Search Results (40)

The development of reusable nanomaterials for the extraction of trace-metals from complex matrices remains challenging because strong metal-chelating functionalities often hinder desorption and regeneration, whereas weaker binding sites compromise selectivity and enrichment efficiency. This limitation has been addressed by designing a ligand-engineered fibrous mesoporous silica nanomaterial (Van-KCC-1) via the integration of the unique structural features of KCC-1 with an o-vanillin-derived Schiff-base chelator. The material was synthesized throughout the chemical grafting of 3-aminopropyltriethoxysilane (APTES) onto fibrous mesoporous silica KCC-1, followed by condensation with 3-methoxy-2-hydroxybenzaldehyde (o-vanillin). The successfulness of functionalization and Schiff-base formation were confirmed by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), Thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). The radially oriented fibrous channels of KCC-1 provide a highly accessible surface that remains available for interaction with the targeted ions even after chemical modification. This architecture facilitates rapid mass transfer and efficient utilization of binding sites, while the incorporated Schiff-base ligand introduces imine, phenolic, and methoxy donor groups capable of selectively and reversibly coordinating Ni(II) and Cd(II). The resulting balance between adsorption strength and desorption efficiency enables both effective metal capture and sorbent reusability. More importantly, the study demonstrates how KCC-1 can serve as a versatile nanosilica scaffold for the incorporation of tailored chelating ligands without sacrificing structural accessibility. The functionalized nanomaterial was evaluated as a dispersive solid-phase extraction (DSPE) sorbent coupled with inductively coupled plasma optical emission spectrometry (ICP-OES). Under optimized conditions, linear ranges of 0.035–50 μg L⁻¹ for Ni(II) and 0.058–50 μg L⁻¹ for Cd(II) were obtained, with limits of detection of 0.011 and 0.019 μg L⁻¹, respectively. The method exhibited excellent precision (relative standard deviation ≤ 3.6%) and recoveries of 92.00–98.83% in certified reference materaisl (NIST CRM 1643d), mineral water, tap water and synthetic wastewater. In addition, the nanochelator has retained more than 87% of its initial sorption efficiency after six adsorption–desorption cycles and showed minimal interference from common coexisting ions. These findings establish Van-KCC-1 as an efficient, selective, and reusable DSPE sorbent in the determination of trace-metals while highlighting the broader potential of fibrous mesoporous silica KCC-1 as a platform for the rational design of next-generation chelated nanomaterials. Full article

Ion-imprinting technology based on biosorbents via sorption demonstrates potential for the selective removal of metal ions from water and wastewater. This offers both high sorption capacity and selectivity for specific metals. Current research trends are toward the development of sorbents with minimal environmental impact. Among the most rapidly evolving classes of sorbents are those derived from biopolymers, such as chitosan—a natural derivative of chitin that can be readily functionalized. Due to the growing interest in this topic, it is necessary to summarize the current knowledge. In this article, we provide a comprehensive overview of the latest advances in ion-imprinted chitosan-based materials designed for the purification of metal-contaminated aqueous systems. We conduct a bibliographic analysis and describe a variety of chitosan-based materials exhibiting selectivity toward heavy metals, including chromium Cr(III/VI), cobalt Co(II), nickel Ni(II), copper Cu(II), zinc Zn(II), arsenic As(III/V), cadmium Cd(II), mercury Hg(II), and lead Pb(II). Finally, we discuss future prospects and highlight current research gaps, aiming to guide further scientific exploration and innovation in this promising field. Full article

A new sorption material (GS) was obtained by the modification of heulandite zeolite (G) with N,N′-bis-(3-triethoxysilylpropyl)thiocarbamide (S). The composition, structure, and surface morphology of the GS material were confirmed using elemental analysis, IR-, NMR-spectroscopy, X-ray diffraction, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), elemental mapping, and nitrogen adsorption/desorption (BET). The potential of GS as a sorbent for the removal of Cu(II) and Ni(II) ions from concentrated solutions was demonstrated. The nature of the adsorption of Cu(II) and Ni(II) ions was investigated using the Langmuir, Freundlich, and Dubinin–Radushkevich models. The adsorption value of Cu(II) and Ni(II) ions by the GS sorbent was found to be 1.7 and 2.1 times higher than that of heulandite, amounting to 0.128 mmol/g (8.1 mg/g) and 0.214 mmol/g (12.6 mg/g), respectively. The free energy of adsorption E for the adsorption of Cu(II) and Ni(II) ions was determined to be 12.5 and 16.2 kJ/mol, respectively. Calculations of changes in Gibbs energy based on quantum chemical modeling results ($\Delta G_{298}^0$ = −38.5 kJ/mol for Ni and $\Delta G_{298}^0$ = −56.5 kJ/mol for Cu) confirmed that adsorption of heavy metal ions onto the GS sample occurs through the formation of metal ion coordination complexes with the sorbent’s functional groups (chemosorption). The proposed method of obtaining new sorption materials based on natural heulandite is straightforward and cost-effective, enabling the production of high-capacity sorption products. Full article

The removal of nickel from industrial wastewater necessitates efficient sorbent materials. This study investigates nanostructured potassium- and sodium-substituted aluminosilicate-based nanocomposites for this application. Materials were synthesized and characterized using SEM-EDS, XPS, XRD, FTIR, low temperature N₂ adsorption–desorption and Ni²⁺ adsorption experiments. SEM and XRD confirmed an X-ray amorphous structure attributable to fine crystallite size. The sodium-substituted material Na₂Al₂Si₂O₈ exhibited the lowest specific surface area (48.3 m²/g) among the tested composites. However, it demonstrated the highest Ni(II) sorption capacity (64.6 mg/g, 1.1 mmol/g) and the most favorable sorption kinetics, as indicated by a Morris-Weber coefficient of 0.067 ± 0.008 mmol/(g·min¹/²). Potassium-substituted analogs with higher Si/Al ratios showed increased surface area but reduced capacity. Analysis by XPS and SEM-EDS established that Ni(II) uptake occurs through a complex mechanism, involving ion exchange, surface complexation, and chemisorption resulting in the formation of new nickel-containing composite surface phases. The results indicate that optimal sorption performance for Ni(II) is achieved with sodium-based aluminosilicates at a low Si/Al ratio (Si/Al = 1). The functional characteristics of Na₂Al₂Si₂O₈ compare favorably with other silicate-based sorbents, suggesting its potential utility for wastewater treatment. Further investigation is needed to elucidate the precise local coordination environment of the adsorbed nickel. Full article

In this work, spent coffee grounds, an abundant agro-waste, were transformed into activated carbon, providing a sustainable substrate for immobilizing 1,10-phenanthroline-5-amine chelating agent, to develop a solid-phase extractant for trace metals. ATR-IR, TGA, and XPS analyses confirmed successful functionalization and revealed the material’s physicochemical properties. Sorption studies showed optimal uptake at pH 6.0–6.5, enabling rapid extraction of Mn(II), Cd(II), Ni(II), and Pb(II) within 30 min, with capacities of 13.5, 8.4, 13.3, and 8.5 mg g⁻¹, respectively. The prepared chelator was employed as a packed sorbent in standard SPE cartridges operated with a conventional SPE apparatus, achieving efficient extraction and preconcentration of the studied ions from both certified reference material (BCR-609) and real groundwater. The results obtained closely matched certified values, while spiked recoveries ranged from 96.00% to 106.80%. These findings highlight the effective valorization of agricultural waste into a reusable, high-performance SPE sorbent with strong potential for water purification and trace metal recovery. Full article

This study evaluates the sorption behavior of natural zeolite (NZ) and Fe(III)-modified natural zeolite (FeZ) for Ni(II) ions, with the objective of assessing their potential for application in the remediation of nickel-contaminated environments. Optimization of sorption parameters, including pH_o, solid/liquid ratio (S/L), contact time, and initial Ni(II) concentration was performed to maximize both the sorption capacity of the zeolites and the removal efficiency of Ni(II) from suspension. The results demonstrated that both pH_o and S/L ratio exert a significant influence on Ni(II) sorption onto both zeolites, with a particularly pronounced effect observed for FeZ. Experimental results confirmed that FeZ exhibits a four-to-five times higher sorption capacity for Ni(II) than NZ, which was additionally verified by elemental analysis, SEM-EDS, and elemental mapping of Ni(II)-saturated zeolites. Intraparticle diffusion was identified as the rate-limiting step in the transfer of Ni(II) ions to the active sorption sites. Ion exchange was identified as the main sorption mechanism accompanied by outer-sphere complexation and electrostatic attraction. Leaching tests of Ni(II)-saturated zeolites, conducted in accordance with the standard DIN 38414 S4 method, demonstrated that both zeolites effectively retained Ni(II) within their structures over a wide pH range, 4.11 ≤ pH_o ≤ 12.02. These findings indicate the potential applicability of zeolites for remediation of nickel-contaminated environments, with FeZ being particularly promising due to its enhanced sorption capacity for Ni(II) ions. Full article

The synthesis and characterization of two novel redox-active MOFs/CPs based on 3d transition metal ions and 3,6-ditriazolyl-2,5-dihydroxybenzoquinone (trz₂An) are reported herein. By combining trz₂An with Ni^II and Mn^II ions via the hydrothermal method, two phases, formulated as [Ni₂(trz₂An)₂]·2.5H₂O (1) and [Mn(trz₂An)(H₂O)]·1.5H₂O (2), are obtained. Both compounds crystallize as neutral polymeric 3D frameworks, where the metal ions are coordinated through the oxygen atoms of the anilate linkers forming either straight (1) or zig-zag (2) 1D chains. In particular, (1) is a MOF, where these chains are connected through the nitrogen atom at the 4 position of the triazolyl group, which completes the coordination sphere of each metal ion, affording a 3D structure containing a void volume of 28.7% and voids that can be useful for the sorption of small molecules. Interestingly, (1) and (2) show a redox behavior due to the presence of the anilate linker, being reduced electrochemically in the −0.7 to −0.9 V range due to the benzoquinone–semiquinone one-electron reduction and magnetic behavior dominated by antiferromagnetic interactions in the anilate 1D chains. Full article

This study investigates the potential of biochars derived from agricultural waste biomass for the removal of heavy metal ions from aqueous solutions. Biochars were produced via slow pyrolysis at 793 K using almond shells (AS), walnut shells (WS), pistachio shells (PS), and rice husks (RH) as feedstocks. The physicochemical properties and adsorption performance of the resulting materials were evaluated with respect to Cd(II), Mn(II), Co(II), Ni(II), Zn(II), total Iron (Fe_tot), total Arsenic (As_tot), and total Chromium (Cr_tot) in model solutions. Surface morphology, porosity, and surface chemistry of the biochars were characterized by scanning electron microscopy (SEM), nitrogen adsorption at 77 K (for specific surface area and pore structure), Fourier-transform infrared spectroscopy (FTIR), and determination of the point of zero charge (pH_pzc). Based on their textural properties, biochars derived from WS, PS, and AS were classified as predominantly microporous, while RH-derived biochar exhibited mesoporous characteristics. The highest Brunauer–Emmett–Teller (S_BET) surface area was recorded for PS biochar, while RH biochar showed the lowest. The pistachio shell biochar exhibited the highest specific surface area (440 m²/g), while the rice husk biochar was predominantly mesoporous. Batch adsorption experiments were conducted at 25 °C, with an adsorbent dose of 3 g/L and a contact time of 24 h. The experiments in multicomponent systems revealed removal efficiencies exceeding 87% for all tested metals, with maximum values reaching 99.9% for Cd(II) and 97.5% for Fe_tot. The study highlights strong correlations between physicochemical properties and sorption performance, demonstrating the suitability of these biochars as low-cost sorbents for complex water treatment applications. Full article

The adsorption capacities of ion exchangers with the primary amine (Lewatit^® VP OC 1065) and polyamine (Diaion™ CR20) functional groups relative to Pd(II) and Cu(II) ions were tested in a batch system, taking into account the influence of the acid concentration (HCl: 0.1–6 mol/L; HCl-HNO₃: 0.9–0.1 mol/L HCl—0.1–0.9 mol/L HNO₃), phase contact time (1–240 min), initial concentration (10–1000 mg/L), agitation speed (120–180 rpm), bead size (0.385–1.2 mm), and temperature (293–333 K), as well as in a column system where the variable operating parameters were HCl and HNO₃ concentrations. There were used the pseudo-first order, pseudo-second order, and intraparticle diffusion models to describe the kinetic studies and the Langmuir and Freundlich isotherm models to describe the equilibrium data to obtain better knowledge about the adsorption mechanism. The physicochemical properties of the ion exchangers were characterized by the nitrogen adsorption/desorption analyses, CHNS analysis, Fourier transform infrared spectroscopy, the sieve analysis, and points of zero charge measurements. As it was found, Lewatit^® VP OC 1065 exhibited a better ability to remove Pd(II) than Diaion™ CR20, and the adsorption ability series for heavy metals was as follows: Pd(II) >> Zn(II) ≈ Ni(II) >> Cu(II). The optimal experimental conditions for Pd(II) sorption were 0.1 mol/L HCl, agitation speed 180 rpm, temperature 293 K, and bead size fraction 0.43 mm ≤ f3 < 0.6 mm for Diaion™ CR20 and 0.315–1.25 mm for Lewatit^® VP OC 1065. The maximum adsorption capacities were 289.68 mg/g for Lewatit^® VP OC 1065 and 208.20 mg/g for Diaion™ CR20. The greatest adsorption ability of Lewatit^® VP OC 1065 for Pd(II) was also demonstrated in the column studies. The working ion exchange in the 0.1 mol/L HCl system was 0.1050 g/mL, much higher compared to Diaion™ CR20 (0.0545 g/mL). The best desorption yields of %D₁ = 23.77% for Diaion™ CR20 and 33.57% for Lewatit^® VP OC 1065 were obtained using the 2 mol/L NH₃·H₂O solution. Full article

Industrial and domestic human activities have a significant impact on the environment, contributing, among other things, to the increased pollution of natural waters. The spread of heavy metals is particularly dangerous to the health and life of living organisms due to the high accumulation potential of, among others, Cr (VI), Zn (II), Cu (II), Cd (II), Fe (II), and Ni (II). In order to remove, concentrate, and/or recover ions of these metals, various physical and/or chemical methods are commonly used. In this study, spent coffee grounds (SCGs) efficiently removed copper ions from simulated aqueous solutions, especially at low metal ion concentrations. Without additional modification, coffee grounds performed comparably to traditional adsorbents like activated carbon or ion exchangers. It was found that used ground coffee grounds effectively removed Cu (II) ions at a wide range of concentrations, with the highest efficiency (over 85%) obtained for dilute solutions. On the other hand, regeneration tests performed using a 10% hydrochloric acid solution successfully restored the coffee residue adsorbent, achieving a desorption efficiency of about 35%. This method concentrated the solution and facilitated efficient metal recovery by minimizing acid usage. The sorbent used is an innovative, cheap, and easy-to-use material with high sorption capabilities. Full article

In this study, the synthesis and characterization of grafted cellulose fiber with binary monomers mixture obtained using a KMnO₄/citric acid redox initiator were investigated. Acrylonitrile (AN) was graft copolymerized with acrylic acid (AA) and styrene (Sty) at different monomer ratios with evaluating percent graft yield (GY%). Cell-g-P(AN-co-AA) and Cell-g-P(AN-co-Sty) were characterized by SEM, FT-IR, ¹³C CP MAS NMR, TGA, and XRD. An AN monomer was used as principle-acceptor monomer, and GY% increases with AN ratio up to 60% of total monomers mixture volume. The adsorption behaviors of Cell-g-P(AN-co-AA) and Cell-g-P(AN-co-Sty) were studied for the adsorption of Ni(II) and Cu(II) metal ions from aqueous solution. Optimal adsorption conditions were determined, including 8 h contact time, temperature of 30 °C, and pH 5.5. Cell-g-P(AN-co-AA) showed maximum adsorption capacity of 435.07 mg/g and 375.48 mg/g for Ni(II) and Cu(II), respectively, whereas Cell-g-P(AN-co-Sty) showed a maximum adsorption capacity of 379.2 mg/g and 349.68 mg/g for Ni(II) and Cu(II), respectively. Additionally, adsorption equilibrium isotherms were studied, and the results were consistent with the Langmuir model. The Langmuir model’s high determinant coefficient (R²) predicted monolayer sorption of metal ions. Consequently, Cell-g-P(AN-co-AA) and Cell-g-P(AN-co-Sty) prepared by a KMnO₄/citric acid initiator were found to be efficient adsorbents for heavy metals from wastewater as an affordable and adequate alternative. Full article

A comparative study of the physicochemical properties of natural bentonite clays of Pogodayevo (Republic of Kazakhstan, mod. 1) and Dash-Salakhli (Republic of Azerbaijan, mod. 2) deposits and modification of the bentonite clay with polyhydroxocations of iron (III) and aluminium (III). The amount of bentonite in the concentration of iron (aluminum) was 5 mmol Me³⁺/g. It was established that the modification of natural bentonites using polyhydroxocations of iron (III) (mod. 1_Fe_5-c, mod. 2_Fe_5-c) and aluminum (III) (mod. 1_Al_5-c, mod. 2_Al_5-c) by the method of “co-precipitation” leads to a change in their chemical composition, structural and sorption properties. The results showed that hydroxy-aluminum cations ([Al₃O₄(OH)₂₄(H₂O)₁₂]⁷⁺) and poly-hydroxyl-Fe or polyoxo-Fe were intercalated into clay layers, which led to an increase in the values of d₀₀₁ and specific surface areas compared to those of the original bentonite, from 37 to 120 m²/g for the Pogodaevo bentonite and from 51 to 172 m²/g respectively, for bentonite from the Dash-Salakhli deposit. It is shown that modified sorbents based on natural bentonite are finely porous objects with a predominance of pores of 1.5–8.0 nm in size. As a result, there is a significant increase in the specific surface area of sorbents. Modification of bentonite with polyhydroxocations of iron (III) and aluminum (III) by the “co-precipitation” method also leads to an increase in the sorption capacity of the sorbents obtained with respect to nickel (II) cations. Modified bentonites were used for the adsorption of Ni (II) ions from the model solution. Ni (II) was absorbed in a neutral pH solution. The study of equilibrium adsorption showed that the data are in good agreement with the Langmuir isotherm model. The maximum adsorption capacity of the Ni (II) obtained from the Langmuir equation was 25.0 mg/g (mod. 1_Al_5-c), 18.2 mg/g (mod. 2_Al_5-c) for Al-bentonite and 16.7 mg/g (mod. 1_Fe_5-c), 10.1 (mod. 2_Fe_5-c) for Fe-bentonite. The kinetics of adsorption is considered. The high content of Al-OH anion exchange centers in them determines the higher sorption activity of Al-modified bentonites. Full article

Zeolites in powder form have the potential to agglomerate, lowering access to active sites. Furthermore, a suspension of fine zeolite powder in liquid media is difficult to separate. Such drawbacks could be improved by dispersing zeolite crystals on support materials. This work demonstrates the dispersion of zeolite NaY crystals on bamboo wood by mixing the wood with zeolite gel before hydrothermal treatment. The syntheses were performed with acid-refluxed and non–refluxed wood. The phase of zeolites, particle distribution and morphology, zeolite content in the wood, and zeolite–wood interaction were investigated using X-ray diffraction, X-ray tomography, scanning electron microscopy, thermogravimetric analysis, nitrogen sorption analysis, and X-ray photoelectron spectroscopy. Higher zeolite content and better particle dispersion were obtained in the synthesis with the acid–refluxed wood. The composite of NaY on the acid-refluxed wood was demonstrated to be an effective adsorbent for Ni(II) ions in aqueous solutions, providing a higher adsorbed amount of Ni(II) per weight of NaY. Full article

This study aims to design novel amine-functionalized alumina nanofibers for the removal of lead (II) and mercury (II) ions from aqueous solutions. The $\gamma$-Al₂O₃ nanofibers were prepared by calcination of boehmite, and then functionalization with 3-(2-aminoethylamino) propyl trimethoxy silane. The characterization of the nanofibers was carried out using TEM, EDS, elemental mapping, XRD, and XPS. The effects of initial concentration, pH, contact time, and selectivity were studied. The results revealed that the nanofibers can remove 98% of Hg²⁺ ions and 90% of Pb²⁺ ions from aqueous solution at concentrations of 40 mg/L and 35 mg/L, respectively. Additionally, the optimal pH conditions for mercury and lead ion adsorption were established to be 6. It was also observed that for concentrations of 100 mg/L and 250 mg/L, the majority of ion contaminants were removed by the nanofibers within the first hour. The adsorption capacities were found to be 129 mg/g and 165 mg/g for Hg²⁺ and 72.3 mg/g and 111 mg/g for Pb²⁺ at 100 mg/L and 250 mg/L concentrations, respectively. The ion-adsorption kinetic data was best fitted to a pseudo-second-order model. High sorption capacities were also demonstrated when employed to selectively adsorb mercury (II) and lead (II) ions from aqueous solutions containing Zn²⁺, Mg²⁺, Cu⁴⁺, Sn⁴⁺, and Ni⁴⁺. Desorption tests were performed to explore the stability of the heavy metals on the nanofiber. Full article

The Stöber version of a sol-gel method of co-condensation of two alkoxysilanes (structuring tetraethoxysilane (TEOS) and functionalising N-containing silane) in an ammonia medium was used for the one-pot synthesis of spherical silica particles with ≡Si(CH₂)₃NH₂, ≡Si(CH₂)₃NH(CH₂)₂NH₂, and ≡[Si(CH₂)₃NH]₂ functional groups with available groups content of 1.3–2.3 mmol/g. The materials were researched by a range of methods, including SEM, TEM, IR spectroscopy, ¹³C, and ²⁹Si solid-state NMR spectroscopy, acid-base titration, and thermal analysis to identify the peculiarities of the morphology, functional groups content, composition, and thermal resistance of the surface layers in the synthesised samples. The type of N-containing silane was shown to affect the structure and properties of the synthesised spherical particles. The silane with the simplest, 3-aminopropyl, functional group caused the formation of nonporous material composed of large 600–800 nm spherical microparticles. Meanwhile, the complication of functional groups enhanced the emergence of small 15 nm primary particles and the origination of porosity, generated by the slits between particles and particle agglomerates. Thereafter, the sorption properties of the synthesised hybrid materials for nickel(II) and copper(II)ions, and bovine serum albumin (BSA) were also found to be dependent on the structure of the materials and the type of incorporated functional group. The maximal static sorption capacity values towards the targeted adsorbates were shown by the samples with 3-aminopropyl groups (1.27 mmol Ni/g), diamine groups (1.09 mmol Cu/g), and secondary amine groups (204.6 mg BSA/g). The conducted research opens up the prospects of directed one-pot synthesis of amino-functionalised hybrid organosilica materials for different applications. Full article