Preparation and Characterization of Isotactic Polypropylene Reinforced with Hydroxyapatite Nanorods

Adsorption of Cd2+ onto apatite surface: Equilibrium, kinetics and thermodynamic studies

This study examined the application of chemically synthesized apatite (CHAp) powder as a potential adsorbent for the elimination of Cd²⁺ in aqueous medium. The synthesized hydroxyapatite (HAp) powder before and after adsorption was elucidated by XRD, EDX, FT-IR, SEM, and TEM analytical techniques. The role of time, initial Cd²⁺ concentration, amount of CHAp used, temperature and solution pH on the adsorption process were investigated. Data from the adsorption process were subjected to Dubinin-Radushkevich, Langmuir, Freundlich, and Tempkin adsorption isotherms, while pseudo-first-order, pseudo-second-order, Elovich and intraparticle diffusion kinetic models were used for the kinetics investigation. Results from XRD confirmed that chief characteristic peaks of HAp powder were detected, while functional groups such as PO₄ ^3-, CO₃ ^2- and OH^- matching pure HAp were displayed in the FT-IR spectra. Round shape morphology of the CHAp was confirmed by SEM and TEM analyses. Langmuir isotherm best described the adsorption process with ceiling adsorption capacity of 195.711 mg/g, whereas, the adsorption mechanism obeys the pseudo-first-order model which suggests a physical adsorption process. The value of entropy change (ΔS) of the adsorption of Cd²⁺ onto CHAp surface was obtained to be 0.610 kJ/mol, while the value of enthalpy change obtained was 175.591 kJ/mol. Results from free energy change obtained adjudged the adsorption process to be spontaneous and endothermic in character. Thus, the chemically synthesized HAp could be an excellent adsorbent for the elimination of Cd²⁺ in bioremediation applications.

Evaluation of the mechanical properties of hydroxyapatite-silica aerogel/epoxy nanocomposites: Optimizing by response surface approach

This study attempted to investigate the effects of adding hydroxyapatite and silica aerogel nanoparticles on the density, tensile, Izod impact, and morphological properties of epoxy using the Response Surface Methodology (RSM). RSM relied on Box-Behnken Design (BBD) was used to design the mechanical tests. The concurrent effects of two parameters including hydroxyapatite content and silica aerogels content on the mechanical properties have been evaluated. Finally, by using the equations obtained from regression for each of the responses, their optimal states were obtained using both the desirability approach and the Multi-Objective Particle Swarm Optimization (MOPSO) method. The results from tensile, and Izod impact tests indicated the combination of hydroxyapatite and silica aerogel nanoparticles led to an improvement in the tensile properties and energy absorption of epoxy matrix. The findings related to density test demonstrated that with addition of silica aerogel to the hydroxyapatite/epoxy nanocomposites, density of these samples was decreased. The maximum tensile strength of 86.9 MPa was obtained with hydroxyapatite content of 2.38 wt% and silica aerogels content of 4 wt%. Also, the maximum impact strength of 18.14 kJ/m2 was obtained with hydroxyapatite content of 1.11 wt% and silica aerogels content of 3.51 wt%. The field emission scanning electron microscope images showed the homogeneous distribution of combined hydroxyapatite and silica aerogel nanoparticles in epoxy matrix, except in 5 wt% of hydroxyapatite nanoparticles.

Functionalized multi-walled carbon nanotubes and hydroxyapatite nanorods reinforced with polypropylene for biomedical application

Modified multi-walled carbon nanotubes (f-MWCNTs) and hydroxyapatite nanorods (n-HA) were reinforced into polypropylene (PP) with the support of a melt compounding approach. Varying composition of f-MWCNTs (0.1–0.3 wt.%) and nHA (15–20 wt.%) were reinforced into PP, to obtain biocomposites of different compositions. The morphology, thermal and mechanical characteristics of PP/n-HA/f-MWCNTs were observed. Tensile studies reflected that the addition of f-MWCNTs is advantageous in improving the tensile strength of PP/n-HA nanocomposites but decreases its Young’s modulus significantly. Based on the thermal study, the f-MWCNTs and n-HA were known to be adequate to enhance PP’s thermal and dimensional stability. Furthermore, MTT studies proved that PP/n-HA/f-MWCNTs are biocompatible. Consequently, f-MWCNTs and n-HA reinforced into PP may be a promising nanocomposite in orthopedics industry applications such as the human subchondral bone i.e. patella and cartilage and fabricating certain light-loaded implants.

From Garbage to Biomaterials: An Overview on Egg Shell Based Hydroxyapatite

The conversion of waste obtained from agricultural processes into biocompatible materials (biomaterials) used in medical surgery is a strategy that will add more value in waste utilization. This strategy has successfully turned the rather untransformed wastes into high value products. Eggshell is an agricultural waste largely considered as useless and is discarded mostly because it contributes to pollution. This waste has potential for producing hydroxyapatite, a major component found in bone and teeth. Hydroxyapatite is an excellent material used in bone repair and tissue regeneration. The use of eggshell to generate hydroxyapatite will reduce the pollution effect of the waste and the subsequent conversion of the waste into a highly valuable product. In this paper, we reviewed the utilization of this agricultural waste (eggshell) in producing hydroxyapatite. The process of transforming eggshell into hydroxyapatite and nanohydroxyapatite is an environmentally friendly process. Eggshell based hydroxyapatite and nanohydroxyapatite stand as good chance of reducing the cost of treatment in bone repair or replacement with little impact on the environment.