Rapid Adsorption Process Research Articles

Thermodynamic, isothermal, and kinetic analysis of mercury (II) adsorption on marine sediments

This study aims to investigate the potential of marine sediments as effective natural adsorbents for the removal of mercury ions (Hg (II)) from aqueous solutions. Sediment samples with total organic matter ranging from 3.7 % to 8.2 % were collected from five stations, river and sea, with different water salinities (28 to 42 g L−1). To explore the role of sediment′s organic matter in removal efficiency, parts of the collected sediments were subjected to hydrogen peroxide (H2O2) oxidation. The morphology, surface area, and structure of all sediments were investigated. The effects of experimental conditions were studied. The results indicated that 0.5 g of the untreated sediment was capable of quantitatively remove Hg (II) ions up to 100 µg L−1 at the salinity of 35 g L−1 while the H2O2-treated sediments resulted in a 40 % efficiency. Moreover, the adsorption capacity of the untreated sediment was 2.5 times higher than those obtained by H2O2-treated sediments. The pseudo-second-order kinetic model successfully described the adsorption process (R2 ≥0.9992), indicating the rapid adsorption process. The adsorption process was mainly controlled by ion-exchange interactions. These research findings may contribute to the development of new water treatment strategies, highlighting the significance of naturally available materials in addressing environmental challenges.

Novel waste wool fabric reinforced alginate-gum hydrogel composites for rapid and selective Pb (II) adsorption

Heavy metals employed in various industrial applications can negatively impact both the ecosystem and human beings. Common techniques for eliminating pollutants often rely on expensive materials. So, this study focuses on exploring economical alternatives obtained from nature and textile waste. In this study, a hydrogel composite was synthesized using wool nonwoven fabric mixed with alginate, gum Arabic (GA), and xanthan gum (XG) to evaluate its efficacy in adsorbing lead (Pb) from aqueous solutions. The composites were characterized using SEM, FTIR, and XPS to understand their structure and composition before and after Pb adsorption. The effects of time, pH, and initial metal ion concentration on Pb adsorption by the composite were also investigated. Maximum adsorption was observed at a basic pH, with the highest value recorded at 85.2 mg/g. Notably, 88.2 % of this maximum adsorption was achieved within 60 min, indicating a rapid adsorption process. Kinetic studies indicated that the adsorption process best fits pseudo-second-order kinetics, while the Freundlich model, with an R² value of 0.95, suggests a chemisorption mechanism. The developed wool-alginate-gum hydrogel composite has shown to be a promising candidate for the removal of Pb²⁺ ions from wastewater.

Adsorption parameters optimization of spent coffee ground biochar for methylene blue removal using response surface methodology

This study investigates the potential of spent coffee ground biochar (SCGB) as a sustainable and cost-effective adsorbent for the removal of methylene blue (MB), a hazardous dye commonly used in the textile and printing industries. A response surface methodology (RSM) approach with central composite design (CCD) was employed to systematically investigate the effects of key process parameters, including adsorbent dosage, solution pH, contact time and temperature, on MB removal efficiency. The analysis revealed that adsorbent dosage and temperature as critical factors influencing MB removal, with a linear model providing a strong correlation. Optimal conditions for MB removal were determined to be 0.99 g of SCGB, 30 min of contact time, 30 °C temperature, and a solution pH of 7. Under these conditions, MB removal reached 99.99%, with a desirability of 1.000. The experimental results closely matched the predicted values, differing by only 0.02%, thus validating the accuracy of the model. Kinetic studies indicated a rapid adsorption process, well-described by both pseudo-first and pseudo-second order models. Isotherm analysis confirmed the applicability of the Freundlich model, suggesting favorable adsorption with increasing MB concentration. The high adsorption capacity of SCGB is attributed to its carbonaceous and porous structure, highlighting its potential as an effective adsorbent for dye removal in wastewater treatment applications.

Efficient wastewater decontamination using magnetic bentonite-alginate beads: A comprehensive study of adsorption dynamics, regeneration, and molecular interactions

This study enhances wastewater treatment methodologies by developing magnetic bentonite-alginate beads (MBent-A beads) for adsorbing methylene blue (MB) from aqueous solutions. Experimental and computational analyses were employed to evaluate the beads' adsorption efficiency, utilizing characterization techniques including Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), point of zero charge (pHpzc), Brunauer-Emmett-Teller method (BET), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) to examine the composite’s morphology and chemistry. Findings reveal a significant adsorption capacity with the beads' specific surface area at 3.94 m2/g and a maximum adsorption capacity of 774.32 mg/g. Adsorption kinetics adhered closely to the pseudo-second-order model, indicating a rapid adsorption process, while Langmuir isotherm analysis confirmed a uniform monolayer adsorption and temperature-dependent capacities. Thermodynamic analysis showed the adsorption process to be spontaneous and exothermic, reflecting a strong affinity between MB molecules and the bead surface. The beads demonstrated durability with more than 90% removal efficiency after five regeneration cycles, highlighting a minimal decrease from 98.54% to 90.60%. In-depth theoretical investigations using density functional theory (DFT), frontier molecular orbital (FMO), reduced density gradient (RDG), and quantum theory of atoms in molecules (QTAIM) analyses identified van der Waals forces and hydrogen bonding as primary interactions driving the adsorption. The synthesis of MBent-A beads and their confirmed efficacy in dye adsorption integrates experimental research with theoretical modeling, offering a robust solution for treating dye-contaminated wastewater and underlining the potential of MBent-A beads in environmental remediation.

Bimetal-Organic Frameworks Incorporating Both Hard and Soft Base Active Sites for Heavy Metal Ion Capture.

The design and synthesis of stable porous materials capable of removing both hard and soft metal ions pose a significant challenge. In this study, a novel metal-organic framework (MOF) adsorbent named CdK-m-COTTTB was developed. This MOF material was constructed using sulfur-rich m-cyclooctatetrathiophene-tetrabenzoate (m-H4COTTTB) as the organic ligand and oxygen-rich bimetallic clusters as the inorganic nodes. The incorporation of both soft and hard base units within the MOF structure enables effective removal of various heavy metal ions, including both soft and hard acid species. In single-component experiments, the adsorption capacity of CdK-m-COTTTB for Pb2+, Tb3+, and Zr4+ ions reached levels of 636.94, 432.90, and 357.14 mg·g-1, respectively, which is comparable to specific MOF absorbents. The rapid adsorption process was found to be chemisorption. Furthermore, CdK-m-COTTTB exhibited the capability to remove at least 12 different metal ions in both separate and multicomponent solutions. The material demonstrated excellent acid-base stability and renewability, which are advantageous for practical applications. CdK-m-COTTTB represents the first reported pristine MOF material for the removal of both hard and soft acid metal ions. This work serves as inspiration for the design and synthesis of porous crystalline materials that can efficiently remove diverse heavy metal pollutants.

Trace cisplatin adsorption by thiol-functionalized sponge (TFS) and Sn/SnO2-coated TFS: Adsorption study and mechanism investigation

To remove trace cisplatin from aqueous solution, commercial sponges were functionalized by esterification with 3-mercaptopropionic acid, followed by reduction with Na2S·9H2O or SnCl2·2H2O. The resulting thiol-functionalized sponges (TFSs), TFS_1 and TFS_2, were tested for the removal of cisplatin (235 μg L−1) achieving maximum removal of 95.5 ± 0.8% and 99.5 ± 0.1% respectively, which were significantly higher than the non-functionalized counterpart. The successful grafting of thiol groups, verified through FTIR, elemental analysis, SEM-EDS, and XPS characterization, facilitated Pt−S complexation during adsorption. The aqua-derivatives of cisplatin, formed through hydration, complexed with thiol sites through ligand displacement. Additionally, the presence of Sn/SnO2 coating on TFS_2 further enhanced the adsorption process. The rapid adsorption process conformed to pseudo-second-order kinetic model, involving both diffusion and chemisorption. While the Langmuir isotherm model generally described the monolayer adsorption behavior of cisplatin, the aggregation of Sn/SnO2 onto TFS_2 at 343 K introduced surface heterogeneity, rendering the Freundlich model a better fit for the adsorption isotherm. Differential pH dependence and the evaluation of mean free energy, derived from the Dubinin-Radushkevich isotherm model, indicated that cisplatin adsorption onto TFS_1 involved physisorption, including electrostatic attraction, while chemisorption predominated for TFS_2. Increasing the temperature notably promoted adsorption by facilitating the thermal-favored formation of Pt−S bonds.

Efficient and ultrafast adsorption of aromatic amino acids by hyper-crosslinked porous cyclodextrin polymers with high adsorption capacity

The adsorption separation technology is of key significance in the purification of aromatic amino acids (AAAs) and the production of their derivatives. However, defects are always present in existing adsorbents for AAAs with slow adsorption rates, low adsorption capacity, and poor regeneration performance. Therefore, there is an urgent need to develop more efficient adsorbents for AAAs to improve separation and purification efficiency and productivity. In this study, partially benzylated cyclodextrin-based hyper-crosslinked porous polymers (PBCD-B-D) were prepared, among which the one with β-cyclodextrin as monomer (PBβ-CD-B-D) exhibited an extremely rapid adsorption process, a high adsorption capacity for AAAs, and a good selectivity toward AAAs over other amino acids. Specifically, the adsorption of AAAs reached equilibrium within one minute, while the equilibrium adsorption capacities of PBβ-CD-B-D for Trp and Phe were up to 524.58 mg·g−1 (almost the highest till now) and 189.48 mg·g−1, respectively. The pseudo-second-order kinetic model and the Freundlich model were better suited for describing the adsorption process. The comprehensive analysis of experimental results suggested that host–guest cooperation and π-π interactions may be the two dominant factors affecting the adsorption of AAAs on PBβ-CD-B-D. In addition, PBβ-CD-B-D exhibited good reusability, with the adsorption capacity remaining at 83.67 % after 4 adsorption–desorption cycles. Due to its low cost, good reusability, and excellent adsorption performance, PBβ-CD-B-D has great potential for application in the adsorptive removal and recovery of AAAs.

Adsorption of Polyetheramine-230 on Expansive Clay and Structure Properties Investigation.

Polyetheramine (PEA) is a swelling inhibitor used to address engineering challenges arising from the interaction between montmorillonite (Mt) and water. This study comprehensively investigates the adsorption characteristics of PEA on three representative expansive clay samples: Na-Mt, Ca-Mt, and engineered expansive soil. Additionally, the desorption of exchangeable ions is examined. The findings reveal that a two-stage adsorption kinetic model and a pseudo-second-order kinetic model can properly describe the adsorption kinetics of PEA on expansive clays. PEA exhibits a strong capacity for ion exchange with sodium ions, while the exchange capacity for calcium ions is limited. Both protonated and non-protonated PEA contribute to rapid adsorption processes. The adsorption isotherms are well-fitted by the Langmuir and Freundlich models, with the Langmuir model being reasonable. At lower equilibrium concentrations, a higher proportion of the adsorption amount is attributed to ion exchange compared to higher equilibrium concentrations. Ion exchange emerges as the primary factor contributing to the adsorption of PEA on Na-Mt, whereas the adsorption of PEA on Ca-Mt and expansive soil is primarily attributed to physical adsorption by non-protonated PEA. X-ray diffraction results reveal significant intercalation effects of PEA as they penetrate the interlayer space and hinder interlayer ion hydration. Fourier transform infrared spectrum results demonstrate that the adsorption of PEA minimally impacts the framework of Mt structural units but primarily reduces the adsorbed water content. Clay-PEA composites exhibit a decreased affinity for water. Zeta potential experiments indicate that the adsorption of PEA significantly diminishes the surface potential of clay-PEA composite particles, effectively inhibiting their hydration dispersion.

Trace cisplatin and carboplatin removal by 3-mercaptopropionic acid and l-cysteine functionalized sponges: Adsorption behaviour and mechanism

This study presents functionalized open-celled cellulose Metalzorb® sponge (Sponge) with 3-mercaptopropionic acid (MPA) and l-Cysteine (Cys), and the resulting MPA@Sponge and Cys@Sponge showed significantly improved removal efficiency towards trace cisplatin and carboplatin against Sponge. MPA@Sponge achieved maximum removal of 88.9 ± 0.5% for cisplatin and 85.2 ± 0.4% for carboplatin, while Cys@Sponge achieved maximum removal of 75 ± 2% and 59 ± 1%. In contrast, Sponge only achieved removal of 29 ± 4% and 4 ± 1%, respectively. It suggests that thiol groups serve as favourable binding sites for Pt complexation. Carboplatin exhibits lower adsorption compared to cisplatin due to its limited hydration. However, the presence of Cl− in stock and high temperature facilitate the hydration and the formation of active derivatives of carboplatin, thereby enhancing its adsorption. The rapid adsorption processes of cisplatin and carboplatin are well described by the pseudo-second-order kinetic model involving diffusion and chemisorption. The results from adsorption isotherms revealed a monolayer adsorption that aligns with the principles proposed by the Langmuir model. High temperature significantly enhances the adsorption, and the positive enthalpies indicate that the binding of Pt with thiol groups is endothermic process. X-ray absorption spectroscopy measurements at the Pt L3-edge revealed a similar coordination environment of the adsorbed Pt on both functionalized adsorbents, which can be attributed to the formation of four Pt-S bonds during the adsorption. To assess the validity of the adsorption results under realistic medium conditions, an adsorption study was carried out by using diluted urine spiked with trace platinum cytostatic drugs to simulate hospital wastewater. 90.2 ± 0.3% of cisplatin and 77.0 ± 0.2% of carboplatin was effectively removed by MPA@Sponge from diluted urine.

Comparative study on removal of platinum cytostatic drugs at trace level by cysteine, diethylenetriamino functionalized Si-gels and polyethyleneimine functionalized sponge: Adsorption performance and mechanisms

To efficiently remove trace Pt-based cytostatic drugs (Pt-CDs) from aqueous environments, a comparative investigation was conducted on the adsorption behavior of three commercial adsorbents including cysteine-functionalized silica gel (Si-Cys), 3-(diethylenetriamino) propyl-functionalized silica gel (Si-DETA) and open-celled cellulose MetalZorb® sponge (Sponge). The research on the adsorption of cisplatin and carboplatin encompasses investigations of pH dependence, adsorption kinetics, adsorption isotherms, and adsorption thermodynamics. The obtained results were compared with those of PtCl42− to better understand the adsorption mechanisms. The adsorption of cisplatin and carboplatin by Si-Cys was significantly better than Si-DETA and Sponge, which suggested that in chelation-dominated chemisorption, thiol groups provided high-affinity sites for Pt(II) complexation. Adsorption of the anion PtCl42− was more pH dependent and generally superior to that of cisplatin and carboplatin, benefiting from the contribution of ion association with protonated surfaces. The removal process of aqueous Pt(II) compounds occurred by the hydrolysis of complexes in solution and subsequent adsorption, and the specific adsorption process was explained by the synergistic action of ion association and chelation mechanisms. The rapid adsorption processes involving diffusion and chemisorption were well described by pseudo-second-order kinetic model. The isotherm studies suggested monolayer adsorption, consistent with the Langmuir model. Indicated from the adsorption enthalpy results, the chelation of cisplatin and carboplatin with thiol groups was an endothermic reaction, while the adsorption of PtCl42− was exothermic. At 343 K, Si-Cys achieved 98.5 ± 0.1 % (cisplatin) and 94.1 ± 0.1 % (carboplatin) removal. To validate the obtained findings, the described process was applied to urine samples doped with Pt-CDs as analog of hospital wastewaters and the removal was very efficient, ranging from 72 ± 1 % to 95 ± 1 %, when using Si-Cys as adsorbent, although limited matrix effects were observed.

Efficient and rapid elimination of 99TcO4−/ReO4− from medium-low level acid – Wastewater using anion exchange adsorbent

Efficient removal of 99TcO4− from nuclear wastewater is of great urgency for both nuclear-related environmental remediation and the safe development of nuclear. In this work, an anion exchange adsorbent PP-g-GMA@EDA/SACl (PGESCl) based on polypropylene (PP) nonwovens is facilely prepared by radiation-induced grafting and chemical modification for 99TcO4− elimination. By the analogy of the ReO4−, the batch adsorption experiments at medium–low acidity show that PGESCl possessed fast adsorption kinetics (within 10 min), higher uptake capacity (251.13 mg/g for Re(VII)), and excellent selectivity in the presence of excessive competing anions such as NO3−, Cl− and SO42−. In the actual adsorption exploration of 99TcO4−, PGESCl still possesses a rapid adsorption process and excellent selectivity. X-ray photoelectron spectroscopy (XPS) and energy disperse spectroscopy (EDS) analyses reveal that anion exchange between the 99TcO4−/ReO4− in solution and the chloride ion in PGESCl plays a dominant role in the adsorption of 99TcO4−/ReO4−. The adsorbed 99TcO4−/ReO4− can be completely eluted by 1 mol/L HCl even after five adsorption–desorption cycles, indicating the excellent recyclability to capture 99TcO4−/ReO4−. The performance of PGESCl shows potential for effective 99TcO4− removal from radioactive nuclear wastewater.

Untreated Opuntia ficus indica for the Efficient Adsorption of Ni(II), Pb(II), Cu(II) and Cd(II) Ions from Water.

The raw cladode of Opuntia ficus indica (OFI) was evaluated as a sustainable biosorbent for the removal of heavy metals (Ni, Pb, Cu, and Cd) from aqueous solutions. The functional groups of OFI were identified by employing DRIFT-FTIR and CP-MAS-NMR techniques before and after contact with the ions in an aqueous media, showing a rearrangement of the biomass structure due to the complexation between the metal and the functional groups. The adsorption process was studied in both single- and multi-component systems under batch conditions at different pHs (4.0, 5.0, and 6.0), different metal concentrations, and different biomass amounts. The results show that the raw OFI had a removal capacity at room temperature of over 80% for all metals studied after only 30 min of contact time, indicating a rapid adsorption process. Biosorption kinetics were successfully fitted by the pseudo-second-order equation, while Freundlich correctly modelled the biosorption data at equilibrium. The results of this work highlight the potential use of the untreated cladode of OFI as an economical and environmentally friendly biosorbent for the removal of heavy metals from the contaminated aqueous solution.

Efficient Removal of Pb(Ⅱ) by Highly Porous Polymeric Sponges Self-Assembled from a Poly(Amic Acid)

Lead (II) (Pb(II)) is widespread in water and very harmful to creatures, and the efficient removal of it is still challenging. Therefore, we prepared a novel sponge-like polymer-based absorbent (poly(amic acid), PAA sponge) with a highly porous structure using a straightforward polymer self-assembly strategy for the efficient removal of Pb(II). In this study, the effects of the pH, dosage, adsorption time and concentration of Pb(II) on the adsorption behavior of the PAA sponge are investigated, revealing a rapid adsorption process with a removal efficiency up to 89.0% in 2 min. Based on the adsorption thermodynamics, the adsorption capacity increases with the concentration of Pb(II), reaching a maximum adsorption capacity of 609.7 mg g-1 according to the Langmuir simulation fitting. Furthermore, the PAA sponge can be efficiently recycled and the removal efficiency of Pb(II) is still as high as 93% after five adsorption-desorption cycles. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses reveal that the efficient adsorption of Pb(II) by the PAA sponge is mainly due to the strong interaction between nitrogen-containing functional groups and Pb(II), and the coordination of oxygen atoms is also involved. Overall, we propose a polymer self-assembly strategy to easily prepare a PAA sponge for the efficient removal of Pb(II) from water.

Preparation of Porous Silica Nanoparticles by Chemical Etching for Removal of Paraquat from Aqueous Solution

In t his study, solid silica nanoparticles (sSiO2 NPs) were chemically etched using sodium hydroxide solution as an etchant to synthesize porous silica nanoparticles (pSiO2 NPs). Etchant dosage and etching time were optimized to obtain the optimum etching condition providing the effective removal of paraquat (PQ). High removal efficiency of PQ by the synthesized pSiO2 NPs was obtained over 90% using 11.1 mL of 1.25 M NaOH and 12 h for the etching process. SEM and TEM images showed that the porosity of pSiO2 NPs increased with increase of the etchant dosage and etching time. The increment of porosity of pSiO2 NPs enhanced the PQ removal efficiency. FTIR result indicated that the characteristic functionalities of silica remain after the etching process. After optimum condition of etching obtained, the adsorption behavior of PQ was investigated. Several key factors influencing the adsorption efficiency, i.e., initial solution pH, initial concentration, and adsorption time were optimized. The maximum removal efficiency of PQ (~98%) by the pSiO2 nanoadsorbent was obtained using 100 mg L-1 of PQ solution at pH ~7 within 5 minutes. The maximum adsorption capacity (qmax) of the pSiO2 NPs for the PQ removal was 65.7 mg g-1. The pSiO2 nanoadsorbent is effective adsorbent for the PQ removal due to the development of a facile synthetic method for adsorbent preparation, rapid adsorption process, and comparable qmax value with other PQ adsorbents.

Abundant cilantro derived high surface area activated carbon (AC) for superior adsorption performances of cationic/anionic dyes and supercapacitor application

With the growing concern about water quality requirements and the looming energy crisis, researchers all over the world have committed to the development of novel single low-cost porous materials for a variety of applications (ex: environmental and energy applications). Treatment of dye contaminants before they are released into the environment is considered as a significant challenge in the field of water treatment. Treatment of such dye contaminants remains as challenging task and evolved as the most persistent issues in the environmental remediation field. To address all these specific limitations present investigation involves the conversion of inexpensive Cilantro plants (C. sativum) into Activated Carbon (AC) which can be utilized as a fascinating alternative potential low-cost AC material for the treatment of toxic dye contaminants (environmental) and supercapacitor (energy) applications with improved performances. The fundamental physical–chemical properties of AC were confirmed by using various analytical and spectroscopic techniques. It is substantial to mention, obtained AC possesses a microporous structure and a large specific surface area of 2200 m2g−1. Further, AC was employed for the adsorption of methyl orange (MO) and rhodamine-6G (Rh-6G) dyes from aqueous solutions. The rapid adsorption process occurred within the contact time of 14 and 20 min for MO and Rh-6G. In addition, demonstrated with > 99 % removal efficiencies and an outstanding maximum adsorption capacity of 467.29 mg/g for MO and 143.47 mg/g for Rh-6G was witnessed surpassing the commercially available activated carbon material (CAC). To prove the efficacy of AC, the real-time application was evaluated by taking an industrial wastewater sample which showed 99.45 % of removal efficiency. Furthermore, a cartridge was developed and utilized for the treatment of dye solution for an on-field demonstration to assess potable water. Moreover, the synthesised AC witnessed a removal efficiency of > 80 % even up to the 4th cycle. Most importantly, to mark the waste management process the regenerated AC adsorbent and desorbed pollutants are treated effectively and can be utilized for further applications. Interestingly, the AC material obtained at 700 °C displayed optimum specific surface area (SSA), surface functionalities which help electrode wetting, surface redox reaction and pseudo-capacitance from ion diffusion and showed specific capacitance of 162.4F/g at 1 A/g (three electrode system). Notably, the AC symmetric supercapacitor provides a high-power density of 243.94 W/kg and could be reversibly cycled with very minimal capacitance loss over 5000 cycles at 10 A/g.

Amidoxime-modified hypercrosslinked porous poly(styrene-co-acrylonitrile) adsorbent with tunable porous structure for extracting uranium efficiently from seawater

To efficiently and economically extract uranium from seawater, novel amidoxime-modified hypercrosslinked poly(styrene-co-acrylonitrile) (SAN) adsorbents with tunable porous structure were synthesized via simple Friedel-Crafts reaction followed by amidoximation. The adsorbent HCPSAN-B-AO obtained by using biphenyl dichlorobenzyl (BCMBP) as an additional crosslinking agent, possessed a larger pore size and higher surface area due to the longer and more rigid molecular structure of BCMBP compared to the original crosslinking agent 1,2-dichloroethane (DCE), resulting in the higher uranium adsorption capacity of HCPSAN-B-AO. Investigations on the adsorption performance in real seawater containing a large amount of interfering ions showed that the adsorbent owned excellent selectivity for uranyl ions, and the removal percentage of uranium could reach 84.4%. Furthermore, the adsorbent maintained good adsorption performance even after 5 adsorption–desorption cycles, indicating a good recyclability. Investigations on adsorption kinetics, thermodynamics, adsorption isotherms and adsorption mechanism manifested that the adsorption was a rapid (adsorption equilibrium within 30 min), spontaneous and chemical adsorption process (maximum adsorption capacity was 228 mg g−1), and the mechanism was mainly the interaction between uranyl ions and amidoxime groups. In summary, the as-prepared adsorbent was a feasible adsorbent for uranium extraction from seawater.

Essential processes involving REE-enrichment in biogenic apatite in deep-sea sediment decoded via multivariate statistical analyses

Deep-sea sediments highly enriched in rare-earth elements (REE), termed “REE-rich mud,” have recently attracted attention as a potential mineral resource for industrially critical metals. Biogenic apatite or fish teeth and bone debris comprises the mineral phase which primarily hosts REE in deep-sea sediments; thus, biogenic apatite is a key material to decipher the formation process of REE-rich mud. We investigated the key process(es) controlling REE-enrichment in biogenic apatite through a novel data-driven approach. We analyzed the in situ chemical composition of biogenic apatite grains collected from REE-rich mud in the western North Pacific Ocean. Subsequently, the dataset of 685 analytical points × 35 elements was statistically analyzed via independent component analysis. Our new approach extracted four independent components (ICs) as geochemically meaningful and statistically independent signatures: substitution of elements into apatite lattice (IC1), the relatively rapid adsorption process that occurred at the sediment-water interface (IC2), elemental transfer from volcanic materials during early diagenesis (IC3), and metalliferous or detrital impurities physically adhering to or infiltrating apatite grains (IC4). Data distributions within the real and IC spaces provide insights into physicochemical processes involving elemental incorporation into biogenic apatite. We argue that after settlement on the seafloor, the fish bones and dentine in teeth adsorb REE from the overlying seawater and REE-enriched porewater at the sediment-water interface, resulting in the preferential enrichment of light rare-earth elements into apatite from these solutions. Further, that REE adsorbed on the apatite crystal surface was incorporated into the crystal lattice via substitution. The IC2 signal was intensified in the layers of “extremely REE-rich mud”, suggesting that the REE adsorption process was facilitated during the formation of layers with remarkably high bulk-sediment REE contents. This may reflect an increased supply of REE-carrier substances such as organic matter, which degraded on the seafloor and released REE at the sediment-water interface, which is associated with changes in paleoceanographic conditions including ocean surface bioproductivity.

Instant and Tough Adhesives for Rapid Gastric Perforation and Traumatic Pneumothorax Sealing.

Hydrogel adhesives are hot spots due to their ubiquity and practical relevance. However, achieving a robust wet adhesion is still a challenge due to the preferential formation of hydrogen bonds between interfacial fluids and bulk hydrogel, as well as targeted substrates. Herein, a half-dry adhesive consisting of a silk fibroin (SF) semi-interpenetrating network and poly(acrylic acid) covalent network, which can allow a rapid liquid adsorption and repulsion process encountering a wet tissue, is reported. The remaining water enables excellent hydrogel flexibility to a dynamic surface, while the β-sheet fold endows its tough bulk strength under the peeling-off process. Notably, the wet adhesion energy versus porcine skin is 1440 J m-2 due to the combination of hydrogen bonds, electrostatic interactions, and chain entanglement derived from SF. In particular, both in vitro and in vivo outcomes indicate excellent hemostatic effects and result in incision closure of skin, artery, gastric perforation, and lung. After the first-stage closure, polyacrylic-silk fibroin adhesive (PSA) sealants can detach from the lung surface, fitting well to the healing period. By virtue of the reliable adhesion and good noncytotoxicity, PSA may be a prospective candidate for tissue sealant and drug carrier applications.

Fabrication of modified alginate-based biocomposite hydrogel microspheres for efficient removal of heavy metal ions from water

Thiol and amido modified alginate was prepared and combined with graphene oxide to fabricate the biocomposite hydrogel microsphere adsorbent for the removal of heavy metal ions from water. Fourier transform infrared (FTIR), scanning electron microscope (SEM) and thermogravimetric analyzer (TGA) were used to characterize the structure and thermal stability of hydrogel microspheres. The adsorption performance and mechanism of the biocomposite hydrogel microspheres for the removal of Pb2+ and Cu2+ from water have also been investigated. The results indicated that the hydrogel microspheres exhibited rapid adsorption process and excellent adsorption capacity for both heavy metal ions. The experimental maximum adsorption capacities for Pb2+ and Cu2+ were 369.6 and 124.1 mg⋅g−1, respectively. The adsorption isothermal and kinetics were well described by Langmuir and pseudo-second-order models. After five consecutive adsorption-desorption cycles, the adsorption capacity of microspheres on Pb2+ and Cu2+ remained above about 90%, indicating their excellent reusability. The rapid and high adsorption efficiency and outstanding regeneration ability suggest that the modified alginate-based biocomposite hydrogel microspheres have potential applications in the field of water treatment.

Nitrogen doped porous carbon polyhedral supported Fe and Ni dual-metal single-atomic catalysts: template-free and metal ligand-free sysnthesis with microwave-assistance and d-band center modulating for boosted ORR catalysis in zinc-air batteries

Constructing dual-metal single-atom catalysts (DSAs) now stands for a unique and worthwhile strategy for developing high-efficiency electrocatalysts for oxygen reduction reaction (ORR). However, the facile synthesis of DSAs uniformly located on nitrogen porous carbon materials is still challenging. Herein, Fe and Ni dual-metal single-atomic active sites uniformly located on nitrogen doped porous carbon polyhedrals (FeNi-DSAs-PNCH) are successfully prepared by a facile and rapid microwave-assisted adsorption and subsequent pyrolysis process with free template and free metal ligand. The FeNi-DSAs-PNCH catalyst exhibits boosted ORR activity and long time stability. Experimental investigations and density functional theory calculation results verify that, besides the hierarchical porous structure, large specific surface area and abundant catalytic active sites, the adjacent Ni-Nx atomic sites can modulate the d-band center of Fe-Nx single atomic active centers and balance the adsorption–desorption affinities to O2 molecules and oxygen-containing intermediates on Fe-Nx, thus leading to an superior ORR activity with a more positive half-wave potential (0.89 V vs. RHE) than the single Fe or Ni atomic catalyst and the commercial Pt/C catalyst. Moreover, with FeNi-DSAs-PNCH as the air cathode and zinc foil as the anode, an assembled Zn-air battery exhibits a higher open-circuit voltage of 1.48 V and a larger specific capacity of 802.18 mAh g−1 than that of the Pt/C-based Zn-air battery (1.37 V and 664.78 mAh g−1, respectively). This work develops a convenient strategy for preparing dual-metal single-atomic cataysts as promising substitutes for the commercial Pt/C catalysts in the practical energy conversion applications, and also offers experimental and theoretical guidance for rational designing and improvement of ORR and other catalysts by tailoring the d-band center of the active sites.