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Research subject: In this study, EDTA-functionalized Fe₃O₄@SiO₂ magnetic nanocomposites with core-shell structure were synthesized to remove divalent cadmium ions from aqueous solutions.
Research approach: During the first step, Fe₃O₄@SiO₂ nanosphere core-shell is synthesized using nano Fe₃O₄ as the core, TEOS as the silica source and PVA as the surfactant. This strategy relies on the covalently bonding of ethylendiaminetetraacetic acid to bis(3-aminopropyl)amine and cyanuric chloride functionalized magnetic nanoparticles. In the next step, characteristics of surface functional groups, crystal structure, magnetic properties, size and surface morphology of these nanoparticles were investigated, identified and analyzed using physico-chemical characterization techniques including fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), dynamic light scattering (DLS), vibration sample magnetometry (VSM) and Brunauer-Emmett-Teller (BET) surface area analyzer.  The adsorbent, due to its magnetic property, could be simply separated from the reaction mixture by a permanent magnet and reused in five consecutive cycles without considerable loss in its activity.
Main results: To probe the nature of the adsorbent, various experiments were investigated like adsorbent dose and contact time were optimized. Kinetic studies and the effect of different amounts of adsorbent to remove divalent cadmium ions from aqueous solutions show a maximum adsorption of 94% at ambient temperature. Moreover, the recyclability of Fe₃O₄@SiO₂-EDTA was investigated in order to remove the divalent cation for successive adsorption-desorption cycles. All the results of studies show that the synthetic nanocomposite Fe₃O₄@SiO₂-EDTA is an effective, recyclable adsorbent with excellent performance for the removal of divalent cadmium.

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Research subject: This study demonstrates a synthetic strategy for the preparation of porous SiO₂ for adsorption applications using natural and waste materials from rice husks which are functionalized with polymer dendrimer molecules and surface amino groups as the source of biosilica and were investigated to remove divalent cadmium ions from aqueous solutions.
Research approach: Porous silica nanoparticles with a mean diameter of 45 nm were successfully fabricated from rice husk (RH) biomass via a multistep method. During the first step, sodium silicate is extracted from rice husks. Then, cetyltrimethylammonium bromide, HCl, and acetic acid were added to the sodium silicate solution, and the resulting mixture was sonicated. After the hydrothermal reaction, the collected samples were calcinated to obtain silica nanoparticles. These synthetic nanoparticles were identified using various techniques such as Fourier-transform infrared spectroscopy, thermogravimetric analysis, transmission electron microscopy, field emission scanning electron microscopy, nitrogen adsorption-desorption analysis and dynamic light scattering analysis. Then, the adsorption kinetics and the effects of synthetic nanoadsorbents dosage on the removal of divalent cadmium ions were investigated. The effect of contact time on cadmium adsorption and recyclability of adsorbent was also investigated.
Main results: The results show that there is no significant reduction in the performance and activity of this nanosorbent in the adsorption of metal ions after 6 times of recycling and reuse. The excellent performance of this nanosorbent in the removal of metal ions is due to its high porosity, active surface amine groups and high surface-to-volume ratio.

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Aim: The removal of heavy metals from drinking water is one of the highest impact challenges in the water and wastewater industry. For this purpose, the use of methods such as solid phase extraction followed by the use of selective adsorbents is considered as one of the most important issues in the water and wastewater industry.
Method: In this research, in order to remove the polluting and toxic heavy metal cadmium from water in the water treatment industry, Fe₃O₄ nanoparticles with a diameter of 10 nm have been synthesized. In order to make these nanoparticles resistant to corrosion and erosive factors of the environment, they are covered with a silica shell and afterwards with the aim of removing cadmium ions from aqueous solutions, the surface of Fe₃O₄@SiO₂ nanoparticles is modified with 1,4-dihydroxyanthraquinone molecules. The synthesized nanoparticles are characterized in order to evaluate the efficiency of these nanoparticles in separating cadmium ions soluble in water has.
Results: The synthesized and functionalized magnetic nanoparticles have an effective surface area of 378 m²/g with black color and spherical morphology. The effects of the parameters of the amount of nano adsorbent, pH of the solution, various concentrations of the solution and test time in the removal of divalent cadmium ions are investigated. According to the experimental data, the optimal values for the absorption process at pH 7 by using 18 mg of adsorbent in 50 ml of cadmium solution with an initial concentration of 0.35 mmol/L lead to the removal of cadmium ions with a maximum absorption of 92% at ambient temperature in a period of 35 minutes. Moreover, the recyclability and reusability of Fe₃O₄@SiO₂-DAQ in the adsorption-desorption process of cadmium ion is investigated using a magnetic magnet, and the results confirm that this synthetic nanocomposite is an effective adsorbent with excellent performance in order to remove divalent cadmium ion from aqueous solutions.
 

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  A total of 100 samples were collected from 5 kinds of Caned fish from retail shops to test for content of Lead, Copper, Tin and Cadmium residues. All the samples were prepared by the method recommended by (A.O.A.C) and were checked by Potentiometric Stripping Analysis Method (P.S.A). Data were compared with the permitted level of each metal by using one sample T test, also the ANOVA test was used to compare the amount of each metal among the samples. The results showed that mean value of Lead, Copper, Tin & Cadmium residues in the samples were 99.6 ppb, 2.087 ppm, 2.578 ppm and 0.031 ppm respectively. The mean value of residues of Lead, Cadmium, Tin and copper in fish cans were in the standard range but 28.4% of the samples contain Lead and 2% contain Cadmium more than standard limit. The amount of Copper, Tin residues were in the standard range. There was the significant difference in the Copper and Cadmium residues among the different kind of cans (P<0.05) but there was no significant difference in Lead and Tin residues among the different kind of cans (P>0.05).  Regarding to the results of this study some of the fish can producing in Iran containing Cupper, Tin and Lead residue more than standard limit of these metals in this product. Therefore it is recommended to conduct the other study to confirm the source of these metals in fish cans.

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  Cultivated mushrooms are considered as a popular delicacy and have an important role in daily intake due to essential Amino Acids, elements and vitamins. Based on Several Studies, mushrooms can accumulate great concentrations of toxic metallic elements like lead and cadmium in Comparative to other Fruits and vegetables. This study has conducted due to following reasons: - Lead and Cadmium have Considerable toxic effects even in low Concentrations. - There is no reports about these elements contents in mushrooms cultivated in Iran. - There is no Proper strategy for this infection control Material and Method: 8 mushroom Samples were collected randomatically from mushroom sale centres in Tehran, and delivered to laboratory. Then they were sorted, cut, washed, and dried at 80°c for 20h. Dried Samples were homogenized and laid in ash. Then they were Solved in Nitric Acid and finally analysed by Atomic Absorption Spectrometer. Results: Cadmium Content was lower than acceptable level (EU 466/2001) (2.0 mg/kg dry weight) in all samples. Lead content was generally lower than acceptable level (3.0 mg/kg dry weight) except for 2 Samples which have 5.35 mg/kg and 3.71 mg/kg Lead Content. Conclusion: Analysed Samples have low content of cadmium due to cultivating environment, good quality of Compost and irrigation with deep underground water. Geographical Condition of Cultivation may cause high content of lead in two Samples. It is recommended to investigate the main reason of this infection.  

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The aim of this study was to measure the level of Arsenic, Cadmium, Nickel and Mercury in gill, muscle and hepatopancrease tissue of Aras dam Astacus leptoductylus and compare of them concentration in different body tissues. For this purpose, 271 samples of Astacus leptoductylus were randomly collected in Aras dam from December 1 to December 31, 2017 and transferred to the laboratory. After that tissue samples processed for injection in atomic absorption for apparatus for measuring the level of Arsenic, Cadmium, Nickel and Mercury. For measuring the protein, ash and moisture content of the samples AOAC method was conducted. The results showed that Arsenic, Cadmium, Nickel and Mercury were present in the Astacus leptoductylus samples and the highest level of these metals was in the muscle and the lowest in the gills. The highest level of metals existing in Astacus leptoductylus muscle was related to Cadmium (0.338± 79 0.79 ppb), and also Nickel (0.285±0.066 ppb) was in the second rank. The level of Arsenic and Mercury in muscle were ranked third and fourth. However, it was found that the total moisture content of the gills was higher than muscle and hepatopancrease tissue. On the other hand, the results of correlation between metals of different tissues of Astacus leptoductylus showed that the correlation between Cadmium and Nickel was higher than Arsenic and Nickel. The level of total protein and ash in Astacus leptoductylus muscles was higher than other tissues. The present study showed that analyzed Arsenic, Cadmium, Nickel and Mercury level were in the muscle, gill, and hepatopancrease tissue samples of the Aras dam A. leptoductylus in detectable concentrations, and Nickel and Mercury in the samples were lower than the WHO standard. As a result, the levels of metals in the Astacus leptoductylus samples collected from Aras dam were safe and reliable and therefore there is no problem.

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In this article, the interaction between lysozyme and CdTe nanoparticles was investigated by UV-Vis spectroscopy, fluorescence, thermal stability, kinetics, and circular dichroism (CD) spectroscopic methods at pH 7.25. It was proved that the fluorescence quenching of lysozyme by CdTe NPs was mainly a result of the formation of the CdTe–lysozyme complex. By the fluorescence quenching results, the Stern–Volmer quenching constant (K_SV), binding constant (Ka), and binding sites (n) were calculated. Under pH 7.25 conditions, the level of binding constant is determined to be 2.33×10³ from fluorescence data. The hydrogen bond or van der Waals force is involved in the binding process. The blue shift of the fluorescence spectral peak of protein after the addition of CdTe nanoparticles reveals that the microenvironments around tryptophan residues are disturbed by CdTe nanoparticles. The effect of CdTe NPs on the conformation of lysozyme has been analyzed by means of UV-Vis spectra and CD spectra, which provided evidence that the secondary structure of lysozyme has been changed by the interaction of CdTe NPs with lysozyme.

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Crucian carp (Carassiu sauratus) is one of the economic species of Anzali wetland. In recent years, the demand of high consumption was found, because of its low price and high level of catch. This study focused on accumulation of heavy metals(Cd, Pb and Zn) in the edible tissues of Crucian.Sampling were done in 3  stations (West,Center and East) of Anzali  wetland in 1391. In this study 10samples were collected from each site in the standard weight by grill net, randomly. After separation of tissues, preparing of samples were conducted by using of wet digestion method and  mixed acid ( HNO3/HCLO4).After filtration, the prepared samples were determined for Cd, Pb and Zn by  using a flam atomic absorption spectophotmeter (AA),SHIMADZU model 680.The levels of metals were compared with the standard of American Food and Drug Administration (FDA)  and the world Health Organization (WHO). The average concentrations of cadmium in the soft tissue of crucian were 0.07 , 0.05 and 0.05 μ g / g dry base for West, East and Center of Wetland. For Zinc, average concentrations for West,Center and East were 58.45, 46.4 and 49.7 μ g / g dw, respectively. The result showed that,there were not significant differences (P>0.05) between stations about the Cadmium, Lead and Zinc in the tissues of Crucian. Concentrations of Pb and Zn were higher than of standars levels of WHO and FDA.

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To estimate plant resistance to Cadmium Chloride (CdCl2) stress for phytoremediation purposes, the effect of cadmium (Cd) phytotoxicity was assessed on total soluble protein, chlorophyll (Chl) content and antioxidant enzymes in the leaves of three different Brassica napus (B. napus) cultivars; Mohican, Reg.Cob and Okapi. Plants were exposed to three levels of CdCl2 (0.75, 1.5 and 2.25 mM) in irrigation water. A reduction in protein and Chl content was noted for all treatments in the three cultivars. Generally, superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities were increased with 0.75 mM CdCl2 and then decreased at higher concentrations. SOD activity was enhanced up to 1.5 mM CdCl2 concentration in Mohican cultivar. Moreover, APX activity of Okapi cultivar was increased at a much higher rate of CdCl2 levels compared to Mohican and Reg.Cob cultivars. Different concentrations of CdCl2 induced a reduction in the catalase (CAT) activity of Mohican and Reg.Cob. However, this activity was increased with 0.75 mM CdCl2 in Okapi and then decreased with higher concentrations. These results indicate that B. napus cultivars have different tolerances to CdCl2 stress and in consequence, different phytoremediation efficiencies. Moreover, because Okapi possesses a higher antioxidant enzyme activity than the other two cultivars, it is suggested that it is probably the most tolerant cultivar to CdCl2 stress.

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In the present study, the effects of different cadmium (Cd) levels of irrigation water (0, 5, 10 and 20 mg L^-1) on corn plants (foliage) under different irrigation intervals (1, 3, and 7 days) were investigated. Clear Cd toxicity symptoms appeared on the plants at the end of the experiment. The results showed that stem dry weight (DW) followed by transpiration (T) and plant height were the measured plant parameters most sensitive to increasing Cd levels of irrigation water. In addition, Cd reduced water uptake by corn and led to more soil moisture. The results also demonstrated that corn might produce more shoot biomass with Cd application, which should be taken into consideration if no visible symptoms of Cd toxicity and considerable amounts of the metal uptake are present. Cadmium application through irrigation did not show a marked impairment in the nutrient status of the plants. Moreover, accumulation of Cd in the leaves was more than the stems by 24, 56, and 27% at 1, 3, and 7-day irrigation frequencies, respectively. Also, corn stem was found to be more sensitive to Cd than leaf. The results showed that corn might be used for phytoremediation of Cd under optimum moisture conditions and light contamination of the soil. Furthermore, shoot Cd concentration followed an asymptote pattern as a function of soil Cd, which was expressed by a plateau-type model under each irrigation interval.

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The aim of this study was determining the concentration of heavy metals as Lead, Cadmium and Tin in canned peas, with pre-treatment by 5 and 10-minute blanching and using citric acid, acetic acid and phosphoric acid at concentrations of 0, 0.25 and 0.5%. The samples were manufactured and sealed commercially. The evaluation of mentioned heavy metals was carried out using by flame photometric method. The response surface method was carried out in central composite design, and data analysis was done using Design Expert software. The effect of the dependent variables in quadratic model is evaluated. According to the results, the highest levels of Lead, Cadmium and Tin were 0.43, 0.61 and 87 parts per million respectively and the lowest was zero, 0.14 and 10.43 parts per million, respectively. The results showed that increasing the blanching time reduced the lead, cadmium and tin amounts at 1% level. On the other hand, increasing the concentration of acetic acid, citric acid and phosphoric acid to its highest level would yield the best results to achieving the lowest amount of these elements during blanching.

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Rice is one of the most widely consumed grains in the world and is widely used in the diet of people. Today, rice contamination with heavy metals is one of the problems confronting humanity. Therefore, the purpose of this study was to evaluate the effect of soaking and cooking in the presence of chelating agents i.e., potassium tartrate and citrate on the amount of  Cadmium reduction of three types of imported rice (India, Thailand, and America). Measurements were carried out with atomic absorption with three replications. The difference in mean was done at Duncan's 5% level. The cadmium of imported rice was higher than the standard values. Cadmium of imported rice from highest to lowest was America, Thailand, and India that was 86.23, 85.93 and 80.07 ppb, respectively. Soaking in the presence of chelating agent but cooking in water without chelating agents(S-chelating agents), in comparison to soaking in water without a chelating agent but cooking in the presence of chelating agents(C-chelating agents), had no significant difference in cadmium elimination(p>0.05). Soaking and cooking of rice in the presence of chelating agents(SC-chelating agents) reduced Cadmium to higher than 93 percent (97.58 for potassium tartrate in Thailand rice and 93.46 for potassium citrate in India rice). Tartrate chelating agents in comparison to citrate had a significant effect in cadmium elimination for imported rice (p<0.05). Finally, the sensory evaluation showed that there was no significant difference between all treatments(p>0.05).

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Remediation of contaminated soil by heavy metals is an important environmental issue which attracted many attentions and was evaluated by several methods. It is highly desirable to apply suitable remedial methods to reduce the risk of heavy metal contamination in soils. Development of new low-cost, efficient and environmental friendly remediation technologies is the main goal of the recent research activities in environmental science and technology. Using nanotechnology in removal of environmental pollutions is of modern and applicable methods. One of the early generations of nanoscale technologies in the field of environment is the use of iron nanoparticles as a ground for sorption of pollutants. These nanoparticles are nontoxic, inexpensive, and very strong absorbents.The aim of this study was to assess the effects of cadmium removal by soil washing with iron (III) oxide nano particles (Fe3O4), stabilized with Polyacrylic Acid (PAA) as nanofluid, on physicochemical characteristics of nanofluid and soil in two defined systems including batch and continuous flow configurations. For this purpose, after complete removal of Cd from the soil in both systems under the optimized conditions, the effects of removal on the physicochemical characteristics of soil and nanofluid including pH, electrical conductivity, and total dissolved solid were assessed. The results of XRD and SEM of soil samples and also zeta potential and size distribution of nanofluid, before and after the removal were investigated. To ensure the absence of other pollutants and elimination of any interaction between soil pollutants, the soil was prepared with clean standard materials and afterwards it was contaminated with cadmium solution prepared by cadmium nitrate. The optimum conditions for cadmium removal in the batch system was as follows: nanofluid concentration=500 ppm, pH=6.5, contact time=24 hr and the ratio of contaminated soil mass (gr) to nanofluid volume (mL) =1:150 . completely Cd removal in continouse flow configuration obtained in the following conditions: nanofluid concentration=500 ppm, pH=6.5, contact time=24 hr, and the flow rate =0.5 mL/min. Cadmium content in the nanofluid after remediation was determined with UV spectrophotometer by using APDC complexes in Tween 80 media. As per the results of this study, pH of the soil samples in the both batch and continuous flow configuration increased from 7.8 to 8.55 and 8.35 respectively. pH of nanofluid increased from 6.5 to 6.8 in the continuous flow configuration and 7.59 in the batch system. EC and TDS of the nanofluid decreased from 1.66 mS/cm and 1110 mg/L to 1.049 mS/cm and 699 mg/L in the continuous flow configuration and these parameters also reached respectively to 0.952 mS/cm and 635 mg/L in the batch system. Soil washing using Fe3O4 nanoparticle did not changed remarkably EC and TDS of the contaminated soil. Nanoparticles size with highest frequency in nanofluid before removal was 205 nmand after Cd removal reached to 23 nm and 29 nm in the continuous flow configuration and batch system respectively, which was an indication of the sorption of nanoparticles with grater size to the soil during the soil washing process. Zeta potential values of influent and effluent of nanofluid from continuous flow configuration and batch system were -61.5, -51.3, and -37.4 mV respectively. The structural changes of soil samples after removal in the both systems were assessed by XRD and SEM tests which confiremed the sorption of nanoparticles through the soil washing.

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In recent years, the use of nano-materials in different engineering and science projects has increased. The study of the impact of nano-materials in combination with other civil engineering constituents in different geotechnical and geo-environmental engineering projects is very common. This study is aimed to investigate the mechanism of cadmium retention in the process of cement based solidification/stabilization of cadmium contaminated bentonite in the presence of nano-silica. The mechanism of contaminant retention is investigated with the evaluation of cadmium and nano-silica behaviour with change in pH of the environment, adsorption, TCLP results, and evaluation of XRD experimental achievements. The bentonite sample for this research is taken from Iran-Barit Company. To establish the availability of silica ions for interaction with cement and bentonite at different pH, a series of solubility experiments of nano-silica at different pH levels were performed. The results of solubility experiments show that as the pH increases to the alkaline range, the solubility of nano-silica noticeably increases. This fact proves that at the high range of pH due to the use of cement, the required pH conditions for solubility of nano-silica will be provided. Therefore, there will be more possibility for the formation of CSH component. Cadmium nitrate was used to contaminate the bentonite sample for the experimental part. For this purpose, bentonite samples were mixed with 10, 30, and 50 cmol/kg-soil of cadmium nitrate in the electrolyte soil ratio of 20:1. Then, these samples were shaken for two hours in every 24 hours. This process was repeated for 96 hours. After this equilibrium step, the soil suspension was centrifuged. After drying these laboratory contaminated samples, they were solidified/stabilized with different percentages of cement and nano-silica. The results of this paper indicate that the contaminant adsorption and retention of cadmium by bentonite is less than that of adsorption for zinc and lead. The achieved results of TCLP experiments for solidified/stabilized samples with different percentages of cement indicate that the EPA criteria for TCLP experiment which emphasizes for test performance after 28 days, is not suitable for solidification and stabilization of cadmium. In fact, a longer period is necessary to achieve equilibrium and stable results. Furthermore, the results show that due to the low adsorption of cadmium by bentonite and due to the noticeable reduction of pH at the presence of cadmium ions, the required percentages of cement for solidification/stabilization of cadmium contaminated bentonite is much more than the required quantity of cement for other heavy metal contaminated bentonite samples. In addition, the results of XRD experiments show that the pozzolanic interaction process is more efficient in the presence of nano-silica. Furthermore, based on the results of TCLP experiments, the formation of CSH in the presence of nano-silica contributes to the contaminant retention by solidification/stabilization of cement based cadmium contaminated bentonite. Finally, according to the results of this study, in solidified/stabilized samples by mixtures of cement and nano-silica, it is shown that due to the contribution of silica ions in pozzolanic interactions, the solidification is the governing phenomenon for the prevention of heavy metal leachate from solidified/stabilized samples.
 

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Pollution in industrial areas due to the release of heavy metals is one of the important environmental concerns. Heavy metals can have very adverse effects on human and animal health. In this regard, food products contaminated with heavy metals, even in low concentrations, can have harmful effects on human health. In this regard, the use of microorganisms is known as a new and low-cost method for the biological removal of metals. The purpose of this study was to investigate the effect of the type of microorganism (Lactiplantibacillus paraplantarum, Lactobacillus paragasseri, and Limosilatobacillus reuteri), temperature, and incubation time on the removal of lead and cadmium metals using the response surface methodology. The results showed that the removal rate of lead metal using microorganisms was significantly higher than that of cadmium. Increasing the time from 0 to 24 hours significantly increased the amount of metal removal. On the other side, increasing the temperature up to about 38 °C positively affected the removal of metals, but increasing the temperature further reduced the ability of microorganisms to remove metals. In general, the software determined the optimal conditions to achieve the maximum removal of lead and cadmium metals by 45.9% and 39.65%, respectively, at 24 hours incubation time and 33.98 °C temperature using Lactobacillus paragasseri bacteria. Therefore, according to the results of this research, the use of microorganisms such as Lactobacillus paragasseri is a useful solution for removing heavy metals from various sources, such as industrial wastewater.
 

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The presence of heavy metal contaminants in clays causes changes in soil properties, which increases the risk of contaminant transport into the clay layer. Various techniques have been developed recently to remediate contaminated soil. These methods include electrokinetics, biological treatment, and immobilization. Among them, cement-based stabilization/solidification technique is very common. Generally, cement-based systems are frequently used because of their affordability and great durability. This method uses the two mechanisms of chemical stabilization and physical solidification to retain heavy metals and decrease the mobility of contaminants. Even though several researches have been performed to address the different aspects of cement-based solidification/stabilization, there has been a lack of research on the stabilization/solidification of heavy metals in the presence of two different heavy metal ions. Therefore, the objective of this study is to determine to what extent the pH variations affect lead and cadmium retention and release in single and double-component cement-based stabilization/solidification systems. To accomplish the aforementioned objective, first, the retention capacity of lead and cadmium, in cement-based S/S of contaminated bentonite in single and double-component heavy metal systems is investigated. The effect of pH on the stabilization/solidification process was determined by conducting a series of XRD tests in order to investigate and differentiate the stabilization and solidification mechanisms. In the next step, the amount of released cadmium and lead ions during the TCLP test was determined in single and double-component systems in order to investigate the effect of pH and the simultaneous presence of lead and cadmium in the release of these heavy metals. According to the achieved results, the maximum retention capacities of lead and cadmium occur in the pH ranges of 8.5 to 11 and 10 to 12, respectively. Furthermore, retention in the double-component system is always lower than that of the single-component system, assuming a similar initial concentration. In addition, XRD results illustrate that the intensity of the peaks of cadmium and lead chemical compounds has increased for the samples their pHs take place in the safe zones. This indicates an increase in the contribution of the stabilization mechanism. According to the results of this paper, at a similar contaminant concentration, the intensity of the C-S-H peak increases with an increase in cement percentages. This indicates progress in the contribution of the solidification mechanism in the retention of heavy metals. Still, the release of these heavy metals is always lower than the maximum allowable value reported by the US EPA in the above-mentioned pH ranges. Moreover, the results of this research show that the amount of released cadmium and lead in the double-component system is more than that of the single-component system, assuming similar initial concentrations. Based on the definition of the safe zone, in the defined pH range, the contaminant is retained during the TCLP test mainly by chemical stabilization (precipitation). In fact, in the above range, an increase in the amount of cement has not shown a significant effect on the amount of heavy metal desorption. This finding is supported by the results of retention tests.