Mixture Of Pb Research Articles

Metal-Induced Isomerization of a Molecular Strand Containing Contradictory Dynamic Coordination Sites

A new hydroxymethyl terminated pyrimidine-hydrazone (pym-hyz) ligand (L1) was synthesized with a central hyz-pyridine-hyz (hyz-py-hyz) motif replacing the usual hyz-pym-hyz unit, to create a molecular strand that underwent metal-induced isomerization with a minimal net change in ligand length. NMR spectroscopy showed that L1 had a horseshoe shape due to the hyz-py-hyz and pym-hyz bonds adopting transoid conformations. The ligand was successfully reacted with Pb(II), Zn(II), and Ag(I) salts in either CH3CN or CH3NO2 resulting in horseshoe-shaped M(n+)3L1A3n (where A = ClO4(-) or SO3CF3(-)) complexes in the solution phase. Crystals were grown from these solutions, the structures of which were highly dependent on the metal ion and solvent used, and were distinctly different from those seen in solution. The crystals grown from mixtures of Pb(ClO4)2·3H2O and L1 in either CH3CN or CH3NO2 resulted in the horseshoe-shaped [Pb3L1(ClO4)4(H2O)2](ClO4)2·CH3CN (1) complex or the {[Pb3L1(ClO4)4(H2O)](ClO4)2}∞·CH3NO2 (2) helical coordination polymer, respectively. The horseshoe-shaped [Pb3L1(SO3CF3)6]·CH3CN (3) complex was crystallized from a solution of Pb(SO3CF3)2·H2O and L1 in CH3CN, while the crystals grown from the solution of Zn(SO3CF3)2 and L1 in CH3CN consisted of the zigzag-shaped [Zn3L1(H2O)7](SO3CF3)6 (4) complex. The [Ag3(L1)2](SO3CF3)3 (5) double-helicate and the macrocycle-like [Ag6(L1)2](SO3CF3)6 (6) complex were crystallized from solutions of AgSO3CF3 and L1 in either CH3CN or CH3NO2, respectively.

Carbonate, organic and clay fractions determine metal bioavailability in periurban calcareous agricultural soils in the Mediterranean area

A set of periurban calcareous agricultural Mediterranean soils, with a natural gradient in the content and composition of organic matter (OM), was spiked with a mixture of Cd, Cu, Pb and Zn at two levels – designated Tt1 and Tt2 – within the limit values proposed by the current European legislation and incubated for ≤12months. We conducted bioassay experiments with romaine and iceberg varieties of lettuce (Lactuca sativa L.). Metal bioavailability patterns were evaluated as a function of soil constituents and extractable metals.Metal contamination produced a decrease in plant biomass (up to 50%) and nutrient imbalance. The redundancy analysis showed that the carbonate, OM and fine mineral fractions account for up to 85% of the variance in metal bioavailability patterns in lettuce plants. Carbonate and fine mineral fractions were negatively related to Cd and Zn bioavailability in plants respectively. Organic matter explained Cu and Pb bioavailability, although patterns varied between plant tissues according to their organic composition. The labile fraction limited metal absorption of Pb by roots at the Tt2 level and Cu at both levels, but Cu and Pb translocation was enhanced at both levels. There were significant correlations between metals in leaves and metals extracted with both neutral salts and complexing agents. The high rate of metal translocation and the considerable influence of soil properties may indicate that the limiting values of metals in soils proposed by the current European legislation should be revised in the case of multi-component systems, and/or be established according to the soil characteristics.

ChemInform Abstract: A New Mixed Metal Borate of BaPb[B5O9(OH)]·H2O with Acentric Structure.

AbstractThe new title compound is hydrothermally synthesized from a mixture of H3BO3, Pb(OAc)2, Ba(OH)2, and H2O (autoclave, 200 °C, 6 d, 78% yield).

CDK5-induced p-PPARγ(Ser 112) downregulates GFAP via PPREs in developing rat brain: effect of metal mixture and troglitazone in astrocytes

The peroxisome proliferator-activated receptor gamma (PPARγ), a group of ligand-activated transcriptional factors, is expressed in glial fibrillary acidic protein (GFAP)-immunoreactive astrocytes. Here, we investigated the role of PPARγ in regulating GFAP using a mixture of As, Cd and Pb (metal mixture, MM) that induces apoptosis and aberrant morphology in rat brain astrocytes. We observed a phospho PPARγ (serine 112 (S112)) (p-PPARγ (S112))-mediated downregulation of GFAP in the MM-exposed astrocytes. We validated this using pure PPARγ agonist, troglitazone (TZ). As reported with MM, TZ induced astrocyte damage owing to reduced GFAP. In silico analysis in the non-coding region of GFAP gene revealed two PPARγ response elements (PPREs); inverted repeat 10 and direct repeat 1 sequences. Gel shift and chromatin immunoprecipitation assays demonstrated enhancement in binding of p-PPARγ (S112) to the sequences, and luciferase reporter assay revealed strong repression of GFAP via PPREs, in response to both MM and TZ. This indicated that suppression in GFAP indeed occurs through direct regulation of these elements by p-PPARγ (S112). Signaling studies proved that MM, as well as TZ, activated the cyclin-dependent kinase 5 (CDK5) and enhanced its interaction with PPARγ resulting into increased p-PPARγ (S112). The p-CDK5 levels were dependent on proximal activation of extracellular signal-regulated protein kinase 1/2 and downstream Jun N-terminal kinase. Taken together, these results are the first to delineate downregulation of GFAP through genomic and non-genomic signaling of PPARγ. It also brings forth a resemblance of TZ with MM in terms of astrocyte disarray in developing brain.

Kinetic and Equilibrium Isotherms Studies of Adsorption of Pb(II) from Water onto Natural Adsorbent

In this research dobera leaves (DL), an agricultural waste, available in large quantity in south region of Saudi Arabia, were used as low-cost adsorbent for removal of metal ions such as Pb(II). Batch operation was used to study the equilibrium behavior of DL. The effects of initial concentration of Pb(II), solution pH, contact time and adsorbent dose were evaluated. To study the kinetics of adsorption of Pb(II) onto DL, pseudo-first-order, pseudo-second-order and intra-particle diffusion were used. Adsorption process undergoes pseudo-second-order kinetic as proved by the high value of R2. Furthermore, to design the equilibrium data of adsorption of process, four adsorption isotherm models such as Langmuir, Freundlich Temkin and Dubinin-Radushkevich (D-R) were used. It is found that Langmuir equation has the highest value of R2 (0.999) compared with other models. In presences of a mixture of Pb(II)/Ni(II), DL were found to be selective for Pb(II) ions with a high adsorptive capacity of 83 mg/g and show favorable adsorption with RL 90%) from drinking water with less competition of other ions present in water.

Phytoremediation of Cu, Cr and Pb Mixtures by Lemna minor

The present study reports the capacity of the aquatic macrophyte Lemna minor to remediate combinations of Cu(II), Pb(II) and Cr(III) from a simulated natural environment. The effect of these metal mixtures on the growth of L. minor was also investigated using growth rate and biomass inhibition calculations. L. minor was successful in removing Cr and Pb from the water, and it remained an effective remediation agent when both metals were present in the environment. However, a relatively low absorption capacity was observed for Cu, increasing concentrations of which were associated with significant decreases in growth rate. No statistically significant difference was found between the 24 h and 7 days absorption rates of Cu, Pb and Cr, suggesting that, at the concentrations tested, equilibrium occurs within 24 h of metal exposure.

Two‐step Synthesis of MoS2 Nanotubes using Shock Waves with Lead as Growth Promoter

AbstractA new two‐step procedure for the synthesis of MoS2 nanotubes using lead as a growth promoter is reported. In the first step, molybdenum suboxide nanowhiskers containing a small amount of lead atoms were created by exposing a pressed MoS2+Pb mixture to highly compressed shock‐heated argon gas, with estimated temperatures exceeding 9900 K. In the second step, these molybdenum suboxide nanowhiskers served as templates for the sulfidization of the oxide into MoS2 nanotubes (by using H2S gas in a reducing atmosphere at 820 °C). Unlike the case of WS2 nanotubes, the synthesis of a pure phase of MoS2 nanotubes from molybdenum oxide has proven challenging, due mostly to the volatile nature of the latter at the high requisite reaction temperatures (>800 °C). In contrast, the nature and apparent reaction mechanism of the method reported herein are amenable to future scale‐up. The high‐temperature shockwave system should also facilitate the synthesis of new nanostructures from other layered materials.

Ni Accumulation and Regulation After Experimental Exposure to a Cd, Pb, and Zn Mixture in the Pacific White Shrimp Penaeus vannamei

Accumulation of metals in aquatic organisms is influenced by several factors, including the presence of other metals; therefore, there is a need to study the effects of mixtures of other metals on the accumulation of a particular metal on the organisms. In this study, the capacity for nickel (Ni) regulation by the juvenile decapod crustacean Penaeus vannamei was analyzed. The effects of both solely Ni exposure and in the presence of other metals such as zinc (Zn), lead (Pb), and cadmium (Cd) in a mixture were analyzed to determine any possible synergism. A previous study revealed that a metal mixture of Zn, Cd, and Pb without Ni induces a higher metal uptake in P. vannamei for all three metals, but in this study, no effect was observed for Ni. The results showed no change in the regulatory capacitance for Ni, even in the presence of other metals. The observed capacity of P. vannamei to regulate body concentrations of nickel prevents its use as a suitable biomonitor for this metal.

Application of O-phenylacetyl β-CD as a carrier for selective transport of lead(II) across polymer inclusion membranes

The o-phenylacetyl β-CD derivative 1 was obtained by substitution of β-CD and characterized by spectroscopic methods. Competitive transport of equimolar mixtures of Pb(II), Cd(II), Cu(II), and Na(I) ions from aqueous nitrate feed phase across polymer inclusion membranes (PIMs) using O-phenylacetyl β-CD 1 derivative as an ion carrier has been investigated. The influence of the phenylacetyl groups attached to β-CD rings on the selectivity and efficiency of metal ions transport across PIMs containing cellulose triacetate (CTA) as the support was studied. The efficiency of a membrane for the selective transport of Pb(II) ions has been investigated, and several parameters affecting metal transport have been evaluated, such as the carrier concentration, the plasticizer content, and the acidity of the aqueous phase. We found that facilitated transport of metal ions across the above PIMs proceeds via a carrier-mediated mechanism and is dependent on pH-driving force. PIMs including 1 selectively transported Pb(II) ions at concentration of ion carrier in membrane equal to 0.6M and have shown the preferential selectivity order: Pb(II) ##xgt;##xgt; Cd(II) ##xgt; Cu(II) ##xgt; Na(I). The repeated transport experiments of PIM indicated the long-term integrity of PIM.

ChemInform Abstract: New Fluoride Carbonates: Centrosymmetric KPb2(CO3)2F and Noncentrosymmetric K2.70Pb5.15(CO3)5F3.

AbstractK2.70Pb5.15(CO3)5F3 (I) and KPb2(CO3)2F (II) are solvothermally synthesized from mixtures of Pb(OAc)2, KF, MeOH, and trifluoroacetic acid (autoclave, 180 °C, 24 h, 70% yield for (I)) and by solid state reaction of KF, PbCO3 and PbF2 (alumina boat, flowing CO2, 250—270 °C, 2—3 d).

Synthesis and photophysics of leadsulphide nanocrystallites

Nanoparticles of lead sulphide have been stabilized in the presence of excess Pb2+ in aqueous basic medium by a simple chemical route of synthesis. These PbS nanoparticles were synthesized very conveniently at room temperature using hexametaphosphate as stabilizer. These nanoparticles have an absorption extending into the NIR region. A significant quantum confinement effect made the bandgap of lead sulphide nanoparticles produce a blue shift from 0.41 eV to about 1.5 eV. The size and morphology of the particles were studied by TEM. Particles were relatively small sized (about 6 nm) having narrow size distribution. XRD data analysis indicate that the product is a mixture of PbS, PbO and Pb(OH)2. Both XRD pattern and HRTEM images confirm the crystalline structure of lead sulphide crystals. IR spectroscopy indicates the formation of PbS. PbS nanoparticles were fairly stable and could be stored for about three weeks at room temperature and for about two months at 5°C without agglomeration. These particles were photoactive and sensitized the reaction of aniline by light leading to the formation of azobenzene.

Developmental Exposure to As, Cd, and Pb Mixture Diminishes Skeletal Growth and Causes Osteopenia at Maturity via Osteoblast and Chondrocyte Malfunctioning in Female Rats

We studied the effect of metal mixture (MM), comprising As, Cd, and Pb, in developing female rat skeleton from gestation day 5 until postnatal day 60 (P-60). MM resulted in synergistic inhibition in viability and differentiation of osteoblasts in vitro, likely induced by reactive oxygen species. MM, administered at their most frequently occurring concentrations present in the groundwater of India, i.e., As: 0.38 ppm, Pb: 0.22 ppm, and Cd: 0.098 ppm or 10× of the ratio to developing rats, exhibited a synergistic decrease in ex vivo mineralization of bone marrow stromal (osteoprogenitor) cells. MM group showed a dose-dependent attenuation in weight and axial lengths and shortening of tibias at P-60. Furthermore, the growth plate was shortened, which was associated with shorter proliferative and hypertrophic zones, decreased parathyroid hormone-related protein and Indian hedgehog expression in the chondrocytes, reduced primary and secondary spongiosa, and hypomineralized osteoids-a major characteristic of osteomalacia. In addition, compared with the control, MM-treated rats were clearly osteopenic based on bone mineral density, microarchitecture, biomechanical strength, and particularly the biochemical profile, that suggested high turnover bone loss. Finally, in comparison to the control, the fracture-healing ability of MM group was delayed and accompanied by inferior quality of the healed bone. Together, these data demonstrated that the mixture of As, Cd, and Pb induced synergistic toxicity to developing skeleton, thereby diminishing modeling-directed bone accrual, inducing osteopenia and dampening fracture healing.

Metal extractability patterns to evaluate (potentially) mobile fractions in periurban calcareous agricultural soils in the Mediterranean area—analytical and mineralogical approaches

A set of periurban calcareous agricultural Mediterranean soils was spiked with a mixture of Cd, Cu, Pb and Zn at two levels within the limit values proposed by current European legislation, incubated for up to 12months, and subjected to various one-step extraction procedures to estimate mobile (neutral salts) and potentially mobile metal fractions (complexing and acidic extraction methods). The results obtained were used to study metal extractability patterns according to the soil characteristics. The analytical data were coupled with mineralogical investigations and speciation modelling using the Visual Minteq model. The formation of soluble metal-complexes in the complexing extracts (predicted by the Visual Minteq calculations) led to the highest extraction efficiency with complexing extractants. Metal extractability patterns were related to both content and composition of carbonate, organic matter, Fe oxide and clay fractions. Potentially mobile metal fractions were mainly affected by the finest soil fractions (recalcitrant organic matter, active lime and clay minerals). In the case of Pb, scarce correlations between extractable Pb and soil constituents were obtained which was attributed to high Pb retention due to the formation of 4PbCO3·3PbO (corroborated by X-ray diffraction). In summary, the high metal proportion extracted with complexing agents highlighted the high but finite capacity to store potentially mobilizable metals and the possible vulnerability of these soils against environmental impact from metal accumulation.

Lead citrate precursor route to synthesize nanostructural lead oxide from spent lead acid battery paste

Nanostructural lead oxides were prepared by the decomposition of a new type of lead citrate precursor (Pb3(C6H5O7)2·3H2O), which was synthesized through leaching of spent lead acid battery paste in citrate salt aqueous system and more economical compared with former precursor (Pb(C6H6O7)·H2O). The products were characterized by thermogravimetric–differential thermal analysis, scanning electron microscopy and X-ray diffraction. The results show that when lead citrate of columnar-shape crystals are calcined in N2 gas, orthorhombic β-PbO is the main product containing small amount of Pb and C. On combusting the citrate in air, a mixture of orthorhombic β-PbO, tetragonal α-PbO and Pb with the particle size of 100–200nm is obtained, with β-PbO as the major product. And the cyclic voltammetry measurements of lead oxides present different electrochemical redox potentials because of the different structure of lead oxide obtained from Pb3(C6H5O7)2·3H2O.

Microwave Actuated Ion Exchange Resins: Morphology and Effect of Polar and Non-Polar Groups on Metal Ion Uptake

Chelating resins, M-SFO, C-SFO, M-SFPh and C-SFPh, were synthesized by condensation polymerization of salicylic acid, formaldehyde and orcinol/phloroglucinol in 1:3:1 molar ratio in DMF media by conventional as well as the microwave method. The physico-chemical properties of the synthesized resins were determined. The chelating resins were characterized by FTIR and elemental analysis. The morphologies of the resins were examined by SEM and XRD analysis. Thermal stabilities of the synthesized resins were estimated by TGA. The metal ion uptake capacities of the synthesized resins were determined for Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II) with respect to pH of the media, metal ion concentration and contact time. The multiple functional groups present in chelating resins and difference in the method of synthesis demonstrate a significant influence on the extent of metal uptake. The clean separation of metal ions from Cu(II)-Pb(II) mixture on M-SFPh resin was achieved at optimized Kd values of metal ions.

Study on Tolerance and Accumulation Potential of Biofuel Crops for Phytoremediation of Heavy Metals

Phytoremediation is a cost-effective and environment-friendly technology that uses plants for environmental remediation. In order to promote practical application of phytoremediation, an income generation phytoremediation strategy was suggested using biofuel crops for utilization and phytoremediation of contaminated soils. In this study, the tolerance and accumulation potential to heavy metals of two biofuel plants and two accumulator plants were investigated in order to evaluate their suitability for phytoremediation. Two biofuel crops, maize (Zea mays L.) and sunflower (Helianthus annuus L.), and two accumulator plants, Elsholtzia splendens (ES) and Kummerowia striata (KS) were exposed to the hydroponic mixtures of Pb, Cu and Cd. Results showed that, at the 0.01 mol/L application level of Pb, Cu and Cd, sunflower had the highest accumulation ability for Pb, Cu and Cd in the shoot part compared to other three plants, and maize had a similar accumulation level to ES and KS. Sunflower also had much higher shoot/root ratios of accumulation for Cu and Cd than maize. However, sunflower showed lower tolerance to Pb, Cu and Cd contamination than maize, ES and KS. This study provided useful data supporting the use of biofuel plants in phytoremediation.

Modelling of breakthrough curves of single and binary mixtures of Cu(II), Cd(II), Ni(II) and Pb(II) sorption onto grape stalks waste

Few studies deal on metal sorption from multi-metal solutions, though in real situations more than one metal ion are present in solution and interactions between them occur. Interaction takes place when the different metal ions compete for the same sorbent active sites. In this work, sorption of Cu(II), Cd(II), Ni(II) and Pb(II) onto grape stalks waste in single and binary mixtures has been investigated. Sorption studies were carried out in continuous mode by using packed columns with grape stalks waste. The obtained metal ions breakthrough curves in binary mixtures showed that lead is not overshoot in binary mixtures with copper, cadmium and nickel. Copper is only overshoot in binary mixtures with lead. Nickel and cadmium suffer >60% overshoot metal sorption loose in binary mixtures with copper and lead. A model based on the Homogeneous Surface Diffusion Model (HSDM) has been developed to describe breakthrough curves. Langmuir model and Extended Langmuir Model (MEL) have been incorporated into the kinetic HSDM for breakthrough curves prediction of single and binary systems, respectively. The proposed model fits successfully the breakthrough curves of metal sorption from single and binary mixtures. In binary mixtures, the model also satisfactorily fits the elution profile of the overshoot metal ion.

Accumulation and Regulation Effects from the Metal Mixture of Zn, Pb, and Cd in the Tropical Shrimp Penaeus vannamei

Environmental metal pollution is one of the major problems faced by humankind. This type of pollution affects aquatic systems (estuaries, coastal lagoons, etc.), which are very dynamic systems, therefore making the study of the effects on the organisms that inhabit them an essential issue. In this study, the capacity of metal regulation by decapod crustacean Penaeus vannamei juveniles was determined. The effects of zinc, lead, and cadmium were tested individually and as a metal mixture exposure to determine possible synergism. The results showed that juvenile shrimps were capable of regulating zinc and lead, whereas cadmium was accumulated without any excretion, at least within the concentrations studied. It was also proved that under the estuarine conditions tested here, P. vannamei juveniles showed capacity to act as a bioindicator for cadmium.

Down-regulated GFAPα: a major player in heavy metal induced astrocyte damage

Exposure to a mixture of As, Pb and Cd induces apoptosis and morphological alterations in the cortical astrocytes of rat brain. The levels of the glial fibrillary acidic protein (GFAP) undergo a reduction. The GFAP exists in several isoforms, viz., α, β, κ, δ and ϵ. However, contribution of the isoforms towards astrocyte damage is not understood. We investigated the effect of the metal mixture (MM) on the expression profiles of mRNAs encoding the GFAP isoforms in astrocytes. The MM was administered in drinking water to developing rats till postnatal day (PD) 60. We observed a fall (10.20 ± 1.04%, 18.91 ± 2.12% and 30.26 ± 3.21% at PD24, PD45 and PD60 respectively) in GFAPα. This may have been compensated by a rise in β, κ, and ϵ. The GFAPδ remained unchanged. To determine the role of the GFAPα, we silenced its gene using SiRNA technology in the rat primary astrocytes. We observed a 23.73 ± 1.56% increase in the number of apoptotic cells. The cleaved PARP and Bax levels increased by 2.48 ± 0.14-fold and 3.73 ± 0.23-fold respectively, and the Bcl-2 and Bcl-xl decreased by 2.38 ± 0.08-fold and 1.76 ± 0.09-fold respectively. The change was comparable to the cells treated with MM. Moreover, silencing the GFAPα gene induced a reduction in the area (6.19 ± 0.18-folds), perimeter (12.65 ± 1.68-folds) and the number of processes (5.88 ± 1.5-folds) in the astrocytes, which closely matched the MM-treated ones. Taken together, these observations are the first to show that MM disturbs the composition of the GFAP isoforms, and a suppressed GFAPα promotes apoptosis in the matured rat astrocytes.

Associations between standardized school performance tests and mixtures of Pb, Zn, Cd, Ni, Mn, Cu, Cr, Co, and V in community soils of New Orleans

In New Orleans a strong inverse association was previously identified between community soil lead and 4th grade school performance. This study extends the association to zinc, cadmium, nickel, manganese, copper, chromium, cobalt, and vanadium in community soil and their comparative effects on 4th grade school performance. Adjusting for poverty, food security, racial composition, and teacher-student ratios, regression results show that soil metals variously reduce and compress student scores. Soil metals account for 22%–24% while food insecurity accounts for 29%–37% of variation in school performance. The impact on grade point averages were Ni > Co > Mn > Cu ∼Cr ∼ Cd > Zn > Pb, but metals are mixtures in soils. The quantities of soil metal mixtures vary widely across the city with the largest totals in the inner city and smallest totals in the outer city. School grade point averages are lowest where the soil metal mixtures and food insecurity are highest.