Hassan Abdelfattah Metwally

Hydroxyapatite (HA) was successfully synthesized from oyster shell waste using a wet chemical precipitation method under magnetic stirring at varying durations (30 min, 1, 3, and 5 h). The synthesized HA samples were characterized to identify their crystalline structure, morphology, elemental composition, and functional groups. The results indicated that stirring time significantly influenced the phase purity and crystallinity of HA. Samples stirred for 30 min and 1 hour exhibited incomplete conversion, retaining traces of CaO, whereas those stirred for 3–5 h demonstrated complete transformation of CaO into hydroxyapatite with enhanced crystallinity and a well-defined apatite structure. The average crystallite and particle size of the prepared HAp at 3 h of stirring time were 18 and 34 ± 0.7nm, respectively. The synthesized HAp at 3-hour stirring time was then successfully applied for the adsorptive removal of Brilliant Black dye from aqueous solutions. To identify the optimal conditions, key parameters (initial concentration, pH, adsorbent dosage, and time) were tuned with a Box-Behnken design, which is part of the response surface methodology (RSM). In each experiment, a predetermined quantity of adsorbent was introduced into a brilliant black dye solution, where the pH was carefully adjusted using 0.1 M HCl or 0.1 M NaOH. The prepared mixtures were stirred for a predetermined time at room temperature, then centrifuged at 5000 rpm for 10 min. The results indicated that hydroxyapatite has a stronger adsorption capacity for brilliant black dye in aqueous solutions than calcite. The maximum adsorption of Brilliant black dye was obtained at the following optimized conditions of 62 min contact time, pH=5, 20 mg/L concentration, 0.045 g dosage and the maximum adsorption capacities obtained at these conditions is 93.52 %. Isotherm studies showed that the adsorption process followed the Languir model, as it is a strong fit for the experimental data.

Background: Copper, an important trace element for life on Earth, is crucial to many metabolic processes. This includes its role in the production and breakdown of nucleic acids and the metabolism of proteins, lipids, and carbohydrates. Objective: We aim to integrate DLLME with a spectrophotometric method to establish a novel approach for quantifying trace amounts of copper in water samples. Methods: In this study, a new ligand known as a 2-(4 aminophenol) benzimidazole azo derivative was successfully synthesized. This ligand was created by converting 2-(4-aminophenyl) benzimidazole into a diazonium salt and coupling it with 8-hydroxyquinoline in an alkaline environment. The resulting product was a brown azo dye, which served as the ligand for detecting copper (II) in aqueous samples. Results: To analyze copper (II) in both pure and aqueous samples, we developed and validated micro-extraction techniques combined with UV-Vis measurement. Specifically, we used the DLLME (dispersive liquid-liquid microextraction) method to separate, enrich, and assess copper (II) in both its pure form and in aqueous samples. UV-Vis spectroscopy at a wavelength of 503 nm was used for this purpose. We considered several variables during the experiment, including the type and volume of the dispersive solvent, the extraction solvents, the temperature, the reaction duration, and the centrifuging time. By optimizing these conditions, we achieved linear procedures within the concentration range of (1.0–25.0) and (2.0–25.0) μg/mL for spectroscopy and DLLME methods, respectively. For the spectroscopic and DLLME approaches, the coefficient of determination (R2) was found to be 0.9963 and 0.9979 for the spectrophotometric and DLLME methods, respectively. The limit of detection (LOD) for copper (II) was found to be 0.23 and 0.04 μg/mL, respectively. Moreover, the recovery of the target analyte in aqueous samples was found to be between 95.6% and 101% for the spectroscopy method and between 102.4% and 108.2% for the DLLME method. Conclusions: These results demonstrate the effectiveness and accuracy of both methods in analyzing copper (II) in aqueous samples.

In the current research, oyster shells have been recycled by reinforcing with aluminum alloy AA7075 using the stir casting method. The oyster shells (OS) were washed and milled via high energy ball mill. The produced castings were fabricated with various content of the OS particles as (0-15 Wt.%). The effect of oyster shell particles (OS) on the microstructures, mechanical properties and corrosion behavior of AA7075/OS composites has been studied. The microstructure results revealed a uniform distribution of oyster shell particles within AA7075 matrix. Compression, brinell hardness, and impact tests of the sample were carried out to identify the mechanical properties of the composite. The hardness was increased from 37%, 61% and 88.7% for AA7075 reinforced with 5, 10 and 15% OS composite compared with unrienforced AA7075. On the other hand, the ultimate compressive strength was improved from 10.7%, 19.8% and 25.9% for AA7075 reinforced with 5, 10 and 15% OS composite compared with unreinforced AA7075. The corrosion rate and weight loss method were carried out by immersing the specimens in 0.1M NaOH and 0.1M H2SO4 solutions. Results revealed that the rate of corrosion and mass loss were decreased with an increase of mass fraction up to 15%.

In the present investigation, Al-5Zn-2.5Mg - 1.6Cu -xSn (x = 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0 wt%) alloys were fabricated using melting and casting technique. The microstructures of the alloys were studied using optical, scanning electronic microscope/EDS and X-ray diffraction. The corrosion behaviour was performed using electrochemical measurements and immersion tests while the wear behaviour was carried out by pin-on-disc technique. The findings revealed that incorporating Sn to the Al-5Zn-2.5Mg alloy improved its corrosion and wear resistance due to refining the grains. The corrosion potentials shifted from −884 to −943,−955, −996,−1008 and −1012 mV (Ag / AgCl), while the coefficient of friction declined from 0.69 to 0.62 , 0.51 , 0.34, 0.29 and 0.22 with increment of Sn content from 0.0 to 0.2, 0.4. 0.6, 0.8 and 1.0 wt%, respectively. On the other hand, the results illustrated that the wear rate diminished from 4.42 *10⁻³to 1.47 * 10⁻³(mm³/Nm) with increasing Sn from 0.0 to 1.0 wt%. Furthermore, the findings showed that increment of Sn content stimulated the uniform corrosion on the surface of alloys.