Effects Of Lead Concentration Research Articles

Влияние концентрации свинца в шерсти на межэлементное взаимодействие и молочную продуктивность голштинских коров

Влияние концентрации свинца в шерсти на межэлементное взаимодействие и молочную продуктивность голштинских коров

Effect of lead concentration and electromigration on the kinetics of contact melting and phase formation in a Sn–(Bi + Pb) system

It is found that the kinetics of contact melting and the formation of contact layer structures depend on both the concentration of lead in the alloy and the direction of electric current during the process of contact melting. It is shown that direct current flowing through the zone of contact melting helps intensify this process and regulate the morphology of inclusions (their shapes, sizes, and direction of migration). The inversion of effective charge z Bi*, compared to two-component systems with Bi participation, is observed.

On the effect of lead concentration on the kinetics of contact melting in the Sn–Pb–Bi system in the presence of electromigration

It is determined by electron microscopy that the contact layer in the Sn–(Bi + 30 wt % Pb) system contains separate solid inclusions, while the contact layer in the Sn–(Bi + 40 wt % Pb) system is microheterogeneous. The observed structural states of alloys in the contact layers are explained by a change in the concentration of the initial contacting samples. The effect of the alloy structure and electromigration on the kinetics of contact melting is found.

Effects of lead concentration and accumulation on the performance and microbial community of aerobic granular sludge in sequencing batch reactors

ABSTRACTThe present study investigated the effects of lead on the morphological structure, physical and chemical properties, wastewater treatment performance and microbial community structure of aerobic granular sludge (AGS) in sequencing batch reactors (SBRs). The results showed that at Pb2+ concentration of 1 mg/L, the mixed liquid suspended solids decreased, the settling velocity increased and the sludge volume index increased sharply. Meanwhile, AGS began to disintegrate and show an irregular shape. In terms of wastewater treatment in an SBR, the phosphorus removal rate was affected only until the Pb2+ concentration was up to 1 mg/L. The removal efficiency began to decline when the Pb2+ concentration increased to 6 mg/L, while the removal of chemical oxygen demand increased slightly within the Pb2+ concentration range of 1–6 mg/L. Significant changes were observed in the microbial community structure, especially the dominant bacteria. Compared to the Pb2+ accumulation on the sludge, the Pb2+ concentration in the aqueous phase played a more important role in the performance and microbial community of AGS in SBRs.

Adsorption of Lead on Gel Combustion Derived Nano ZnO

Many naturally available materials were used as adsorbents to remove heavy metal ions from water, which are not effective because of low surface area. Novel nano materials are used as adsorbents to remove metal ions to treat potable water. In the present work nano sized large surface area Zinc Oxide (ZnO) was synthesized by gel combustion method and used as an adsorbent to remove lead (II) (Pb2+) from aqueous solution. The nano ZnO was characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy Dispersive X-Ray analysis (EDAX) and surface area analysis. Effect of lead concentration, adsorbent dosage and pH on adsorption was studied. Increase in the initial concentration of Pb, decreases the percentage of adsorption, whereas increase in the adsorbent dosage and pH of the solution, increases the adsorption of Pb2+ on ZnO. Synthesized nano ZnO shows almost complete Pb adsorption at lower initial concentration. The equilibrium adsorption capacity of Pb on nano ZnO adsorbent were measured and extrapolated using Langmuir and Freundlich adsorption isotherm models and the experimental data perfectly fits both adsorption isotherms.

Immobilization of [Bmim+Tf2N−] hydrophobic ionic liquid on nano-silica-amine sorbent for implementation in solid phase extraction and removal of lead

A method is described for highly efficient adsorptive removal of lead with a maximum metal capacity value of 1.300mmolg−1 by using physically immobilized [Bmim+Tf2N−] on the surface of nano-silica-amine sorbent. Lead sorption was found to be highly dependent and controlled by several experimental factors. The effect of sorbent dose played a significant role by yielding the maximum lead adsorption capacity when 100mg sorbent was used. The effect of lead concentration was examined by various adsorption isotherms. The potential applications for removal of Pb(II) were studied and the percentage recovery values were 99.0–100.0±2.0–5.0%.

Kinetic Modeling of the Biosorption of Lead(II) from Aqueous Solutions by Solid Waste Resulting from the Olive Oil Production

Solid waste from olive oil production, the two-phase olive mill solid (OMS), was investigated for the removal of Pb(II) from aqueous solutions. This work focuses mainly on the kinetics of biosorption. The sorption kinetics was experimentally measured using stirred-batch systems under different initial concentrations and at varying solution temperatures. The pseudo-nth order kinetic model, pseudofirst-order kinetic model, pseudosecond-order kinetic model, and the Elovich equation were used to represent the kinetic data. The pseudosecond-order equation fitted the dynamic data very well under all the operating conditions. A contact time of approximately 60 min was required to reach the equilibrium. The results obtained for the effect of initial concentration on lead uptake by OMS showed that the equilibrium sorption capacity and the initial sorption rate increase as the initial metal concentration increases, while the kinetic constant of the process decreases. The effect of temperature on kinetic parameter values is less significant than the effect of lead concentration although a decrease on kinetic constant and initial sorption rate is produced as temperature rises, mainly at lower lead concentrations. Finally, the apparent activation energy of sorption was determined as −18.62 kJ·mol–1 for an initial lead concentration of 10 mg·L–1. The negative value of activation energy showed that the Pb(II) adsorption process by OMS may involve a nonactivated chemical adsorption or a physical adsorption.

Effects of Blood Lead Concentration on Intelligence and Personality in School Children

This study was conducted to evaluate the effects of lead concentration in the blood on intelligence and personality in school children in Korea. This study was designed as a cross sectional study. The Korean Intelligence Test-Primary was administered to the 302 school age children (154 3rd-grade and 155 6th-grade) of three areas, urban, fishery, and agricultural area, Korea. Blood lead (Pb-B) was measured by means of atomic absorption spectroscopy equipped with graphite furnace atomizer. Geometric means of Pb-B for boys and girls were 2.79±1.58 μg/dL and 2.54±1.51 μg/dL, respectively. No children exceeded Pb-B of 10 μg/dL that is the recommended level of Pb-B in children by CDC, U.S.A. When the subjects were classified by median into two groups, upper and lower Pb-B groups, the IQ of upper and lower groups were 106.4±13.7 and 110.0±14.9 respectively. IQ score of upper group was lowered about 4 points than that of lower group. We founded that hyperactivity and autism score of Pb-B groups was higher than that of lower group. These results are coincident with the large-scale study results developed countries that chronic exposure to lead may reduce the intelligence of child. This study may provide the first suggestive evidence that Pb-B has an impact on childhood intelligence and personality in Korean children. It is necessary to consider the effects of other important factors, such as parental intelligence in the next study.

Evaluation of Cement Hydration Properties of Cement-Stabilized Lead-Contaminated Soils Using Electrical Resistivity Measurement

In this study, electrical resistivity was related to the fundamental geotechnical properties of cement solidified/stabilized heavy metal–contaminated soils. Lead-contaminated soils were artificially prepared with various concentrations and treated by portland cement Type I at three content levels. The compacted cylindrical specimen was prepared with a diameter of 50 mm and height of 100 mm. The apparent electrical resistivity, electrical conductivity of pore fluid, unconfined compressive strength, and water contents were measured at different curing times. The result shows that the apparent electrical resistivity increases with the increase of curing time and the decrease of porosity and saturation degree as a result of cement hydration development. The effects of lead concentration, cement content, and curing time on the apparent electrical resistivity were discussed. The cementation index m was used to evaluate the cementation degree of cement-treated lead-contaminated soils. Lead pollutant at high concentrations could suppress or retard the hydration of solidified/stabilized soils. Electrical resistivity measurements can be used as a nondestructive method to evaluate the hydration development of solidified/stabilized lead-contaminated soils.

Effects of lead concentration on dielectric properties of ferroelectric Ni/PZT/Pt thin films at low and infralow frequencies

Results of the studies of dielectric properties of PZT thin films of different excess lead concentrations are reported. Samples of excess lead concentration x = 0, 30, and 50 mol % are examined. The observed relaxation of polarization at infralow frequencies is interpreted on the basis of Cole-Cole relaxation. Polarization loops of samples with x = 0 and 50 mol % are compared and the reasons of their asymmetric view and displacement in the direction of negative field are discussed.

Effect of lead concentration on the level of glutathione, glutathione S-transferase, reductase and peroxidase in human blood

Incubation of human whole blood for 24 h at 37°C in the presence of 100–400 μg/dl lead chloride or lead acetate caused a concentration-dependent decrease in the level of reduced glutathione up to 40%. Similarly, the activities of glutathione reductase, glutathione peroxidase and glutathione S-transferase were decreased up to 25%, 50%, and 19%, respectively. Moreover, 100 μg/dl lead chloride or lead acetate slowed the process of glutathione regeneration, and delayed the time for complete regeneration from 20 to 40 min. When glutathione S-transferase was purified by affinity chromatography on Sepharose-linked glutathione, incubated with lead chloride or lead acetate, a concentration-dependent inhibition of the enzymatic activity was observed reaching 50% inhibition at a lead salt concentration of 6000 μg/dl.

Removal of Lead(II) by Mordenites

AbstractBatch studies were conducted to investigate the removal of Pb2+ using mordenite. Effects of lead concentration, solution pH, particle size and dosage of mordenite on the removal kinetics and the removal capacity of lead were investigated. It was found that the main removal mechanism was ion exchange, with Na, Ca, and K as major exchange cations. The exchange kinetics and the exchange capacity of lead with the cations in mordenite increased as the lead concentration increased. The solution pH affected the exchange rate but not the lead exchange capacity. The reaction rate at pH 5 was faster than that at pH 3. As the particle size of mordenite decreased, the reaction rate increased. The exchange rate of lead also increased as the mordenite dosage increased. A significant removal of lead by mordenite was observed. For a lead concentration of 3 ppm, 99% of the lead was removed, and for a high lead concentration (200ppm), 70% lead removal can still be achieved. It can be concluded that mordenite has a great potential to remove lead from wastewaters.

The effect of lead concentration on the corrosion susceptibility of [formula omitted] steel in a lead-lithium liquid

The intergranular penetration of 2 1 4 Cr-1Mo steel by lead-lithium liquids containing 0, 17.6, and 53 w/o lead has been investigated at temperatures from 300°C to 600°C for times up to 1000 hours. Limited tests using a 99.3 w/o lead-lithium liquid were also conducted. Tempering was found to remove the susceptibility of as-quenched 2 1 4 Cr-1Mo steel to penetration at 500°C by lead-lithium liquids containing up to 53 w/o lead. Penetration by the 99.3 w/o lead-lithium liquid in 1000 hours at 500°C was found to be negligible even when the steel was in the as-quenched condition. An Arrhenius analysis yielded the same low initial activation energy (~25 kJ/mole) for liquids containing 0, 17.6, and 53 w/o lead. The initial penetration rate for lead-free lithium was significantly greater than that for the lead-bearing liquids, a factor thought to be related to the effect of lead on the wettability of the liquid. The same secondary activation energy (~120 kJ/mole) was also found for the three liquids. Furthermore, the secondary penetration rate was found to be insensitive to lead content. Anamolous behavior at 500°C, observed in this study as well as in previous studies, is discussed, and a hypothetical explanation for the behavior is presented.