Fabrication and Characterization of Magnetic Hydroxyapatite Entrapped Agarose Composite Beads with High Adsorption Capacity for Heavy Metal Removal

Resource utilization of wastepaper and bentonite: Cu(II) removal in the aqueous environment

Contamination of heavy metals has always been a pressing concern. The dry-wet alternately treated carboxymethylcellulose bentonite (DW-CB) was successfully prepared by intercalating bentonite (BT) with carboxymethyl cellulose (CMC) obtained by solvent processes using enzymatically digested wastepaper as cellulosic raw material, and the adsorption capacity of Cu2+ on DW-CB in aqueous solution was investigated. A 98.18 ± 2.31 % removal efficiency was achieved by 4 g/L of DW-CB after 8 h in a solution containing 100 mg/L of Cu2+, which were 4.1 times and 1.5 times of that of BT and adsorbent prepared without alternating dry-wet process, respectively. The introduction of -COOH groups during the preparation of DW-CB enhanced the electrostatic interaction between DW-CB and Cu2+, which was the main driving force for Cu2+ removal. The pseudo-first-order kinetic model and Langmuir model better described the adsorption process and adsorption capacity of Cu2+ on DW-CB. DW-CB still showed high removal of Cu2+ (19.61 ± 0.99 mg/g) in the presence of multiple metal ions, while exhibiting the potential for removal of Zn2+, Mg2+ and K+, especially Mg2+ (22.69 ± 1.48 mg/g). However, the interactions of organics with Cu2+ severely affected the removal of Cu2+ by DW-CB (removal efficiency: 17.90 ± 4.17 % - 95.33 ± 0.27 %). In this study, an adsorbent with high targeted adsorption of Cu2+ was prepared by utilizing wastepaper and BT, which broadened the way of wastepaper resource utilization and had good economic and social benefits.

Mussel-Inspired Hydrogels for Fluoride Delivery and Caries Prevention

Fluoride agents hold promise for the repair and prevention of caries lesions, but their interaction with enamel is often hampered and diminished because of the dynamic wet environment in the oral cavity, which affects the efficacy of fluoride delivery and limits treatment success. We herein developed a mussel-inspired wet adhesive fluoride system (denoted TS@NaF) fabricated by the self-assembly of tannic acid (TA), silk fibroin (SF), and sodium fluoride (NaF). TS@NaF demonstrated remarkable biological stability and biocompatibility, showed reliable wet adhesion, released fluoride ions (F−) topically, and induced significant deposition of calcium fluoride (CaF2) onto enamel in vitro. Furthermore, TS@NaF provided an anticaries effect in vitro and induced a detectable increase in enamel mineral density. Advanced fluoride-releasing bioadhesives are therefore promising candidates for caries prevention and highlight the great potential of mussel-inspired dental materials in clinical applications.

Adsorption of Inositol Phosphate on Hydroxyapatite Powder with High Specific Surface Area

Chelate-setting calcium-phosphate cements (CPCs) have been developed using inositol phosphate (IP6) as a chelating agent. However, the compressive strength of the CPC fabricated from a commercially available hydroxyapatite (HAp) powder was approximately 10 MPa. In this study, we miniaturized HAp particles as a starting powder to improve the compressive strength of chelate-setting CPCs and examined the adsorption properties of IP6 onto HAp powders. An HAp powder with a specific surface area (SSA) higher than 200 m²/g (HApHS) was obtained by ultrasonic irradiation for 1 min in a wet synthesis process, greatly improving the SSA (214 m²/g) of the commercial powder without ultrasonic irradiation. The HApHS powder was found to be a B-type carbonate-containing HAp in which the phosphate groups in apatite were replaced by carbonate groups. Owing to the high SSA, the HApHS powder also showed high IP6 adsorption capacity. The adsorption phenomena of IP6 to our HApHS and commercially available Hap powders were found to follow the Freundlich and Langmuir models, respectively. We found that IP6 adsorbs on the HApHS powder by both physisorption and chemisorption. The fine HapHS powder with a high SSA is a novel raw powder material, expected to improve the compressive strength of chelate-setting CPCs.

Structure and properties of cellulose/HAP nanocomposite hydrogels

The exploiting of abundant natural polymers as potential absorbents for heavy metal ions is attracting. Cellulose is the most abundant natural polymer and exhibits amazing properties such as high chemical stability, hydrophilicity and biodegradability. However, some properties of pure cellulose-based materials including adsorbability are usually not enough, so it is important to improve their properties to broaden their applications. In the present work, hydroxyapitite (HAP) nanoparticles were prepared and introduced to improve the cellulose hydrogel (CG) properties. The structure and properties of the resultant cellulose/HAP nanocomposite hydrogels (CHG) were characterized and studied systematically. The results indicated that HAP nanoparticles was fixed and distributed evenly in CG. The maximum decomposition temperature increased gradually from 334.6 °C for CG to 346.7 °C for CHG, and the compressive strength increased gradually from 100 kPa for CG to 570 kPa for CHG with the increase of HAP content, respectively. Moreover, the adsorption capacity (q_e) value of CHG towards Cu²⁺ could reach more than 300% higher than that of CG. As a potential absorbent, CHG exhibited relatively good recyclability of more than 78% after 10 cycles. Therefore, the introduction of HAP improved the properties of CG greatly, showing wide potential applications.

Porous BMTTPA-CS-GO nanocomposite for the efficient removal of heavy metal ions from aqueous solutions

In this study, a stable, cost-effective and environmentally friendly porous 2,5-bis(methylthio)terephthalaldehyde-chitosan-grafted graphene oxide (BMTTPA-CS-GO) nanocomposite was synthesized by covalently grafting BMTTPA-CS onto the surfaces of graphene oxide and used for removing heavy metal ions from polluted water. According to well-established Hg2+-thioether coordination chemistry, the newly designed covalently linked stable porous BMTTPA-CS-GO nanocomposite with thioether units on the pore walls greatly increases the adsorption capacity of Hg2+ and does not cause secondary pollution to the environment. The results of sorption experiments and inductively coupled plasma mass spectrometry measurements demonstrate that the maximum adsorption capacity of Hg2+ on BMTTPA-CS-GO at pH 7 is 306.8 mg g-1, indicating that BMTTPA-CS-GO has excellent adsorption performance for Hg2+. The experimental results show that this stable, environmentally friendly, cost-effective and excellent adsorption performance of BMTTPA-CS-GO makes it a potential nanocomposite for removing Hg2+ and other heavy metal ions from polluted water, and even drinking water. This study suggests that covalently linked crucial groups on the surface of carbon-based materials are essential for improving the adsorption capacity of adsorbents for heavy metal ions.

Synthesis and characterization of eco-friendly cellulose beads for copper (II) removal from aqueous solutions

In this study, novel cellulose-bead-based biosorbents (CBBAS) were successfully synthesized from almond shell using a simple three-step process: (i) dissolution of bleached almond shell in ionic liquid (1-butyl-3-methylimidazolium chloride), (ii) coagulation of cellulose-ionic liquid solution in water and (iii) freeze-drying. Their morphological, structural and physicochemical properties were thoroughly characterized. These biomaterials exhibited a 3D-macroporous structure with interconnected pores, which provided a high number of adsorption sites. It should be noted that CBBAS biosorbents were efficiently employed for the removal of copper (II) ions from aqueous solutions, showing high adsorption capacity: 128.24 mg g^-1. The biosorption equilibrium data obtained were successfully fitted to the Sips model and the kinetics were suitably described by the pseudo-second-order model. Besides, CBBAS biosorbents can be easily separated from the solution for their subsequent reuse, and thus, they represent a method for the removal of copper (II) from aqueous solutions that is not only eco-friendly but also economical.

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

In this paper, a simple chemical precipitation method was proposed to obtain zoledronate functionalized hydroxyapatite (zole-HAP) hybrid nano- biomaterials (zole-HAP-HNBM) which were firstly applied to adsorption. The characterizations of materials verified that the addition of zoledronate declined the crystallinity and transformed the morphology of HAP from short rod shape to microsphere, changed micro structure of the hybrid nanobiomaterial. Adsorption experiments carried out under different conditions showed that adsorption capacity of the nanobiomaterial, enhanced by the addition of zoledronate in preparation, which is equal to 1460.14 mg/g on Pb²⁺ and 226.33 mg/g on Cu²⁺ in optimum qualifications, was elevated more than the reported values in many literatures. At last, the sorption mechanisms of HAP and zole-HAP for Pb²⁺and Cu²⁺ were probed by experiments and Multifwn program calculation in details. It suggested that the dominant sorption mechanisms of HAP for Pb²⁺ were ion exchange and dissolution-precipitation rather than surface complexation, while besides the dissolution-precipitation mechanism, surface complexation may contribute more in the adsorption process of 10zole-HAP for Pb²⁺. Once considering HAP and 10zole-HAP, removal mechanisms of Cu²⁺ could involve surface complexation and ion exchange.

Synthesis of MgO micro-rods coated with charred dextrose and its application for the adsorption of selected heavy metals from synthetic and real groundwater

MgO micro-rods supported on porous carbon were synthesized by an economical method and applied for the adsorption of three different heavy metals ions (As (III), Cd (II) and Pb (II)). Here, we used dextrose as the source of carbon during the synthesis. The synthesized material has been characterized by different techniques like XRD, TEM, FE-SEM, BET and FT-IR for the determination of various physical properties. Compared with MgO synthesized without dextrose, the carbon-supported MgO or C-MgO demonstrated consistent rod-shaped morphology, higher surface area and better absorptivity. The adsorption data were analysed using various isotherm models and the Freundlich isotherm model seemed to provide the best fit to the data. The adsorption kinetics data on the other hand was well explicated by the pseudo second-order kinetic model. The maximum adsorption capacity of C-MgO was 508.47 mg g^-1 for As (III), 566.01 mg g^-1 for Cd (II) and 476.19 mg g^-1 for Pb (II), respectively after 6 h of reaction. To check the real-life usability and efficiency of C-MgO, it was added to a groundwater sample which had 169.55 ppb of As (III) and within 20 min it was adsorbed with 99% efficiency. Reusability studies reveal that C-MgO could be used up to 6 times with more than 60% efficiency. This study shows that C-MgO has high adsorptive ability, is an economic and non-toxic material with versatile applications and can be used for groundwater remediation in real life.

Copper Nanocluster-Doped Luminescent Hydroxyapatite Nanoparticles for Antibacterial and Antibiofilm Applications

Novel strategies in the field of nanotechnology for the development of suitable multifunctional drug delivery vehicles have been pursued with promising upshots. Luminescent copper nanocluster-doped hydroxyapatite nanoparticles (HAP NPs) were synthesized and applied for the delivery of antibacterial drug kanamycin. The negatively charged doped HAP NPs could electrostatically interact with the positively charged kanamycin. The kanamycin-loaded doped HAP NPs showed pronounced activity in the case of Gram-negative bacteria compared to that in Gram-positive bacteria. Upon interaction with the bacteria, kanamycin could probably generate harmful agents such as hydroxyl radical that leads to bacterial cell damage. After being incorporated with copper nanoclusters (Cu NCs), the doped HAP NPs were applied for the bioimaging of bacterial cells. The biocompatibility of doped HAP NPs was also studied in HeLa cells. As compared to copper nanoclusters, the doped HAP NPs showed excellent biocompatibility even at higher concentrations of copper. The kanamycin-loaded doped HAP NPs were further applied toward Pseudomonas aeruginosa biofilm eradication. Thus, the as-synthesized copper nanocluster-doped HAP NPs were applied as nanocarriers for antibiotic drug delivery, bioimaging, and antibiofilm applications.

Functionalized hollow MnFe2O4 nanospheres: design, applications and mechanism for efficient adsorption of heavy metal ions

A l-cysteine functionalized magnetic hollow MnFe₂O₄ nanosphere material has been synthesised, with high magnetism, large interior cavities, and high porosity and surface activity. It has high adsorption efficiency and regenerated adsorption capacity for the removal of Cr⁶⁺ and Pb²⁺ in contaminated water.

Pyrolytic behavior of a zero-valent iron biochar composite and its Cu(ii) removal mechanism

The reduction behavior of Fe³⁺ during the preparation of a zero-valent iron cocoanut biochar (ZBC8-3) by the carbothermic reduction method was analyzed. Fe³⁺ was first converted into Fe₃O₄, which was subsequently decomposed into FeO, and finally reduced to Fe⁰. A minor amount of γ-Fe₂O₃ was produced in the process. The isothermal thermodynamic data for the removal of Cu(ii) over ZBC8-3 followed a Langmuir model. The Langmuir equation revealed a maximum removal capacity of 169.49 mg g⁻¹ at pH = 5 for ZBC8-3. The removal of Cu(ii) over ZBC8-3 fitted well to a pseudo-first-order equation, which suggested that the rate limiting step of the process was diffusion. The Cu(ii) removal mechanism on ZBC8-3 involved the reduction of Cu(ii) by Fe⁰ to produce Cu⁰ and Cu₂O, while C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C, C–O–, and –O–H formed a complex with Cu(ii).

The Cu(ii) removal mechanism on ZBC8-3 involved the reduction of Cu(ii) by Fe⁰ to produce Cu⁰ and Cu₂O, while CC, C–O–, –O–H formed a complex with Cu(ii).