الفهرس 
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Abstract
The present study focused on introducing nano/micro structures for efficient removal of dye pollutants (Safranin, methylene blue, and Congo red dye) based on some natural minerals and solid wastes. Firstly natural bituminous coal was used in the fabrication of different modified forms including coal modified by nitric acid (N.Coal), coal coated by nano zinc oxide (Z.Coal) and porous graphite synthesized from the coal sample (PG). The formation of the three coal modified forms was confirmed by XRD analysis, FT-IR analysis, and SEM imaging. The analytical results reflected clear changing the structural properties, crystalline phases, chemical functional groups, and the morphological features. The adsorption properties of raw kaolinite and the modified products for efficient removal of safranin dye from water were addressed based on contact time, adsorbent mass, initial dye concentration, and pH value as the experimental parameters. At fixed operating conditions of pH8, 120min contact time, 0.1g adsorbents doses and 100mg/L dye concentration, the obtained removal percentages by PG, Z-cola, N-coal, and raw coal are 96%, 93.5%, 74.5% and 62%, respectively. This reflected the noticeable enhancement in the removal efficiency of safranin dye with the simple modifications of raw coal samples. Regarding the adsorption mechanism, the adsorption system for raw coal and the modified products are of chemical nature and represented mainly by pseudo-second-order than the other models. Additionally, the uptake occurs in a monolayer form and can be described by Langmuir models for all the studied products. The theoretical maximum adsorption capacities (qmax) were estimated based on Langmuir parameters and the values are 21.3, 27.4, 32.46, and 33.67 mg/g for raw coal, N-coal, Z-coal, and PG, respectively. Monolayer model with one energy and monolayer model with two energies as advanced equilibrium models were investigated for more physical interpretation of the adsorption process. The calculated parameters (number of adsorbed molecules per site and number of receptor sites per unit mass) reflected the role of modification processes in adsorption behavior of safranin.
Then novel composite from bentonite/Zeolite-NaP was synthesized for the first time from natural bentonite and confirmed by XRD, FT-IR, BET, SEM and ion exchange capacity. Composite was synthesized by alkaline treatment of bentonite at 150 oC for 4h and exhibits enhanced physiochemical properties of higher surface area and higher ion exchange capacity higher than the individual components of bentonite and zeolite-P. The composite exhibits nearly cubic zeolite-NaP crystals dispersed throughout bentonite aggregates. This composite shows 512 m2/g surface area, 387meq/100g cation exchange capacity, and 5.4 nm averages pore diameter. The composite shows high removal efficiency for methylene blue (94%) and Congo red dye (93%) after 720 min at an initial concentration of 5mg/L. The detected adsorption removal percentages reflected the great improvement in the adsorption capacity for both acidic Congo red dye and basic methylene blue dye as compared to bentonite and zeolite-P as individual components. The adsorption systems for the uptake of both Congo red dye and methylene blue dye are of chemical types and described based on the suggestion of pseudo-second order kinetic model. The equilibrium studies revealed fitting of the results with Langmuir model as well as the Freundlich model. The theoretical values for the maximum adsorption capacity for Congo red dye and methylene blue dye are 46.29mg/g and 36.26mg/g, respectively.
Additionally, the study involved evaluation of natural chromite mineral as cheap heterogenous catalyst for efficient photocatalytic degradation and photo-fenton,s oxidation of Congo red dye. Refined natural Fe-chromite was characterized by XRD, FT-IR, reflected polarized microscope, XRF and UV-vis spectrophotometer. Photocatalytic degradation and photo Fenton’s oxidation of Congo red dye by Fe-chromite was investigated using 1mL H2O2. The degradation of dye was studied as a function of illumination time, chromite mass, initial dye concentration, and pH. Fe-chromite acts as a binary oxide system from chromium oxide and ferrous oxide. Thus, it exhibits photocatalytic properties under UV illumination and photo Fenton’s oxidation after addition of H2O2. The degradation in the presence of H2O2 reached the equilibrium stage after 8hours (59.4%) but in the absence of H2O2 continued to 12h (54.6%). Photocatalytic degradation results fitted well with zero, first order and second order kinetic model but it represented by second-order rather than by the other models. While the photo Fenton’s oxidation shows medium fitting with the second-order kinetic model only. The values of kinetic rate constants for the photo-Fenton oxidation were greater than those for the photocatalytic degradation. Thus, degradation of Congo red dye using chromite as a catalyst is of better efficieny in the photo Fenton’s oxidation pocess. Based on the response surface analysis, the predicted optimal conditions for maximum removal of Congo red dye by photocatalytic degradation (100%) were 12mg/L, 0.14g, 3, and 11h for dye concentration, chromite mass, pH, and illumination time, respectively. Whereas, the optimum condition for photo-Fenton oxidation of dye (100%) are13.5 mg/L, 0.10g, 4, and 10h, respectively.
Chapter four in this study involved recycling of rice husk in the production of advanced type from modified porous graphite of nitrogen functional groups. Mesoporous graphitic carbon (PG) was successfully synthesized from alkaline treated rice husk ash through chemical activation by phosphoric acid at 800 oC for 1h and modified by nitric acid to produce porous graphite with nitrogen functional group (N.PG). The morphology and structure of N.PGC were characterized by XRD, SEM and Micromeritics ASAP2010 analyzer at 77 K. N.PG was applied as an adsorbent material for safranin-O dye from aqueous solution. The removal of safranin dye by the synthetic porous graphite with nitrogen functional groups shows higher capacity as compared to the pure phase of porous graphite. The adsorption process was investigated as a function of contact time, adsorbent mass, pH, initial dye concentration and ionic strength. The kinetic studies revealed that the adsorption equilibrium was reached after 480 min and the obtained data well fitted with the pseudo-second-order kinetic model and Elovich kinetic model. The equilibrium adsorption isotherm of safranin by the synthetic N.PG was described with Langmuir isotherm model, and the calculated qmax is 20.66 mg/g. The removal process is highly dependent on the pH value of the solution, and the optimum pH for maximum removal of safranin-O is pH 6. The response surface methodology (RSM) in conjunction with the central composite rotatable design (CCRD) was used to optimize the sorption process. from the second order polynomial model, the predicted optimum conditions for maximum removal of safranin (100%) are 365 min contact time, 0.3g dose, 5g/L NaCl and pH 6 at initial concentration 127 mg/L.
Chapter six in the thesis focus on recycling of silica fume into advanced mesoporous silica MCM-41 and using it as support for nickel oxide to enhance its adsorption and photocatalytic properties for efficient removal of Congo red dye. Mesoporous silica MCM-48 was synthesized from silica fume solid wastes by hydrothermal methods and loaded by nickel oxide; and the resulted composite was characterized using X-ray diffraction, scanning electron microscopy and UV-Vis spectrophotometer. The loading of Ni2O3 resulted in considerable reduction in the band gap energy to 2.4eV. The role of MCM-48 as catalyst support for Ni2O3 in enhancing the adsorption capacity and photocatalytic properties of nickel oxide was evaluated through a series of equilibrium studies and photocatalytic degradation of Congo red dye under visible light. The photocatalytic degradation experiments were investigated as a function of illumination time, dye concentration, catalyst mass, and solution pH. Silica fume based MCM-48 as catalyst support for Ni2O3 cause enhancing in the adsorption capacity by 32.2% and 17.5% higher than the adsorption capacity of Ni2O3 and MCM-48, respectively. Also, the photocatalytic degradation percentage increased by about 68.2% relative to the degradation percentage using Ni2O3 as a single component. The adsorption mechanism of MCM-48/Ni2O3 is chemisorption and occurs in multilayer form throughout the heterogeneous surface. The adsorption data described well with Freundlich equilibrium model and the results concordant with the nature of the composite (MCM-48/Ni2O3). The using of MCM-48 as support for Ni2O3 photocatalyst enhanced the adsorption capacity through increasing the surface area and prevents the nickel oxide particles from agglomeration. This through fixing such particles throughout the structure of MCM-41which provides more exposed active adsorption sites and active photocatalyst sites for the incident photons. Based on the obtained results, supporting of nickel oxide particles onto MCM-48 are promising active centers for the degradation of Congo red dye molecules.