Competitive Metal Research Articles

Reactive Fluorescent and Colorimetric Probe for Highly Selective and Sensitive Detection of Hg2+ in Real Water Samples.

Construction of efficient chemosensors for highly specific and sensitive detection of mercury ions remains a great challenge. In this work a highly selective and sensitive probe CY was designed and synthesized by using coumarin fluorophore as the matrix and thioacetal moiety as the reactive recognition site for Hg2+. By virtue of the thiophilicity of Hg2+, probe CL could be hydrolyzed to deprotect and the thioacetal was transformed to the acyl group after the addition of Hg2+, the blue-green fluorescence was quenched and meanwhile the solution changed from light green to yellow. The detection limit of probe CY for Hg2+ was as low as 6.8 nM, and it could completely react with Hg2+ within 3min. Moreover, probe CY exhibited good resistance against interference from competitive metal ions and biothiols, high stability in pH 1-11 and applicability for fluorogenic and chromogenic dual-modal detection of Hg2+ in real water samples over a broad range of pH 5-10.

Novel coumarin-Schiff base derived electronically distinct fluorescent probes: Synthesis and comparative investigations of their unique selective sensing properties with Cu2+ and Cu+ ions

The present work describes the synthesis and comparative investigations of Cu2+ and Cu+ ions sensing properties of two novel π-extended coumarin-Schiff base-derived electronically distinct fluorescent probes (4 and 5). Due to the additional electron donating group substituent (-NEt2) close proximate to the binding site of Schiff base in probe 5, it exhibits distinct electronic properties compared to probe 4. Our studies indicate that probe 5 displays efficient and highly selective fluorescence quenching behaviors with Cu2+ and Cu+ ions compared to other competitive metal ions (Ca2+, Mg2+, Al3+, Hg2+, Pb2+, Cd2+, Mn2+, Co2+, Ni2+, Fe2+, Fe3+, Cr3+ and Zn2+). In our studies, Job's plot experiments revealed that the binding stoichiometry of the ligand-Cu2+ was 1:1 for both probes. The limit of detection (LOD) of 2.35 × 10–5 M and 1.56 × 10–5 M were obtained for the probes 4 and 5, respectively. Further, the Stren-Volmer equation has been used to calculate the binding abilities of probes with Cu2+ ions; it reveals the binding constant of 6.70 × 104 M-1 and 22.0 × 104 M-1 for probes 4 and 5, respectively. Also, in the present studies, our DFT computed results were comparatively presented to understand the electronic parameters (HOMO-LUMO energy band gaps, ESP and Mulliken atomic charge distribution) of compound 1, probes 4 and 5. We anticipate that the developed probes can be used to analyze Cu2+ and Cu+ ions in environmental and biological samples.

Ultrafast Two-Color X-Ray Emission Spectroscopy Reveals Excited State Landscape in a Base Metal Dyad.

Effective photoinduced charge transfer makes molecular bimetallic assemblies attractive for applications as active light-induced proton reduction systems. Developing competitive base metal dyads is mandatory for a more sustainable future. However, the electron transfer mechanisms from the photosensitizer to the proton reduction catalyst in base metal dyads remain so far unexplored. A Fe─Co dyad that exhibits photocatalytic H2 production activity is studied using femtosecond X-ray emission spectroscopy, complemented by ultrafast optical spectroscopy and theoretical time-dependent DFT calculations, to understand the electronic and structural dynamics after photoexcitation and during the subsequent charge transfer process from the FeII photosensitizer to the cobaloxime catalyst. This novel approach enables the simultaneous measurement of the transient X-ray emission at the iron and cobalt K-edges in a two-color experiment. With this methodology, the excited state dynamics are correlated to the electron transfer processes, and evidence of the Fe→Co electron transfer as an initial step of proton reduction activity is unraveled.

Investigation of the Potential of Repurposing Medium-Density Fiberboard Waste as an Adsorbent for Heavy Metal Ion Removal.

Medium-density fiberboard (MDF) waste generation has increased steadily over the past decades, and therefore, the investigation of novel methods to recycle this waste is very important. The potential of repurposing MDF waste as an adsorbent for the treatment of Cd(II), Cu(II), Pb(II), and Zn(II) ions in water was investigated using MDF offcuts. The highest adsorption potential in single-metal ion solution systems was observed for Pb(II) ions. The experimental data of Pb(II) ions fit well with the Freundlich isotherm and pseudo-second-order kinetic models. Complexation and electrostatic interactions were identified as the adsorption mechanisms. The adsorption behavior of multi-metal ion adsorption systems was investigated by introducing Cd(II) ions as a competitive metal ion. The presence of the Cd(II) ions reduced the adsorption potential of Pb(II) ions, yet the preference for the Pb(II) ions remained. Regeneration studies were performed by using 0.1 M HCl as a regeneration agent for both systems. Even though a significant amount of adsorbed metal ions were recovered, the adsorption potential of the MDF was reduced in the subsequent adsorption cycles. Based on these results, MDF fines have the potential to be used as an economical adsorbent for remediation of wastewater containing heavy metal ions.

Competitive sequestration behavior and mechanism of Cd2+, Pb2+and Ni2+ ions from single, binary and ternary metal laden solution by Hevea brasiliensis wood sawdust (HBS)

HeveaBrasiliensis wood sawdust (HBS), a lignocellulosic material, was employed for the eradication of Cd(II), Pb(II), and Ni(II) from synthetic single and multi-metalsystem. In the realm of multimetal adsorption, HBS exhibited the most substantial adsorption capacities for heavy metals, in the order: Pb(II) > Cd(II) > Ni(II). Experiments involving batch process were carried out to explore the rolesofpH, contact duration, HBS quantity, and preliminary metal concentrations on the adsorption capacity. Optimal conditions for biosorption of metal ions were determined as pH 5.0, dosage of 7 gL−1, and an equilibrium time of 90 min. The pseudo-second-order kinetics andLangmuirisotherm had a favorable alignment with the biosorption of all individual metal ions. Adsorption capacity was 8.45, 13.01 and 6.04 mg g− 1 for Cd, Pb and Ni respectively in single metal system. In binary and ternary system the capacity and adsorption percentages decreases significantly due the presence of competitive metal ions. HBS demonstrated effectiveness in treating real wastewater containing Cd2+, Pb2+and Ni2+ ionsin both single and mixed metal solutions, highlighting the necessity of thoroughly considering the impact of competitive adsorption. SEM with EDS results indicated single metal fixing in a multi-ion solution followed complex mechanisms. The surface area and functional group studies were conducted utilizing BET and a FTIR Spectrometer. Electrostatic attraction and complexation mechanisms were identified as responsible factor for capturing metal ions to the active surfaces of the bio sorbent. Cost analysis reflected the adsorbent cost was $0.021 per liter of mixed contaminated ternary effluent (30 mg L−1).

A solid-state sensor based on nanosilica/methylcellulose composite and chromoionophore 8-carboxamidoquinoline derivative as an optode pellet for Zinc(II) ion

Zinc is known to play a central role in the immune system that creates a resistance barrier against viral infection. A naked-eye zinc(II) (Zn2+) ion sensor of 2-oxo-2-(quinolin-8-ylamino)acetic acid (OQAA) as a recognition probe was designed and synthesized. By inserting functional groups of amide and carboxylic acid into a conjugated molecule of 8-aminoquinoline, Zn2+ ion (borderline acid) coordinated favorably with aromatic nitrogen atoms (borderline bases) and N-amide. Characterization of OQAA was done by FTIR, 1H NMR, 13C NMR, UV–vis, and ESI-MS. The Zn2+ ion chemosensor was fabricated by immobilizing OQAA chromogenic ionophore onto a nanosilica/methylcellulose (Si/MC) composite pellet to form a solid-state pellet sensor. A distinguishable color change from pale light-yellow to yellowish-brown of the optode pellet was observed in the presence of Zn2+ ions. Optimization of the pellet-based Zn2+ ion sensor was carried out with a fiber optic reflectance spectrophotometer at 0.25 M OQAA in tris buffer (pH 7.4). The optical fiber sensor demonstrated a linear reflectance response between 0.8 M and 2.4 M Zn2+ ion (R²=0.9741) at λmax=635 nm with a limit of detection (LOD) of 3.6 × 10−2 M and response time of 5 min. The reflectance sensor exhibited good selectivity towards Zn2+ ion over other competitive heavy metals e.g., iron(II) (Fe2+), nickel(II) (Ni2+), cobalt(II) (Co2+), copper(II)(Cu2+) and cadmium(Cd2+) ions. Additionally, the proposed Zn2+ ion sensor showed high shelf-life stability of 75 days operational duration with 80.0 % initial optical response remaining. The quick, easy, and uncomplicated preparation of the OQAA-modified Si/MC (OQAA-Si/MC) composite pellet novel material gave a reproducible reflectance signal towards the determination of Zn2+ ion concentration with a low relative standard deviation (RSD) obtained at ∼1.0 % (n=12), and was reusable three times for assay of Zn2+ ion (RSD=1.3 %). The optical chemosensor imparts remarkable color change towards the analysis of Zn2+ ions, and could offer direct and fast in-situ visual inspection of Zn2+ ion levels in complex samples without an instrument.

A reversible fluorescent chemosensor based on a naphthalene dyad for Pb(II) ions: Applications in food, water, and bio-imaging

Lead (Pb2+) ions, among heavy toxic metals, are extensively distributed and bioaccumulate in food chains, prompting researchers to monitor their levels in water and biosystems. Consequently, aiming to protect the environment and human health, this study synthesizes a straightforward naphthalene-naphthalene dyad-based "turn-on" fluorescent chemosensor (S) tailored for detecting Pb2+ ions. This selective response to Pb2+ ions over other competing metal ions is characterized by hypsochromic changes in fluorescence enhancement resulting from an intramolecular charge transfer (ICT) process from -OH group (donor) to the naphthyl ring (acceptor) following the complexation of S-Pb2+. Moreover, cross-contamination titration for probe S was conducted in the presence of various distinct competitive metal ions. By employing Job's plot and B-H plot, the complicated stoichiometry (1:2) and association constant (Ka = 9.45×104 M−1) of S-Pb2+ were studied. The probe's interaction with Pb2+ is studied using spectroscopic measurements and DFT calculations. The probe demonstrated exceptional selectivity and sensitivity, achieving a limit of detection (LOD) value of 12.50×10−6 M for Pb2+ in a buffered THF:H2O (50:50, v:v) medium. The applicability of chemosensor S spans across various water, food, and E. coli samples, indicating its potential in monitoring and managing Pb2+ toxicity in wastewater and biosystems.

Adsorption and distribution of heavy metals in aquatic environments: The role of colloids and effects of environmental factors

The study investigated the distributions of heavy metals (Cd, Cr, Cu, Mn, and Pb) between dissolved fraction (<0.7 µm) and particles (>0.7 µm) during the adsorption process. The dissolved fraction was further separated into truly dissolved (<3 kDa) and colloidal (3 kDa-0.7 µm) fractions. Significant metal adsorption occurred on the colloids, resulting in their aggregation into particles, which in turn influenced the particle adsorption kinetics. Colloids could either accelerate or inhibit the transformation of metal ions into particulates, depending on their stability. Competitive metals for colloids (Pb and Cr) were more susceptible to the effects of colloids than other elements. DOM was the predominant environmental factor influencing colloid behavior. The XDLVO theory showed that DOM enhanced the negative charge of colloids and made the colloid surface more hydrophilic, inhibiting the aggregation of colloids. DOM resulted in substantial increases in the concentrations of colloidal Pb and Cr from 0.31 μg/L and 4.58 μg/L to 20.52 μg/L and 43.51 μg/L, respectively, whereas the increment for less competitive metals (Cd and Mn) was smaller. These findings suggest that the distribution of heavy metals is influenced not only by adsorption from particles and ions but also by the complex dynamics of colloids.

A turn-off fluorescent sensor based on Schiff base incorporating diformyl phenol moiety for the detection of Cu2+ in aqueous solution at nanomolar level and its application in living cells

Given the critical role of trace copper ion in human health, its sensitive detection in environmental and biological samples is crucial. We, herein, designed and synthesized a diformyl phenol-based turn-off fluorescent sensor ((5-(tert-butyl)-2-hydroxy-1,3-phenylene)bis (methanylylidene)) bis (azanylylidene)) bis(4-hydroxy-2H-chromen-2-one) (MH-4)) for the spectrofluorometric detection of Cu2+ ion, which has sensitive and selective fluorescence quenching over other competitive metal ions. The efficiency and fast response of the sensor were confirmed by UV–Visible, fluorescence spectral changes, which may be due to the formation of coordination bond between MH-4 and Cu2+ ions. The binding stoichiometry of MH-4 with Cu2+ was examined with the help of UV–Vis and fluorescence titrations, and Job’s plot, which gives a 1:1 coordination stoichiometry; this is further confirmed through MS studies. The binding constant of the complex was found to be 9.4 x 107 M−1. Then, the absorbance and fluorescence-based detection limits were calculated to define the sensitivity range of the proposed sensor and were found to be 69.30 nM and 37.40 nM, respectively. Finally, a live cell image study of MH-4 in L929 (murine aneuploid fibrosarcoma) cells was also performed to test the cell permeability of MH-4 and its effectiveness for selective detection of Cu2+ in living cells.

Thiourea Functionalised Receptor for Selective Detection of Mercury Ions and its Application in Serum Sample.

A thiourea functionalised fluorescent probe 1-phenyl-3-(pyridin-4-yl)thiourea was synthesized and utilised as a fluorescent turn-on chemosensor for the selective recognition of Hg2+ ion over competitive metal ions including Na+, Mn2+, Li+, Cr2+, Ni2+, Ca2+, Cd2+, Mg2+, K+, Co2+, Cu2+, Zn2+, Al3+ and Fe2+ ions based on the inter-molecular charge transfer (ICT). Intriguingly, the receptor demonstrated unique sensing capabilities for Hg2+ in DMSO: H2O (10:90, v/v). The addition of Hg2+ ions to the sensor resulted in a blue shift in the absorption intensity and also enhancement in fluorescence intensity at 435nm. Fluorescence emission intensity increased linearly with Hg2+ concentration ranging from 0 to 80 µL. The detection limit and binding constant were determined as 0.134 × 10-6M and 1.733 × 107M-1, respectively. The sensing behavior of Hg2+ was further examined using DLS, SEM and FTIR. The probe could detect Hg2+ ions across a wide pH range. Furthermore, the receptor L demonstrated good sensing performance for Hg2+ in bovine serum albumin and actual water samples.

Switchable metal extractant integrated miniaturized 3D-printed device: A semi-online multi-metal separation system for matrix-free ICP-MS analysis

BackgroundThis study tackles the critical challenges in metal analysis by presenting an innovative miniaturized metal extraction device prototype. This device features a functional nanocomposite (FNC) enhanced 3D-printed polylactic acid (PLA) metal extractant (FNC@3D PLA). The research is motivated by the constraints of traditional solid-phase extraction (SPE) methods, specifically their limitations in handling competitive metal ion environments and matrix interference during inductively coupled plasma mass spectrometry (ICP-MS) analysis. The designed prototype aims to overcome these challenges and enhance the extraction efficiency of diverse metals. ResultsThe FNC, designed to incorporate various functional groups critical for metal ion extraction efficiency, was meticulously engineered through the reaction of acid-treated and delaminated graphitic carbon nitride nanosheets (Thiol-gCN NSs) with 3-mercaptopropyl trimethoxysilane (MPTMS). The competitive metal ion extraction efficiency of FNC@3D PLA was demonstrated, showcasing notable limit of detection values of 3.2 ± 0.7 ng mL−1 and 8.57 ± 3.05 ng mL−1 for Cu and Ag, respectively. Furthermore, the miniaturized 3D-printed metal-preconcentration setup incorporating FNC@3D PLA exhibited favorable intraday relative standard deviation (RSD) percentage (%) values ranging from 1.23 to 8.6 for both Cu and Ag. Interday RSD % between 1.41 and 8.14 were observed under spiked real urine sample conditions. The sustainability and robustness of the proposed approach were underscored by substantial recovery % values exhibited by FNC@3D PLA, even after eight consecutive regeneration processes. SignificanceThis study significantly contributes to the advancement of analytical methodologies by providing a reliable and efficient platform for metal extraction and preconcentration in practical metal analysis applications. Developed FNC@3D PLA system demonstrates its potential to address the challenges associated with SPE in metal analysis, especially in complex sample matrices. We believe implications of this research can be extended to various fields, from environmental monitoring to clinical diagnostics, where accurate and reliable metal analysis is paramount.

Synthesis of phosphonic acid and amide functionalized core–shell magnetic composite and its mechanisms for synergistic adsorption of thorium from strongly acidic solution

To develop adsorbents for the preeminent extraction of thorium in strongly acidic solutions is very imperative, due to strong inorganic acids are frequently used in the fuel cycle of thorium. Herein, a robust core–shell magnetic nanocomposite Fe3O4@SiO2/P (MBA-VPA-AM) possessing phosphonic acid and amide was developed via distillation-precipitation copolymerization of N, N'-methylene diacrylamide (MBA), vinylphosphonic acid (VPA) with acrylamide (AM) employing Fe3O4 decorated by SiO2 (Fe3O4@SiO2) as magnetic core. Due to the synergistic effect of phosphonic acid and amide ligand, the sorbent could capture thorium from concentrated HNO3 media efficiently, and the maximum adsorption capacity (qmax) at 4 mol L−1 of HNO3 solution reached up to 232.5 mg g−1, superior to that of all magnetic sorbents reported previously. Furthermore, the sorbent displayed good selectivity towards thorium in the presence of competitive metal ions including La3+, Nd3+, and Ce3+. The excellent thorium sorption behavior in strong hydrogen nitrate solution was merely ascribed to the complexation of thorium with phosphonic acid ligand, and the amide ligand could not complex with thorium, evidenced by XPS, FT-IR and DFT method. However, the presence of amide ligand could enhance the hydrophilicity of the sorbent and the free movement degree of phosphonic acid ligand to a certain extent, both of which could help to promote the thorium sorption on the sorbent in strong HNO3 media. Besides, due to its core–shell structure and superparamagnetism, the sorbent not only exhibited excellent acidic resistance in strong acid medias, but could be magnetically recouped, which could avoid tedious centrifugation or filtration of traditional adsorbents. This work provides a novel strategy to develop magnetic sorbent for the preeminent entrapment of thorium from strong acid solutions.

A novel 1,3-diazepine-based fluorescent probe for highly selective detection of Hg2+

A novel 1,3-diazepine based fluorescent probe for Hg2+ has been successfully synthesized and characterized. Comprising a furan and pyridine, the probe L1 is a blue-emitting 1,3-diazepine derivative, which transforms into an imine form with high fluorescent yellow-emitting under alkaline conditions. Fluorescence quench of the probe in ethanol was observed with the addition of Hg2+ aqueous in the presence and absence of other metal ions, with a visible color change from colorless to yellow, and this fluorescence quench can be observed in a wide pH range of 3–11. An important feature for this probe is its high selectivity towards mercury ions for the aqueous-phase detection of Hg2+ over the other competitive metal ions, making the “naked-eye” detection of mercury ions possible.

A novel tryptanthrin-based "on-off-on" probe for sequential sensing Cu2+/S2- in water samples.

Copper ions (Cu2+) and sulfide (S2-) play essential roles in many physiologies and pathologic processes. Herein, a new "on-off-on" tryptanthrin-based probe TR-1 (TR-1) has been designed and synthesized inafacileandeconomicalway. TR-1 exhibited highly selective and sensitive response to Cu2+ without any interference over 14 competitive metal ions and the detection limit downs to 24nM, which is far below the Chinese standard of fishery water quality (157nM). The 'in situ' prepared complex TR-1 + Cu2+ could also be applied to detect S2- with the detection limit of 62nM. Further, TR-1 was potentially applied for the analysis of copper ions in water samples.

Integration of metal organic framework nanoparticles into sodium alginate biopolymer-based three-dimensional membrane capsules for the efficient removal of toxic metal cations from water and real sewage

Sodium alginate (SA) biopolymer has been recognized as an efficient adsorbent material owing to their unique characteristics, including biodegradability, non-toxic nature, and presence of abundant hydrophilic functional groups. Accordingly, in the current research work, UiO-66-OH and UiO-66-(OH)2 metal organic framework (MOF) nanoparticles (NPs) have been integrated into SA biopolymer-based three-dimensional (3-D) membrane capsules (MCs) via a simple and facile approach to remove toxic metal cations (Cu2+ and Cd2+) from water and real sewage. The newly configured capsules were characterized by FTIR, SEM, XRD, EDX and XPS analyses techniques. Exceptional sorption properties of the as-developed capsules were ensured by evaluation of the pertinent operational parameters, i.e., contents of MOF-NPs (1–100 wt%), adsorbent dosage (0.001–0.05 g), content time (0–360 h), pH (1–8), initial concentration of metal cations (5–1000 mg/L) and reaction temperature (298.15–333.15 K) on the eradication of Cu2+ and Cd2+ metal cations. It was found that hydrophilic functional groups (-OH and -COOH) have performed an imperative role in the smooth loading of MOF-NPs into 3-D membrane capsules via intra/inter-molecular hydrogen bonding and van der waals potencies. The maximum monolayer uptake capacities (as calculated by the Langmuir isotherm model) of Cd2+ and Cu2+ by 3-D SGMMCs-OH were 940 and 1150 mg/g, respectively, and by 3-D SGMMCs-(OH)2 were 1375 and 1575 mg/g, respectively, under optimum conditions. The as-developed capsules have demonstrated superior selectivity against targeted metal cations under designated pH and maintained >80 % removal efficiency up to six consecutive treatment cycles. Removal mechanisms of metal cations by the 3-D SGMMCs-OH/(OH)2 was proposed, and electrostatic interaction, ion-exchange, inner-sphere coordination bonds/interactions, and aromatic ligands exchange were observed to be the key removal mechanisms. Notably, FTIR and XPS analysis indicated that hydroxyl groups of Zr-OH and BDC-OH/(OH)2 aromatic linkers played vital roles in Cu2+ and Cd2+ adsorption by participating in inner-sphere coordination interactions and aromatic ligands exchange mechanisms. The as-prepared capsules indicated >70 % removal efficiency of Cu2+ from real electroplating wastewater in the manifestation of other competitive metal ions and pollutants under selected experimental conditions. Thus, it was observed that newly configured 3-D SGMMCs-OH/(OH)2 have offered a valuable discernment into the development of MOFs-based water decontamination 3-D capsules for industrial applications.

Synthesis and assessment of spherogranular composite tin pyrophosphate antimonate adsorbent for selective extraction of rubidium and cesium from salt lakes

In this study, a spherogranular porous composite tin pyrophosphate antimonate (SSbPP) adsorbent was developed for the efficient extraction of rubidium (Rb) and cesium (Cs) resources. This granular composite adsorbent was prepared using the anti-solvent method with polyvinyl chloride (PVC) as carrier and the incorporated SSbPP powder as adsorbent. The composition, molecular structure, and adsorption performance of SSbPP, along with the microstructure and adsorption behavior of the granulated PVC-SSbPP adsorbent, were comprehensively investigated. The results showed that the SSbPP adsorbent with superior performance was synthesized at a Sn:Sb:P molar ratio of 0.5:0.25:2. The adsorption behavior of PVC-SSbPP was evaluated using the pseudo-second-order kinetic model and Langmuir isotherm. The maximal adsorption capacities of PVC-SSbPP for Rb+ and Cs+ were found to be 81.3 mg g−1 and 95.23 mg g−1 at optimal condition, respectively. The PVC-SSbPP also exhibited high adsorption selectivity for Rb+/Cs+ in the presence of competitive metal ions such as K+, Na+, Li+, Mg2+ and Ca2+. Furthermore, through dynamic adsorption-desorption experiment using a fixed-bed column, a low-concentration Rb+/Cs+ solution (10 mg L−1) could be concentrated by approximately 140 times. This research offers a promising approach for the selective extraction of low-concentration Rb and Cs resources from highly saline solutions.

Respective evolution of soil and biochar on competitive adsorption mechanisms for Cd(II), Ni(II), and Cu(II) after 2-year natural ageing

To reveal the respective evolution of soil and biochar on competitive heavy metal adsorption mechanisms after natural ageing, three soils and two biochars were tested in this study. The soil-biochar interlayer samples were buried in the field for 0.5, 1, and 2 years, for which competitive adsorption characteristics and mechanisms of soils and biochars in four systems (Cd, Cd+Ni, Cd+Cu, and Cd+Ni+Cu) were investigated. Results showed that physicochemical properties, adsorption capacity and mechanisms of soils and biochars all changed the most in the first 0.5 years. The properties and adsorption capacity of biochars gradually weakened with the ageing time, meanwhile, those of soils gradually enhanced. After co-ageing with acidic soil for 0.5 years, the Cd(II) adsorption capacity of modified biochar decreased by 86.59% in the ternary system; meanwhile, that of acidic soil increased by 65.52%. The contributions of mineral mechanisms decreased significantly, while non-mineral mechanisms were slightly affected by ageing. This study highlighted that when using biochar to remediate heavy metal-contaminated soils, biochar should be applied at least half a year in advance before planting crops so that biochar can fully contact and react with the soil.

Efficient sorption of As(III) from water by magnetite decorated porous carbon extracted from a biowaste material.

Arsenic is a highly toxic metal that causes cancer even at a low concentration and its removal from water resources is challenging. Herein, carbon extracted from waste onion bulbs is activated to cater for porosity and functionalized with magnetite (Fe3O4) nanoparticles (named MCK6) to address the challenge of As(III) removal. Synthesized MCK6 was highly mesoporous having a surface area of 208 m2/g, where magnetite nanoparticles (≤ 10nm) are homogeneously distributed within a porous network. The developed adsorbent inherited functional groups from the biosource and magnetic property from magnetite making it ideal for removal of As(III). Further, MCK6 showed a maximum monolayer adsorption capacity (qm) of 10.2mg/g at 298K and pH 7. The adsorption thermodynamics delineates a non-spontaneous and endothermic reaction, where the kinetics followed pseudo 2nd order (R2 value of 0.977), while monolayer formation is explained by the Langmuir model. Moreover, MCK6 efficiently works to remove As(III) in a competitive metal ions system including Pb+2, Cd+2, and Ca+2, making it a suitable adsorbent to tackle contaminated water.

Preparation of magnetic DTPA-modified chitosan composite microspheres for enhanced adsorption of Pb(II) from aqueous solution

In this study, magnetic DTPA-modified chitosan composite microspheres (MDCM) were prepared by reverse emulsion-double crosslinking method (carbodiimide followed by glutaraldehyde) for removal of Pb(II) from aqueous solution. The obtained magnetic adsorbents were characterized by FTIR, SEM, XRD, VSM, BET, and 13C NMR. The effects of the pH, contact time, initial concentration, and competitive metal cations (Na(I), Ca(II), or Mg(II)) on Pb(II) adsorption were investigated. The results revealed that MDCM exhibited high removal performance over a wide pH range and in the presence of competitive metal cations. The maximum adsorption capacity of MDCM for Pb(II) is 214.63 mg g−1 at pH 3, which is higher than most recently reported magnetic adsorbents. Adsorption kinetics and isotherms can be described by the pseudo-second-order model and Langmuir model, respectively. In addition, MDCM is easy to regenerate and can be reused five cycles with high adsorption capacity. Finally, the adsorption mechanism was further revealed by FTIR and XPS analysis. Overall, MDCM has practical application potential in removing Pb(II) from contaminated wastewater due to its high adsorption efficiency, good reusability, and convenient magnetic separation.

Investigating the Absorption of Quaternary Ammonium Salt-Functionalized Silica Towards Vanadium in Hydrochloric Acid Solution

ABSTRACT A quaternary ammonium salt-functionalized silica based on N-benzyl-N-methylethanolamine (BMEA-SD) was prepared for the removal and recovery of pentavalent vanadium [V(Ⅴ)] from hydrochloric acid solutions. The impact of pH, contact time, ionic strength, competitive metal ions, and recyclability of the adsorption factors were investigated. The results showed that BMEA-SD was an effective V(Ⅴ) adsorbent with a maximum adsorption capacity of 51.42 mg g−1 at solution pH 3, contact time of 30 minutes, and temperature of 298 K. Characterization of BMEA-SD materials by TG, FTIR, SEM, and XPS. In addition, the adsorption kinetics followed a pseudo-second-order model, with film diffusion being the determined step. The Langmuir isotherm suggested that monolayer chemical adsorption occurred on the adsorbent surface, and thermodynamics data indicated that the V(Ⅴ) adsorption process was spontaneous and endothermic. Selective separation studies (βV/Cr = 109.87, βV/Mn = 1171.40) highlighted its potential for selective adsorption of V(Ⅴ) over hexavalent chromium [Cr(Ⅵ)] and divalent manganese [Mn(II)]. Desorption was most effective using HCl aqueous solution, and this material maintained good adsorption capacity after five cycles. The experimental results indicated that the adsorption behavior might stem from the interplay of electrostatic forces, redox transformations, and ligand-exchange. This investigation revealed the potential of the adsorbent as a promising, efficient, and renewable for enriching and recovering V(Ⅴ) ions from hydrochloric acid solution.