Hydrothermal synthesis of hydroxyapatite powders using Response Surface Methodology (RSM).

Hydroxyapatite (HAp)-[Ca10 (PO4)6(OH) 2] has a similar chemical composition to bone material, making it the main mineral supplement in bone-making. Due to its high biocompatibility, hydroxyapatite is widely used in the repair of bone deficiencies and in the production of dental or orthopedic implants. In this research, hydroxyapatite nanopowder was synthesized using a hydrothermal technique. Fourier Transform Infrared Spectroscopy (FTIR) and transmission electron microscopy (TEM) were used to investigate the chemical structure and morphology of the synthesized hydroxyapatite powder. X-ray diffraction (XRD) was used to evaluate the phase analysis of HAp nanopowder. In addition, bioactivity HAp assessment was conducted by scanning electron microscopy (SEM) attached with Energy Dispersive X-Ray Spectroscopy (EDX) analysis. Response Surface Methodology (RSM) with central composite design (CCD) was used in order to determine the optimal conditions for yield, size, and crystallinity. Three independent variables (pH, temperature, and hydrothermal treatment time) were investigated. The yield was observed to increase in alkaline conditions; pH showed the greatest influence on the yield, size, and crystallinity of the synthesized hydroxyapatite, based on Analysis of Variance. The results of bioactivity evaluation are showed high bioactivity due to the formation of apatite on the surface of the synthesized nanopowder.

Synthesis of Silica-Supported Hydroxamic Ligand for Removal of Metals Ions from Water.

Mesoporous silica supported adsorbents have been used towards metal ion removal from water due to their thermally stability and good sorption capacity. Thus, mesoporous silica-based methyl acrylate monomer (Silica-APTES-DPNO) was converted into hydroxamic acid (SBHA) by using oximation reaction and all products are analyzed by by FT-IR. The SBHA showed satisfactory binding properties with copper, cobalt, nickel and lead are 242, 206, 195 and 516 mg g-1, respectively, with the batch adsorption system was set to pH 6. The kinetics of metal ions binding obeyed the pseudo-1st-order process up to 60 min. In this study also consider the Langmuir and Freundlich isotherm to find out the sorption behavior. The isotherm study demonstrated the well fit with Freundlich isotherm (R² > 0.99). Thus, adsorption take place as a multilayer system, therefore, SBHA material is useful for the metal ions removal from water.

Optimization and Analytical Behavior of Electrochemical Sensors Based on the Modification of Indium Tin Oxide (ITO) Using PANI/MWCNTs/AuNPs for Mercury Detection.

In the present study, indium tin oxide (ITO) was used as a transparent working electrode for the development of an electrochemical sensor for the detection of mercury (II) ions (Hg2+). The electrode was modified by direct electrodeposition of polyaniline (PANI), multiwalled carbon nanotubes (MWCNTs) and gold nanoparticles (AuNPs) followed by optimization of the analyte and operating conditions, aiming to improve the selectivity, sensitivity and reliability of the electrode for mercury detection. Successful immobilization of the PANI and nanomaterials (MWCNTs and AuNPs) on the ITO electrode was confirmed by Scanning Electron Microscope (SEM), Energy Dispersive X-ray (EDX) and Fourier Transform Infrared Spectroscopy (FTIR) analyses. The optimum conditions for mercury detection using the modified ITO electrode were pH 7.0 of Tris-HCl buffer (50 mM) in the presence of 1 mM methylene blue (MB) as a redox indicator, a scan rate of 0.10 V·s-1 and a 70 s interaction time. The electrochemical behavior of the modified electrode under the optimized conditions indicated a high reproducibility and high sensitivity of mercury detection. It is therefore suggested that the PANI/MWCNT/AuNP-modified ITO electrode could be a promising material for the development of on-site mercury detection tools for applications in fields such as diagnostics, the environment, safety and security controls or other industries.

Ion-Imprinted Polymer for Selective Separation of Cerium(III) Ions from Rare Earth Mixture.

Ion-imprinting polymers (IIPs) materials draw the great recognition because of the powerful selectivity to the desired metal ions. Therefore, the ion-imprinting polymer (Ce-IIP) was prepared by using cerium metal with amidoxime ligand as the complexing agent, in addition ethylene glycol dimethacrylate (EGDMA) and 2,2-azobisisobutyronitrile (AIBN) are crosslinking agent and free radical initiator, respectively. Aqueous HCl was applied to leach the cerium ions from the imprinted polymer for the creation of cavities of template, which is utilized for further cerium ions adsorption with high selectivity. The Ce-IIP was characterized by using ICP-MS, FE-SEM and also solid state analysis by UV-vis NIR spectroscopy. FT-IR study confirmed the complexation of the Ce-IIP was successful. The optimum pH was found to be 6 and the highest adsorption capacity was estimated about 145 mg g-1. Thus, the prepared Ce-IIP gave very good selectivity to cerium ions in the presence of lanthanide ions and also Ce-IIP can be reused 10 times without a substantial loss in adsorption capacity.