Magnetic γ-Fe2O3/Fe-doped hydroxyapatite nanostructures as high-efficiency cadmium adsorbents

Magnetic Hydroxyapatite Nanoparticles in Regenerative Medicine and Nanomedicine

This review focuses on the latest advancements in magnetic hydroxyapatite (mHA) nanoparticles and their potential applications in nanomedicine and regenerative medicine. mHA nanoparticles have gained significant interest over the last few years for their great potential, offering advanced multi-therapeutic strategies because of their biocompatibility, bioactivity, and unique physicochemical features, enabling on-demand activation and control. The most relevant synthetic methods to obtain magnetic apatite-based materials, either in the form of iron-doped HA nanoparticles showing intrinsic magnetic properties or composite/hybrid compounds between HA and superparamagnetic metal oxide nanoparticles, are described as highlighting structure-property correlations. Following this, this review discusses the application of various magnetic hydroxyapatite nanomaterials in bone regeneration and nanomedicine. Finally, novel perspectives are investigated with respect to the ability of mHA nanoparticles to improve nanocarriers with homogeneous structures to promote multifunctional biological applications, such as cell stimulation and instruction, antimicrobial activity, and drug release with on-demand triggering.

New insights into the environmental application of hybrid nanoparticles in metal contaminated agroecosystem: A review

Heavy metals (HMs) contamination in agricultural soils is a major constraint to provide safe food to society. Cultivation of food crops on these soils, channels the HMs into the food chain and causes serious human health and socioeconomic problems. Multiple conventional and non-conventional remedial options are already in practice with variable success rates, but nanotechnology has proved its success due to higher efficiency. It also led the hypothesis to use hybrid nanoparticles (HNPs) with extended benefits to remediate the HMs and supplement nutrients to enhance the crop yield in the contaminated environments. Hybrid nanoparticles are defined as exclusive chemical conjugates of inorganic and/or organic nanomaterials that are combinations of two or more organic components, two or more inorganic components, or at least one of both types of components. HNPs of different elements like essential nutrients, beneficial nutrients and carbon-based nanoparticles are used for the remediation of metals contaminated soil and the production of metal free crops. Characterizing features of HNPs including particle size, surface area, reactivity, and solubility affect the efficacy of these HNPs in the contaminated environment. Hybrid nanoparticles have great potential to remove the HMs ions from soil solution and restrict their ingress into the root tissues. Furthermore, HNPs of essential nutrients not only compete with heavy metal uptake by plants but also fulfill the need of nutrients. This review provides a comprehensive overview of the challenges associated with application of HNPs in contaminated soils, environmental implications, their remediation ability, and factors affecting their dynamics in environmental matrices.

Green synthesized hydroxyapatite for efficient immobilization of cadmium in weakly alkaline environment

The development of cost-effective passivators for the remediation of heavy metal-contaminated soils has been a research hotspot and an unsolved challenge. Herein, a novel hydroxyapatite (GSCH) was synthesized by co-precipitating distiller effluent-derived Ca with (NH₄)₂HPO₄ using straw-derived dissolved organic matter (S-DOM) as the dispersant. Batch adsorption experiments and soil incubation tests were performed to assess the immobilization efficiency of GSCH for Cd in weakly alkaline environments. As a result, GSCH showed an excellent adsorption efficiency to Cd with a maximum adsorption amount of ∼222 mg g^-1, which was fairly competitive compared to other similar previously materials reported. The kinetic data indicated that the adsorption of Cd on GSCH was a chemical and irreversible process, while the thermodynamic data revealed a spontaneous (ΔG° < 0) and endothermic (ΔH° > 0) adsorption process. Based on mechanism analysis, both physisorption (e.g., electrostatic attraction and pore filling) and chemisorption (e.g., ion exchange and complexation) were responsible for Cd adsorption on GSCH. Particularly, the incorporated S-DOM and hydroxyapatite phase in GSCH acted synergistically in the adsorption process. The incubation results showed that GSCH application could significantly reduce the bioavailability, phytoavailability and bioaccessibility of Cd in soil by 48.4%-57.8%, 20.4%-28.6% and 12.6%-24.0%, respectively. Moreover, GSCH application also improved soil bacterial communities and enhanced soil nutrient availability. Overall, this is the first study to demonstrate the potential application value of GSCH in Cd immobilization, providing promising insights into the development of green and cost-effective hydroxyapatite-based passivators for the remediation of heavy metal-contaminated soils.

Iron-doped hydroxyapatite for the simultaneous remediation of lead-, cadmium- and arsenic-co-contaminated soil

Since lead, cadmium and arsenic have completely opposite chemical behaviors, it is very difficult to stabilize all these three heavy metals simultaneously. Herein, a novel iron-doped hydroxyapatite composite (Fe-HAP) was developed via an ultrasonic-assisted microwave hydrothermal method for the simultaneous remediation of lead-, cadmium-, and arsenic-co-contaminated soil in Hunan Province, South China. Using DTPA/sodium bicarbonate extractant to extract bioavailable Pb, Cd and As in soil after Fe-HAP remediation for 60 days, the immobilization efficiencies were 79.77%, 51.3% and 37.5% for Pb, Cd and As, respectively. The soil extractable and exchangeable fractions of Pb, Cd and As decreased significantly. In batch experiments, the adsorption kinetics of Pb, Cd and As on Fe-HAP were well described by pseudo-second-order models, indicating that the adsorption is controlled by chemisorption. In the Langmuir adsorption isotherm, the maximum adsorption capacities of Cd²⁺ and As(V) were 476.2 mg g^-1 and 195.69 mg g^-1, respectively, while Pb²⁺ fit the Freundlich model better. The XRD, SEM and XPS analyses indicated that Fe-HAP formed stable minerals of Pb₅(PO₄)₃OH, Cd₃(PO₄)₂·4H₂O, Cd(OH)₂ and Fe₃(AsO₄)₂·6H₂O with Pb, Cd and As. Overall, its facile and efficient immobilization performance indicate that Fe-HAP has potential for practical applications in integrative remediation of Pb-, Cd-, and As- co-contaminated soil.

Adsorptive removal of AB113 dye using green synthesized hydroxyapatite/magnetite nanocomposite

In the present study, magnetite nanoparticles (Fe₃O₄NPs) synthesized using Thunbergia grandiflora leaf extract as a reducing agent were doped with hydroxyapatite sourced from waste bivalve clamshells to produce hydroxyapatite/magnetite nanocomposite (HA/Fe₃O₄NPs). The magnetic nanocomposite was examined using several characterization techniques. The results of XRD and FESEM, analysis showed HA/Fe₃O₄NPs have a crystalline phase and irregular spherical particles respectively. EDAX and FTIR confirmed the presence of specific elements and functional groups of both iron oxide and hydroxyapatite nanoparticles respectively. The surface area and superparamagnetic property of the composite were determined by BET and VSM analysis. Central Composite Design (CCD) was used to optimize the adsorption process to remove of AB113 from aqueous solutions. The optimal adsorption efficiency was found out to be 94.38% at pH 8, AB113 dye concentration 54 ppm, HA/Fe₃O₄NPs dose 84 mg, and an agitation speed of 174 rpm. The monolayer Langmuir isotherm was the best model with a sorption capacity of 109.98 mg/g which was higher than the reported values. The pseudo-second-order kinetic model displayed a good fit with an R² = 0.99. Thermodynamic parameters were assessed which confirmed the exothermic adsorption process. Therefore, the synthesized magnetic nanocomposite can be employed as a novel nanoadsorbent for the removal of anionic dyes from waste effluents.

Hydroxyapatite with magnetic core: Synthesis methods, properties, adsorption and medical applications

This review presents the actual state of knowledge and recent research results on the magnetic composite synthesized from iron oxide (γ-Fe₂O₃ or Fe₃O₄) and hydroxyapatite. It can be obtained applying some methods, i.e. chemical precipitation, hydrothermal, sol-gel, and biomimetic or combined techniques which exhibit characteristic properties affecting the form of the prepared product. More specific details are discussed in this paper. A comparison of the discussed synthesis methods is presented. On the basis of selected publications, a comparison of the results of the analysis by XRD, FTIR, SEM and EDX methods for hydroxyapatite with a magnetic core was also presented. Moreover, the characteristics large adsorption capacity and specific area allow employing nanocomposites as adsorbents particularly in removal of toxic metal ions. Nowadays this issue is extremely vital due to large amounts of pollutants in the environment and greater ecological awareness of people. Moreover, magnetic hydroxyapatite can be also applied as a catalyst in various syntheses or oxidation reactions as well as in medicine in magnetic resonance imaging, hyperthermia treatment, drug delivery and release, bone regeneration or cell therapy.

Facile synthesis of nanosheet-assembled γ-Fe2O3 magnetic microspheres and enhanced Sb(III) removal

The development and utilization of magnetic nanoadsorption materials with large adsorption capacity and easy separation are the research hotspot nowadays. In this study, nanosheet-assembled maghemite (γ-Fe₂O₃) magnetic microspheres were successfully synthesized by an environmental friendly, quick, and simple method, for enhanced Sb(III) removal from aqueous solution. Scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometer (VSM), and Brunauer-Emmett-Teller (BET) were used to characterize the material. The results showed that the product contained flower-like γ-Fe₂O₃ microspheres composed of petal-shaped nanosheets interspersed with each other. The specific surface area and pore volume were 69.23 m²/g and 0.15 cm³/g, respectively. The material has a strong magnetic response, which allows rapid solid-liquid separation under the action of an external magnetic field. The effects of different dosages, solution pH, and contact time on the adsorption effect were studied by batch adsorption experiments, and the reusability of the materials was evaluated. Both Freundlich isothermal adsorption model and pseudo-second-order kinetic model were able to describe the uptake of Sb(III). The maximum adsorption capacity of the material was 47.48 mg/g under optimal conditions. The adsorption mechanism is mainly that Sb and lattice oxygen (O_X^2-) form Fe-O-Sb coordination bonds, which is incorporated into the crystal structure of γ-Fe₂O₃ as inner-sphere surface complexes. The synthetic material has the advantage of simple preparation process, good adsorption capacity, operation over a wide range of pH, and easy physical separation from treatment systems with good potential for future application to treat polluted wastewater.

Adsorptive removal of heavy metals from battery industry effluent using MOF incorporated polymeric beads: A combined experimental and modeling approach

In this study, the metal organic framework (MOF) ZIF-8 was investigated as potential adsorbent for heavy metal ions. The MOF powder was used further to prepare mixed matrix beads (MMBs) using polysulfone as the base material. Both the MOF powder and the MMBs were characterized using Field emission scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller (BET) analyzer and zetasizer. Adsorption capacity of the MMBs were 164-220 mg/g for Pb and 92-161 mg/g for Cd. A fundamental pore diffusion-adsorption model was used to predict the batch kinetics for both single and multicomponent cases and effective pore diffusivities and mass transfer coefficients were determined. Mutual interactions among heavy metals were quantified using interaction parameters. ZIF-8, incorporated in the PSF matrix, plays the predominant role in capturing the metal ions through surface complexation with the NH and metal-OH groups. A first principle-based model involving convection, diffusion and adsorption was used to quantify the breakthrough behavior for the continuous fixed bed column using the MMBs. The column performance was tested with battery industry effluent. The saturated beads were suitably regenerated using 0.1(M) HCl solution. Finally, the model parameters were used for scaling up of the columns.

Immobilization of cadmium by hydroxyapatite converted from microbial precipitated calcite

As one of the most toxic heavy elements, humans are mainly exposed to cadmium (Cd) via daily diets and smoking. Calcite can be used as an amendment directly or precipitated in situ based on microbial-induced carbonate precipitation (MICP) technology to immobilize Cd in soil with potential release of Cd due to calcite dissolution. Therefore, we converted microbial-induced calcite to less soluble hydroxyapatite and investigated the phase and morphology evolutions of the solids, as well as the immobilized efficiency, distribution and release of Cd. The results showed that the conversion of calcite to hydroxyapatite enhanced Cd removal efficiency up to 1.67% and 33.14% compared to the MICP process and adsorption by calcite, respectively. Accordingly, the released Cd decreased up to 94.10% and 99.96%, respectively. Our findings demonstrated that the conversion of calcite to hydroxyapatite might control the environmental behavior of heavy metals like Cd and can potentially be applied for soil remediation.