Water is the most important resource for life, but it has been greatly exhausted over the past century as a result of the human population and environmentally harmful activities. The excessive quantity of dyes exists in the wastewater produced from the textile industries which is the main reason for serious human health and environmental problems. There are many dye removal techniques, and the most promising one is the adsorption technique. The novelty of this research is using unmodified synthesized hydroxyapatite (HAp) as an adsorbent for the removal of gentian violet (GV) dye from aqueous solutions as there are no sufficient data in the literature about using it in the adsorption of GV dye from aqueous solutions. Unmodified HAp was synthesized by a combined precipitation microwave method. The prepared adsorbent was characterized by scanning electron microscopy (SEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and zeta potential analyses. The kinetic study showed that the pseudo-second-order (PSO) model was the best fitted model with the experimental data. Analysis of adsorption isotherms using different models showed that this adsorption system was better described by the Halsey isotherm with a maximum adsorption capacity (qmax) of 1.035 mg/g. The effects of experimental factors such as initial solution pH, initial dye concentration, adsorbent dose, and contact time were studied during the investigation of GV dye removal efficiency. The experimental results indicated that the maximum adsorption efficiency (99.32%) of the GV dye using HAp adsorbent was achieved at the following conditions: contact time = 90 min, pH = 12, initial GV dye concentration = 3 mg/L, and adsorbent dose = 1 g/L. The adsorption mechanism of the GV dye using HAp might be explained by the electrostatic interaction between the negatively charged surface of the HAp and the positively charged group of the GV dye. Thermodynamics study was performed on the adsorption process of GV dye from aqueous solutions using the synthesized HAp which revealed that this process was endothermic and spontaneous due to positive values of ΔH and ΔS and negative values of ΔG.
This article is focused main problem during and after FSW especially when joining blanks AA2024 embedded with interlayer strip widths AA7075, in microstructure of the welded zone, that will in turn affect its mechanical properties of the welded joints. So, a number of interlock strip widths of AA7075 as 1, 1.5, 2, 2.5 and 3 mm were added between two substrates of base metal AA2024 during FSW technique then followed heating and cooling procedures to incorporate into the heat treatment process, which is conducted to create changes in a material’s microstructure that will in turn affect its mechanical properties. The analyses by optical microscope and scanning electron microscope were used to clarify microstructural characterization of FSWed with interlock strip widths after PWHTed. On the other hand, the microhardness and tensile tests were performed to determine mechanical properties of FSWed with interlock strip widths after PWHTed. The observations of microstructural elucidated that the good bonding connection between interlayer strip widths AA7075 and base metal AA2024 was due to use the procedures of PWHT. The mechanical properties such as microhardness and tensile of produced joints with PWHTed were showed higher than without PWHTed. Specifically, the ultimate tensile strength, and hardness values of the post-heat joint when using 3mm interlayer strip were obtained the highest values 299MPa, 186 HV respectively. This presents improvement by 11.2% in tensile strength, and 84% in hardness, compared to as weld joint.
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