جستجوی مقالات مرتبط با کلیدواژه « حذف » در نشریات گروه « فنی و مهندسی »

In recent times, the growth of various industries has led to an increase in the generation of colored wastes and effluents. Dyes, in particular, are significant water pollutants that contribute to the production of colored effluents. Physical, chemical, and biological methods have been employed to treat and purify colored wastewater. With the progress of polymer science, the fabrication of diverse types of membranes for dye removal has increased based on the properties of different dyes. By manufacturing membranes in varying sizes, dyes can be eliminated from wastewater. In addition, the use of clay and metal-organic frameworks has facilitated the development of membranes for efficient dye purification and removal. This article discusses the production and application of different types of polymer membranes for the removal of dyes while introducing dyes</em>

The presence of heavy metal ions in polluted wastewater represents a serious threat to human health, making proper disposal extremely important. The utilization of nanofiltration (NF) membranes has emerged as one of the most effective methods of heavy metal ion removal from wastewater due to their efficient operation, adaptable design, and affordability. NF membranes created from advanced materials are becoming increasingly popular due to their ability to depollute wastewater in a variety of circumstances. Tailoring the NF membrane’s properties to efficiently remove heavy metal ions from wastewater, interfacial polymerization, and grafting techniques, along with the addition of nano-fillers, have proven to be the most effective modification methods. This paper presents a review of the modification processes and NF membrane performances for the removal of heavy metals from wastewater, as well as the application of these membranes for heavy metal ion wastewater treatment. Very high treatment efficiencies, such as 99.90%, have been achieved using membranes composed of polyvinyl amine (PVAM) and glutaraldehyde (GA) for Cr3+ removal from wastewater. However, nanofiltration membranes have certain drawbacks, such as fouling of the NF However, nanofiltration membranes have certain drawbacks, such as fouling of the NF membrane. Repeated cleaning of the membrane influences its lifetime. membrane. Repeated cleaning of the membrane influences its lifetime.

One of the most widely used polymers in the treatment and absorption of pollutants is polyethylene terephthalate, which optimizes their consumption and protects the environment by purifying water sources. The problem with this polymer is the lack of a functional group on the surface to bind the nanoparticles. Therefore, in this study, we first functionalized the polymer with the carboxylic group by chemical synthesis, then we synthesized silver nanoparticles on them by ultrasonic method. Optimal nanoparticle synthesis conditions were obtained (pH=9 and concentration 0.2 M). Under these conditions, the average particle size was 64 nm. In the second part, modified polymer was used to remove Methyl orange dye. Optimal parameters for removal were investigated (pH=9, temperature of 35 °C and ratio of dye concentration to adsorbent of 5 μM/0.1 g). The highest percentage of paint removal under optimal conditions was 92% after 120 minutes. The antibacterial effect of PET-AgNPs polymer was observed on two types of bacteria, Staphylococcus aureus and Escherichia coli, gram-positive and gram-negative. In the second part, the gold electrode was modified with a combination of PET-AgNPs polymer and carbon nanotubes and was used to detect methyl orange dye. The linear range was 5×10-6 to 2×10-8 M and the detection limit was 7.6×10-9 M. Parameters affecting removal and isotherm and removal kinetics were investigated. The functionalized and modified polymer is well able to measure and remove the contaminant dye and, in addition, it has an antibacterial effect.

Thermal decomposition of copper (II) acetate monohydrate and polyvinyl alcohol results in CuO/Cu2O nanocomposite synthesis. It was characterized by FT-IR, XRD, and TEM techniques. The peaks appeared in the FT-IR spectrum and the XRD pattern, confirming the CuO/Cu2O nanocomposite preparation. The TEM image shows that the particles are agglomerated. The CuO/Cu2O nanocomposite was used as a new adsorbent to remove methyl orange dye from the aqueous solution. The results of the dye removal study show that initial dye concentration has no effect on the removal percentage, and the dye removal percentage was constant at about 97%. However, dye removal increased with an increase in pH from 2 to 8, with the highest yield occurring at pH equal to 8. After increasing the pH and reaching 12, the removal percentage has been reduced. The dye removal efficiency increases to 99.5% by increasing the amount of adsorbent from 5 to 20 mg and by increasing the contact time from 5 to 30 minutes.

The problem of toxic-metal-contaminated water has become a great environmental concern and presents significant hazards to the public health and economy. In this study, drinking water treatment sludge was activated and used as an efficient, cheap and cost effective sorbent in the removal of Pb (II) ion from water samples. The prepared material was characterized by Fourier transfer infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), scanning electronic microscopy (SEM), surface analysis (BET method) and X-ray fluorescence (XRF) analysis. The effects of various parameters such as the solution pH, adsorption time, adsorbent dosage, and initial metal ion concentration upon adsorption were investigated. Equilibrium isotherm studies were carried out with different initial concentrations of Pb (II), and three models (Langmuir, Freundlich and Temkin isotherms) were utilized to analyze the equilibrium adsorption data. The best adsorption performance was obtained at the following conditions: pH of sample, 7.5; contact time, 15 min; adsorbent dosage, 0.3 g; intitial concentration of Pb (II), 20 mg/L; agitation speed, 200 rpm. The results revealed that the adsorption process obeyed the Langmuir model, with the maximum monolayer capacity (qmax) and the Langmuir constant (KL) calculated as 54.9 mg/g and 0.973 mg/L, respectively. Kinetic studies indicated that the adsorption process followed a pseudo-second-order model based on the obtained R2 values. Comparison study with the other natural adsorbents revealed that the activated sludge has the highest adsorption capacity and provides the lowest adsorption time. Desorption study exhibited that the Pb (II) ions can be desorbed from the adsorbent by 0.25 mol/L HCl solution with a recovery percentage of 98%. The results exhibited that activated sludge is an efficient and cost-effective material for the adsorption of Pb (II).

Excess fluoride is one of the water pollutants in the world, which is removed from the water by chemical methods to produce sludge, and other methods such as R.O. also have problems in electricity consumption and wastewater disposal. Metal-organic complexes are one of the newest adsorbents used in the separation of anions. In this study, MOF 1 was used to remove fluoride from aqueous solution. Existing factors such as pH, contact time, adsorbent amount and temperature were examined. Based on the results, the MOF synthesized in acidic media absorbs more fluoride ions. Contact time of up to 20 minutes has a significant effect on the removal of fluoride ions and then its effect is greatly reduced. The amount of adsorbent used is up to saturation and the water environment has no significant effect on the absorption of fluoride ions. Also, the results of kinetic studies confirm the pseudo-second-order kinetic model for fluoride adsorption reactions in the presence of MOF1. Also in this research, zinc metal is used as a zebrafish as a central metal with the aim of reducing the environmental MOF.

Because of its significant toxicological effects on the environment and human health, arsenic (As) is a major global issue. In this study, a zirconium-based metal-organic framework, {[Zn3L3 (BPE) 1.5]•4.5 DMF}n , was synthesized using both solothermal and mechanochemical methods and successfully applied in the arsenic removal reaction. Adsorption efficiency was high in the presence of this MOF and equilibrium was achieved within 20 minutes for As (III) and As (V) at a concentration of 1 mg / l of contaminants. The maximum adsorption efficiencies of As (III) and As (V) at pH 7 were 62 and 81%, respectively. The adsorbent showed high stability in the pH range of 2-12 and the adsorbent can be recovered for at least nine consecutive periods without significant reduction in its efficiency. The adsorption process can be described by a pseudo-second-order kinetic model and the adsorption mechanism was of the electrostatic interaction type.

Nowadays, provision of sanitary water is one of the main concerns of the world society, and heavy metals are one of the most important pollutants in water resources. Heavy metals, including copper, can enter the food chain and the body of living organisms and can affect humans through toxic and carcinogenic effects. Therefore, in this study, nanoporous SBA-15 functionalized with di and tetra carboxylic acid was synthesized and used for remove copper ions from aqueous solutions. The adsorbents were characterized by scanning electron microscopy, N2 adsorption-desorption measurements and infrared spectroscopy for investigation of porosity and functional groups of mesoporous silica. Flame atomic absorption spectroscopy was used for determination of ions. Effective parameters on removal process including amount of adsorbent, contact time, pH of solution and presence of other metal ions in the medium, were evaluated and optimized. The best removal efficiency with di and tetra carboxylic acid functionalized SBA-15 was obtained at pH>5 with 10 mg of adsorbent in the stirring time of 15 minutes. The recovery of copper from adsorbents was done with 20 ml solution of nitric acid (3 mol/L). Langmuir and Freundlich adsorption isotherms were evaluated for both adsorbents. According to the Langmuier model, the maximum adsorption capacity of 232.56 and 93.46 mg of copper per gram of adsorbent and correlation coefficients (R2) of 0.857 and 0.9688 for di and tetra carboxylic acid functionalized SBA-15 were obtained, respectively. But, the correlation coefficients (R2) obtained from the fitting of the data using the Friendlich isotherm were 0.991 and 0.972 for di and tetra carboxylic acid functionalized SBA-15 silicas, respectively, which indicates that this model is suitable to explaining the behavior of copper adsorption on both adsorbents. Finally, the removal of copper from real wastewater samples was performed. The results indicate that nanoporous SBA-15 silicas functionalized with di and tetra carboxylic acid are desirable adsorbents for copper ions removal.

High soluability of nitrate ions in water cause the dysfunction of many existing treatment methods in the removal of this very dangerous ion from aqueous media. On the other hand, due to the need for in situ treatment methods, in particular for groundwater, the replacement of old inefficient methods with new compounds is required. In this study, for the first time, the efficiency of activated dendrimer- graphene oxide for nitrate removal from an aquatic solution was investigated. Experiments were performed in a batch reactor and the main factors of pH, reaction time, and concentration of PAMAM-GO were investigated. The highest removal efficiency was obtained as 90% at 0.025mg/L activated dendrimer- graphene oxide, pH of 7.5 and 15 min reaction time. The results showed that nitrate removal by activated dendrimer-graphene oxide is correlated with nanocomposite concentration, contact time, pH and initial concentration of nitrate. It seems that ion exchange between nitrate and chloride is the main mechanism of nitrate removal by activated dendrimer-graphene oxide according to functionalization of activated dendrimer-graphene oxide using hydrochloric acid. This method can be used as a suitable method for in situ removal of nitrate from water and wastewater due to the desirable ability of the nanocomposite and its optimal compatibility with the environment.

Heavy metals are environmental pollutants that nowadays a lot of efforts are made to remove them. In this research, the sawdust modified with diethylenetriamine as an effective adsorbent for Fe (III) removal from water samples was conducted. First, the sawdust was modified by diethylenetriamine. SEM analysis showed that the particle surface is changed by modification. Then the effective factors in Fe (III) removal such as pH, adsorbent dose, shaker speed and contact time were studied and optimized. The optimum conditions were employed for various Fe (III) concentrations (20–300 mg L-1) and in all cases, the removal rate was significant. The adsorbent has high capacity for Fe (III) removal in a way that it removed more than 95.0±0.3 % of Fe (III) (50 mg/L) by 1.5 g/L of adsorbent in 15 minutes. The Langmuir and Freundlich isotherms were applied to the adsorption process and their constants were evaluated. The adsorption equilibrium data fitted well to Langmuir isotherm. The maximum Langmuir adsorption capacity of Fe (III) ions was 200.0 mg/g. According to kinetics experiments of Fe (III), the adsorption process had more conformity to pseudo-second-order kinetic model. This method was successfully applied for Fe (III) removal from potable water, well water, river water and industrial wastewater samples.

Arsenic is one of the most hazardous pollutants of water resources which threaten human health as well as animals. Therefore arsenic removal from water resources is the priority of health programs. There are several ways to remove arsenic. In this study, reverse osmosis and zero-valent iron nanoparticles methods have been used in a laboratory scale. To perform the test, the variables of temperature, arsenic concentration, pH, iron nanoparticle concentration and mixing time were considered. The results indicated that in both methods of reverse osmosis and iron nanoparticle, through increasing arsenic concentration, arsenic removal efficiency has been also increased. At concentration of 1.5 mg per litre in reverse osmosis method, the maximum efficiency was achieved by 98% and 95.2% removal of arsenic respectively. The effect of temperature and pH were similar in reverse osmosis; by increasing these two variables, arsenic removal percentage also increased. The highest removal rates of 95.98% and 95.56% were observed at pH 9 and Temperature 30oC respectively. The results indicated that in iron nanoparticles method the arsenic removal efficiency increases by increasing mixing time and temperature, while it decreases with increasing pH.

Aniline is an almost undegradable compound found in many industrial effluents. It was the objective of this lab-scale applied-experimental study to determine the efficiency of the dissolved air flotation process in the removal of aniline from aquatic environments. Initially, the optimal conditions of pH and dosage of poly-aluminum chloride were determined using the jar test. The parameters involved in the dissolved air flotation process including coagulant concentration (10, 20, 30, 40, and 60 mg.l‒1), coagulation time (5, 10 , 15, and 20 min), flotation time (5, 10, 15, and 20 s), saturation pressure (3.5 / 3, 4, and 5.4 atmospheres), and turbidity (10, 20, 30, 40, and 60 NTU) on the reduction of COD and aniline were then calculated. Results showed that the dissolved air flotation process was capable of reducing COD and aniline by 86.6% and 95%, respectively (at pH = 6, an initial aniline concentration of 200 mg/ L, a coagulation time of 10 min, a flotation time of 20 s, a saturation pressure of 4 atmospheres, and a concentration of 20 mg/L PAC). It was also shown that removal efficiency declines with increasing turbidity. It may, therefore, be claimed that the dissolved air flotation process is an effective method of removing aniline from aquatic environments.

1,1-Dimethylhydrazine (UDMH) is used as a liquid fuel for missile and is a toxic matter. In this work to decontaminate UDMH from aqueous solution, hybridized photocatalytic and hydrogen peroxide oxidation processes have been used. The process was performed in a suspension reactor equipped with a UV-C lamp (150 W). Fe3O4@SiO2@TiO2 (FST) catalyst was used as a magnetic recyclable photocatalyst. To synthesize the catalyst, precipitation and sol gel methods have been applied and its characterization was performed using X-ray diffraction XRD, Fourier transform infrared FTIR, transmission electron microscopy TEM, and vibrating sample magnetometer VSM instruments. Effective parameters such as hydrogen peroxide concentration, amount of catalyst, and pH were optimized using response surface method. To analyze the amount of mineralization, the TOC analysis was used. The results showed that at the optimum conditions of [FST] = 85 ppm, [H2O2] = 800 ppm, and pH=7 the process could be mineralize 50 ppm of UDMH solution, about 79% after 120 min.

In this study, TiO2-graphene oxide composites with different weight ratio of Titanium (ІV) butoxide /Graphene Oxide were synthesized by sol-gel method. The products were characterized by X‐ray diffraction method and UV-Vis spectrophotometer. The TiO2-graphene oxide composites possessed a large adsorption capacity for methylene blue and extended light absorption range in comparison to the pure TiO2. Evaluation of non-linear adsorption isotherm models including Langmuir and Freundlich suggests that adsorption data can be well described by Freundlich isotherm models. Adsorption of methylene blue on the surface of composite is chemisorption.

One of the major water pollution factors in receiving water bodies is the presence of excessive nutrients (nitrogen & phosphorous compounds) due to wastewater discharge to the environment. If phosphorus level exceeds its discharge standard (6 mg/L), it will cause eutirification which resulted in secondary water pollution due to algal blooming crisis. Development of different methods to remove phosphorus from the year 1950 was performed in response to the need of reducing the discharged phosphorus amount to surface waters. Phosphorus is removed using different chemical and biological methods that have disadvantages such as greater capital and operational costs, operational problems, high sludge production and safety operational & maintenance requirement. So phyto-remediation method can be used to overcome these disadvantages. This useful technology is actually a genneric term for several ways in which plants can be used to clean up contaminated soils and water. Considering this fact phyto-remediation is a bioremediation process in which a particular type of plant used to remove, transfer, stabilize, degrade and volatilize of contaminants (such as pathogens, heavy metals, pesticides, solvents, crude oil, arsenic, cyanide and radioactive elements) by accumulation, stabilization, extraction, rhizofiltration, rhizodegradation or volatilization mechanisms. Phytoextraction is the name given to the process where plant roots uptake polltants from the soil and translocate them to their above soil tissues. Rhizofiltration is similar in concept to Phytoextraction but is concerned with the remediation of contaminated groundwater rather than the remediation of polluted soils. The contaminants are either adsorbed onto the root surface or are absorbed by the plant roots. Phytostabilisation is the use of certain plants to immobilise soil and water contaminants. Contaminant are absorbed and accumulated by roots, adsorbed onto the roots, or precipitated in the rhizosphere.Selection of appropriate plant and microbial species, biological accumulation and transmission of pollutants, contaminant concentration and its disposal are the most important factors in phyto-remediation process. Environmental factors including ambient temperature, solar radiation, the presence of nutrients, water and oxygen and the type of material removal will also affect the process. In this study reed, bamboo and umbrella plant were evaluated in removal phosphorus from water in different concentration of 2,10, 25, 50 and 100 ppm in vitro condition (ambient temperature of 23-25 ◦C, DO of 4.5 – 6.5 and pH of 6.5- 8.5). According to the results, the maximum phosphorous removal was observed in reed plant pilot at concentration of 25 ppm. The percent removal efficiencies were found to be 17.3, 35.81, 87.94, 78.77, 48.63, 52.4, 92.01 for reed, 15.66, 21.07, 68.08, 57.89, 34.41, 48.33 and 73.69 for bamboo and 15.89, 21.5, 37.23, 32.41, 22.33, 30.48 and 54.47 for umbrella plant at mentioned concentrations, respectively. Overall phosphorous removal for reed plant, bamboo and umbrella plant were 59, 45.5 and 30.65, respectiv.

The Electrocoagulation/Electroflotation process is one of the successful methods in dyes wastewater treatment. This process by direct current electrical and metal electrodes can be removal of contaminants. The aim of this study was optimization of affecting parameters in (EC/EFP) by titanium and aluminum electrodes for decolorization of Acid Black 1 (AB1) from aqueous. In this study was used of four titanium and aluminum electrodes. By applying an electric current in 10-30 V range with control of ampere, initial pH in 5- 9 range and initial concentration of dye in 50-500 mg/L range study was done. The results indicate when pH=5, voltage and initial concentration were 30 V and 50 mg/L respectively the high efficiency of decolorization by EC/EFP done. Therefor this process has a good ability in dye removal. Efficiency of process decreased by changing the parameters.

In the present work, adsorptive removal of Cd)II(from aqueous solution was studied by using nanoclay (Cloisite Na+). This study was implemented under laboratory conditions in single batch system by adsorption under various environmental conditions such as pH, contact time, adsorbent dose and adsorbate concentration. The kinetics of Cadmium adsorption was determined based on Ho et al & Lagergern. Then Langmuir and Freundlich coefficient were determined based on optimum conditions. The Result of this study was showed with increasing of pH from 2 to 8; the adsorption efficiency will be increased. With increasing contact time adsorption efficiency increased. It was also fundwith increasing amount of nanoclay adsorbent, efficiency increased. The results revealed that the results of this research for nanoclay adsorbent is closed to fit Ho et al and Lagergren kinetic and Freundlich isotherm Based on data obtained in this study it can be concluded that adsorption by nanoclay is an efficient and reliable method for cadmium removal from liquid solutions.

1. Access to safe drinking water is an important factor for human life. Presence of both chemical and microbial contaminants in water can lead to different types of disease. In areas which groundwater is contaminated to fluoride via dissolution from geological formations and earth crust, drinking water can be considered as a major source of exposure to fluoride. Dental fluorosis and skeletal fluorosis are health outcomes of exposure to high concentration of fluoride via drinking water. World Health Organization (WHO) guidelines [1] suggested that in areas with warm climate, the optimal fluoride concentration in drinking water should remain below 1 mg/L (1 ppm or part per million), while in cooler climates it could go up to 1.2 mg/L. The differentiation derives from this fact that we perspire more in hot weather and consequently drink more water. The guideline value (permissible upper limit) for fluoride in drinking water was set at 1.5 mg/L, considered a threshold where the benefit of resistance to tooth decay did not yet shade into a significant risk of dental fluorosis. It has long been known that excessive fluoride intake carries serious toxic effects. But scientists are now debating whether fluoride confers any benefit at all or no. There are different options for overcoming to fluoride problem in drinking water including replacement of contaminated water resources with safer one or removal of excessive fluoride from water through application of different treatment methods. Those methods are generally based on chemical absorption, chemical precipitation, ion exchange and physical removal [reverse osmosis (RO) and electrodialysis process (ED)] [2]. Present study aimed to investigate the efficiency of a modified activated alumina for removal of fluoride from aqueous solution. 2. Methodology2.1. Batch experiments:Modified Activated Alumina (MAA) by iron compounds was used in current study which was a commercial product of Alcan Company, Canada [3]. During batch absorption experiments, effects of solution pH (5-9), initial fluoride concentration (1-10 mg/L), adsorbent dose (1-50g/L), contact time (15-180min) and shaking rate (100-400rpm) on fluoride removal was investigated in the laboratory temperature (20±1ºC). 2.2. Fluoride measurement:SPADNS method was used for the measurement of fluoride based on standard methods for the examination of water and wastewater. The SPADNS colorimetric method is based on the reaction between fluoride and a zirconium-dye lake. Fluoride reacts with the dye lake, dissociating a portion of it into colorless complex anion (ZrF62-) and the dye. As the amount of fluoride increases, the color produced becomes progressively lighter. Spectrophotometer (Model: Jenway 6105 UV/Vis) was used at 570 nm for measurements [4]. 3. 3.1. Effect of absorbent dose, contact time, pH and shaking rate on fluoride removalAbsorbent dose of 1, 5, 10, 25 and 50 g/L removed respectively 70, 91, 95, 97 and 98 of fluoride with initial concentration of 10 mg/L during 120 minutes. Optimum dose of absorbent was determined 5 g/L in 120 minutes. Fluoride level was decreased from 10 mg/L to 0.8 mg/L by 5g/L MAA (as optimum dose). This concentration is in the range of national guideline for fluoride in drinking water. Results of the study indicated that fluoride removal efficiency increased by increasing the contact time. Removal efficiency in 15, 30, 60, 120, and 180 minutes were 70, 80, 88, 92 and 93 percent using optimum dose, respectively. The best removal efficiency was observed at neutral pH in which removal efficiency was 90-92%. The best removal performance was observed in both shaking rate of 300 and 400 rpm (93%). 3.2. Absorption isotherm:Langmuir and Freundlich isotherms were investigated for absorption model. Fig. 1 and Table 1 show achieved results of batch experiments for absorption models. As can be seen in the figure, the equilibrium isotherm for fluoride uptake corresponds closely to the Langmuir model.Table 1. Absorption isotherm parameters for removal of fluoride by MAAModel qm (mg/g) B (L/mg) Kf N R2Langmuir 8.23 0.147 - - 0.85Freundlich - - 5.16 5.22 0.434. According to observed removal efficiencies during the study, MAA used in the study can be considered as an efficient absorbent for the removal of fluoride from drinking water. However, conducting more research using real water samples and column experiments is highly recommended before filed application of the method.