الفهرس 
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Abstract
Minimizing adverse effect of generation more industrial wastes and their management on the human health and environment, as well as to save the natural mineral resources has become a necessity.
Thus, the hazardous aluminum waste is used to prepare zeolite as an added-value material of great industrial interest. The prepared zeolite is used as adsorbents for removal of heavy metals from electroplating waste.
Synthesis of pure zeolite Nap was studied. It can be controlled by changing different factors such as Si/Al ratio, crystallization temperature and crystallization time. Synthetic solutions of different ratios of Si/Al ratio were applied to achieve the optimum conditions for preparation of pure phase of zeolite Nap.
The same zeolite was prepared from industrial wastes using the obtained optimum conditions for pure chemicals. To our knowledge, there is no information available about application of the industrial hazardous aluminium waste as a raw material for the synthesis of zeolite.
This work includes the development of the following:
Synthesis of zeolite NaP from synthetic solution of sodium silicate and sodium aluminate at different Si/Al ratios (0.5, 0.6, 0.8 and 1.2).
Lab-scale hydrothermal synthesis and characterization of zeolites synthesis from pure chemicals.
Characterization of aluminum wastes.
Applying the optimum preparation conditions to prepare zeolite from industrial wastes.
Lab-scale hydrothermal synthesis and characterization of zeolites from industrial aluminium and silicon wastes.
Exploring zeolites, whether it is prepared from chemicals or from waste as adsorbents for heavy metal ions from synthetic solution contain copper and nickel.
Investigation of zeolite performance for treatment of the electroplating effluents which contain copper and nickel.
The thesis can be classified into three parts:
Synthesis of zeolite from pure chemicals
In this part, different factors which affect the zeolite synthesis such as crystallization time and temperature as well as Si/Al ratio were studied. So, preparation of zeolite from sodium silicate (water glass) and sodium aluminate at different molar ratios 0.5, 0.6, 0.8 and 1.2; at different crystallization time 24, 48, 72 h and different crystallization temperature 100, 120 and 150 C was studied. A pure zeolite Nap with high crystallinity is obtained at molar ratio of 1.2. The product is characterized using XRD, SEM, EDX, FTIR, surface area and thermal analysis.
The XRD pattern shows that the prepared NaP zeolite at crystallization temperature of 120 C and after 48 and 72 h has high crystallinity. Traces of mordenite were detected beside zeolite Nap at crystallization temperature of 150 C and 72 h.
SEM results show a formation of zeolite NaP with multi-faced plate shape. EDX results show that the Si/Al ratio at different area is almost similar to NaP zeolite. Also, FTIR showed the strong vibration bands characteristic to T-O (T= Al or Si) at 1015 and 420-500 cm1. The FTIR spectrum of NaP Zeolite matches the reported infrared spectral data for zeolite P. Strong vibration and broad band at around 1000 cm1 was assigned to the asymmetric stretch for tetrahedral T-O-T. Another intense sharp peak occurs at 435 cm1 which is related to T-O bending mode. The peak at about 600-780 cm1 is attributed to the symmetric stretch vibration of internal tetrahedron. The characteristic peaks of hydrate water in the solid phase are occurred at 3434 and 1641 cm1. TGA and DSC curves show that the water desorption is occurred in two steps. At temperature below 100 °C, the weight loss is due to the removal of physically adsorbed water from external surface; while it is corresponding to desorption of water from the pores above 100 °C.
Synthesis of zeolite from solid aluminium and silicon industrial wastes
The second part includes the applying molar ratio of 1.2 as the optimum molar ratio for preparation of zeolite from solid aluminum waste and fumed silica to form sodium aluminate and sodium silicate at crystallization temperature 150, 120 and 100 C and 72, 48 and 24 h. Pure zeolite Nap with high crystallinity was obtained crystallization temperature 120 C and crystallization time 48 and 72 h.
By increasing temperature up to 150 C at 24, 48 and 72 h; pure zeolite Nap with high crystallinity was obtained. The XRD results confirmed the formation of same zeolite as that formed from pure chemicals but without any impurities. SEM ensure the presence of zeolite NaP only with multi-faceted shape consist of “cauliflower-like”. EDX results show that the Si/Al molar ratio at different area is almost similar to NaP zeolite.
DSC showed that the first event in the temperature range of 25-200 C. The strongest endothermic peaks at about 85 C are described to losses of adsorbed water. The corresponding weight loss is about 6 % up to 200 C while the second event at 200-400 C. The weight loss is about 4 %, which is attributed to the removal of hydroxyl groups. There are weak endothermic peaks, which are not connected with weight losses. These are related to phase transformation. FTIR results show the characteristic bands of zeolite P are appeared at 120 and 150 C for all crystallization time. Bands frequencies near 1000 cm–1 is attributed to asymmetric stretching of bonds Si-O or Al-O. These bands are close to1000 cm1 for Si-O-Al bond of the tetrahedron TO4 and confirm the presence of zeolitic material. The symmetric stretching vibrations of zeolite NaP framework structure of Si-O and Al-O were noticed at, 669, 740 cm1. Also, the vibration band at 420 cm1 region is assigned to a Si-O or Al-O bending mode.
Applications as adsorbents for heavy metal ions
In this part, the performance of zeolite NaP as adsorbent for heavy metal ions was investigated. Synthetic solutions of copper and nickel ions were used for simulation the electroplating waste. The affecting parameters such as pH, time, concentration, zeolite dose and temperature were studied.
The maximum sorption capacities and removal efficiency of zeolite is achieved at pH 6. The sorption capacities of chemically zeolite for nickel and copper ions are 57.5 and 14.4 mg/g, while it is 52.7 and 13.9 mg/g for waste zeolite. selectivity of zeolite follows the order of Cu2+ > Ni2+. It can be concluded that the hydration energy, the charge density (ratio of charge/ionic radius) and the dimensions of the hydrated ions provide an indication of the mineral’s preference for different metal ions during competitive adsorption.
The removal efficiency is reached to 15 % and 11 % for Cu2+ and Ni2+ at equilibrium time 40 and 60 min; with maximum adsorption capacity of 78 and 58 mg/g by chemically zeolite and 66 and 45 mg/g by waste zeolite. The pseudo-second-order model is better describing adsorption kinetics of heavy metal ions by zeolite.
Different concentrations for copper (10-100 ppm) and nickel ions (100-500 ppm) were studied at zeolite dose of 0.05 g/25 ml (2g/L), at pH = 5, Temperature 25 C, Time = 60 min. The maximum adsorption capacity for copper and nickel of chemically zeolite is 20.0 and 51 mg/g; while it is 18 and 46 mg/g of waste zeolite.
For both Nickel and Copper ions adsorption processes the results fit well by Freundlich model with a little better than that by Langmuir model. It means that both ion exchange adsorptions affect the adsorption process.
The increasing of the zeolite dose led to increase adsorption capacity and removal efficiency. The removal efficiency for chemically zeolite is reached to about 99.2 % and 93.6 % for Cu2+ and Ni2+, while it is 97 % and 90 % for waste zeolite. The adsorption capacity for Copper and Nickel are 3 and 23 mg/g, while it is 2 and 22 mg/g for waste zeolite.
The thermodynamic study showed that the value of enthalpy change (ΔH) is 37.7 and 39.8 kJ/mol for nickel ions adsorption process by chemically and waste zeolites, respectively. On the other hand, the value of ΔH° is 14.9 and 15.7 kJ/mol for copper ions adsorption process by chemically and waste zeolites, respectively. It suggests that the reaction is endothermic and their values are lower than (40 kJ/mol) indicating the physically controlled process.
The positive value of entropy change (ΔS) for all systems indicates the increase of randomness at the solid/liquid interface during the adsorption. It indicated the adsorption is more favorable at higher temperatures.
The free energy change (ΔG) values at lower temperature are positive. It indicates that the adsorption process is not spontaneous in nature whereby energy input from outside of the system is required. On the other hand, they are negative at higher temperature up to 65 C which indicates that this adsorption process is spontaneous at in nature whereby energy input from outside of the system is not required.
Employing the zeolites for electroplating effluent treatment showed that the maximum sorption capacities of nickel and copper ions from synthetic solution and wastewater that contain approximately the same concentrations are 153 and 68 mg/g for Nickel, and 15 and 5.9 mg/g for copper. The maximum sorption for synthetic zeolite from wastes is reduced to 60 and 5.36 for nickel and copper ions, respectively. It is noticeable that the higher absorption capacity for nickel compared to copper, is due to the initial concentration of nickel is ten times the copper.