مجله آب و فاضلاب
پیاپی 133 (خرداد و تیر 1400)

Environmental pollution due to heavy metals has increased enormously in the world in the last two centuries. The presence of some heavy metals in aquatic ecosystems is a continuous hazard to human health. Electrospinning technology is the most effective way to produce nanofibers. In this study, the technology of producing nanofiber aluminum for maximum separation of nickel through the adsorption process has been investigated. In this research, nanofiber alumina has been synthesized by electrospinning method. Spinning solution with a concentration of 10% by weight of aluminum precursor was selected. Considering different weight ratios of polymer to precursor, the electrolysis process was better selected. The stable spinning voltage was in the range of 17-20 kV and the flow rate was 0.5 ml/h. Eventually, XRD, SEM, FTIR, and Raman tests were performed to ensure the formation of nanoparticles and to determine their physical, chemical, and morphological structure. The pH, contact time, nano-adsorption value, pollutant concentration, and solution volume parameters were evaluated. Therefore, the optimal conditions for separating nickel-metal were provided and isothermal and kinetic absorption calculations were performed for it. The results indicate that the best conditions for nickel adsorption by this type of nano-adsorbent occurs at pH=8, a contact time of 60 minutes, nano-adsorbent in the amount of 0.05 gr, concentration of 5 mg/L of nickel metal and the solution volume of 50 ml and it has been 99%. In addition, the adsorbent behavior was consistent with the Langmuir and Freundlich isotherms and the first and second-degree quasi-quintet kinetic models. Finally, it is clear that the method of nanofiber aluminum synthesis by electrospinning is complex but at the same time very practical and effective, leading to its use as a new and promising solution in removing nickel metal ions from water.

Nanocellulose, as an emerging nanoscale material with important physical and chemical properties, is intended for a variety of applications that go beyond the applications seen in industrial composites. The nanocomposite membrane of thin film cellulose nanocrystalline/polyamide film for nanofiltration applications was made by interfacial polymerization. The characteristics of the membrane synthesized by scanning electron microscopy and infrared spectroscopy were analyzed. The function of the membrane made on the solution of sodium sulfate salts (Na2SO4) and magnesium chloride (MgCl2) was investigated using the Central Compound Design method. The correlation coefficient of the computational model (R-Sq adj) for salt excretion of Na2SO4 and MgCl2 was obtained to be equal to 99.67% and 86.89%, respectively, which indicates the good compatibility of computational models with experimental points, and the high accuracy of the models. The results of the statistical analysis showed that, with increasing CNC concentration to intermediate level (0.05 %Wt), fluid flow to intermediate level (2.25 lit/min) and pressure to high level (10 bar), the highest rejection percentage of Na2SO4 and MgCl2 salts was 93.44 and 79.52%, respectively.

Condensed air in the water stream causes serious problems such as head drop, localized pressure increases high noise generation, shaking in the pipes, as well as the loss of pumps in the system will be transmitted. To remove air from the system, air valves should be used. In this research, the hydraulic properties of air flow contained in the water pipes is studied, then a program is developed for providing the optimal solution regarding the size and position of the valves in the right place by using MATLAB software. The general method is to examine all the tube parts at the failure location by the direct search algorithm and find the lowest gradient and calculate the initial discharge rate of the line as following: First, the minimum amount of air intake in the water pipeline will occur. Second, the air outlet speed of the system will be optimal. To enhance the applicability of the proposed method, the model was developed in the GUI environment. Finally, for the verification and evaluation of the results, an identical model of water pipeline using Valmatic software and the present developed software has been analyzed.

In recent years, reverse osmosis method has played a major role in desalination of brackish and saline waters. The purpose of this study is to provide a proper desalination system for the use of aqueduct water in the University of Tabriz for health consumption in order for proper water management. According to the results of qualitative experiments, in the first step, the reverse osmosis desalination system was selected and designed. Through that, according to the different types of membranes and pre-purifiers, 15 scenarios were evaluated by 4 main criteria (economic, technical, environmental and social) and 6 sub-criteria. With the help of water application value engine (WAVE) software, the scenarios were modeled based on the opinion of decision makers and the weight of each criterion was calculated. Finally, group fuzzy decision making (GFDM) software was used to analyze group multi-criteria decision making to determine the best scenarion. In this study, by combining the WAVE and GFDM software the opinions of officials and experts are directly applied in the design and selection of the treatment system, leading to increase in the users’ satisfaction. Finally, the results show that the M scenario is the best choice of the decision-makers' point of view, which includes XLE-440 membranes for reverse osmosis and SFD-2880 ultrafiltration filter. In addition, to more accurately examine the behavior of the scenarios, sensitivity analysis on the parameters has also been performed.

Today, water desalination methods are of great importance in solving the freshwater crisis in the world, so that in recent years, the world's water desalination capacity has increased dramatically. Among them, the reverse osmosis membrane technology has been the most popular and the most commonly used. There are problems such as high energy consumption, high operating costs, and fouling in this method. The objective of this paper was to use reverse and forward osmosis membrane methods simultaneously in a hybrid reverse-forward osmosis setting, which enabled us to take advantage of the benefits of forward osmosis such as not being dependent on high hydraulic pressure, lower cost and less membrane fouling compared to reverse osmosis. Another objective of the study was to evaluate the permeate water production efficiency of desalination with this hybrid method. It is expected that using the hybrid method will reduce the required pressure for conducting reverse osmosis process to achieve a specified permeate flux, because it reduces cost and energy. An HRFO laboratory pilot with a capacity of 50 m3/day was designed and set up in the Hydraulic Lab of Shahid Chamran University of Ahvaz for running hybrid experiments. The design of the pilot was such that it could operate in both reverse osmosis and HRFO. HRFO experiments were carried out at pressures of 4.5 to 10.5 bar for Ahvaz urban water as feed solution, as well as NaCl as draw solution with a concentration of 2000 to 10000 mg/L via the experimental HRFO plant. It was found that adding the forward osmosis to reverse osmosis at the best situation (lowest pressure and highest concentration of draw solution) can increase the permeate water production efficiency of desalination by 55.12%. The best hybridization degree of these two methods was determined to be 64.5% for reverse osmosis and 35.5% for forward osmosis.

Strontium is one of the alkaline earth metals in the periodic table. This element has various uses. In this research, solvent extraction of strontium from leach liquor of central Iran metasomatic ores was studied with macrocyclic crown ether ligands. Many crown ethers were used as extractants. Strontium was quantitatively extracted from picrate media by dicyclohexyl 18-crown-6 (DCH18-C-6) in 1,2-dichloroethane, and determined by flame emission spectrometry. Here, the factors affecting SX of Sr from synthetic solutions of strontium (containing 40 mg/L Sr) in sulfuric acid medium were identified. 0.01 mol/L DCH18C6 in 1,2-dichloroethane, 0.01 mol/L picric acid in aqueous phase, aqueous to organic (A/O) ratio of 1, pH 4 and extraction time of 5 min are the optimum values for affective factors. The precipitation with sodium hydroxide was conducted to remove the leaching impurities such as Fe, Mg, Al. Under optimal conditions, strontium extraction from leaching filtrate of metacomatic ores of central Iran (pH=2.7), in the presence of 0.01 mol/L picric acid, using 0.01M DCH18-C-6 in 1,2-dichloroethane was performed with a yield of 92.3%. The Sr stripping was obtained with 6 mol/L of hydrochloric acid, with A/O volume ratio of 1:1, with a yield of ~60%.

The friction factor of pipes in water distribution networks is different from the laboratory values due to the connections, installation method and created bights. Passing of time, erosion and sedimentation in pipes are also factors affecting roughness. Therefore, the roughness of pipes should be calibrated during network modeling. In this research, a new optimization method, called sensitivity analysis method was introduced for roughness calibration. In this method, first the pipes are grouped based on the material and diameter of pipes. Then, using sensitivity analysis it is determined what the effect of changing the roughness of different groups on node pressures is. In the following, roughness calibration is performed according to the importance of the groups respectively. This method was investigated on a real network with assumed changes. In order to compare the efficiency of the present method, the results obtained were compared with the results obtained from the calibration tool of WaterGEMS software. Fitness that is obtained by present study method and output of WaterGEMS in studied network are 0.02 and 8.11 centimeters, respectively. Obtained results show the high ability of this method in pipes network roughness calibration.

Submerged outfalls by discharging buoyant jets in the depth of seawater are widely used for the disposal of various types of effluents into the marine environment. A 60° inclined jet to the horizontal is accepted as the optimal angle of inclination for dense flow, but this angle is comparatively problematic for shallow waters; hence smaller inclination is preferred. The present paper investigates the geometrical characteristics of free (far from boundaries) and boundary-affected 30° inclined dense jets in unstratified stagnant ambient using laser-induced fluorescence technique. The major geometrical characteristics, including the centerline trajectory, centerline peak, terminal rise height, and horizontal location of return point, were analyzed by normalized data and plots. The free jets generally follow trends in previous experimental studies. It was observed that a dramatic reduction in the bed proximity parameter results in an asymmetry in the centerline trajectory and a decrease in the horizontal distance of the return point.

One of the hazardous compounds for humans and the environment is polycyclic aromatic hydrocarbons, which are the naphthalene of the precursor of two-ring aromatic hydrocarbons. These compounds are carcinogenic and toxic, they cause anemia and damage to the retina and are also toxic to plants and aquatic animals, these compounds have been identified as priority pollutants by the World Health Organization, yet these compounds are difficult to remove by biological methods. This study was performed in batch in vitro where the effect of parameters such as retention time 15, 30, 45, 60, 90 and 120 minutes, concentration of multi-walled carbon nanotubes and activated carbon from coconut skin 0.1, 0.25, 0.5, 0.75, 1 and 2 g/L), solution concentration 1, 5, 10, 15, 20, 50 and 100 mg/L and pH 3, 4, 5, 6, 7 and 8 the concentration of 10 mg/L naphthalene solution in naphthalene removal was investigated. Experimental data of adsorption equilibrium with different Langmuir and Freundlich adsorption isotherm models are evaluated and analyzed with adsorption kinetics by comparing R2 coefficient of analysis and analyzed by excel software. Maximum naphthalene adsorption on both carbon nanotubes and activated carbon nanotube adsorbent at initial concentration of 10 mg/L naphthalene and adsorbent dose equal to 0.75 g/L at pH=7 is an appropriate time to achieve maximum naphthalene adsorption;the balance mode is 90 minutes. The adsorption mechanism is consistent in both adsorbents of Langmuir adsorption isotherm and their coefficient of determination in carbon nanotubes is (R²=0.9589) and in coconut shell activated carbon (R²=0.9319). and both adsorbents are from adsorption synthetics second-degree followers. Multiwalled carbon nanotubes and activated carbon from coconut skin due to their small size, high cross-sectional area as a result of high reactivity, as an adsorbent for removal of naphthalene from water. And the nanotube has a higher absorption than activated carbon from the coconut skin, so it is considered as a better adsorbent because of its affordability and availability.

4-Nonylphenol (4-NP) as one of the most abundant and toxic alkylphenols is the most effective of endocrine disruptive compounds. It is produced in high quantities and then enters the aquatic environment via discharge of sewage treatment effluents. Therefore, its removal from surface water and municipal wastewater effluents is more commonly considered. This study has been done with the aim of the investigation of the grapheneoxide chitosan aerogel beads’ performance for removal of 4-NP from aquatic solutions. In this regard, the characteristics of the synthesized nano-adsorbent have been investigated by SEM, TEM, FTIR, BET and pHpzc techniques. Then, batch adsorption experiments have been done to determine the adsorption behavior. In this method, the effect of some parameters such as adsorbent dosage, 4-NP concentration, pH, contact time, and temperature was evaluated with the aim of determining optimum conditions. The results show that the adsorption efficiency could reach 100% in 10 min at neutral pH with 1.5 mg/L of 4-NP concentration and 0.8 g/L of the adsorbent. The achieved results were compared with different kinetic and isotherm models, which found that the 4-NP adsorption by the synthesized nano-adsorbent are explained by the Pseudo-Second-Order kinetic (R2=0.9992) and Dubinin-Radushkevich isotherm (R2=0.9988) models with the adsorbents’ maximum capacity of 70.97 mg/g. Thermodynamic investigations indicated that the adsorption process was spontaneous and feasible (-ΔG), endothermic (+ΔH), and reversible (+ΔS).