An investigation of heavy metal adsorption by hexa-dentate ligand-modified magnetic nanocomposites

Interaction between polydopamine-based IONPs and human serum albumin (HSA): a spectroscopic analysis with cytotoxicity impact

Iron oxide nanoparticles (IONPs) have been extensively explored in biomedicine, bio-sensing, hyperthermia, and drug/gene delivery, attributed to their versatile and tunable properties. However, owing to its numerous applications, the functionalization of IONPs with appropriate materials is in demand. To achieve optimal functionalization of IONPs, polydopamine (PDA) was utilized due to its ability to provide a superior functionalized surface, near-infrared light absorption, and adhesive nature to customize desired functionalized IONPs. This notion of involving PDA led to the successful synthesis of magnetite-PDA nanoparticles, where PDA is surface-coated on magnetite (Fe3O4@PDA). The Fe3O4@PDA nanoparticles were characterized using techniques like TEM, FESEM, PXRD, XPS, VSM, and FTIR, suggesting PDA's successful attachment with magnetite crystal structure retention. Human serum albumin (HSA), the predominant protein in blood plasma, interacts with the delivered nanoparticles. Therefore, we have employed various spectroscopic techniques, along with cytotoxicity, to inspect the effect of Fe3O4@PDA NPs on the stability and structure of HSA. The structural alterations were examined using circular dichroism (CD) and synchronous fluorescence spectroscopy (SFS). It has been observed that there are no structural perturbations in the secondary structure of the HSA protein after interaction with Fe3O4@PDA. Studies using steady-state fluorescence revealed that the inherent fluorescence intensities of HSA were suppressed after interaction with Fe3O4@PDA. In addition, temperature-dependent fluorescence measurements suggested that the type of quenching consists of both static and dynamic quenching simultaneously. A cytotoxicity study in Drosophila melanogaster larvae revealed no cytotoxic effects but did show a minor genotoxic effect only at higher concentrations.

Assessing metal extraction from metalliferous waste: A study using deep eutectic solvents and chelating agents vs. ethylenediaminetetraacetic acid

Conventional methods of metal recovery involving solvents have raised environmental concerns. To address these concerns and promote sustainable resource recovery, we explored the use of deep eutectic solvents (DES) and chelating agents (CA) as more environmentally friendly alternatives. Goethite and blast oxide slag dust (BOS-D) from heap piles at their respective sites and characterised via ICP-MS. The greatest extraction of critical metals was from goethite, removing 38% of all metals compared to 21% from the blast oxide slag. Among the tested CA, nitrilotriacetic acid (NTA) was the most effective, while for DES, choline chloride ethylene glycol (ChCl-EG) demonstrated superior performance in extracting metals from both blast oxide slag dust and goethite. The study further highlighted the selectivity for transition metals and metalloids was influenced by the carboxyl groups of DES. Alkaline metals and rare earth lanthanides extractions were favoured with DES due to improved mass transfer and increased denticity, respectively. In comparison to ethylenediaminetetraacetic acid (EDTA), typically used for metal extraction, CA and DES showed comparable extraction efficiency for Fe, Cu, Pb, Li, Al, Mn, and Ni. Using these greener chelators and solvents for metal extraction show significant promise in enhancing the sustainability of solvometallurgy. Additional conditions e.g., temperature and agitation combined with a cascading leaching process could further enhance metal extraction potential.

A multifunctional adsorbent based on 2,3-dimercaptosuccinic acid/dopamine-modified magnetic iron oxide nanoparticles for the removal of heavy-metal ions

Overexploitation of nature by humans has led to an increasingly serious issue of heavy-metal water pollution. To reduce the threat of water pollution to humans and the environment, it is imperative to develop or improve the water treatment technology for heavy-metal-containing wastewater. Functionalized Fe₃O₄ magnetic nanoparticles (Fe₃O₄ MNPs) have been widely used as effective adsorbents for the removal of heavy-metal ions from water owing to their high efficiency, low cost, selective adsorption ability, and recyclability. In this study, Fe₃O₄@DA-DMSA magnetic nanoparticles (FDDMs) were prepared by the functionalization of Fe₃O₄ MNPs with environmentally friendly dopamine (DA) and a heavy-metal detoxifying agent such as 2,3-dimercaptosuccinic acid (DMSA) for the efficient and rapid adsorption of Pb²⁺, Cu²⁺, and Cd²⁺, with maximum adsorption capacities of 187.62, 63.01, and 49.46 mg/g, respectively. FDDMs exhibited the best ability to remove Pb²⁺ with a maximum adsorption capacity than that of the most reported Fe₃O₄ MNP-related adsorbents. In actual wastewater and multi-component simulated water samples contaminated with Pb²⁺, Cu²⁺, and Cd²⁺, the as-prepared adsorbent maintained a good removal ability for Pb²⁺ with low influence by ionic strength and interfering ions, as well as exhibited an excellent selectivity. According to the results of batch experiments and X-ray photoelectron spectroscopy (XPS) analysis of the adsorbent before and after adsorption, the adsorption mechanism of the adsorbent for the removal of heavy-metal ions mainly involves coordination and ion exchange. In addition, the adsorbent exhibited a good regeneration performance. Therefore, FDDMs can be considered as a promising adsorbent for the treatment of heavy-metal wastewater.

Adsorption of Pb (II) and Cu (II) by magnetic beads loaded with xanthan gum

Green and environmentally friendly and efficient separation adsorbents have attracted much attention in the treatment of heavy metal ions wastewater. In this study, xanthan gum (XG) was supported by fly ash magnetic beads (FAMB) to prepare adsorbent XG@FAMB. The effects of XG@FAMB dosage, pH value of the solution, adsorption time, and initial Pb (II) and Cu (II) concentration on its adsorption performance for Pb (II) and Cu (II) were investigated. The results show that under the conditions of pH 6, dosage of XG@FAMB 4.0 g/L, adsorption time 120 min, and initial concentration 60 mg/L, the maximum adsorption capacity of XG@FAMB for Pb (II) and Cu (II) was 14.93 mg/g and 14.88 mg/g, respectively. The adsorption process of Pb (II) and Cu (II) by XG@FAMB could be better described by the quasi-second-order kinetic model and Langmuir isothermal adsorption model, that is, the adsorption process is monolayer adsorption controlled by chemical action. The adsorption mechanism is that Pb (II) and Cu (II) coordinate with oxygen-containing functional groups hydroxyl and carboxyl on XG@FAMB surface, accompanied by electrostatic adsorption. XG@FAMB has the advantages of environmental protection of XG and easy solid-liquid separation of FAMB, and has a good removal effect on Pb (II) and Cu (II).

WITHDRAWN: Heavy metal ions and dyes removal from aqueous solution using Aloevera-based biosorbent: A systematic review

This article has been withdrawn: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been withdrawn at the request of the authors, editor and publisher. The publisher regrets that an error occurred which led to the premature publication of this paper. The publisher apologizes to the readers for this unfortunate erro

Hydroxypicolinic acid tethered on magnetite core-silica shell (HPCA@SiO2@Fe3O4) as an effective and reusable adsorbent for practical Co(II) recovery

The soaring demand and future supply risk for cobalt (Co) necessitate more efficient adsorbents for its recycling from electronic wastes, as a cheaper and less hazardous option for its production. Herein, a magnetic adsorbent covalently tethered with 5-hydroxypicolinic acid (HPCA) as Co(II) ligand was developed. The magnetic component (Fe₃O₄) was protected with silica (SiO₂), then silanized with chloroalkyl linker and subsequently functionalized with HPCA via S_N2 nucleophilic substitution (HPCA@SiO₂@Fe₃O₄). Results from FTIR, TGA, EA, and XPS confirm the successful adsorbent preparation with high HPCA loading of 2.62 mmol g^-1. TEM-EDS reveal its imperfect spherical morphology with ligands well-distributed on its surface. HPCA@SiO₂@Fe₃O₄ is hydrophilic, water-dispersible and magnetically retrievable, which is highly convenient for its recovery. The Co(II) capture on HPCA@SiO₂@Fe₃O₄ involves monodentate coordination with carboxylate (COO^-) and lone pair acceptance from pyridine (aromatic -N = ) moiety of HPCA, with minor interaction from acidic silanols (Si-O^-). The binding occurs at 2 HPCA: 1 Co(II) ratio, that follows the Sips isotherm model with competitive Q_max = 92.35 mg g^-1 and pseudo-second order kinetics (k₂ = 0.0042 g mg^-1 min^-1). In a simulated LIB liquid waste, HPCA@SiO₂@Fe₃O₄ preferentially captures Co(II) over Li(I) with α_Li(I)^Co(II)=166 and Mn(II) with α_Mn(II)^Co(II)=55, which highlights the importance of HPCA for Co(II) recovery. Silica protection of Fe₃O₄ rendered the adsorbent chemically stable in acidic thiourea solution for its regeneration by preventing the deterioration of the magnetic component. Covalent functionalization averted ligand loss, which allowed HPCA@SiO₂@Fe₃O₄ to deliver consistent and reversible adsorption/desorption performance. Overall results demonstrate the potential of HPCA@SiO₂@Fe₃O₄ as a competitive and practical adsorbent for Co(II) recovery in liquid waste sources.

Disulfide Cross-Linked Poly(Methacrylic Acid) Iron Oxide Nanoparticles for Efficiently Selective Adsorption of Pb(II) from Aqueous Solutions

The efficient selectivity of heavy metal ions from wastewater is still challenging but gains great public attention in water treatment on a world scale. In this study, the novel disulfide cross-linked poly(methacrylic acid) iron oxide (Fe3O4@S-S/PMAA) nanoparticles with selective adsorption, improved adsorption capability, and economic reusability were designed and prepared for selective adsorption of Pb(II) ions in aqueous solution. In this study, nuclear magnetic resonance, dynamic light scattering, scanning electron microscopy, X-ray diffraction, vibrating sample magnetometry, and thermogravimetric analysis were utilized to study the chemophysical properties of Fe3O4@S-S/PMAA. The effect of different factors on adsorption properties of the Fe3O4@S-S/PMAA nanoparticles for Co(II) and Pb(II) ions in aqueous solution was explored by batch adsorption experiments. For adsorption mechanism investigation, the adsorption of Fe3O4@S-S/PMAA for Co(II) and Pb(II) ions can be better fitted by a pseudo-second-order model, and the adsorption process of Fe3O4@S-S/PMAA for Co(II) and Pb(II) matches well with the Freundlich isotherm equation. Notably, in the adsorption experiments, the Fe3O4@S-S/PMAA nanoparticles were demonstrated to have a maximum adsorption capacity of 48.7 mg·g-1 on Pb(II) ions with a selective adsorption order of Pb2+ > Co2+ > Cd2+ > Ni2+ > Cu2+ > Zn2+ > K+ > Na+ > Mg2+ > Ca2+ in the selective experiments. In the regeneration experiments, the Fe3O4@S-S/PMAA nanoparticles could be easily recovered by desorbing heavy metal ions from the adsorbents with eluents and showed good adsorption capacity for Co(II) and Pb(II) after eight recycles. In brief, compared to other traditional nanoadsorbents, the as-prepared Fe3O4@S-S/PMAA with improved adsorption capability and high regeneration efficiency demonstrated remarkable affinity for adsorption of Pb(II) ions, which will provide a novel technical platform for selective removal of heavy metal ions from actual polluted water.

SBA-16 Cage-Like Porous Material Modified with APTES as an Adsorbent for Pb2+ Ions Removal from Aqueous Solution

Tridimensional cubic mesoporous silica, SBA-16, functionalized with aminopropyl groups, were employed as adsorbents for Pb²⁺ ion removal from aqueous solution. The adsorption capacity was investigated for the effect of pH, contact time, temperature, and concentration of 3-aminopropyltriethoxysilane (APTES) employed for adsorbent functionalization. The textural properties and morphology of the adsorbents were evaluated by N₂ physisorption, small-angle X-ray diffraction (XRD), diffuse reflectance spectroscopy (UV-vis), and transmission electron microscopy (TEM). The functionalization of the SBA-16 was evaluated by elemental analysis (N), thermogravimetric analysis (TG), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). Batch adsorption studies show that the total Pb²⁺ ions removal was archived on adsorbent having an optimized amount of aminopropyl groups (2N-SBA-16). The maximum of Pb²⁺ ions removal occurred at optimized adsorption conditions: pH = 5–6, contact time 40 min, and at a low initial lead concentration in solution (200 mg L⁻¹). Under the same adsorption conditions, the amino-functionalized SBA-16 with cubic 3D unit cell structure exhibited higher adsorption capability than its SBA-15 counterpart with uniform mesoporous channels.

Adsorption of uranium from its aqueous solutions using activated cellulose and silica grafted cellulose

The present work provides a thorough description of the preparation of two cellulose anion exchange resins. In addition, the application of the prepared resins for treatment the uranium-contaminated wastewater. In the preparation, the first resin was cellulose reacted with 0.3 M HNO3 to produce Activated Cellulose (AC), while the second was AC treated with sodium metasilicate and phosphoric acid to yield Silica Grafted Cellulose (SGC). The efficiency of the two prepared resins for uranium adsorption from aqueous solution was testifying on a batch scale. In solutions of pH ranging from 4 to 7, results showed a high exchange rate and uptaking capacity up to 105 mg/g. However, the addition of NO3 −, Fe3+ and Th4+ ions to the target media has an adverse impact on the uranium sorption for AC adsorbent. Otherwise, the addition of uranyl sulfate complexes could ameliorate Fe3+ and Th4+ adsorbed into the SGC.

Novel high-gluten flour physically cross-linked graphene oxide composites: Hydrothermal fabrication and adsorption properties for rare earth ions

Graphene oxide (GO) nanosheets were immobilized and cross-linked by high-gluten flour (HGF), and a series of biomass-GO composites with various HGF-to-GO mass ratios were fabricated through a one-step hydrothermal method. The HGF-GO composites were used as novel adsorbents to adsorb rare earth ions (REE³⁺: La³⁺, Yb³⁺, Y³⁺, Er³⁺ and Nd³⁺) from aqueous solutions, and their adsorption properties were also investigated detailly. To evaluate the physicochemical properties of HGF-GO composites and further understand the mechanisms of adsorption of REE³⁺ onto HGF-GO composites, the HGF-GO composites were characterized by scanning electron microscopy (SEM), thermal gravimetric analyzer (TGA), Raman spectroscopy and Fourier transform infrared (FT-IR) spectroscopy. Several important condition parameters including contact time, initial REE³⁺concentrations, solution pH values and temperature that might affect the adsorption process were studied in detail. The maximum adsorption capacities of HGF-GO_1:1 composite toward La³⁺, Yb³⁺, Y³⁺, Er³⁺ and Nd³⁺ were 30.32, 36.64, 32.84, 42.36 and 48.68 mg g^-1, respectively. The experimental data indicated that the adsorption of REE³⁺ onto HGF-GO_1:1 was well fitted by the pseudo-second order kinetic model and the Langmuir isotherm model, and the adsorption process was a spontaneous and endothermic reaction. The HGF-GO_1:1 composite could be well regenerated and reused after five adsorption-desorption cycles, and its removal efficiency for Yb³⁺ remained as a constant of 100%.

Single-Step Synthesis of Magnesium-Doped Lithium Manganese Oxide Nanosorbent and Their Polymer Composite Beads for Selective Heavy Metal Removal

Magnesium-doped lithium manganese oxide nanosorbent is prepared by a single-step solid-state method and characterized with appropriate analytical techniques, adsorption kinetic model, and isotherms. Competitive and noncompetitive adsorption studies are performed for a range of heavy metal ions. Prepared nanosorbent has shown explicit selectivity for various heavy metal ions and no remarkable influence of coexisting common interfering ions (Na⁺, K⁺, Mg²⁺, and Ca²⁺), which generally coexist with all natural sources of water, contaminated water, and industrial waste. To achieve easy handling of an adsorbent, polysulfone-nanosorbent (PS-nanosorbent) composite beads are prepared, and their competitive heavy metal removal performance is determined. Competitive adsorption and regeneration studies have shown that PS-nanosorbent beads can be employed for selective heavy metal removal and reuse for multiple cycles.