فهرست مطالب مجید قهرمان افشار

In the present study, magnetite nanoparticles were synthesized by co-precipitation method with surface coating by silica nanoparticles. Afterwards, these nanoparticles were functionalized with glucosamine molecules. In the next step, these functionalized core-shell nanoparticles were used as a suitable adsorbent to remove nickel ions from aqueous solutions.

The synthetic adsorbent was investigated using techniques such as X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), particle size distribution (DLS), vibrating sample magnetometer (VSM), X-ray energy diffraction (EDX) and thermogravimetric analysis (TGA) to evaluate the structure, morphology and size of the particles. Moreover, the absorption performance of the synthetic adsorbent was investigated by optimizing the amount of adsorbent, pH of the solution and contact time.

The results indicate that the maximum absorption capacity occurs when 24 mg of the adsorbent is added to 75 mL of the solution with an initial concentration of 0.65 mmol/L at pH=7 with contact time of 18 min. Additionally, the synthetic adsorbent possess the ability to be recovered and used repeatedly in successive absorption processes up to 7 times without a serious decrease in activity.

The average consumption of raw water in Tarasht power plant is 2800 m3/day, which is considerable, and therefore it is necessary to provide effective solutions in order to improve the consumption pattern and prevent water wastage. After technical investigations, effective solutions such as recirculation of clean drains of boilers, drains of resin filters backwash, purification and recirculation of cooling tower drains, etc. were studied. Considering the volume and quality of the produced effluent of the power plant, the solution of recirculating clean drains was chosen as the most effective method. Among the various implementation methods of clean drain recycling, two methods of fountain pool and heat exchanger were investigated as two more effective technical and economic methods. Economic studies showed that for the provision of equipment and the implementation of 8 m3/h recycling solution of boiler blowdown, it is necessary to spend 1,070,000,000 Tomans for the fountain pool method and 1,425,630,000 Tomans for the heat exchanger method, that the fountain pool method needs about 25% less cost. Also, recirculation of boiler sludge (200 m3/day) to the raw water with the fountain method (functional efficiency 75%) leads to a 5.3% reduction in water consumption and the use of the heat exchanger method (functional efficiency 95%) leads to a reduction of about 6.8% of input raw water. In addition to the economic results, technical studies showed that the fountain pool method has more advantages than other methods of recirculating boilers due to the simplicity of operation, the possibility of removing iron and hydrazine.

Today, the progress of industries, health, energy and food security, which are the main components of the sustainable development of societies depend on water more than anything else. Moreover, water shortage is a serious problem for human survival and the natural ecosystem. The average amount of raw water consumption in Shahid Montazer Ghaem steam power plant is 25,000 m3/day, which is significant considering the production capacity and the existence of a cooling tower in this power plant. Therefore, it is important to provide effective solutions that is able to be implemented in order to modify the consumption pattern and prevent water wastage in this power plant. Effective proposed solutions according to the in-person visit, receipt of documents and consultation with specialists, experts and operators in this power plant in order to modify the consumption pattern is including the recycling of clean drain (boilers blowdown, backwash of filters, samplers) in the final stage of washing resin filters, purification and recirculation of cooling tower sludge, increasing the degree of concentration and optimization of cooling towers (replacing drippers, changing nozzles, changing the angle of lavers, etc.), the use of ozone in order to purify the water of the cooling tower, water storage during equipment repair, especially in the cooling towers, installation of the RO system in the inlet of the cooling tower's compensating water.  Finally, considering the technical-economic conditions and volume and quality of water, a high priority solution was proposed in this power plant in order to modify the consumption pattern and prevent water wastage.

The water of Persian Gulf, which is currently used as the water in the cooling tower for Bandar Abbas power plant has high alkalinity, conductivity and salinity. The examination of microbial tests for the cooling tower indicates the high concentrations of all kinds of microbial species which is related to the high level of fluoride, sulfate ions and sediments. The TBC shows 104 cfu/ml which is considered a high value.  On the other hand, the presence of magnesium and calcium ions in carbonate form is a reason for the huge amount of hardness. The high level of ions concentration especially chloride and magnesium in the cooling water increase the growth of microbial parameters. Furthermore, the reason of such a huge growth of sulfate-reducing bacteria (SRB) is the high concentration of sulfate. Therefore, the solution of reducing the general concentration of ions using methods such as reverse osmosis and ion exchange resins is suggested as the first priority to prevent microbial corrosion. Additionally, chlorination methods are proposed as the second priority due to economic efficiency and high-performance capability. Finally, ozonation method is presented as the third priority due to the higher cost compared to chlorination, high power and the absence of side products. Also, the high concentration of sulfate leads to the activity of SRB bacteria and causes various types of corrosion, and therefore, the use of methods for reducing the concentration and selective removal of sulfate as an effective and priority solution should be considered.

There is a great importance in investigating and measuring microbial corrosion in the cooling tower of thermal power plants, especially in the case of open cycles. Moreover, this issue becomes more important in the situation where the source of water supply for cooling tower is river or sea water. In this research, the cooling tower water for Ramin Power Plant, which is supplied from the Karun River, is examined as a point of of microbial growth. For this purpose, microbial tests including TBC (general test) and specific bacteria tests such as APB, FP, IRB, NRB, Aero, SRB and TRB, physicochemical tests (conductivity, salinity, pH, turbidity) and the amount anions and cations, are carried out in the water sample of the cooling tower. In the TBC test, the approximate number of bacterial colonies is 107 cfu/ml, which is in a very heavy range. The results of APB and IRB test indicate the value is much higher than the permissible limit and the presence of Aero bacteria. On the other hand, in the analysis of anion and cation, sulfate and chlorine species have a very high concentration of more than 1000 ppm. Therefore, to deal with microbial factors, and as a solution in the first priority, the method of chlorination with water shock is recommended. The second priority includes the general method based on oxidizers such as ozonation and bromination. Selective removal of sulfate and nitrate ions is suggested as the third priority solution due to the high concentration of these ions and the intense activities of SRB and NRB bacteria.

Contamination of soil and water with heavy metal ions poses serious dangers and threats to the environment and human health, therefore it is very important to find an effective solution to remove these heavy metals from water. In this study, surface modified magnetic nanoparticles by N-phosphono-methylamino - diacetic acid with a core-shell structure were first synthesized. These nanoparticles were characterized. The performance of this synthetic nanoadsorbent for removing nickel (II), lead (II) and vanadium (V) ions from aqueous solutions was evaluated by various parameters such as adsorbent amount, contact time effect on adsorption rate and pH effect. The results show that the adsorption efficiency increases with raising pH and the best adsorbent performance in the adsorption process of nickel (II), vanadium (V) ions at pH = 6-7 and lead (II) at pH = 5-5.5 was observed. Also, the adsorption data were analyzed by the Langmuir and Freundlich isotherm model. In addition, the recyclability and reuse of the adsorbent shows that the adsorbent can be easily separated by using a magnetic magnet without any significant reduction in activity that can be used in successive metal ion adsorption-desorption cycles.

A novel, bis-salophen schiff base ligand anchored magnetic Fe3O4@SiO2 nanoparticles was prepared and applied for removal of Cu(II) from aqueous solutions. The obtained Fe3O4@SiO2/Schiff base MNPs was characterized by fourier transform infrared (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray analysis (EDX) and vibration sample magnetometry (VSM). Then, the adsorption activity for copper ions was studied by nonmagnetic, in terms of effect of adsorbent dosage on the adsorption and kinetics behavior. Furthermore, the adsorption and regeneration experiment showed there was about 5% loss in the adsorption capacity of the prepared Fe3O4@SiO2/Schiff base MNPs for copper ions after 6 times reuse. Finally, our results suggested that the Fe3O4@SiO2/Schiff base composites have a great potential to be employed for treatment of wastewater containing Cu(II).

Paper bleaching is a concern of many conservationists. Research has been conducted with the aim of evaluating some traditional bleaching materials used in the preservation of documents and books, such as hydrogen peroxide and sodium borohydride, which shows that these materials do not significantly improve the mechanical properties of historical papers. Also, investigating the effect of reducing agents on oxidized papers has shown the effectiveness of tert-butylamine borane complex. In another study, five dyeing processes with oxidizers (calcium hypochlorite, hydrogen peroxide in two concentrations, light bleaching and potassium permanganate) and two dyeing processes with reducing agents (sodium borohydride and tert-butylamine borane) were compared. And their effect on pure cellulose (Whatman filter paper) and two different historical papers have been investigated. The results indicate that all the tested dye removal methods have led to a clear increase. Due to the differences of opinion, in this research, the effectiveness of two reducing agents sodium borohydride and sodium dithionite on the appearance and structural characteristics of paper is investigated. In this research, Whatman Filter Paper No. 1 (Whatman Filter Paper No. 1) made in England with a thickness of 180 microns, a diameter of 11 cm, a base weight of 87 grams per square meter and an ash percentage of 0.06% was used. Chemical reagents including potassium persulfate, sodium borohydride and sodium dithionite in the highest purity were prepared in a laboratory from Merck, Germany.Three solutions including potassium persulfate (2% by weight/volume), sodium borohydride (1% by weight/volume), sodium dithionite (1% by weight/volume) in distilled water (distilled water, pH; 7), to perform tests on zinc. Paper samples have been used by immersion.Whatman filter paper samples were subjected to oxidation in 2% peta persulfate in distilled water for 2 days (48 hours) and then the samples were immersed. Next, the identified samples were modified by two solutions of sodium borohydride and sodium dithionite 1% in distilled water for 1 to 5 hours and then purified in holy water. Also, the samples were subjected to accelerated aging according to ASTM standard number D4714-96 at a temperature of 90±2 centigrade and a relative humidity of 50±2% for 384 hours. Test methods include potentiostat, colorimetry, tensile strength, pH measurement, scanning electron microscope and infrared examination. The results show that potassium persulfate is the most neutralizing solution among the three solutions used on the first day, and it also indicates the reducing power of two solutions of sodium dithionite and sodium borohydride, which according to the test results, sodium borohydride is the reducing power. Compared to sodium dithionite. The sample prepared with pH 92.3, after accelerated aging, was accompanied by an increase of several units of pH after modification with two reducing substances. Examining the data obtained from the tensile strength test shows that in comparison with the tested samples with a tensile index of 1.06, the samples modified with sodium borohydride and sodium dithionite increased the index in all five modified periods. Tensile of paper samples. The infrared spectrometry investigation of the samples modified with sodium borohydride and sodium dithione shows that this old material improves the structure of cellulose after aging by reviving the C=O bonds to C-O and reducing the area of 1640 cm-1. Accelerated. The reduction of the absorption band in the region of 1640 cm-1 has been opened in almost all time cases with this material compared to the modified sample. Based on the data, samples modified with sodium borohydride and sodium dithionite had a significant increase (approximately 25 units) in the L-factor (light-darkness) after aging, indicating that two substances have increased the brightness of the sample by reviving the color compounds. In the microscopic examination of the surface of the fibers, in the samples identified with potassium persulfate, local separation of the fibers is observed. In the samples modified with sodium borohydride and sodium dithionite, fibers with higher consistency and entanglement are observed. Double bonds and carbon groups in paper samples formed with potassium persulfate have been the main responsible for the yellowness and darkness of the paper, the reducing agents sodium borohydride and sodium dithionite reduce this aldehyde and ketone to hydrocarbon and as a result. With the loss of multiple conjugates, the light absorption of the paper is reduced and this causes the paper to lighten. The double bonds and their regeneration also cause rearrangement of the chain cells, which has resulted in increasing the mechanical resistance and strength of the paper samples.

Contamination of water and soil with heavy metals poses serious risks and threats to human health and the environment, and therefore finding an effective solution to remove these metals is very necessary. In this research, magnetic nanoparticles MnFe2O4 @ SiO2 functionalized with N-phosphonomethyl aminodiacetic acid with core-shell structure were synthesized. These nanoparticles were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, (TGA) thermal gravimetric analysis, transmission electron microscope (TEM), and (VSM) vibration sample magnetometer. The performance of this synthetic nanoadsorbent for removing Cr (VI), Cu (II) ions from aqueous solutions was evaluated by various parameters such as adsorbent amount, contact time effect on adsorption rate and pH effect. The results show that the adsorption efficiency increases with raising pH (2.5-5) and the best adsorbent performance in the adsorption process of Cr ((VI) and Cu (II) ions at pH 7 was observed. The amount of R in the Freundlich adsorption diagram of copper ion is higher than the Langmuir isotherm. As a result, the adsorption of copper ions on the adsorbent follows the Freundlich adsorption equation. In addition, the amount of R in the Freundlich adsorption diagram for chromium ion is higher than the Langmuir isotherm. Therefore, the absorption of chromium ions on the adsorbent follows the Freundlich adsorption equation. In conclusion, a high n value indicates a favorable and effective absorption in the Freundlich equation. The adsorption data were analyzed by the Langmuir and Freundlich isotherm model. In addition, the recyclability and reuse of the adsorbent was investigated. The results show that no significant reduction in adsorbent activity is observed.

The water of cooling tower for Shahid Moftah power plant is supplied from treated wastewater. Therefore, chemical control of water in order to control corrosion in this cycle is very complicated.

The results of the TBC (total bacteria count) test of cooling tower indicate the approximate number of bacterial colonies equal to 103 cfu/ml, which is in the light range. According to the microbial tests, the amount of TRB, IRB and APB bacteria is very high and has values ​​of 1200, 500-2300 and 105 cfu/ml, respectively. Using treated wastewater as a feed of cooling tower due to the presence of high concentration of calcium ions leads to intensification of sedimentation and increase the growth of microbial organism. Moreover, the presence of high nitrate is predictable due to the origin of water supply, which causes the increase of nitrate and nitrite reducing bacteria (NRB). On the other hand, the presence of high phosphate and sulfate in the sample increase sedimentation and intensify microbial growth, especially sulfate-reducing bacteria (SRB) in the sample.

As a result, high concentrations of TRB, IRB, and APB bacteria is required to be selectively removed in the first priority. In the second priority, nitrate and sulfate ions, which are food for NRB and SRB bacteria, need to be removed by selective removal of nitrate ions using ion exchange resins and sulfate with biological regeneration method. Due to the high level of microbial agents TRB, IRB and APB as well as the high concentration of microbial agents feed, as the third priority, methods based on non-oxidizing biocides needs to be applied in this power plant.

Lack of water is considered the most important threat to the survival of human beings and natural ecosystems. Food and energy security, health and industrial progress, which are the main components of the sustainable development of societies, depend on water more than anything else. Water consumption in Loshan power plant is 2600 L/MWh raw water, which is very high compared to the production capacity and is due to having a tower in its cooling system. Considering the high volume of water consumed in this power plant compared to the production efficiency and on the other hand, reducing the amount of rainfall and droughts that have occurred, it is necessary to provide a solution to modify the consumption pattern for this power plant. Considering the special position of this power plant, solutions to modify the water consumption pattern by recycling clean drains (blow down of boilers, back wash of sand filters and water sampling), purification and recycling the blow down of cooling towers into the water cycle and optimization of cooling towers (replacing drippers, replacing nozzles and optimizing water distribution to increase efficiency, using a rotating nozzle to increase the time and speed of the water droplets hitting the air in order to transfer more heat) are suggested. According to the experimental data, the conductivity of boiler blowdown is about 10 μs/cm and the expenses of recycling the blowdown of boiler by using heat exchanger is estimated about 324.425.000 Rials.

The corrosion and especially microbial corrosion in thermal power plants due to the frequent use of contaminated water sources has long been a source of economic problems, efficiency reduction, equipment and technical failure. The main reasons of these problems are a of existence of microbial organism in the water of cooling tower. In this work, the aim is to collect information on the microbial corrosion in the cooling water of Shahid Beheshti power plant of Lushan and to provide several solutions to reduce the occurrence of microbial corrosion Therefore, physicochemical properties, microbial tests and ion measurement are conducted in order to investigate the parameters affecting this phenomenon for the cooling tower of Shahid Beheshti power plant of Lushan. The microbial tests include the TBC test to measure the total number of bacteria (general test) and specific tests to measure specific bacteria such as APB, FP, IRB, NRB, Aero, SRB and TRB. Moreover, physicochemical parameters (pH, electrical conductivity, salinity percentage, hardness and water temperature), anions and cations are determined. It is observed that the calcium ion in the sample is in the range of high concentration (517 ppm) which leads to increase sedimentation and retention of water in the cooling cycle. On the other hand, the high concentration of sulfate (2126 ppm) causes the growth of SRB in the sample. For this purpose, it is very important to control and tackle these problems by applying sediment-forming and destructive microbial agents in the cycle. Common methods such as chlorination and ozonation are the first priority to deal with microbial corrosion in this power plant. Due to the high concentration of sulfate ions, it is suggested that selective removal of sulfate ions counts as a second priority. High concentration of calcium ion might be resolved by applying the chemical regimes in the clarifier such as adding CaOH, FeCl3 and coagulant and control and inhibit the microbial corrosion.

Here in this research a novel bis-salophen schiff base ligand anchored magnetic Fe3O4@SiO2 nanoparticles was prepared and applied for removal of Pb(II) from aqueous solutions. The obtained adsorbent Fe3O4@SiO2/Schiff base MNPs was characterized by using broad range of characterization techniques including fourier transform infrared (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray analysis (EDX) and vibration sample magnetometry (VSM). After synthesizing bis-salophen schiff base ligand immobilized on Fe3O4@SiO2 nanoparticles, the adsorption activity of this adsorbent for lead ions by nonmagnetic, in terms of effect of adsorbent dosage on the adsorption and kinetics behavior was investigated in detail. Furthermore, the adsorption and regeneration experiment showed there was about 91% in the adsorption capacity of the prepared Fe3O4@SiO2/Schiff base MNPs for lead. Finally, our results suggested that the Fe3O4@SiO2/Schiff base composites have a great potential to be employed for treatment of water and wastewater containing lead(II).

A novel ethylenediaminetetraacetic acid (EDTA) supported on Fe₃O₄@SiO₂ nanocomposite with a core-shell structure was developed, aiming to remove of copper ions from aqueous media. 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. Then, Fe3O4@SiO2 was coated with ethylenediaminetetraacetic acid. The properties of surface functional groups, crystal structure, magnetism and surface morphology of magnetic nanoparticles were characterized by 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) and vibration sample magnetometry (VSM). The effect of parameters influencing adsorption efficiency including adsorbent dosage and contact time of adsorbent on the sorption behavior was assessed and discussed. The adsorption kinetics studies of the novel adsorbent in removing copper ions from waste water showed that the maximum absorption amounts of Cu(П) were 95% at 25⁰C. Desorption and reusability of Fe₃O₄@SiO₂-EDTA was also investigated for tested copper ions based on sequential adsorption desorption cycles. Therefore, all the studied results indicated that Fe₃O₄@SiO₂-EDTA nanocomposites were an efficient and reusable adsorbent for removal of copper ions from aqueous solutions.

Pharmaceutical industries, due to the production of a wide range of drugs, have pharmaceutical effluents and wastewater in various types of synthetic, chemical, biological drugs, etc. The entry of these substances into the cycle of the environment and human life is extremely harmful and carries serious risks. Therefore, pharmaceutical wastewater treatment is of great importance in industry. There are various methods on an industrial scale to remove contaminants and pharmaceutical effluents, among them, electrochemical and oxidation-based methods are very suitable for industrial and medical applications due to technical-economic justification. In this study, the removal of contaminants in drug effluents was investigated using the oxidation process. In order to evaluate and determine the characteristics of high-consumption drugs (aspirin, atorvastatin, metformin, metronidazole, and ibuprofen), using a potentiostat device with a three-electrode cell, a cyclic voltammetric diagram with a 100 mV/s scanning rate was performed until the initial and peak conditions were reached. Oxidation of drug samples were evaluated. Then, using the chronoamperometry process (constant potential application), the drugs were subjected to an electrochemical oxidation process (using three-electrode cells), and the drug removal process was performed for insoluble and liquid samples. At the end of the chronoamperometry method (drug removal), the samples were again subjected to cyclic voltammetry test, and the level below the oxidation peaks of the sample was calculated and compared with the level below the initial peak, thus determining the removal efficiency of the sample (removal rate). The results indicate that this method has shown about 70% efficiency for removing selected drugs with a high removal efficiency and for the atorvastatin sample specifically, it was about 100%. It should be noted that the oxidation time of each drug varies according to the type of drug and the concentration of the drug under study. About 100 to 500 seconds seems to be enough to remove the drug in most cases. The oxidation potential of selected drugs is in the range of -0.8 V. Therefore, according to the results obtained, this method has high and sufficient accuracy (RSD about 2%).

In this study, magnetic nanoparticles of MnFe2O4@SiO2 activated with N-phosphonomethyl amino di-acetic acid were synthesized with a core-shell structure. Moreover, the characteristics of surface functional groups, crystal structure, magnetic properties, size and surface morphology of these nanoparticles were investigated by using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), microscope Scanning electrons (FESEM, Thermal Weight Analysis (TGA) and vibrating sample magnetometer(VSM). In this study, the antiscalant effect of precipitation for magnetic nanoparticles MnFe2O4@SiO2 were examined according to the reference test (NACE TM0374) by using 5 ppm MnFe2O4@SiO2. In this experiment, the precipitation effect of calcium sulfate and calcium carbonate on the surface of carbon steel was investigated. For this purpose, in one test a piece of carbon steel is placed in the presence of the precipitative compound and absence of antiscalant (control test) and in the other test of carbon steel is placed in precipitative compound with the antiscalant (main test) for a certain period of time. Afterwards, the amount of precipitation of the control and main experiment for carbon steel in the similar environment of the cooling tower of thermal power plants containing 1000 ppm sulfate and 500 ppm chloride were investigated. The tafel polarization test and impedance spectroscopy were used to measure the amount of fouling on the surface of the control and main carbon steel samples. The results indicate that the rate of precipitation formation is greatly reduced in the presence of antiscalant.

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.

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.

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.

Paper turns yellow over time. Bleaching with oxidizing agents is one of the most common methods, which creates a colorless result by breaking down the light-absorbing chromophores. In this research, the changes in the properties of paper by applying oxidizing agents are studied. The paper samples were characterized by colorimetric, infrared spectroscopy, tensile, acidity, and SEM microscopes. Four oxidizing solutions were deployed for whitening the samples of Whatman paper using the Immersion method, including Hydrogen Peroxide (2 % V/V), Sodium Peroxide (2 % W/V), Potassium Periodate (2 % W/V), and Potassium Persulphate (2 % W/V) all solved in distilled water. The samples were treated within 48 hours, and characterizing tests were deployed. The results show that hydrogen peroxide with the highest tensile strength (17.75 Nm/g) and the lowest color difference (∆E= 1.48) after accelerated aging has the best performance among other samples. Also, hydrogen peroxide can be improved tensile strength, increase brightness, reduce yellowing, cause fibers stability, and keep the paper at an almost neutral acidity.

In this study, EDTA-functionalized Fe3O4@SiO2 magnetic nanocomposites with core-shell structure were synthesized to remove divalent cadmium ions from aqueous solutions.

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.

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.