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The electronic and magnetic properties of armchair-hexagonal (AHEX) and zigzag-triangular (ZTRI) graphene quantum dots doped with alkali metals are investigated using density functional theory. The binding energy confirms the stability of the undoped systems. Although doping decreases stability of single layer structures, in bilayer ones the binding energy between the layers increases. The former is due to the broken bonds and the deformation at the surface, while the later is due to the chemical bonds formation between the layers. We found that the lowest ground state energy for AHEX/AHEX-doped is the singlet/quadruplet spin state. Therefore, AHEX dots experience transformation from diamagnetic to ferromagnetic state after doping. In addition, the optimized spin state for ZTRI/ZTRI-doped is the quintet/sextet spin-polarized state. In few cases, the doped AHEX/ZTRI dots have doublet/quadruplet spin state due to the strong interaction between the flake atoms that passivates some unpaired electrons. Magnetic properties depend also on stacking, for instance pristine bilayer triangular flakes become antiferromagnetic due to pairing between edge states. The energy gap significantly affected by doping, for instance the gap decreases from ~3.7 eV in hexagonal flakes to 1.5 eV when it is doped with Na in the upper position. Electrons from the broken bonds around the doped metal form orbitals loosely bound to the flake consequently decreasing the energy gap. On the other hand, stacking increases the energy gap in bilayer triangular flakes due to the mutual passivation of the reactive edge states from both the layers. The calculated spin up/down density ratio is high in hexagonal flakes leading to high spin polarization (P), for instance P = 0.64 in hexagonal flakes doped with K atom. The found enhanced spin polarization, in addition to the tunable magnetic properties, makes doped graphene flakes promising candidates for spintronic devices.

Sustainable development with environmental protection is one of the greatest challenges of the 21st century. There is a growing consideration of the sustainable development and environmental management in new industrial cities. Investigational aspects were carried out in El Obour city as Egyptian new industrial city for estimating the current wastewater problems as well as applying mitigation actions. Industrial inventory was constructed for selected industrial sectors as food, chemical and textile sectors including water consumption, materials and energy resources. Wastewater samples from different factories and lifting stations were analyzed for estimating the industrial effluent loads. The obtained data revealed that food sector represents the highest load for BOD and TSS with values of 80 ton BOD/day and 2.33 ton SS/day. For selected industrial sectors, cost-effective technology is applied to reduce the loads on the centralized wastewater treatment plant (WWTP) as well as on the lifting stations. Inorganic polymeric ferric chloride (POFC) coagulant gives higher removal efficiency for TSS and COD without pH control. Moreover, the chemicals cost for treating wastewater is reduced by 40 % with using POFC instead of conventional coagulants.

Zirconia (ZrO2) is a noteworthy metal oxide because of its characteristics. It can be implemented in different applications; adsorption of pollutant, and photocatalytic oxidation. The main focus of this research was to synthesize ZrO2 from low cost and locally available materials; zircon. As well the preparation of ZrO2 was conducted at different temperature procedures. Characterization of prepared materials was performed using X-ray diffraction (XRD), Fourier transform infrared spectra (FTIR) and scanning electron microscope (SEM) which confirmed the production of homogeneous spherical crystalline ZrO2 compared with commercial ZrO2. Moreover, ZrO2-500 was examined for removal of dye using adsorption and photocatalytic activities. The removal adsorptive capacity of ZrO2-500 for red dye 195 was decreased from 37.1 to 2.2 mg/g with increasing dose up to 3 g/L. Meanwhile, red dye was removed with rate constant of 0.132 - 0.324 h-1 under solar simulator. Finally, zirconia was successively prepared from low cost materials with lower energy and materials consumption.

Pomegranate peel waste was milled using ball milling to get particles of size of 90 μm and used for adsorption of toxic pollutants. The response surface methodology was used for modeling of the adsorption capacity of copper ions and C.I. Reactive Yellow 145 (3RS) from wastewater using ball-milled pomegranate peel (BMPP). The predicted removal capacities obtained from the model are in a good agreement within the experimental results with correlation regression of 0.94 for dye adsorption and 0.92 for metal adsorption. The maximum removal capacity over adsorbent biomass is expected to be 209.7103 mg g − 1 for dye and 103 mg g − 1 for metal at optimal values of the independent variables. The analogue experimental results are 224 mg g − 1 for dye and 106 mg g − 1 for metal. Conclusively, the obtained results confirm the applicability of used model for predicting the adsorptive capacity of ball-milled pomegranate peel of dye and metals. As well ball-milled pomegranate peel is considering a powerful, cost effective and anionic/cationic adsorbent for decontamination of wastewater.

The electronic and adsorption properties of chevron and cove-edged graphene nanoribbons (GNRs) are studied using first principles calculations. The positive binding and adsorption energies in conjunction with the positive infrared frequencies insure the stability of the considered GNRs. The results show that the binding strength of coved-edged GNRs is higher than that of chevron ones because the morphology of the latter requires a higher number of C-atoms at the edges than the former. The edge atoms in chevron GNRs create interactive edge states that significantly decreases the energy gap (Eg = 0.03 eV) with respect to the wide gap between bulk states in cove-edged ones (Eg = 2.19 eV). The molecular orbitals distributions of these edge states are localized only on the arms of the nanoribbon making it a potential topological insulator. The energy gap between bulk states in cove-edged decreases by increasing the width due to quantum size effect, while in chevron GNRs the gap between edge states increases because of the interaction among these states. The adsorption of methylene blue shows interesting properties depending on the type of the nanoribbons, the interaction position, and the attached chemical group. The interactive edge states provide moderate adsorption on the arms of the nanoribbons and the attached chemical groups enhance the adsorption by adding new adsorption positions. The additional molecular orbitals from the physically adsorbed dye lower the band gap and create semimetal GNRs with zero or negative band gap.