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

Considering the origin of heavy metals, mines and their extraction and their sewage can play an important role in polluting the environment by these elements. In this study, water pollution in the Shour River, some wells and aqueducts were investigated and changes in cadmium element in surface and groundwater of the region were investigated. Then, statistical comparison and preparation of preliminary maps and distribution maps of cadmium contamination were compared in Shour River water, several aqueducts and wells in the watershed of the river were in two seasons of high water and low water. Statistical comparison of river, well and aqueduct water samples was performed in wet and dry seasons using t-test method. The results showed that due to the high amount of cadmium in surface and underground waters of Sarcheshmeh watershed, therefore, not all of these waters are suitable for drinking and considering that cadmium is a toxic, hazardous and carcinogenic metal in the environment, it can pose irreparable risks to human health and even livestock .

Pollution of environment with heavy metals and its transfer to products is a global problem. The aim was to measure heavy metals in the effluent of Gorgan wastewater treatment plant which with 32 effluent samples of Gorgan wastewater treatment plant were sampled during 6 months in 2016 and concentration of lead, cadmium by polarograph and atomic absorption was assessed. Risk of carcinogenicity and non-carcinogenicity was calculated in three cases: minimum, moderate and maximum. Average concentration of lead in the effluent was 0.003943547 mg/L, which is value for cadmium measured 0.000143571 mg/L.The concentrations of heavy metals in wastewater effluent and dried sludge, except in returned sludge, were below the standards. Due to long-term use of effluents, necessity of treatment of other parameters, and effect of bioaccumulation of metals in sludge, caution should be taken for their agricultural application. Because of importance of this type of contaminants in soil and food products, continuous monitoring by water companies is highly necessary.In mean state, for every one hundred million people, 7.21 people, in max mode, for every ten million people, 1.13 people and in the case of min, for every one hundred million people, 2.82 people are at risk of cancer.

Heavy metals are recognized as one of the most toxic groups. They enter the food chain through the waste disposal into the water and environment. This study was carried out with the aim of investigating cadmium ions removal from aqueous solution using conocarpus nanostructure. For this purpose, conocarpus was grinded to nano-size by the ball mill. The effect of experimental parameters such as pH, time, adsorbent dosage and initial concentration of cadmium were studied in batch system. The PSA, FTIR and SEM tests were used to determine the absorbent characteristics. The imaging of adsorbent indicated that surface of conocarpus had many deep pores, which represents the better adsorption of cadmium. 8.5% of adsorbent particles were in the range of nanoparticles and 91.5% of them were in the range of nanostructure. The results showed that optimum pH for cadmium adsorption is 6 and the maximum removal efficiency and adsorption capacity of cadmium are 80.9% and 0.86 mg/g., respectively. Comparing the adsorption isotherm and kinetics models showed that the Langmuir and Ho models, with R2 values of 0.998 and 0.990 respectively, had a better fitting and description of adsorption data than other models. The study showed that conocarpus nanostructure is an effective adsorbent for cadmium removal from aqueous solution.

Application of sewage sludge as a fertilizer on farmlands is a common practice in most countries. Although the practice may play a positive role in plant performance, the organic amendments introduced may increase the soil heavy metals content. This study was conducted in Arak, Iran, to investigate the effectiveness of DTPA chelate on corn Cd availability in a sewage sludge treated soil. The treatments consisted of sewage sludge (0, 15, and 30 t ha-1) polluted with cadmium applied at 0, 5, 10, and 15 mg kg-1 as well as DTPA applied at 0 and 1.5 mmol kg-1 soil. Corn plants were then grown in the soil in each treatmnent and, on day 60, the physic-chemical characteristics and Cd quantities were measured ion both the corn plants and soil samples. Application of 1.5 m mol of DTPA chelate in soil contaminated with 5 mg Cd led to a significant increase in the soil available Cd content. It was also observed that application of DTPA chelate to soils containing 30 t ha-1 of sewage sludge polluted with 10 mg Cd increased root and shoot Cd concentrations by 17 and 25%, respectively. Results indicated the effectiveness of DTPA chelate in reducing Cd phytoremediation with increasing sewage sludge loading rate. This was evidenced by the lowest phytoremediation effectiveness observed for the treatment with the greatest sewage sludge loading (30 t ha-1) and the lowest cadmium pollution (5 mg Cd).

In this study, the phytoremediation capacity of the hydrophilic tree species populus deltoides and Taxodium distichum and their ability to absorb cadmium (Cd) are investigated as a method for addressing the need for the removal of heavy metals from contaminated water and soil resources as a measure to counteract their environmental effects. For this purpose, a completely randomized design was used with 4 treatments (namely, 0, 50, 100, and 150 mg kg-1 of cadmium) and 3 replications. Results showed that Cd concentrations in the organs of the two species increased with increasing soil Cd content. The highest Cd concentrations in the leaves, stems, and roots (18.6, 35.33, and 89.06 in T. distichum and 29.44, 61.56, and 104.6 in p. deltoids, respectively) were observed for a Cd concentration of 150 mg Cd kg-1. The highest and lowest values of Cd concentration were observed in the roots and leaves, respectively, for all the Cd concentrations examined. Cd concentration exhibited a decreasing trend moving from roots to stems and leaves. The translocation factor increased in both species compared to the control and its greatest values (1.1065 and 1.006) were observed in the treatment with 50 mg Cd kg‒1 for p. deltoides and T. distichum, respectively. Given the importance of biological wastewater treatment and the removal of contaminants, especially heavy metals, from the environment aimed at optimal use of soil and water resources as goals of sustainable development, the cultivation of the hydrophilic species of p. deltoides and T. distichum may be recommended due to their high biomass production while the species also offer a high potential for phytoremediation and a great capacity for stabilizing soil cadmium.

Mesoporous silica adsorbents have been gaining increasing importance in the removal of heavy metal ions from water and wastewater. MCM-48 is a mesoporous silica adsorbent whose adsorption capacity of heavy metal ions can be drastically improved when it is modified by functional groups. The present study investigated the removal of lead and cadmium metal ions from aqueous solutions using the modified NH2-NH-NH-MCM-48. The nanoparticles were characterized by Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD). The adsorption process was optimized by varying adsorbent doses from 0.125 to 10 g/l, the initial solution pH from 2 to 6, and the initial metal ion concentration from 5 to 60 mg/l. The equilibrium data were analyzed using the Langmuir and Freundlich isotherms using a nonlinear regression analysis. According to the parameters of the Langmuir isotherm, NH2-NH-NH-MCM-48 recorded a higher maximum adsorption capacity for both Cd(II) and Pb(II) than MCM-48. The maximum adsorption capacities of NH2-NH-NH-MCM-48 for Cd(II) and Pb(II) were calculated to be 82.7 and 119.24 mg/g, respectively. The results suggest that MCM-48 modified with the amine functional group to synthesize NH2-NH-NH-MCM-48 significantly improves its adsorption capacity so that it can be recommended as an effective adsorbent for the efficient removal of Cd(II) and Pb(II) metal ions from aqueous solutions.

In this study, the electrospinning method was used to manufacture polyacrylonitrile (PAN) nanofibers. The procedure involved spinning a solution of 10%wt PAN in dimethyl formamide (DMF) in an electric field of 21 kV and with a tip to collector distance of 16 cm. The nanofibers thus obtained had an average diameter of 100 nm. Then, scanning electron microscopy (SEM) images were used to investigate the morphology of the nanofibers. In the next step, the nanofiner surface was modified with diethylenetriamine and FTIR was employed to ensure the presence of amines on the nanofiber surface. The functionalized nanofibers were then used for the first time to adsorb ions of cadmium (a heavy metal with industrial applications) and its adsorption capacity was evaluated. The chemical charactristics of the nanofibers and the effects of such parameters as pH, temprature, and contact time on adsorption efficiency were investigated. The results showed that maximum adsorption efficiency was achieved within the first 10 minutes of the process at a pH in the range of 5‒7 when about 80% of the cadmium ions were adsorbed.. Moreover, only slight changes were observed with longer contact times or with increasing temperature. Finally, the adsorption data fitted well with the Langmuir isotherm

Since a major portion of the food we use is provided by corps irrigated with water that is supplied from groundwater resources, remediation of contaminated groundwater using in-situ methods like permeable reactive barriers (PRBs) seems to be a top priority. Given the need to reduce Cd contamination in southern Tehran, the present study was designed to compare the rate of Cd absorption by nZVI with that by Zeolite and Calcite. The results of the study revealed a higher Cd adsorption by nZVI as compared to that by Calcite and Zeolite. Also, when nZVI concentration was raised from 1 to 2 g/l, enhancements were observed after two hours in Cd adsorption by up to 5.5%, 3.4%, and 11.5% in solutions containing 0.2, 0.5, and 4 ppm of Cd, respectively.Moreover, for a contact time of 24 hours and when the initial concentration of the contaminant was raised from 0.2 to 0.5 ppm, the adsorption rate declined to 5.45% and 7.75% for nZVI injections of 1 and 2 g/l, respectively. In a second part of the study, such environmental conditions as changes in pH and temperature were investigated for their effects on Cd adsorption. Compared to the initial concentration of 4 ppm, Cd adsorption reduced by 37.15% under acidic conditions (pH=3.7) and by 92.75% under alkaline conditions (pH=13.1) after a contact time of 3 hours. Similarly, a reduction equal to 38.5% was observed in Cd adsorption after 6 hours when temperature was raised from 20 °C to 75 °C. In order to explore the bioenvironmental impacts of injecting nanoparticles aimed at adsorption and precipitation of Cd, the concentration of iron nanoparticles present in the environment was measured. As a result of the reaction between the solutions containing 0.5 ppm of Cd with the absorbent solution containing 2 g/l iron, the iron nanoparticle concentration in the solution was observed to decline to 0.0041% of its initial concentration after 24 hours. In the experiments conducted in a vertical saturated porous and homogeneous medium, injection of 3 g/l of nZVI, as the absorbent, into water containing 2.92 ppm of the contaminant reduced the contaminant concentration to levels below the limits recommended for drinking water. The reaction between nZVI and Cd dissolved in the medium revealed that the nanoparticles served as an efficient absorbent as they not only adsorbed Cd over time, but also removed it from the medium through precipitation.

Environmental pollution due to the accumulation of heavy metals in soil and their subsequent transfer to crops is a global concern that arises from improper application of industrial wastewaters. This study was conducted to investigate the effects of different levels of soil Cd on its accumulation rate in the various organs of four common crops in Iran (namely, wheat, spinach, cucumber, and carrot). The experiment was performed in a factorial design with random blocks including 3 treatments with 0 (control), 50, and 100 mg/kg.soil in 4 replicates. Soil was collected from the farm belonging to the Research Institute for Plant and Seed Breeding (Karaj) and filtered twice using 2-mm sieves before Cadmium Nitrate (Cd(NO3)2) was added and completely mixed. Crops were planted in plastic pots 40 cm in diameter and 60 cm in height. The water demand was determined using the Jenman Mantite method. At the end of the growing season, samples were taken from various organs of the crops and their Cd concentrations were measured. The results revealed a direct relationship between Cd accumulation and Cd concentration in the root region. All the treatments other than the control exhibited Cd concentrations higher than the standard limits for human consumption. Cadmium accumulation in the different organs of the crops exhibited the following orders: Root: Cucumber

Keywords: : Cadmium, Crop Uptake, Industiral Wastewater}

The objective of this study was to determine the efficiency of lead removal from aqueous (both single- and multi-element) solutions using the nanostructured ash cedar absorbent. Nanostructured ash cedar was synthesized and the effects of pH, absorbent dosage, and contact time on lead removal efficiency were investigated in a batch system. The absorbent was characterized by SEM, PSA, XRF, and FTIR. SEM results showed that all the particles had diameters smaller than 207 nm. It was also found that the optimum pH values for lead adsorption were 6 and 5 for the single-element and the multi-element systems, respectively. The maximum removal efficiencies of 94% and 98% and maximum adsorption capacities of 27 mg/g and 21 mg/g were obtained for the single- and multi-element systems, respectively. Comparison of the Freundlich, Langmuir, and Sips isotherms showed that the Langmuir model with R2 =0.99 and RMSE = 1.01 for the single element system described the adsorption data better than other models did. Also, this model with R2 = 0.99) and RMSE = 0.024 better fitted the adsorption data in the multi-element system.

The main objective of the present study was to investigate Cd(II) adsorption by immobilized silica nanopowder within calcium alginate and to determine the isotherm, kinetics, and thermodynamics of the adsorption process. Batch flow mode reactors were used to investigate the effects of initial pH, contact time and metal ion concentration on Cd(II) adsorption. The optimal contact time and initial pH for Cd(II) adsorption were found to be 120 min and 4.0, respectively. Increasing Cd(II) ion concentration from 10 to 1000 mg/L led to increasing adsorbed Cd(II) ions from 5.71 to 100.65 mg/g. The results showed that the Langmuir isotherm model was the best model to describe the experimental data (R2=0.997). The maximum adsorption capacity (qm) for Cd(II) adsorption onto the adsorbent was estimated to be 72.99 mg/g. Based on the mean free energy of adsorption (E) obtained from Dubinin-Radushkevich (D–R) isotherm model, Cd(II) adsorption onto immobilized silica nanopowder follows a chemical mechanism (E=8.451 kJ/mol). The kinetic study indicated that the pseudo-second order model was a more suitable model than the pseudo-first order one for describing Cd(II) adsorption (R2=0.999). Additionally, the negative ∆Hº and ΔGº values demonstrated an exothermic and spontaneous Cd(II) adsorption onto immobilized silica nanopowder.

Magnetic nanoparticles modified by olive leaf ash were used in this study for the removal of heavy metal ions from aqueous solutions. The equilibrium adsorption level was determined as a function of solution pH، temperature، contact time، initial adsorbate concentration، and adsorbent dosage. Adsorption isotherms of heavy metal ions on adsorbents were determined and correlated with common isotherm equations such as Langmuir، Freundlich، and Tempkin models. The apparent characters and physical chemistry performance of the magnetic nanoparticles modified by olive leaf ash were investigated by scanning electron microscopy (SEM)، transmition electron microscopy (TEM)، and FT-IR. Results showed that the Langmuir isotherm model was fitted well with adsorption data. Kinetic studies were also carried out using various kinetic models such as Pseudo-first order، Pseudo-second order، Elovich and Intra particle diffusion model. The Pseudo-second order kinetic model was fitted very well with the experimental data. Based on thermodynamic studies، this process was found to be both endothermic and spontaneous and the enthalpy and entropy were found to be negative.

Heavy metals have been identified as major pollutants and also as one of the most serious environmental hazards. The aim of this study was to evaluate the efficacy of NF membrane to remove the heavy metals Pb, Cd, Cu and Cr+6 from waters containing sulfate. The membrane used in this study was of the NF, spiral-wounded model with a MWCO equal to 27Da, a cross-flowed stream, and a nominal capacity of 0.8 L/min. The effects of the parameters initial metal concentration (within the range of 5 to 50 mg/L for Pb, Cd, and Cu and 0.1 to 0.4mg/L for Cr+6 at four different concentrations), pH (4-9), flow rate (0.2, 0.4, 0.6, and 0.8 mg/L), and sulfate anion concentration (four concentrations ranging from 200 to 800 mg/L) on heavy metal removal efficiency of the membrane were investigated. Measurements were performed using atomic absorption and spectrophotometry. The maximum removal rates of Pb, Cd, Cu and Cr+6 for synthetic samples under optimal experimental conditions were 91, 97, 98, and 95%, and those for real samples were 72, 53, 87, and 99%, respectively. It was observed that the membrane efficiency for removing the three metals of Pb, Cd, and Cu decreased with increasing pH and initial metal concentration while it increased in the case of Cr+6. Increasing flow to 0.6 L/min led to a slight increase in membrane removal efficiency for all the four metals. Based on the results obtained, NF membranes are capable of removing a high percentage of heavy metals and a significant increase is observed in their heavy metal removal efficiency in the presence of sulfate ions and with increasing flow up to a certain level.

In order to investigate the effects of application of industrial wastewater on accumulation of heavy metals in soil and cultivated rice, the farms effected by Amol Industrial wastewater Park were selected and samples of irrigation water, soil and also roots, shoots and grains of rice were collected. Then, the amounts of Cr, Cd, Ni and Pb in these samples were determined. The results showed that the amount of these elements in samples of water, soil and rice were increased due to application of wastewater. The total amount of cadmium in the soil in highest amount increased to 29.75% which was higher than the other elements. Available lead in the soil at highest amount was increased to 40% compared to control. Due to using industrial wastewater, increase in the accumulation of heavy metals in studied rice roots were more than that in other organs. Accumulation of the elements in the grain was Cr> Cd ~ Pb> Ni, respectively. Accumulation of Pb in root and shoot of rice were more than other metals. Heavy metals transfer factor from the soil to the shoots was more than grain. Transfer factor for Cd in grain and shoots in site 2 was equal to 1.52 and 1.44, respectively, which were more than other elements. Cadmium risk index was highest among the elements investigated.

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.

Heavy metals in municipal and industrial wastewater can pollute surface water, sediment and soil. In order to evaluate the concentration of heavy metals (Zn, Cd, Pb) in Goharrood sediment and water, a project was designed and to this end, samples of water and sediment were collected. Coordinates of the sample points were determined by GPS (Global Positioning System). Moreover, in the sediment samples, the total amount of Zn, Pb and Cd were determined by atomic absorption spectorophotometer after extraction. The amount of metals, Ph, EC, TDS, SAR were determined in samples of water. Total Pb,Cd and Zn concentration was extracted by 4M HNO3.. Statistical assessments were carried out by SPSS. Results showed that water in all stations were not contaminated by cadmium. Moreover, Zn and Pb contamination were lower than toxic levels. Collected sediment samples were polluted by Pb and Zn but cadmium concentration was insignificant. Maximum concentration of pb (18.20 mg/kg) was observed in the eighth station and minimum concentration of pb (2.10 mg/ kg) in the twenty second station. Furthermore, maximum concentration of Zn (101/64 mg/kg) was observed in the fourteenth station and minimum concentration of Zn (37.80 mg/kg) in the twelfth one. In the last station, maximum concentration of Cd (0 /49 mg/kg) was observed.

A series of clay pillaring agents with Ti، Cu، Al and Fe elements were synthesized. These pillaring agents were used to modify montmorillonite clay by ion-exchange reactions. Clay d-spacings increased modestly when Na+-MMT clay was intercalated with these pillaring agents. The modified red mud (MRM) and pillared clay (PILC) complex can be used as a strong absorbent pollutant. In this study، MRM and PILC complex was used for the removal of cadmium from water. The complex was characterized using XRD، SEM and XRF microanalysis and adsorption of cadmium was studied as a function of pH، time، and temperature by AAS method. The maximum adsorption efficiency reached 96. 69% when the pH was 6 at 40 ºC. Langmuir and Freundlich isotherms equation were used to fit the adsorption isotherms. It is evident from this study that MRM and PILC complex is a suitable material for the uptake of Cd (II) from aqueous solutions.

In order to study، the amount of cadmium and nickel in different plant organs of borage planted in calcareous، following the application of sewage sludge and municipal solid wastes compost، an experiment was conducted in split-plot design based on complete randomized block design in 2009. The main plot was sewage sludge and municipal solid wastes compost at five levels (control، 20، and 40 ton/ha) and the sub plot was years in six treatments (2006، 2006 and 2007، 2006 and 2008، 2006-2008، 2006 and 2007 and 2009، and 2006-2009). The amount of available Cd and Ni in soil and Cd and Ni accumulated in the roots، leaves and flower of Borage were compared with the control. Results indicated that the application of 40 ton/ha sewage sludge and municipal solid wastes compost increased the available Cd and Ni in soil (about 2 and 2. 5 times، respectively) and the amount of Cd and Ni in the roots of Borage by 5 and 2. 5 times compared to control. The maximum amount of Cd in leaves and flowers of borage was observed in the 40 ton/ha sewage sludge treatment. Furthermore، the treatment of 40 ton/ha sewage sludge and municipal solid wastes compost produced the most amount of Ni in leaves and flowers of Borage، respectively. Meanwhile، the maximum amount of Cd translocated to the shoots was observed in the flower in the 40 ton/ha sewage sludge and Ni in the same organic fertilizer treatments to leaves of borage.

The objectives of this research were to synthesize magnetite nanoparticles (Fe3O4) and determining its efficiency in Cadmium removal from aqueous solutions. Consequently, magnetite nanoparticles were synthesized and the effect of pH, contact time, Cadmium concentration and nanoparticles amount on cadmium removal efficiency were investigated in batch system. Scanning Electron Microscope (SEM), XRD and FTIR were used to characterization of the synthesized magnetite nanoparticles. SEM results showed that the diameter of the particles is 40-60 nm. Results also showed that the optimum pH value for adsorption was 6. The adsorption capacity increased and the adsorption efficiency decreased with increasing concentration of Cadmium ions and reducing the amount of adsorbent. The magnetite nanoparticles have advantages such as high removal efficiency and short reaction time and can be used as a method to remove Cadmium from aqueous solutions.