect parameters such as activation volume, activation entropy and activation Gibbs free energy were calculated as a function of temperature. The estimated activation volumes (3.2–3.9 ± 0.3 cm³ mol^?1) of He diffusion in olivine are comparable with other reported results for hydrogen and tracer diffusion of Mg cations in olivine. The pressure dependence of He diffusion coefficients was also determined, based on single experimental diffusion measurements at 2.6 and 2.7 GPa along the [001] direction in forsterite at 400 and 650 °C.     

Fungal biodiversity in sewage water under the effect of calcium hydroxide and hydrogen peroxide into two-steps treatment

Microorganisms, organic matter, heavy metals are the main pollutants in sewage water. The increasing water demand pressurized people to use the sewage water. Different systems, chemicals and physical treatments were used in sewage water treatment. The aim of this work is to study the effect and correlations of primary (Ca(OH)₂ filtration and H₂O₂) and secondary (dissolved oxygen, organic matter, conductivity, pH and OD) factors on fungi present in sewage water in addition to proving the sequence of the system used in the current study. After treatment, fungi were examined, identified on Czapek agar and analyzed using multivariate tools (CANOCO: DCA and CCA) and R software. The treatment includes two main steps: liming filtration and oxidation, respectively. All parameters were negatively or positively correlated (organic matter, pH, conductivity %, optical density, fungal CFU ml^?1, dissolved oxygen). Heavy metals were decreased due to the application of Ca(OH)₂ and H₂O₂, respectively. There were two main groups of fungi. The larger was correlated with the organic matter, whereas the second was tolerating calcium hydroxide concentrations. Aspergillus sydowii tolerated hydrogen peroxide (0.2 mll^?1(33%); Ca(OH)₂, 0.25 gl^?1). Sequential steps treatment was healthy and economically efficient. The proposed system improved water characteristics. The recommended amount of Ca(OH)₂ and H₂O₂ was 0.25 gl^?1 and 0.2 mll^?1(33%), respectively, and can remove more than 99.9% of fungal CFUs. The current study minimized the optimum dose of hydrogen peroxide used in the disinfection of sewage water from 1.5 (Mohamed in Chem Eng J 119:161–165, 2006) to 0.2 mll^?1 of H₂O₂ (the current study).     

Degradation of polyvinyl alcohol in aqueous solutions using UV-365 nm/S2O8 2− process

This investigation evaluates the effectiveness of UV-365 nm/S₂O₈ ^2? process in degrading polyvinyl alcohol in aqueous solutions. The effects of pH, Na₂S₂O₈ dosage, and temperature on the degradation efficiency of polyvinyl alcohol were studied. Under acidic conditions, the degradation efficiency of polyvinyl alcohol exceeded that under alkaline conditions. Additionally, a higher Na₂S₂O₈ dosage and a higher temperature were associated with a higher degradation efficiency of polyvinyl alcohol. The degradation rates of polyvinyl alcohol followed a pseudo-first-order kinetic model. Moreover, the observed degradation rate coefficient increased from 0.0078 to 0.4081 min^?1 when the temperature was increased from 10 to 55 °C. Also, the activation energy estimated using the observed degradation rate coefficients and the Arrhenius equation was 64 kJ/mol. At UV-365 nm, pH 3, an Na₂S₂O₈ dosage of 0.06 g/L, a temperature of 55 °C, and an initial polyvinyl alcohol concentration of 20 mg/L, around 100 % of polyvinyl alcohol was degraded, indicating that UV-365 nm/S₂O₈ ^2? process has great potential in degrading polyvinyl alcohol in aqueous solutions.     

Catalytic hydrothermal carbonization of invasive macrophyte Hornwort (<Emphasis Type="Italic">Ceratophyllum demersum</Emphasis>) for production of hydrochar: a potential biofuel

Biofuels are environment friendly and economical. First-generation biofuels are made from sugar, starch and vegetable oils, and have an impact on food security, while second generation biofuels are generated from plant or algal material and are greener and sustainable. The present work focused on lab-scale application of hydrothermal carbonization to convert aquatic weed Ceratophyllum demersum into a second-generation biofuel—hydrochar. Hydrothermal carbonization has been carried out with and without catalysts in a high-pressure reactor under subcritical temperatures 240–320 °C, residence times 10–40 min and biomass to water dilution ratios varying from 1:4 to 1:12. Under noncatalytic conditions higher heating value and energy density were highest, 24.11 MJ/kg and 1.64 respectively at temperature of 300 °C and residence time of 30 min. The calorific value of noncatalytic hydrochar was enhanced further, respectively, to 29.0, 27.5 and 26.48 MJ/kg by catalysts KOH, Na₂CO₃ and acetic acid. Catalytic hydrochar had H/C and O/C atomic ratios of same order as that of high-rank bituminous coal. Van Krevelen diagram indicated KOH to be better catalyst followed by Na₂CO₃ and acetic acid. Hydrochar yield of 38% obtained in noncatalytic hydrothermal carbonization decreased with catalysts in following order; acetic acid > Na₂CO₃ > KOH, however, energy density was enhanced in order KOH > Na₂CO₃ > acetic acid. The research can prove a way forward in the direction of meeting part of global energy demand. At the same time, the problem of secondary pollution caused by piling up and decay of aquatic weeds will also be addressed to.     

Multi-time-scale analysis of hydrological drought forecasting using support vector regression (SVR) and artificial neural networks (ANN)

In this study, the preprocessing of the gamma test was used to select the appropriate input combination into two models including the support vector regression (SVR) model and artificial neural networks (ANNs) to predict the stream flow drought index (SDI) of different timescales (i.e., 3, 6, 9, 12, and 24 months) in Latian watershed, Iran, which is one of the most important sources of water for the large metropolitan Tehran. The variables used included SDI _t , SDI _t ? 1, SDI _t ? 2, SDI _t ? 3, and SDI _t ? 4 monthly delays. Two variables including SDI _t and SDI _t ? 1 with lower gamma values were identified as the most optimal combination of variables in all drought timescales. The results showed that the gamma test was able to correctly identify the right combination for the forecasting of 6, 9, and 12 months SDI using the ANN model. Also, the gamma test was considered in selecting the appropriate inputs for identifying the values of 9, 12, and 24 months SDI in SVR. The support vector machine approach showed a better efficiency in the forecast of long-term droughts compared to the artificial neural network. In total, among forecasts made for 30 scenarios, the support vector machine model only in scenario 3 of SDI₃, scenario 1 of SDI₆, and scenarios 2 and 3 of SDI₂₄ represented poorer efficiency compared to the artificial neural network (MLP layer), but in other scenarios, the results of SVR had better efficiency.     

Adsorption kinetics and thermodynamics of organophosphorus profenofos pesticide onto Fe/Ni bimetallic nanoparticles

Bimetallic Fe/Ni nanoparticles were synthesized and used for the removal of profenofos organophosphorus pesticide from aqueous solution. These novel bimetallic nanoparticles (Fe/Ni) were characterized by scanning electron microscopy, energy-dispersive X-ray analysis spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The effect of the parameters of initial pesticide concentration, pH of the solution, adsorbent dosage, temperature, and contact time on adsorption was investigated. The adsorbent exhibited high efficiency for profenofos adsorption, and equilibrium was achieved in 8 min. The Langmuir, Freundlich, and Temkin isotherm models were used to determine equilibrium. The Langmuir model showed the best fit with the experimental data (R ² = 0.9988). Pseudo-first-order, pseudo-second-order, and intra-particle diffusion models were tested to determine absorption kinetics. The pseudo-second-order model provided the best correlation with the results (R ² = 0.99936). The changes in the thermodynamic parameters of Gibb’s free energy, enthalpy, and entropy of the adsorption process were also evaluated. Thermodynamic parameters indicate that profenofos adsorption using Fe/Ni nanoparticles is a spontaneous and endothermic process. The value of the activation energy (E _a = 109.57 kJ/mol) confirms the nature of the chemisorption of profenofos onto Fe/Ni adsorbent.     

Rate and budget of blown sand movement along the western bank of Lake Nasser,southern Egypt

Three sets of Landsat? satellite images for the years 1993, 1998, and 2003 show that the sand dunes at the southwestern Desert of Egypt are generally moving towards southeast direction with a mean annual creeping speed over ground attaining 15 m/year. The manual-stickled field measurements show that the net annual extension of the longitudinal dunes in the coastal area is between 4 and 5 m/year, while the inland longitudinal dunes showed a net movement ranging between 5 and 6 m/year. Seasonal variations of drift potential and sand movement refer to a strongly high energy wind desert environment in the spring season, high energy wind desert environment in the summer season, and relatively high to intermediate in the autumn and winter seasons, respectively. The total annual estimated volume of transported sand which falls down into Lake Nasser basin attains 16,225,808 m³ as calculated by Bagnold's equation and quantities of sand collected from the sand traps. Comparing this value with the total volume of Lake Nasser Basin, which attains 120?×?10⁹ m³, we can conclude that the sand sheets or sand accumulations may represent serious natural hazards to Lake Nasser in some locations. However, the sand drifting towards the lake may be obstructed by high contour topography hindrance, and the mean grain size of the sand sheets is bigger than 0.25 mm, which needs high wind velocity more than 4 m/s. In addition, the direction of the prevailing wind is N-NNW to S-SSE, and this direction sometimes is parallel to Lake Nasser in some places according to the meandering of the lake. The total lengths of hazardous areas along the western bank of Lake Nasser, which receive the most amounts of the drifted sands, attain 43.6 km only.