جستجوی مقالات مرتبط با کلیدواژه « arsenic » در نشریات گروه « مهندسی آب »

Increasing urbanization and industrialization of cities has led to an increase in pollutants and the production of many toxic elements. One of these pollutants is arsenic, which is known as one of the most toxic and dangerous elements in drinking water. The aim of this study is to investigate the method of minimizing the amount of this toxic substance by coagulation and flocculation in drinking water. In order to determine the optimal conditions for arsenic removal by coagulation and flocculation methods, in the first stage, the optimal pH is determined by Jar test as 6. Then by selecting alum as coagulant, lime as coagulant and the optimal pH, the optimal amount of chemical material is obtained as 7.5 mg/lit. Determining the optimal places in the current situation can be the novelty of this paper. At the end, the residual concentration of arsenic is determined by atomic hydride absorption spectroscopy. According to the concentration of arsenic in the incoming water sample which is equal to 91 micrograms per liter, the Jar test is performed in two stages with alum coagulants. Based on the optimal pH obtained in different concentrations of coagulants and also a constant concentration of coagulants, the arsenic removal efficiency in the best case in alum coagulants reached 88.46%, which is equal to 10 micrograms per liter, which according to the WHO, is an acceptable result. The result of this study indicates that the coagulation and flocculation method with alum coagulant and a constant amount of lime as a coagulant has a high efficiency in arsenic removal.

Supplying safe drinking water is one of the necessary actions of today's human societies because of the lack of water resources and successive droughts. Arsenic is a toxic element that can cause serious problems such as cancer if its amount was higher than the allowed limit, and it is used for the long term. In this study, the removal of arsenic by monolithic nylon 6 and hybrid nylon 6/zirconia nanomembrane was investigated. The monolithic nylon 6 and hybrid nylon 6/zirconia NMs were synthesized using a novel electrospinning method. The microstructure and presence of zirconia nanoparticles were evaluated by means of scanning electron microscope, X-ray energy dissipation spectrometer and Fourier transform infrared spectrometer. The mechanical properties of NMs were investigated. The value of zeta potential (ξ) was measured as an important factor in arsenic absorption. The filtration process was performed with a constant pressure of 0.82 bar and with an initial concentration of arsenic equal to 0.05 mg/L. Characterization of monolithic nylon 6 and hybrid nylon 6/zirconia nanomembrane (NMs) showed that the average fiber diameter was 163 ± 15 nm and 180 ± 38 nm, respectively. Also, the presence of zirconia nanoparticles within the hybrid NMs was confirmed by infrared spectroscopy analysis. The zeta potential of zirconia NPs was measured as a key factor to create the driving force for arsenic adsorption. The value of zeta potential was calculated as -14 mV at the neutral pH. The results of the stress-strain test showed that the tensile strength of monolithic nylon 6 and hybrid nylon 6/zirconia NMs is equal to 6.9 and 3.1 MPa, respectively. The filtration performance of both membranes was evaluated and it was found that the efficiency coefficient of monolithic nylon 6 and hybrid nylon 6/zirconia NMs is 25.01% and 31.61%., respectively. The fitting of blockage models on the experimental data showed that the intermediate blockage model was the dominant model. According to the 31.61% performance of arsenic removal, and also due to the findings of this research it is confirmed that the incorporation of zirconia NPs into the nylon 6 NFs can enhance the filtration ability to remove arsenic from the water sources.

Increasing urbanization and industrialization of cities have led to an increase in pollutants and the production of many toxic elements. One of these pollutants is arsenic, which is known as one of the most toxic and dangerous elements in drinking water. The aim of this study was to investigate the method of minimizing the amount of this toxic substance by coagulation and flocculation in drinking water. In order to determine the optimal conditions for arsenic removal by coagulation and flocculation methods, in the first stage, the optimal pH was determined by Jar experiment, then by selecting ferric chloride as a coagulant and lime as coagulant and also the optimal pH. The optimal amount of chemical is obtained, at the end, the residual concentration of arsenic is determined by atomic hydride absorption spectroscopy. According to the concentration of arsenic in the incoming water sample which is equal to 91 micrograms per liter The jar test was performed in two stages with chloroform coagulants, which according to the optimal pH obtained in different concentrations of coagulants and also a constant concentration of coagulants, the arsenic removal efficiency in the best case in chlorofricter coagulants. It reached 98.3%, which is equal to 1.5 micrograms per liter, which according to the standard of the WHO (2011), 10 micrograms per liter had an acceptable result. The result of this study indicates that the coagulation and flocculation method with chloride-chloride coagulant and a constant amount of lime as a coagulant has high efficiency in arsenic removal.

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.

Arsenic in water is one of the highly toxic elements which has harmful influences on the human health and ecosystems. To address this problem, single-walled carbon nanotubes modified with poly (allylamine hydrochloride) (PAH/Ox-SWCNT) composite were synthesized and applied as an adsorbent for arsenic removal from aqueous solution in this study. The properties of PAH/Ox-SWCNT nanocomposite were characterized using scanning electron microscopy, Thermogravimetric, Fourier-transform infrared spectroscopy, and X-ray powder diffraction analysis. Batch experiments were executed to determine the ability of PAH/Ox-SWCNT to adsorb As from solution under various operational conditions. The experimental data were fitted by pseudo-first-order kinetic and pseudo-second-order kinetic models by nonlinear regression analysis using Mathematica software. Langmuir and Freundlich models were employed to describe the adsorption equilibrium isotherms. The removal percentage of As increased with initial solution pH from 3 to 7 while it decreased with the initial concentration of As. Moreover, the enhancement of contact time caused better adsorption efficiencies. The percentage removal of As using 10 mg of synthesized nanocomposite was more than 90% at pH=7 and contact time of 30 min. The adsorption experimental data had better agreement with pseudo-second-order kinetic and the Freundlich isotherm models. The maximum adsorption capacity of PAH/Ox-SWCNT was 275.07 mg/g at 298 K. The As removal percentage after eight adsorption-desorption cycles was higher than 65%. All results implied that the synthesized PAH/Ox-SWCNT could potentially be a promising adsorbent in arsenic water remediation.

Heavy metals are among the environmental pollutants that human exposure to some of them through water and food can cause chronic and dangerous poisoning. The problem of poisoning drinking water to arsenic is a pervasive problem and has been seen in almost all countries, whether developed or developing, which endangered the lives of many people. In the present study, the removal of arsenic from water using iron / N-isopropyl acrylamide / chitosan nano-adsorbent was studied and evaluated. In this research, a magnetic nanoparticle was used to absorb arsenic, which is an innovative method. In order to increase the absorption capacity, we use polymer grafting operations on the surface of the nanoparticles, which will greatly increase the specific surface of the adsorbent. In fact, by placing polymers on the adsorbent, the combined desire increases. The results show that synthesized nano-adsorbants have the ability to absorb arsenic at different concentrations. But its concentration varies in different concentrations. Langmuir, Freundlich, Tamkin and Dobbin Radhushev isotherms were fitted with arsenic adsorption at 45 °C, pH = 7.5 at different concentrations. And the results show that a high (R = 0.995) R2 value for Langmuir model confirms that this model is suitable for fitting experimental data. The percentage of arsenic removal in optimal conditions at pH= 7.5, the amount of adsorbent 10 mg, contact time 60 min, temperature 45 °C and concentration of 10 μg/ml was 82.2%.

There are many springs in Iran that are contaminated by arsenic and therefore are not suitable for drinking purposes. Garu spring around Masjed Soleyman city is an indicator of such springs. In order to study the concentration of arsenic, 20 samples from spring and Asmari anticline observation wells were collected. Concentration of major and trace elements in the samples were measured. ICP-OES studies were carried out on 3 samples of the surrounding formation. The results showed that Garu spring has arsenic levels higher than 10ppb. Hydrochemical and statistical analyzes of water samples and sediment as well as significant correlation of arsenic with main cations, (i.e. Nickel and Vanadium) shows that anthropogenic factors do not have an effect on the amount of arsenic. It is found, that the origin of arsenic is geogenic (Gachsaran formation and oil brine influx). The mechanism of arsenic mobility during the wet season is the anaerobic respiration of Fe+3 reducing bacteria. Whereas, in the dry season, the environment is further reduced, as a result activity of the SRB and IRB in the span of springs leads to the reduction of iron by sulfide from sulfate respiration, this causes arsenic deposition. Also, gas chromatography analysis of the oil presented in spring shows that H2S is the result of thermochemical reduction of sulfate in carbonate reservoirs. According to the results of this study, the use of water resources in the region threatens the health of the inhabitants of the region, and arsenic removal methods should be used.

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.

Arsenic is one of the most hazardous elements in drinking water. Water contaminated with arsenic causes a variety of diseases in humans including cancer. The present study was conducted to survey Arsenic concentration in rural water resources in Rivash Twon, Kashmar, Iran. For the purposes of this cross-sectional study, 60 samples were collected from 10 underground drinking water supplies during the period from April to June, 2013. Samplings and sample preservation were performed according to standard methods. Measurements were performed via the VGA method using atomic absorption. Such water quality parameters as pH, TDS, EC, residual chlorine, and temperaturte were also measured to determine any relationships likely to exist between As concentration and the parameters measured. As levels were then compared with national and international standards. It was found that the average values of As concentration at the stations A, B, C, D, E, F, G, H, I, and J were 1.53±1.03, 1.30±1.07, 10.55±3.83, 11.21±5.01, 10.57±3.68, 2.34±0.73, 3.22±0.58, 9.89±3.57, 10.48±5.07, and 2.23±0.53 µg/L-1, respectively. As concentrations at five stations were found to be higher than the values recommended in WHO guidelines; the remaining stations revealed values below the national standard. While the differences between As level and the national standard were statistically significant (p

In this research, oak sawdust, in both modified and unmodified forms, was used as an economical and low-cost material for the removal of arsenic from aqueous solutions. For this purpose, arsenic synthetic samples were prepared using NaAsO2 in distilled water and the effects of pH, adsorbent dosage, contact time, and initial As(V) concentration were investigated on As(V) adsorption using the adsorbents prepared. The results showed that modified sawdust achieved the highest efficiency (>91%) over a contact time of 60 min and at pH 7 when the adsorbent dosage was 4gr/L and the initial As(V) concentration was 150 µg/L. The data from both adsorbents fitted well to the Langmuir isotherm. Under optimum conditions (an initial As(V) concentration of 150 µg/L and optimal absorption pH, contact time, and adsorbent dosage), maximum As(V) removal efficiencies were 93.85% and 91.034% with the modified and unmodified sawdust adsorbents, respectively. Given the availability and low cost of the adsorbent used and the high removal efficiency obtained at lower adsorbent dosages and contact times, the modified oak sawdust may be recommended as an effective adsorbent for the removal of arsenic (v) from aqueous solutions, especially since it requires no need for pH modification.

In order to identify and control of heavy metal pollutions such as arsenic، the areas with high anomaly، distribution and trend of the changing of pollution in the study area should be determined. Due to the importance of Sahand dam in providing of water for drinking، industrial and agricultural and the reports of the unfavorable effects of drinking water containing high levels of arsenic on people''s health، the study of water quality is essential in this area. In the present study، to assess the temporal variation of arsenic anomalies hydrochemical data of quality monitoring provided by East Azerbaijan Regional Water Authority during 2002-2012 was used. Also، hydrochemical data related to 50 collected samples during September 2012، by the geology department of Tabriz University was used to determine the origin of high concentration of arsenic، the region of high potential of groundwater pollutions and depict the map of the spatial distribution of arsenic anomalies in the region. Among statistical methods، cokriging method was selected for interpolation of arsenic concentration in the study area. The process of geostatistical modeling، drawing the variogram، and selecting optimal model done using geostatistical software (GS+) and depicting the arsenic distribution map was prepared with Arc GIS software.

Arsenic which is present in the underground and surface water is one of the most toxic elements threating human health and animals. Arsenic has been removed in different type of ways. In this study Arsenic removal from drinking water and its decreasing rates were investigated by NZVI (nanoparticle zerovalent iron) to standard limit (I.e. 0.01 mg/lit). The tests were conducted on reactor containing 100 ml water containing 1mg/L. Arsenic by virtue of Batch method. The mixture was executed in mixing was done an Oultrasnic device in order to have better mixture and complete distribution of nanoparticles in water. Then the arsenic was removed from the water by VATMAN paper of 0.45 Hm. The remained arsenic in the water was measured by ICP device. In this article the influence of the parameters including mixture time, PH, NZVI and arcenic doses were examined. Having perfomed many tests the results showed that 1 mg arsenic can be removed 100 percent by 0.05 g NZVI in 8 min. It is possible to remove by 98 percent arsenic in 5-10 PH range. Iron nanopaticle way is an effective and rapid way to remove arsenic from water and various conditions have not considerable effect on it.