Pb(II)
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A sonochemical method was used to synthesize nano-peanuts of a new lead(II) coordination 1D polymer, [Pb(qcnh)(NO3)2]n (1), where qcnh=2-quinolincarbaldehyde nicotinohydrazide. The compound was characterized by scanning electron microscopy (SEM), elemental analysis, IR spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray powder diffraction (XRD), and single crystal X-ray analysis. The X-ray structure revealed that the Pb(II) atom is coordinated by one oxygen and three nitrogen atoms from two qcnh ligands and five oxygen atoms from three nitrate ligands in an 8+1 fashion with a PbN3O6 donor set. One of the PdN distances in the vicinity of the central atom is a bit longer (Pb1N1=2.939(4) Å), which shows the effect of the 6s2 lone electron pair localized within the valence shell of the lead(II) atom. PbO nanoparticles were obtained by thermolysis of 1 at 180°C with oleic acid as a surfactant. The average diameter of the nanoparticles was estimated by XRD to be 28nm. The morphology and size of the prepared PbO nanoparticles were further studied using SEM.
- Klíčová slova
- Crystal structure, Nano-peanuts, Pb(II) nano coordination polymer, PbO nanoparticles,
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The remediation of Pb(II) through biomineralization is rergarded as a promising technique as well as an interesting phenomenon for transforming heavy metals from mobile species into very stable minerals in the environment. Studies are well needed for in-depth understanding the mechanism of Pb(II) immobilized by bacteria. In the present study, we investigated the uptake and biomineralization of Pb(II) using Bacillus cereus 12-2 isolated from lead-zinc mine tailings. The maximum Pb(II) uptake capacity of B. cereus 12-2 was 340 mg/g at pH 3.0. Zeta potential analyses and selective passivation experiments demonstrated that electrostatic attraction was the main force driving the uptake of Pb(II), while the carboxyl, amide and phosphate functional groups of the bacteria provided the binding sites for immobilizing Pb(II). XRD and TEM investigation revealed that the Pb(II) loaded on bacteria could be stepwise transformed into rod-shaped Ca2.5Pb7.5(OH)2(PO4)6 nanocrystal. Combined with protein denaturalization experiments, we proposed that the biomineralization of Pb(II) possibly consisted of two steps: (1) Rapid biosorption of Pb(II) on B. cereus 12-2 through the synergy of electrostatic attraction, ionic exchange and chelating activity of functional groups; (2) enzyme-mediated mineral transformation from amorphous precipitate to rod-shaped crystalline minerals happening gradually inside the bacteria.
- Klíčová slova
- Bacillus cereus, Biomineralization, Biosorption, Lead,
- MeSH
- Bacillus cereus chemie metabolismus MeSH
- hornictví MeSH
- hydroxyapatit * chemie metabolismus MeSH
- nanočástice * chemie metabolismus MeSH
- olovo * chemie metabolismus MeSH
- průmyslový odpad MeSH
- zinek MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- hydroxyapatit * MeSH
- olovo * MeSH
- průmyslový odpad MeSH
- zinek MeSH
A combined modeling and spectroscopic approach is used to describe Cd(II), Cr(VI), and Pb(II) adsorption onto nanomaghemite and nanomaghemite coated quartz. A pseudo-second order kinetic model fitted the adsorption data well. The sorption capacity of nanomaghemite was evaluated using a Langmuir isotherm model, and a diffuse double layer surface complexation model (DLM) was developed to describe metal adsorption. Adsorption mechanisms were assessed using X-ray photoelectron spectroscopy and X-ray absorption spectroscopy. Pb(II) adsorption occurs mainly via formation of inner-sphere complexes, whereas Cr(VI) likely adsorbs mainly as outer-sphere complexes and Cd(II) as a mixture of inner- and outer-sphere complexes. The simple DLM describes well the pH-dependence of single adsorption edges. However, it fails to adequately capture metal adsorption behavior over broad ranges of ionic strength or metal-loading on the sorbents. For systems with equimolar concentrations of Pb(II), Cd(II), and Cr(VI). Pb(II) adsorption was reasonably well predicted by the DLM, but predictions were poorer for Cr(VI) and Cd(II). This study demonstrates that a simple DLM can describe well the adsorption of the studied metals in mixed sorbate-sorbent systems, but only under narrow ranges of ionic strength or metal loading. The results also highlight the sorption potential of nanomaghemite for metals in complex systems.
- MeSH
- adsorpce MeSH
- chrom chemie MeSH
- fotoelektronová spektroskopie MeSH
- kadmium chemie MeSH
- kinetika MeSH
- koncentrace vodíkových iontů MeSH
- křemen chemie MeSH
- nanostruktury chemie MeSH
- olovo chemie MeSH
- osmolární koncentrace MeSH
- rentgenová absorpční spektroskopie MeSH
- teoretické modely * MeSH
- železité sloučeniny chemie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- chrom MeSH
- chromium hexavalent ion MeSH Prohlížeč
- ferric oxide MeSH Prohlížeč
- kadmium MeSH
- křemen MeSH
- olovo MeSH
- železité sloučeniny MeSH
In this work, the synthesis of ordered mesoporous silica of MCM-41 type was investigated aimed at improving its morphology by varying the synthesis conditions in a one-pot process, employing different temperatures and solvent conditions. 2-methoxyethanol was used as co-solvent to ethanol. The co-solvent ratio and the synthesis temperature were varied. The pore morphology of the materials was characterized by nitrogen porosimetry and small angle neutron scattering (SANS), and the particle morphology by transmission electron microscopy (TEM) and ultra-small angle neutron scattering (USANS). The thermal behavior was investigated by simultaneous thermogravimetry-differential scanning calorimetry (TG-DSC) measurements. The SANS and N2 sorption results demonstrated that a well-ordered mesoporous structure was obtained at all conditions in the synthesis at room temperature. Addition of methoxyethanol led to an increase of the pore wall thickness. Simultaneously, an increase of methoxyethanol content led to lowering of the mean particle size from 300 to 230 nm, according to the ultra-small angle scattering data. The ordered porosity and high specific surfaces make these materials suitable for applications such as adsorbents in environmental remediation. Batch adsorption measurements of metal ion removal from aqueous solutions of Cu(II) and Pb(II) showed that the materials exhibit dominantly monolayer surface adsorption characteristics. The adsorption capacities were 9.7 mg/g for Cu(II) and 18.8 mg/g for Pb(II) at pH 5, making these materials competitive in performance to various composite materials.
- Klíčová slova
- 2-methoxyethanol, Langmuir isotherm, MCM-41, SANS, SAXS, Stöber method, USANS,
- Publikační typ
- časopisecké články MeSH
In this work, we report on the efficient removal of heavy metal ions with nanostructured lithium, sodium and potassium titanates from simulated wastewater. The titanates were obtained via a fast, easy and cost effective process based on extraction of sulfate ions from the crystals of titanyl sulfate and their replacement with hydroxyl groups of NaOH, LiOH and KOH solutions leaving the Ti-O framework intact. The as-prepared titanates were carefully examined by scanning and transmission electron microscopy. Furthermore, the effect of contact time, pH, annealing temperature, together with adsorption in real conditions including competitive adsorption and reusability were studied. It was found that the maximum adsorption capacity, as calculated from the Langmuir adsorption model, is up to 3.8 mmol Pb(ii) per g, 3.6 mmol Cu(ii) per g and 2.3 mmol Cd(ii) per g. Based on the characterization results, a possible mechanism for heavy metal removal was proposed. This work provides a very efficient, fast and convenient approach for exploring promising materials for water treatment.
- Publikační typ
- časopisecké články MeSH
In this study, two alternative synthesis routes for magnetic adsorbents were evaluated to remove Pb(II) and Cd(II) in an aqueous solution. First, activated carbon was prepared from argan shells (C). One portion was doped with magnetite (Fe3O4+C) and the other with cobalt ferrite (CoFe2O4+C). Characterization studies showed that C has a high surface area (1635 m2 g-1) due to the development of microporosity. For Fe3O4+C the magnetic particles were nano-sized and penetrated the material's texture, saturating the micropores. In contrast, CoFe2O4+C conserves the mesoporosity developed because most of the cobalt ferrite particles adhered to the exposed surface of the material. The adsorption capacity for Pb(II) was 389 mg g-1 (1.88 mmol g-1) and 249 mg g-1 (1.20 mmol g-1); while for Cd(II) was 269 mg g-1 (2.39 mmol g-1) and 264 mg g-1 (2.35 mmol g-1) for the Fe3O4+C and CoFe2O4+C, respectively. The predominant adsorption mechanism is the interaction between -FeOH groups with the cations in the solution, which are the main reason these adsorption capacities remain high in repeated adsorption cycles after regeneration with HNO3. The results obtained are superior to studies previously reported in the literature, making these new materials a promising alternative for large-scale wastewater treatment processes using batch-type reactors.
- Klíčová slova
- adsorption, argan shells, magnetic adsorbents, metals removal, wastewater treatment,
- Publikační typ
- časopisecké články MeSH
Although the mechanisms of metal(loid) removal from aqueous solutions using LDHs (layered double hydroxides) and mixed oxides (thermally treated LDHs; CLDHs) have been studied, research dealing with their stability, stabilizing efficiency and remediation potential for contaminated soils remains scarce. We present a complex study investigating the stabilizing efficiency of Mg-Fe LDHs and CLDHs at different conditions, including aqueous solutions and real soils with highly elevated As(V), Pb(II) and Zn(II) concentrations. All studied materials showed excellent (ad)sorption efficiency for As(V), Pb(II) and Zn(II) in aqueous solutions. Additionally, the reconstruction ability of CLDHs at different conditions that could improve their adsorption properties was also evaluated, and the dependence on time, pH and the concentrations of metal(loid)s was shown. In general, CLDHs showed higher stability and stabilizing efficiency in aqueous and soil solutions; however, LDHs were more efficient in contaminated soils. Furthermore, solid state analyses coupled with geochemical modeling showed the formation of new phases corresponding to Mg‑carbonates/silicates on the surfaces of LDH/CLDH after their incubation in soils. Both LDHs and CLDHs significantly decreased the bioavailable/labile fraction of As(V) and Zn(II) in the studied soils. In general, our work shows Mg-Fe LDHs and CLDHs as prospective materials for water and soil remediation.
- Klíčová slova
- Arsenic, Chemical stabilization, Geochemical modeling, Lead, Zinc,
- Publikační typ
- časopisecké články MeSH
The (13)C and (29)Si NMR signals of ligand atoms directly bonded to Tl(I) or Pb(II) heavy-element centers are predicted to resonate at very high frequencies, up to 400 ppm for (13)C and over 1000 ppm for (29)Si, outside the typical experimental NMR chemical-shift ranges for a given type of nuclei. The large (13)C and (29)Si NMR chemical shifts are ascribed to sizable relativistic spin-orbit effects, which can amount to more than 200 ppm for (13)C and more than 1000 ppm for (29)Si, values unexpected for diamagnetic compounds of the main group elements. The origin of the vast spin-orbit contributions to the (13)C and (29)Si NMR shifts is traced to the highly efficient 6p → 6p* metal-based orbital magnetic couplings and related to the 6p orbital-based bonding together with the low-energy gaps between the occupied and virtual orbital subspaces in the subvalent Tl(I) and Pb(II) compounds. New NMR spectral regions for these compounds are suggested based on the fully relativistic density functional theory calculations in the Dirac-Coulomb framework carefully calibrated on the experimentally known NMR data for Tl(I) and Pb(II) complexes.
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Cyanobacteria have developed responses to maintain the balance between the energy absorbed and the energy used in different pigment-protein complexes. One of the relatively rapid (a few minutes) responses is activated when the cells are exposed to high light intensities. This mechanism thermally dissipates excitation energy at the level of the phycobilisome (PB) antenna before it reaches the reaction center. When exposed to low intensities of light that modify the redox state of the plastoquinone pool, the so-called state transitions redistribute energy between photosystem I and II. Experimental techniques to investigate the underlying mechanisms of these responses, such as pulse-amplitude modulated fluorometry, are based on spectrally integrated signals. Previously, a spectrally resolved fluorometry method has been introduced to preserve spectral information. The analysis method introduced in this work allows to interpret SRF data in terms of species-associated spectra of open/closed reaction centers (RCs), (un)quenched PB and state 1 versus state 2. Thus, spectral differences in the time-dependent fluorescence signature of photosynthetic organisms under varying light conditions can be traced and assigned to functional emitting species leading to a number of interpretations of their molecular origins. In particular, we present evidence that state 1 and state 2 correspond to different states of the PB-PSII-PSI megacomplex.
- Klíčová slova
- Cyanobacteria, Singular value decomposition, Spectrally resolved fluorometry, Time-resolved spectroscopy,
- MeSH
- fluorescence MeSH
- fluorescenční spektrometrie MeSH
- fotosystém I (proteinový komplex) metabolismus účinky záření MeSH
- fotosystém II (proteinový komplex) metabolismus účinky záření MeSH
- světlo MeSH
- Synechocystis účinky záření MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- fotosystém I (proteinový komplex) MeSH
- fotosystém II (proteinový komplex) MeSH
