الفهرس 
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Abstract
Industrial and technological development contributed to the increase in the environmental pollution, which negatively affected organisms and their surrounding sources of life. Environmental pollution is no longer a local issue and reducing environmental pollution is a global demand. The sulfur oxides emitted from car engines and factories are one of these pollutants that have many harmful effects on the environment. The main cause of these emissions is the presence of sulfur compounds in the fuel. When fuel is burned to produce energy and run all engines, from car engines to factory engines, sulfur compounds oxidize, which leads to emissions of sulfur oxides. Their presence in the air is a cause of many respiratory diseases, asthma attacks, and heart diseases as well. Also, when it interacts with rainwater, it produces sulfuric acid, which makes rain acidic, causing the death of plants and marine and terrestrial organisms. They also harm industrial processes by deactivating catalysts used in refining and by causing rust or corrosion of the metals used to construct pipelines for transferring petroleum. Therefore, sulfur compounds pose a threat to the environment, and the production of clean, sulfur-free fuel has become a goal that all countries seek.
In this work, fluids containing nanoparticles will be prepared in a cheap and safe manner. The availability of inexpensive and cost-effective materials, as well as their high adsorption efficiency, favours the use of these nanoparticles over traditional methods of removing sulphur compounds.
This study is divided into three chapters
Chapter I: Introduction and literature review: This chapter includes a general introduction to the harmful effects of the sulfur compounds present in fuels; their origin in the fuel, the methods used to remove them; the adsorption method in detail; and a list of solid adsorbents that were used in the research. This chapter also includes a general introduction to nanofuids and their properties, and a presentation of some chemical and biological methods for their preparation, as well as a narration of the reasons for choosing the fluid of silver, gold, and nickel nanoparticles.
Chapter II: This chapter includes the method of preparing nanofluid samples of silver, gold, and nickel and removing thiophene using these nanofluids as follows:
Preparation of nanofluids:
A- Preparation of silver nanofluids:
1- Under the influence of microwave irradiation, four concentrations of silver nanoparticles (T1, T2, T3, T4) were prepared by adding silver nitrate solution (0.313, 0.625, 1.250, and 2.500 mmol) to different concentrations of tannic acid (0.0156, 0.03125, 0.0625, and 0.125 mmol) with a fixed molar ratio of 1 mole of tannic acid to 20 moles of silver nitrate.
2- To track the effect of tannic acid, four concentrations of tannic acid (0.01563, 0.03125, 0.0625, 0.125, and 0.1563 mmol) were added in four separate experiments, respectively, to 0.3125 mmol of silver nitrate solution under the influence of microwave radiation.
3- To track the effect of PH, 0.01563 mmol of tannic acid was added to 0.3125 mmol of silver nitrate solution at different PH numbers (3, 4, 5, 6, 7, and 8) and then exposed to microwave radiation.
B- Preparation of gold nanofluids:
1- Five concentrations of gold nanoparticles (T1, T2, T3, T4, T5) were prepared by adding gold salt solution (0.0235, 0.047, 0.094, 0.188, and 0.375 mmol) to different concentrations of tannic acid (0.0156, 0.03125, 0.0625, and 0.125 mmol) with the fixed molar ratio ( 1 mole of tannic acid to 6.6 moles of gold chloride salt solution).
2- To track the effect of tannic acid, four concentrations of tannic acid (0.047, 0.094, 0.188, 0.375, and 0.75 mmol) were added in five separate experiments, respectively, to 0.3125 mmol of gold chloride salt solution.
3- To track the PH effect, 0.047 mmol of tannic acid was added to 0.3125 mmol of silver nitrate solution at different PH numbers (3, 4, 5, 6, 7, and 8).
C- Preparation of nickel nanofluids:
1- Under the influence of microwave radiation, six concentrations of nickel nanoparticles (N1,N2,N3,N4,N5,N6) were prepared by adding nickel chloride solution (1.25, 1.88, 2.5, 3.125, 3.75, and 4.375 mmol) to different concentrations of hydrazine (5, 7.5, 10, 12.5, 15, and 16.25 mmol) respectively, with the molar ratio fixed: 4 moles of hydrazine to 1 mole of nickel chloride salt solution and PH 12.5.
2- The sample N1 of nickel nanoparticles was subjected to ultrasonic irradiation at different times to follow the effect of ultrasonic on the dispersion of nickel nanoparticles.
3- For follow up the effect of tannic acid on the nickel nanofluid stability, 0.5 ml of 0.1M tannic acid was added to the reaction (1.25mM NiCl2 + 5mM hydrazine) in two ways: 1- Before exposure to microwave power and nickel nanoparticle formation (during synthesis process). 2- After exposure to microwave power and nickel nanoparticle formation (during ultrasonic).
Adsorptive desulfurization using nanofluids:
A- Adsorptive desulfurization using silver nanofluid:
1- To study the relationship between the stability of nanofluid and reactivity toward thiophene removal, the stabilized water-based silver nanofluid which synthesized at PH 8 (15 ml, 0.033 g/L Ag) was mixed with 500 ppm thiophene (1 ml) using the bench top vortex for 30 min.
2- The water-based silver nanofluid that synthesized at PH 3 (15 ml, 0.033 g/L Ag) was mixed with 500ppm thiophene (1 ml) using the benchtop vortex for 30 min for a different aging time of silver nanoparticles (2, 3,4, 5, 6, 8,10,12, 24, 48hours from the synthesis) in separate experiments.
3- To investigate the effect of silver nanoparticles concentrations, different volumes of silver nanofluid (kept for 4 hours growth time firstly) 0.5 to 15 ml (0.0011 - 0.033 g/L Silver) were mixed with a constant volume of a fixed thiophene concentration, 500 ppm at room temperature.
4- For kinetic experiments, silver nanoparticle (corresponding to 0.033 g/L Ag) was added to 500 ppm thiophene and vigorously mixed for different times 1- 60 minutes. For adsorption isotherm experiment, different concentration of thiophene was vigorously mixed with the fluid of silver nanoparticles (corresponding to 0.033 g/L Ag) for an hour.
5- For selectivity study, silver nanoparticle (corresponding to 0.033 g/L Ag) was vortex mixed with mixture of 3 sulfur compounds (100 ppm Thiophene, 100 ppm DBT and 100 ppm DMDBT) as a model diesel fuel. The concentration of thiophene, DBT and DMDBT were analyzed by HPLC chromatograph.
B- Adsorptive desulfurization using gold nanofluid:
1- To examine the relationship between the stability of gold nanofluid and reactivity toward thiophene removal, The stabilized water-based gold nanofluid which synthesized at PH 8 (15 ml, 0.03 g/L Au) was mixed with 500 ppm thiophene (1 ml) using the benchtop vortex for 30 min.
2- the water-based gold nanofluid that synthesized at PH 3 (15 ml, 0.03 g/L Au) was mixed with 500ppm thiophene using the benchtop vortex for 30 min.
3- To follow the effect of gold nanoparticles concentration in the fluid on the adsorptive desulfurization, two concentrations of gold nanoparticles (0.03 g/L Au &0.06 g/L) would be studied.
C- Adsorptive desulfurization using nickel nanofluid:
1- To examine the relationship between the stability of the nickel nanoliquid dispersion and the reaction toward the removal of thiophene, four samples of nickel nanofluids were mixed with 500 ppm of thiophene for 30 minutes in separate experiments.
Four nickel nanofluids (15ml, 0.033 g/L Ni) samples:
• The nickel nanofluid which synthesized without sonication after synthesis.
• The nickel nanofluid which synthesized with 1hour sonication after synthesis.
• The nickel nanofluid which synthesized with addition of tannic acid as stabilizer during sonication.
• The nickel nanofluid which synthesized with addition of tannic acid as stabilizer during synthesis.
2- To investigate the effect of nickel nanoparticles concentrations, different volumes of nickel nanofluid (1 hour sonication firstly) 5 to 15 ml (0.024- 0.073 g/L Ni) were mixed with a constant volume of a fixed thiophene concentration, 500 ppm at room temperature.
3- For kinetic experiments, nickel nanoparticles (15 ml, 0.073 g/L Ni) were added to 500 ppm thiophene and vigorously mixed for different times 1- 60 minutes.
4- For adsorption isotherm experiment, different concentration of thiophene was vigorously mixed with the fluid of nickel nanoparticles (15 ml, 0.073 g/L Ni) for an hour.
5- For selectivity study, nickel nanoparticles (corresponding to 0.073 g/L Ni) were vortex mixed with mixture of 3 sulfur compounds (100 ppm Thiophene, 100 ppm DBT and 100 ppm DMDBT) as a model diesel fuel.
Analytical instruments:
1- UV–visible spectral analysis.
2- Transmission electron microscopy (HR-TEM).
3- X-Ray Diffraction.
4- Dynamic Light Scattering.
5- Field Emission Scanning Electron microscope.
6- Dispersive Raman spectroscopy analysis.
7- High performance liquid chromatography.
Chapter III: This chapter includes the presentation and discussion of the results in detail. It is divided into three sections as follows:
Section I represent using of silver nanofluid as adsorbent for sulfur compound as thiophene and we found that:
1- Tannic acid was act as green reducing agent which able to convert Ag+ to Ag nanoparticles under the effect of microwave power. Also, it used as stabilizing agent.
2- The total concentration went up from diluted nanofluid T1 to concentrated nanofluid T4 accompanied by a shift in the λmax from 402nm to 456 nm. This red-shift is considered as a result of icrease of the silver nanoparticles size. This result was confirmed by electron microscopy measurements and dynamic light scattering (DLS) analysis.
3- The increased TA concentrations leading to slow nucleations and accordingly larger particles size with a higher extent of polydispersity. This was due to the stronger ability of tannic acid to form complexes with silver ions.
4- A PH of the reaction media has an important effect on the size and stability of the silver nanoparticles. The absorbance increased with increasing PH with blue shift indicating decrease in the size of silver nanoparticles. This result was confirmed by TEM images and DLS results. Also, increasing the alkalinity of the media cause increase zeta potential and so on the stability of the nanoparticles. Therefore, the Turbidity appears after 3 days, and sedimentation occurred within one week in all samples except nanofluid with alkaline PH (PH8).
5- the nucleation and the growth of silver nanoparticles in an acidic medium follow Finke–Watzky (F-W) model.
6- There was an inverse relationship between stability of the silver nanoparticles and adsorption reactivity. The stabilization method completely isolated the nanoparticles from each other and from the external environment so it makes them inert and ineffective.
7- The best adsorption to thiophene (88.4%) occurred for silver nanoparticles of 8.3±4 nm that corresponding to 4 hours aging from the synthesis in the acidic medium.
8- The adsorption mechanism was studied thoroughly.
9- The highest adsorption capacity (5.78 mg/mg) was observed for 0.0011 g/L silver.
10- the adsorption of thiophene onto silver nanoparticles is greatly fitted with the pseudo-second-order kinetic model. This indicates that the concentration of both adsorbent and adsorbate are involved in the rate determining step and the adsorption process is chemisorption.
11- The adsorption of thiophene from model oil is described better by langmuir isotherm model.
12- the adsorption capacity was in the order of dibenzothiophene (0.183mg/mg) >thiophene (0.142) > 4,6 dimethyle dibenzothiophene (0.039 mg/mg).
Section II represent using of gold nanofluid as adsorbent for sulfur compound as thiophene and we found that:
1- Tannic acid was act as green reducing agent which able to convert Au+3 to Au0 nanoparticles without microwave irradiation. Also, it is used as stabilizing agent for the gold nanoparticles.
2- Increasing the total concentration (while maintaining the same molar ratio 3 tannic acid: 20 gold molecules) from the dilute nanofluid T1 to the concentrated nanofluid T5 accompanied by a shift in the wavelength λmax from 526 nm to 536 nm. This red shift is a result of increase the size of the gold nanoparticles. This result was confirmed by electron microscopy measurements and dynamic light scattering (DLS) analysis.
3- Increasing the concentrations of tannic acid leads to increasing the speed of the reduction process and thus the small size of the formed gold nanoparticles. It differs here from silver because there is no possibility of forming compounds between tannic acid and gold ions. This is due to the fact that the reduction potential of gold is higher than that of silver.
4- The gold nanofluid that prepared in mild alkaline PH (PH 8) was failed in the thiophene adsorption. This was mainly due to the capsulation of the gold nanoparticles inside a shell of poly thiophene which hinder the access of thiophene to the nanoparticles surface.
5- Unfortunately, although the gold nanoparticles were better than silver nanoparticles in thiophene adsorption, they were not applicable for removal of thiophene and sulfur compounds due to formation of stabilized emulsion that difficult to be separated.
Section III represent using of nickel nanofluid as adsorbent for sulfur compound as thiophene and we found that:
1- Hydrazine was used as a strong reducing agent capable of converting Ni+2 to Ni0 under microwave irradiation. Ethylene glycol was also used as a stabilizer for the formed nanoparticles.
2- The nickel nanoparticles have magnetic properties, so the particles quickly collect together forming clusters. Therefore, by increasing the concentration of nanoparticles, the size of the clusters increased and the dispersion stability decreased. This result was confirmed by TEM and DLS.
3- Ultrasonic vibration led to dispersion of the nickel nanoparticles in the base fluid (ethylene glycol).
4- Tannic acid was added to enhance the nickel nanofluid stability. when the tannic acid was added during synthesis, the size become larger with bad morphology. On the other hand, the size and morphology of nickel nanofluid remain constant with good dispersion when the tannic acid was added during sonication.
5- The mixing of nickel nanofluid containing 0.073 g/L Ni with thiophene caused the removal of 83 % from thiophene.
6- The adsorption mechanism was studied thoroughly.
7- the adsorption of thiophene onto nickel nanoparticles is greatly fitted with the pseudo-second-order kinetic model. This indicates that the concentration of both adsorbent and adsorbate are involved in the rate determining step and the adsorption process is chemisorption.
8- The adsorption of thiophene from model oil is described better by langmuir isotherm model.
9- The adsorption capacity was in the order of dibenzothiophene (0.081mg/mg) >thiophene (0.057) > 4,6 dimethyle dibenzothiophene(0.008 mg/mg).
X- Ray diffraction pattern was used to identify and know the purity of the formed nanoparticles. XRD pattern indicate that the three synthesized nanoparticles (gold, nickel and silver) are face centered-cubic (fcc)
In conclusion, silver nanofluids give higher efficiency than nickel nanoparticles in thiophene adsorption. Unfortunately, the gold nanofluid was not viable for removing thiophene due to the formation of a stable emulsion that is difficult to separate.