Optimal Synthesis of Novel Phosphonic Acid Modified Diatomite Adsorbents for Effective Removal of Uranium(VI) Ions from Aqueous Solutions.

The authors synthesized a series of functionalized diatomite-based materials and assessed their U(VI) removal performance. Phosphor-derivative-modified diatomite adsorbents were synthesized by the three-route procedures: polymerisation (DIT-Vin-PAin), covalent (DIT-Vin-PAcov), and non-covalent (DIT-PA) immobilization of the functional groups. The effects of the diatomite modification have been studied using powder XRD, solid state NMR, FTIR spectroscopy, electronic microscopy, EDX, acid-base titrations, etc. The maximum adsorption capacities of DIT-Vin-PAcov, DIT-PA, and DIT-Vin-PAin samples were 294.3 mg/g, 253.8 mg/g, and 315.9 mg/g, respectively, at pH0 = 9.0. The adsorption amount of U(VI) ions using the prepared DIT-Vin-PAin was 95.63%, which is higher compared with that of the natural diatomite at the same concentration. The adsorption studies demonstrated that the phosphonic and hydroxyl groups on the surface of the diatomite played pivotal roles in the U(VI) adsorption. The U(VI) ions as a "hard" Lewis acid could easily form bonds with the "hard" donor P-containing ligands, so that the as-prepared DIT-Vin-PAin sample had excellent adsorption properties. The monolayer adsorption of the analyte on the surface of the raw diatomite and DIT-PA was observed. It was found from the thermodynamic parameters that the uptake of the U(VI) ions by the obtained adsorbents was a spontaneous process with an endothermic effect. Findings of the present work highlight the potential for using modified diatomite as effective and reusable adsorbents for the extraction of U(VI) in the waste, river, and tap waters with satisfactory results.

Cichorium intybus L. "hairy" roots as a rich source of antioxidants and anti-inflammatory compounds.

The present study aimed to determine the bioactive profile of various extracts of Cichorium intybus L. "hairy" roots. In particular, the total content of flavonoids as well as the reducing power, antioxidant and anti-inflammatory activity of the aqueous and ethanolic (70%) extracts were evaluated. The total content of flavonoids the ethanolic extract of the dry "hairy" root reached up to 121.3 mg (RE)/g, which was twofold greater than in the aqueous one. A total of 33 diverse polyphenols were identified by the LC-HRMS method. The experimental results showed a high amount of gallic (6.103 ± 0.008 mg/g) and caffeic (7.001 ± 0.068 mg/g) acids. In the "hairy" roots, the presence of rutin, apigenin, kaempferol, quercetin, and its derivatives was found in concentrations of 0.201±0.003 - 6.710±0.052 mg/g. The broad spectrum of pharmacological activities (antioxidant, anti-inflammatory, antimutagenic, anticarcinogenic, etc.) of the key flavonoids identified in the chicory "hairy" root extract was predicted by the General Unrestricted Structure-Activity Relationships algorithm based on in the substances detected in the extract. The evaluation of the antioxidant activity showed that the EC50 values of the ethanol and the aqueous extracts were 0.174 and 0.346 mg, respectively. Thus, the higher ability of the ethanol extract to scavenge the DPPH radical was observed. The calculated Michaelis and inhibition constants indicated that the ethanolic extract of C. intybus "hairy" roots is an efficient inhibitor of soybean 15-Lipoxygenase activity (IC50 = 84.13 ± 7.22 µM) in a mixed mechanism. Therefore, the obtained extracts could be the basis of herbal pharmaceuticals for the therapy of human diseases accompanied by oxidative stress and inflammation, including the pandemic coronavirus disease COVID-19.

Morphology-Controlled Green Synthesis of Magnetic Nanoparticles Using Extracts of 'Hairy' Roots: Environmental Application and Toxicity Evaluation.

Magnetic nanoparticles (MNPs) were "green" synthesized from a FeCl3/FeSO4/CoCl2 mixture using ethanolic extracts of Artemisia tilesii Ledeb 'hairy' roots. The effect of chemical composition and reducing power of ethanolic extracts on the morphology, size destribution and other features of obtained MNPs was evaluated. Depending on the extract properties, nanosized magnetic materials of spherical (8-11 nm), nanorod-like (15-24 nm) and cubic (14-24 nm) shapes were obtained via self-assembly. Microspherical MNPs composed of nanoclusters were observed when using extract of the control root line in the synthesis. Polyhedral magnetic nanoparticles with an average size of ~30 nm were formed using 'hairy' root ethanolic extract without any additive. Studied samples manifested excellent magnetic characteristics. Field-dependent magnetic measurements of most MNPs demonstrated a saturation magnetization of 42.0-72.9 emu/g with negligible coercivity (∼0.02-0.29 emu/g), indicating superparamagnetic behaviour only for solids with a magnetite phase. The synthesized MNPs were minimally aggregated and well-dispersed in aqueous medium, probably due to their stabilization by bioactive compounds in the initial extract. The nanoparticles were tested for magnetic solid-phase extraction of copper (Cu), cadmium (Cd) and arsenic (As) pollutants in aqueous solution, followed by ICP-OES analysis. The magnetic oxides, mainly magnetite, showed high adsorption capacity and effectively removed arsenic ions at pH 6.7. The maximum adsorption capacity was ~150 mg/g for As(III, V) on the selected MNPs with cubic morphology, which is higher than that of previously reported adsorbents. The best adsorption was achieved using Fe3O4-based nanomaterials with low crystallinity, non-spherical form and a large number of surface-localized organic molecules. The phytotoxicity of the obtained MNPs was estimated in vitro using lettuce and chicory as model plants. The obtained MNPs did not exhibit inhibitory activity. This work provides novel insights on the morphology of "green" synthesized magnetic nanoparticles that can be used for applications in adsorption technologies.

Magnetic nanocomposites based on Zn,Al-LDH intercalated with citric and EDTA groups for the removal of U(vi) from environmental and wastewater: synergistic effect and adsorption mechanism study.

The efficient removal of U(vi) ions from contaminated natural waters and wastewaters of industrial processing plants by novel magnetic nanocomposites based on magnetite and Zn,Al-layered double hydroxides intercalated with citric and EDTA groups (Fe3O4/Zn,Al-LDH/Cit and Fe3O4/Zn,Al-LDH/EDTA) was shown. These adsorbents were obtained using co-precipitation and ion-exchange techniques. The infrared spectroscopy confirmed the existence of O-containing groups on the surfaces of Fe3O4/Zn,Al-LDH/Cit and Fe3O4/Zn,Al-LDH/EDTA, which could provide active sites in the interlayer of the adsorbents for the pollutants removal. The intercalation of Zn,Al-LDH with chelating EDTA-groups significantly increased the adsorption capacity toward U(vi) ions (131.22 mg g-1) compared to citric moieties in a wide range of pH (3.5-9.0). The maximum adsorption capacities of U(vi) at pH 7.5 were 81.12 mg g-1 for Fe3O4/Zn,Al-LDH/EDTA and 21.6 mg g-1 for Fe3O4/Zn,Al-LDH/Cit. The higher adsorption capacity of Fe3O4/Zn,Al-LDH/EDTA vs. the citric sample might be explained by high affinity of LDH-supports and high-activity of the chelating groups in formation of the complexes in the interlayer space of the magnetic nanocomposite. The removal of U(vi) by the magnetic nanocomposites occurred due to interlayer complexation and electrostatic interactions. The cations (Na+, K+, Ca2+), HCO3 - and fulvic acid anions being typical for natural waters were practically not affected upon the removal of U(vi) from aqueous media. The adsorption performance of Fe3O4/Zn,Al-LDH/EDTA nanocomposites was evaluated in the analysis of environmental and wastewater samples with recoveries in the range of 95.8-99.9%. This superior intercalation performance of LDH-supports provides simple and low-cost adsorbents, providing a strategy for decontamination of radionuclides from wastewater.

Steam Activation of Acid-Chars for Enhanced Textural Properties and Pharmaceuticals Removal.

The present work aims to explore steam activation of sisal or glucose-derived acid-chars as an alternative to KOH activation to prepare superactivated carbons, and to assess the adsorption performance of acid-chars and derived activated carbons for pharmaceuticals removal. Acid-chars were prepared from two biomass precursors (sisal and glucose) using various H2SO4 concentrations (13.5 M, 12 M, and 9 M) and further steam-activated at increasing burn-off degrees. Selected materials were tested for the removal of ibuprofen and iopamidol from aqueous solution (kinetic and equilibrium assays) in single-solute conditions. Activated carbons prepared from acid-char carbonized with 13.5 M and 12 M H2SO4 are mainly microporous solids composed of compact rough particles, yielding a maximum surface area and a total pore volume of 1987 m2 g-1 and 0.96 cm3 g-1, respectively. Solid state NMR reveals that steam activation increased the aromaticity degree and amount of C=O functionalities. Steam activation improved the acid-chars adsorption capacity for ibuprofen from 20-65 mg g-1 to higher than 280 mg g-1, leading to fast adsorption kinetics (15-20 min). The maximum adsorption capacities of selected activated samples for ibuprofen and iopamidol were 323 and 1111 mg g-1, respectively.

In situ Functionalized Mesoporous Silicas for Sustainable Remediation Strategies in Removal of Inorganic Pollutants from Contaminated Environmental Water.

Low-cost mesoporous silicas of the SBA-15 family were prepared, aimed for removal of a broad spectrum of both cationic and anionic forms of hazardous metal pollutants (Cr(III, VI), Mn(II, VII), Pb(II), Cd(II), and Cu(II)) from environmental water. Series of mono- and bifunctional materials with immobilized ethylenediaminetriacetic acid (EDTA), primary amine (NH2), and quaternary ammonium (QAS) groups were prepared in a cost-efficient one-step synthesis using two silica sources, low-cost sodium metasilicate (Na2SiO3 9H2O) and the conventional source-tetraethylorthosilicate (TEOS). The functionalized SBA-15 samples obtained from both silica sources were highly ordered, as evidenced by TEM and SAXS data. All obtained materials were mesoporous with high surface area values of up to 745 m2/g, pore volumes from 0.99 to 1.44 cm3/g, and narrow pore distributions near 7 nm. The adsorption affinity of the EDTA-functionalized samples followed the common order Pb(II)> Cd(II)> Cu(II)> Cr(III)> Mn(II), which could be explained based on the Pearson theory. The highest adsorption capacities were observed for samples functionalized by EDTA groups using TEOS for synthesis (TEOS/EDTA): 195.6 mg/g for Pb(II), 111.2 mg/g for Cd(II), 58.7 mg/g for Cu(II), 57.7 mg/g for Cr(III), and 49.4 mg/g for Mn(II). Moreover, organic matter (humic acid up to 10 mg/L) and inorganic (Na(I), K(I), Mg(II), Ca(II), etc) macrocomponents present in environmental water had almost negligible effect on the removal of these cations. The NaSi/EDTA/NH2 sample revealed a better selectivity compared to the NaSi/NH2 sample towards such species as Cr(III), Mn(II), Cd(II), and Cu(II). The chromate-ions uptake at pH 7.5 by the TEOS/QAS sample turned practically unaffected by the presence of doubly charged anions (CO3 2-, SO4 2-). The content of functional groups on the surface of MS decreased only slightly (∼1-5%) after several regeneration cycles. The complete desorption of all heavy metal ions can be achieved using 1 mol/L EDTA solution. Reusability tests demonstrated the complete stability of the adsorbent for at least five to six consecutive adsorption/desorption cycles with no decrease in its adsorption characteristics compared to those obtained by 0.05 mol/L HNO3 treatments. The synthesized mesoporous materials were evaluated for removal of the heavy metal ions from drinking and different natural water samples, proving their potential as sustainable, effective, and cost-efficient adsorbents.

Biosynthesis of magnetite and cobalt ferrite nanoparticles using extracts of "hairy" roots: preparation, characterization, estimation for environmental remediation and biological application.

The "green" synthesis of magnetite and cobalt ferrite nanoparticles (Fe3O4-NPs and CoFe2O4-NPs) using extracts of Artemisia annua L "hairy" roots was proposed. In particular, the effect and role of important variables in the 'green' synthesis process, including the metal-salt ratio, various counter ions in the reaction mixture, concentration of total flavonoids and reducing power of the extract, were evaluated. The morphology and size distribution of the magnetic nanoparticles (MNPs) depended on the metal oxidation state and ratio of Fe(iii) : Fe(ii) in the initial reaction mixture. MNPs obtained from divalent metal salts in the reaction mixture were non-uniform in size with high aggregation level. Samples obtained by the FeCl3/FeSO4 mixture with a ratio of Fe(iii) : Fe(ii) = 1 : 2 showed an irregular shape of the nanoparticles and high aggregation level. MNPs obtained by the FeCl3/FeSO4/CoCl2 mixture showed a regular shape with slight aggregation, and were in the nanosize range (10-17 nm). Thus, this mixture as a metal-precursor was used for MNP biosynthesis in the subsequent experiments. The XRD data showed that the magnetic specimens contained mainly spinel type phase. The data of EDX and XPS analysis indicated that the product of the "green" synthesis was magnetite with some impurities, owing to the obtained ratio of Fe : O being similar to the theoretical atomic ratio of magnetite (3 : 4). The Fe3O4-NP samples were superparamagnetic with high magnetization (until 68 emu g-1). The Co-containing MNPs demonstrated low ferromagnetic properties. The MNPs with pure magnetite phase, very good magnetization and uniform size distribution (ca. 12-14 nm) were prepared by the "hairy" root extract characterized by the highest amount of total flavonoids. According to the FTIR data, the synthesized Fe3O4-NPs had a core-shell like structure, in which the core was composed of Fe3O4, and the shell was formed by bioactive molecules. The presence of several organic compounds (such as flavonoids or carboxylic acids) plays a key role in the suppression of Fe3O4-NP aggregation without addition of a stabilizing agents. Synthesized Fe3O4-NP samples effectively removed Cu(ii) and Cd(ii) with the maximum adsorption capacity, reaching 29.9 mg g-1 and 33.5 mg g-1, respectively. It is probable that the presence of organic components in extracts plays an important role in the adsorption properties of biosynthesised MNPs. The obtained MNPs were successfully applied to the removal of heavy metal ions in the environmental water samples. Fe3O4-NPs also negatively affected plant growth in the case of using "hairy" roots as a test model, and the greatest inhibitory activity (99.56 wt%) was possessed by MNPs with high magnetic properties.

Advanced core-shell EDTA-functionalized magnetite nanoparticles for rapid and efficient magnetic solid phase extraction of heavy metals from water samples prior to the multi-element determination by ICP-OES.

A method for preconcentration and simultaneous determination of trace heavy metals in water media by core-shell superparamagnetic nanoparticles with the immobilized derivative of ethylenediaminetriacetic acid (referred to as MNPs/SiO2-EDTA) is proposed. The specific layer-by-layer covering of magnetite endowed the new material with essentially increased chemical stability of MNPs including acidic media and improved the affinity toward traces of toxic metal ions. The initial and modified materials were characterized by X-ray powder diffraction, Fourier transform infrared spectroscopy, transmission and scanning electron microscopies, elemental analysis, and vibrating sample magnetometry. The obtained particles were nanodimensional with a 7-12-nm magnetic core and a 4-6-nm silica shell. The MNPs/SiO2-EDTA quantitatively removes heavy metals from contaminated media at pH ≥ 3.5 within 15 min. The adsorption data were successfully fitted to the pseudo-second-order kinetic model. The preconcentration factor was 150 and maximum adsorption capacity was 36.9 mg g-1 for Cu(II), 108.8 mg g-1 for Pb(II), 30.9 mg g-1 for Zn(II), 34.32 mg g-1 for Cr(III), and 59.5 mg g-1 for Cd(II). Due to high stability in the wide range of pH, the magnetic adsorbent can be regenerated at least six times using 0.1 M HNO3. Following adsorption/desorption, determination of metal ions is provided by inductively coupled plasma optical emission spectrometry (ICP-OES) . The linear range of the proposed method is 0.1 - 200 µg L-1. The limits of detection (LOD) are 0.12 µg L-1 for Zn(II); 0.06 µg L-1 for Cd(II); 0.39 for Cu(II); 0.15 µg L-1 for Cr(III); and 0.76 µg L-1 for Pb(II). The method performance was evaluated in the analysis of environmental, tap, and wastewater samples with recoveries in the range of 94.0-104.0%.

'Hairy' root extracts as source for 'green' synthesis of silver nanoparticles and medical applications.

The research was focused on the synthesis of silver nanoparticles (AgNPs) using extracts from the "hairy" root cultures of Artemisia tilesii Ledeb. and Artemisia annua L. The effect of operational parameters such as type of solvent, temperature of extraction, flavonoids concentration, and reducing power of the wormwood "hairy" root extracts on the particle size and yield of the resultant nanoparticles is reported for the first time. From the studied solvents, a water-ethanol mixture with a concentration of 70 vol% was found to be the best for the extraction of flavonoids from all "hairy" root cultures. The total flavonoid contents in A. annua and A. tilesii "hairy" root extracts were up to 80.0 ± 0.9 and 108 ± 4.4 mg RuE per g DW, respectively. Identification of flavonoids was confirmed by UPLC-ESI-UHR-Qq-TOF-MS analysis. Luteolin-7-ß-d-glucopyranosid, isorhamnetin 3-O-glucoside, baicalein-7-O-glucuronide, apigenin-7-O-glucoside, quercetin, sitosterol, caffeoylquinic, galic, chlorogenic and caffeic acids were founded in the extracts. These extracts demonstrated the high reducing activities. Spherical, oval and triangular nanoparticles with effective sizes of 5-100 nm were observed. The TEM data revealed great differences in the shapes of NPs, obtained from the extracts from different root clones. The clustered and irregular NPs were found in the case of using ethanol extracts, mostly aggregated and having the size of 10-50 nm. The sizes of AgNPs decreased to 10-30 nm in the case of using aqueous extracts obtained at 80 °C. Biosynthesized AgNPs showed surface plasmon resonance in the range of 400-450 nm. The antimicrobial activity of the as-produced AgNPs was studied by disc diffusion method on Gram-positive (Staphylococcus aureus ATCC 25923 (F-49)), Gram-negative (Pseudomonas aeruginosa ATCC 27853 (F-51), Escherichia coli ATCC 25922 (F-50)) and Candida albicans ATCC 88-653 strains. It was found that the nanoparticles in some cases possessed the greater ability to inhibit microorganism growth compared to 1 mM AgNO3 solution. The colloidal solutions of the obtained AgNPs were stable in the dark for 12 months at room temperature. Thus, the A. annua and A. tilesii "hairy" root extracts can be used for obtaining of bioactive AgNPs.

Magnetite nanoparticles with aminomethylenephosphonic groups: synthesis, characterization and uptake of europium(III) ions from aqueous media.

Two adsorbents with covalently bound aminomethylenephosphonic acid functions (and referred to as MNPs/AMPA and MNPs/SiO2-AMPA) were synthesized from two types of amino-functionalized magnetic nanoparticles (MNPs) via Moedritzer-Irani reaction. The sorbents with anchored dopamine ligand (MNPs/dopa) or aminopropyl groups (MNPs/SiO2-NH2), and the MNPs/AMPA were characterized by X-ray diffraction, FTIR, transmission electron microscopy and vibrating sample magnetometry. Surface modification does not adversely impact the physical properties of the starting magnetite. Compared to the size of the unmodified Fe3O4 (magnetite) nanoparticles (7-12 nm), the average size of functionalized nanoparticles is increased to 10-16 nm. Similarly, the magnetic saturation decreased from 67.5 emu g-1 to 42.0 emu g-1, and the surface area is increased up to 205 m2 g-1 for MNPs/SiO2-AMPA. The kinetics of the adsorption of Eu(III) on the sorbent is ultra-fast, and equilibria are attained within 5-10 min at room temperature. The adsorption kinetics can be described by a pseudo-second-order model. Adsorption and desorption conditions were tested with respect to the removal of Eu(III) ions from water solution. The adsorption capacities for Eu(III) at pH 7.0 are 77 mg g-1 and 69 mg g-1 for MNPs/AMPA and MNPs/SiO2-AMPA nanoparticles, respectively. Eu(III) was quantified by ICP-MS. The limit of detection (LOD) for Eu(III) is 0.05 ng L-1 (based on the 3σ criterion), with an enrichment factor of 150. The selectivity over ions such as Tb(III), Fe(III), Zn(II), Cu(II), and Ca(II) ions was studied. Under optimal condition the distribution coefficient for Eu(III) relative to these ions is near 105 mL g-1. The sorbents can be easily retrieved from even large volumes of aqueous solutions by magnetic separations. The method was tested for spiked water samples (with recoveries from 96.6-102.5%) and for rock minerals. Graphical abstract A schematic showing the regeneration of magnetite nanoparticles (MNPs), core-shell (MNPs/SiO2), and the structures with covalently bonded aminomethylenephosphonic acid (AMPA) after preconcentration of Eu(III) from largewater sample volumes onto a small specimen.