The facile synthesis of zoledronate functionalized hydroxyapatite amorphous hybrid nanobiomaterial and its excellent removal performance on Pb2+ and Cu2

Study on a co-hybrid nano-hydroxyapatite with lignin derivatives and alendronate and the reinforce effect for poly(lactide-co-glycolide)

A novel co-hybrid nano-apatite (n-HA) by introducing lignin derivatives (LDs) and alendronate (ALE) was designed to reinforce poly(lactide-co-glycolide) (PLGA). The effect of different addition methods and contents of LDs, lignin derivatives sorts of lignosulfonate (LS), alkali lignin (AL) and carboxymethyl lignin (CML), and the addition order of ALE on the dispersion of hybrid n-HA, and reinforce effective for PLGA were investigated by FTIR, XRD, TEM, TGA, XPS, N2 adsorption/desorption, zeta potential, dispersion experiments, universal testing machine, SEM, DSC and POM. The results showed that the addition order could regulate the growth of n-HA crystal planes by binding with Ca2+, and co-hybrid HA by LDs and ALE possessed better dispersion owing to the synergistic effect. Moreover, 10 wt% LS-ALE-n-HA displayed the best reinforce effect, and the tensile strength of composite was 24.43 % higher than that of PLGA, even 15 wt% LS-ALE-n-HA was added, it still exhibited reinforce effect for PLGA. In vitro soaking in simulated body fluid (SBF) results indicated that LS-ALE-n-HA delayed tensile strength reduce of PLGA and promoted bone-like apatite deposition. The cell proliferation results demonstrated that the hybrid n-HA by the introduction of ALE endowed PLGA with better cell adhesion and proliferation.

Mechanistic insight into lead immobilization on bone-derived carbon/hydroxyapatite composite at low and high initial lead concentration

The contamination of heavy metal lead has a serious impact on the natural environment and organisms. Among various materials for lead removal, animal bone derived hydroxyapatite has received extensive attention. However, there are different opinions among researchers regarding the mechanism of lead removal by hydroxyapatite, possibly due to varying initial lead concentrations used in different studies and lack of accuracy in the study of lead removal mechanisms. In present work, we synthesized a carbon-containing hydroxyapatite (CHAP) through pyrolysis of bovine bone with excellent lead removal efficiency, and further investigated the lead removal mechanism of CHAP under high and low initial lead concentrations by combining XRD Rietveld refinement, FTIR, XPS, HRTEM etc. methods. The results showed that under low initial Pb2+ concentration condition, the main mechanism of lead removal by CHAP was chemical precipitation (94.1 %), with small contributions of lead complexation with carbon functional groups and cation-π interactions on the amorphous carbon in CHAP, and surface adsorption on the precipitates. Under high initial Pb2+ concentration condition, chemical precipitation remained the main mechanism (74.68 %), but the contributions of the other three mechanisms increased, and ion exchange appeared in the later stage of the removal process. This study provides new insights on the lead immobilization mechanism by CHAP at different initial Pb2+ concentrations in water.

Synergistic Cr(VI) reduction and adsorption of Cu(II), Co(II) and Ni(II) by zerovalent iron-loaded hydroxyapatite

Multi-metal contaminated soil, such as Cr(VI), Cu(II), and Co(II), still challenge the environmental remediation. In this work, zerovalent iron-loaded hydroxyapatite (ZVI/HAP) was first applied to simultaneously adsorb multi-metal in contaminated soil. During the remediation, the co-existing Cu(II), Ni(II), and Co(II) were adsorbed and precipitated onto ZVI/HAP. This "spontaneous deposition" simultaneously achieved the adsorption of the cationic metals and improved the isoelectric point of ZVI/HAP to 4.83 from 1.59, thus significantly alleviating the electronegativity to enhance the capture and reduction efficiency of Cr(VI). The application of ZVI/HAP resulted in the reduction of more than 99% of total Cr(VI) in contaminated soil, and the almost complete adsorption of water-soluble and DTPA-extractable Cu, Ni and Co within 20 d. Based on the sequential extraction and risk reduction assessment, soil Cr, Cu, Ni, and Co speciation was transformed from an unstable state (exchangeable and carbonate-bound fractions) to a relatively stable state, reducing the risk of heavy metals in contaminated soil significantly. This study developed an efficient strategy for the remediation of multi-metal contaminated soil.

Efficient removal of heavy metal ions by diethylenetriaminepenta (methylene phosphonic) acid-doped hydroxyapatite

Diethylenetriaminepenta (methylene phosphonic) acid (DTPMP) was first used as a dopant to modify hydroxyapatite and applied to remove Pb²⁺. The adsorption capacity of modified hydroxyapatite for Pb²⁺ can reach 2185.92 mg/g, which was 10.4 times that of commercial nanohydroxyapatite. The characterizations after adsorption of Pb²⁺ indicated the existence of chelation and the formation of the low bioavailability Pb₁₀(PO₄)₆(OH)₂. Moreover, the interaction of different components containing DTPMP, HAP, and pollutant Pb²⁺ was investigated by molecular dynamics (MD) simulation, which indicated that the organic-phosphonic group of DTPMP (PO₃H^-) had a stronger complex effect with calcium ions or lead ions than that of the inorganic-phosphate group of HAP (PO₄^3-) with the two metal ions, which affected the crystallinity of HAP, and greatly improved the removal effect of DTPMP doped HAP composites for Pb²⁺ contaminants, the existence of amino groups can further enhance the affinity between DTPMP and HAP or lead ions. The chelation mechanism of DTPMP and Pb²⁺ was probed in depth by combining basin analysis, topology analysis of atoms in molecules (AIM), electron localization function (ELF) analysis, bond order density (BOD) & natural adaptive orbital (NAdO)analysis and orbital component analysis.

Zinc- and magnesium-doped hydroxyapatite-urea nanohybrids enhance wheat growth and nitrogen uptake

The ongoing and unrestrained application of nitrogen fertilizer to agricultural lands has been directly linked to climate change and reductions in biodiversity. The agricultural sector needs a technological upgrade to adopt sustainable methods for maintaining high yield. We report synthesis of zinc and magnesium doped and undoped hydroxyapatite nanoparticles, and their urea nanohybrids, to sustainably deliver nitrogen to wheat. The urea nanohybrids loaded with up to 42% nitrogen were used as a new source of nitrogen and compared with a conventional urea-based fertilizer for efficient and sufficient nitrogen delivery to pot-grown wheat. Doping with zinc and magnesium manipulated the hydroxyapatite crystallinity for smaller size and higher nitrogen loading capacity. Interestingly, 50% and 25% doses of urea nanohybrids significantly boosted the wheat growth and yield compared with 100% doses of urea fertilizer. In addition, the nutritional elements uptake and grain protein and phospholipid levels were significantly enhanced in wheat treated with nanohybrids. These results demonstrate the potential of the multi-nutrient complexes, the zinc and magnesium doped and undoped hydroxyapatite-urea nanoparticles, as nitrogen delivery agents that reduce nitrogen inputs by at least 50% while maintaining wheat plant growth and nitrogen uptake to the same level as full-dose urea treatments.

Removal of Pb2+ from synthetic aqueous solution using hydroxyapatite and hydroxyapatite@AD37 composite materials

In this paper, a simple method was proposed to obtain hydroxyapatite (HA) and hydroxyapatite/partially hydrolysed polyacrylamide (HA/AD37) composite materials which where applied to lead retention from aqueous solution by means of the batch method. The characterization of the materials verified that the presence of AD37 created interconnected porosity in the composite HA/AD37 giving it a good swelling properties that conducted to an easy separation of the material from aqueous solutions. Retention experiments carried out by varying the dose of lead and the contact time between adsorbent and adsorbate showed that the maximum adsorption capacity (Qmax) obtained for 2072.2 mg/L as initial concentration of Pb2 + was equal to 984.63 mg/g for HA and 924.50 mg/g for HA/AD37. Furthermore, AD37 used alone cannot retain Pb2 + ions. Indeed, the calculated Qmax of AD37 part of the composite was of 806.57 mg/g. The obtained Qmax values was elevated more than the reported values in many literatures. Based on the correlation coefficient, the kinetic study proved that pseudo-second order model agrees well with the obtained experimental data for Pb2+ retention by both HA and HA/AD37. Also, isotherm study explored that adsorption of lead was best fitted by Langmuir model for HA and Temkin model for HA/AD37. At last, the mechanism of retention was probed by characterizing the adsorbents after contact with lead ions by XRD and SEM. The results showed the transformation of calcium-hydroxyapatite to different structures of lead hydroxyapatite confirming the presence of ion exchange mechanism between Ca2+ and Pb2+.

Porous P, Fe-doped g-C3N4 nanostructure with enhanced photo-Fenton activity for removal of tetracycline hydrochloride: Mechanism insight, DFT calculation and degradation pathways

This study fabricated an efficient P and Fe co-doping graphitic carbon nitride catalyst (Fe- CN/P) by thermal polymerization of melamine, FeCl₃, and 2-hydroxyphosphonoacetic acid (HPAA) mixture. The Fe-CN/P catalyst exhibited much better tetracycline hydrochloride (TCH) degradation performance than that of single doping and neat CN. Various characterizations indicated that the introduction of HPAA significantly increased the specific surface area of CN and improved charge separation as well as transfer efficiency. Based on Fe 2p XPS analysis and indirect determination of hydroxyl radical (·OH) content, the separated photogenerated electrons accelerated the reduction of Fe(III) and activated photo-Fenton reaction, resulting in more ·OH species generation. The effect of pH value, catalyst dosages, H₂O₂ concentration, the type of cations and anions as well as water matrices on the degradation of TCH by Fe-CN/P was systematically investigated. The main degradation pathways of TCH were proposed according to the LC-MS intermediates detection and DFT calculation. The results indicated that reactive oxide species (ROS) were more likely to attack the atoms with high Fukui index (f⁰). This work provides new ideas for adjusting the morphology and electronic structure of CN to enhance its photo-Fenton catalytic activity.

α-calcium sulfate hemihydrate with a 3D hierarchical straw-sheaf morphology for use as a remove Pb2+ adsorbent

Novel three-dimensional hierarchical α-calcium sulfate hemihydrate with a straw-sheaf morphology (3D α-HH straw-sheaves) are synthesized successfully in glycerin aqueous solution by a simple one-pot method, using as an efficient adsorbent for Pb²⁺ removal from water. The 3D straw-sheaf morphology, that closely depends on the glycerin/water volume ratio (V_Gly/V_H2O), can be accurately fabricated only when V_Gly/V_H2O is not lower than 3/1. 3D α-HH straw-sheaves are generated via multistep-splitting growth coupled with self-assembly. The obtained 3D α-HH straw-sheaves are further used as an adsorbent to remove Pb²⁺ from water, exhibiting excellent Pb²⁺ removal performance with an equilibrium adsorption capacity of 79.19 mg_Pbg_α-HH^-1 and removal efficiency of 98.98%, that both higher than those of plate- and columnar-like α-HH. Moreover, the experimental adsorption data for the 3D α-HH straw-sheaves is well fitted with pseudo-second-order kinetic model, and the adsorption isotherm is in good agreement with Langmuir model. The Pb²⁺ adsorption mechanism is thought to be a chemical adsorption process enforced by chemical bonding and ion exchange. This work demonstrates that 3D α-HH straw-sheaves are highly promising in removing Pb²⁺ from wastewater, thereby broadening the research field for the practical application of gypsum-based materials.

Recent Progress in the Application of Hydroxyapatite for the Adsorption of Heavy Metals from Water Matrices

Wastewater treatment remains a critical issue globally, despite various technological advancements and breakthroughs. The study of different materials and technologies gained new valences in the last years, in order to obtain cheap and efficient processes, to obtain a cleaner environment for future generations. In this context, the present review paper presents the new achievements in the materials domain with highlights on apatitic materials used for decontamination of water loaded with heavy metals. The main goal of this review is to present the adsorptive removal of heavy metals using hydroxyapatite-based adsorbents, offering a general overview regarding the recent progress in this particular area. Developing the current review, an attempt has been made to give appropriate recognition to the most recent data regarding the synthesis methods and targeted pollutants, including important information regarding the synthesis methods and precursors, morphological characteristics of the adsorbent materials and effectiveness of processes.

N-alkylation briefly constructs tunable multifunctional sensor materials: Multianalyte detection and reversible adsorption

A series of N-alkyl-substituted polybenzimidazoles (SPBIs), synthesized by simple condensation and N-alkylation, act as functional materials with tunable microstructures and sensing performance. For their controllable morphologies, the formation of nano-/microspheres is observed at the n(RBr)/n(PBI) feed ratio of 5:1. Products with different degrees of alkylation can recognize metal ions and nitroaromatic compounds (NACs). For example, SPBI-c, obtained at the feed ratio of 1:1, can selectively detect Cu2+, Fe3+, and NACs. By contrast, SPBI-a, obtained at the feed ratio of 0.1:1, can exclusively detect Cu2+ with high sensitivity. Their sensing mechanisms have been studied by FT-IR spectroscopy, SEM, XPS, and DFT calculations. Interestingly, the SPBIs can adsorb Cu2+ in solution and show good recyclability. These results demonstrate that polymeric materials with both sensing and adsorption applications can be realized by regulating the alkylation extent of the main chain, thus providing a new approach for the facile synthesis of multifunctional materials.

"In-situ synthesized" iron-based bimetal promotes efficient removal of Cr(VI) in by zero-valent iron-loaded hydroxyapatite

Anionic Cr(VI) and cationic heavy metals generally co-exist in industrial effluents and threaten the public health. Zero-valent iron (ZVI) particles tent to passivate rapidly, which results in a gradual drop in its reactivity. In this work, a strategy of "in-situ synthesized" iron-based bimetal was first developed to stimulate the self-activation of passivated ZVI. During this process, ZVI-loaded hydroxyapatite (ZVI/HAP) was prepared to enhance the affinity for co-existing Cu²⁺, which promoted the in-situ Cu⁰ deposition on ZVI/HAP to form a Fe-Cu bimetal. The deposited Cu⁰ significantly decreased the activation energy (E_a) of Cr(VI) reduction by 24.9%, and its corresponding Cr(VI) removal (96.53%) was much higher that of single Cr(VI) system (68.67%) within 9 h. More importantly, the removal of Cr(VI) and Cu²⁺ were synchronously achieved. Systematical electrochemical characterizations were first introduced to explore the galvanic behaviors of iron-based bimetal. The charge transfer resistance and the negative open circuit potential of ZVI/HAP significantly decreased with the Cu⁰ deposition, thereby accelerating the electron transfer from Fe⁰ to Cu²⁺. The enhanced electron transfer further facilitated the Fe(II) release to promote Cr(VI) reduction. This "in-situ synthesized" iron-based bimetal strategy provides a novel pattern for ZVI activation and exhibits practical application in remediation of combined contaminant.

Fabrication of Fe3O4/ZIF-8 nanocomposite for simultaneous removal of copper and arsenic from water/soil/swine urine

In this study, a magnetic nanocomposite (denoted as FZ) was fabricated using Fe₃O₄and zeolitic imidazolate framework-8 (ZIF-8), based on a coprecipitation method. FZ could efficiently remove Cu²⁺(Cu(II)) and AsO₂^- (As(III)) ions simultaneously from water, soil, and swine urine samples through hydrogen bonding and electrostatic interactions. The Cu(II) and As(III) removal efficiencies of the optimal FZ sample increased gradually with time and reached 99.1% and 98.4%, respectively, in 180 min. The maximum adsorption capacities of FZ4 for Cu(II) and As(III) were determined to be 33.48 mg/g and 21.12 mg/g, respectively. Additionally, the FZ with a high saturation magnetization (49.8 emu/g) was easily recovered from aqueous solutions and soil samples. Furthermore, zebrafish experiments indicated that FZ possessed a high biosafety. Thus, this study introduces a promising method for treating water, soil, and swine urine samples contaminated with Cu(II) and As(III), and verifies that FZ is suitable for practical application.

N-methylene phosphonic chitosan aerogels for efficient capture of Cu2+ and Pb2+ from aqueous environment

In this paper, N-methylene phosphonic acid chitosan (NPCS-PEI) was synthesized from chitosan, phosphorous acid, formaldehyde and hyperbranched polyethyleneimine (PEI), and Cu²⁺ and Pb²⁺ removal performance was examined in aqueous solution. NPCS-PEI exhibited three-dimensional porous architectures, with a specific surface area of 490.61 m²/g. The effects of pH, initial concentration, adsorption time, temperature and ionic strength on the adsorption capacity were investigated. The adsorption kinetics indicated that Cu²⁺ and Pb²⁺ adsorption onto NPCS-PEI follows a pseudo-second-order model. The adsorption isotherms agree well with the Langmuir isotherm model, and the maximum adsorption capacities of Cu²⁺ and Pb²⁺ on the NPCS-PEI are approximately 276.12 and 645.16 mg/g, respectively. The adsorption efficiency of NPCS-PEI remained above 85% after 5 adsorption-desorption successive cycles. Moreover, the NPCS-PEI aerogels had selective adsorption toward Cu²⁺. The FTIR and XPS analysis proved that amino, hydroxyl, and phosphonic acid groups were involved in the chelation with metal ions.

Efficient absorption properties of surface grafted HEDP-HAP composites for Pb2+ and Cu2+: Experimental study and visualization study of interaction based on Becke surface analysis and independent gradient model

A simple hydrothermal method was employed to prepare the surface grafted 1-hydroxyethylidene-1,1-diphosphonic acid-hydroxyapatite (HEDP-HAP) composites, which were termed as 0.2HEDP-HAP, 0.5HEDP-HAP and 1HEDP-HAP respectively, according to the HEDP content. Adsorption experiments showed that the maximum adsorption capacity of 0.5HEDP-HAP for Cu²⁺ reached 168.9 mg/g, which was 4.19 times that of HAP, while the maximum adsorption capacity of 1HEDP-HAP for Pb²⁺ was as high as 1521 mg/g, which was approximately 10 times that of HAP. For the first time, the interaction mechanism of HEDP with HAP, or HEDP-HAP composite with the two heavy metal ions was illustrated by the combination of quantum chemistry (QC) calculation, quantitative analysis of molecular surface, Becke surface analysis and Independent Gradient Model (IGM) method. The active reaction sites, the types, relative strength and essence of the interactions were revealed based on the visual analysis of interactions. The results demonstrated that the phosphonic acid group (PO₃H^-) of HEDP^2- can form hydrogen bonds with the phosphate group (PO₄^3-) and the hydroxyl group (OH) of HAP. The oxygen atom of PO₃H- provided lone pair electrons to form chelate with Ca²⁺ of HAP, which resulted in the strong affinity of HEDP with HAP. Moreover, the significant improvements of uptake of surface grafted HEDP-HAP for Cu²⁺ and Pb²⁺ were due to the formation of the ternary surface complexes.