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EN
The present work measures the adsorption capacity of sugarcane bagasse to remove excess lead from groundwater. Batch adsorption experiments were carried out to evaluate the adsorption equilibrium, and the effects of four parameters (pH, adsorbent dosage, equilibrium time and particle size) on the adsorption of lead were investigated. Characterization of the adsorbent was carried out through SEM and FTIR instruments. Results confirm that the adsorption of lead takes place successfully on the surface of the adsorbent. The maximum efficiency of adsorption is up to 50% achieved in 5g adsorbent dosage, at an optimum pH 5, with a contact time of 120 minutes and 53 μm adsorbent size at 38.
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100%
EN
Lead exposure is a common public health problem. Exposure to the metal can cause hematological, gastrointestinal, rheumatological, endocrine, neurological and renal problems in humans. However, effects on the thyroid gland are controversial. We retrospectively investigated thyroid function parameters in 65 adult males who had been occupationally exposed to lead. We then compared the findings with those of 60 male patients who had no history of lead exposure or thyroid abnormalities, who served as the control group. The mean ages of the lead-exposed workers and the controls were 34.3 ± 7.9 and 32.9 ± 6.6 years respectively. Blood lead levels in the lead-exposed workers were significantly higher than in the control group. The lead-exposed workers were assigned to one of three groups according to their blood lead levels, as follows: 40–59 μg/dl, 60–79 μg/dl, or 80 μg/dl and above. Thyroid Stimulating Hormone (TSH) levels in the 80 μg/dl and above group were significantly higher than in either the 40–59 μg/dl group or the 60–79 μg/dl group. However, TSH levels in the 40–59 μg/dl group did not differ significantly from those in the 60–79 μg/dl group. These results suggest that high levels of lead in the blood may affect thyroid physiology. Clinicians should be aware of the potential hazardous effects of lead on the thyroid, especially in patients who have been occupationally exposed to lead.
3
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Cadmium and lead recovery from yeast biomass

88%
Open Chemistry
|
2011
|
vol. 9
|
issue 2
320-325
EN
The feasibility of the application of various eluents for recovery of lead and cadmium from Saccharomyces biomass has been investigated. Desorbing agents such as HCl, HNO3, H2SO4, Na2SO4, Na2CO3, EDTA and NaOH at concentrations of 0.05–0.5 M were used. The possibility of re-using of S. pastorianus for cadmium removal was assessed. Among the desorbing agents EDTA and mineral acids were the most effective, as approximately 85% of lead and cadmium could be recovered. However, when HNO3 and EDTA were used as desorbing agents, a dramatic loss in the cadmium adsorption by the biomass in the next cycles was observed.
EN
Lead (+2) was selectively adsorbed on a solid phase extraction (SPE) gel (molecular recognition technology, MRT), quantitatively extracted, and spectrophotometrically determined as the Pb(II)-PAR (4-(2-pyridylazo)-resorcinol) complex. The linear range was 0.01 to 0.75 mg L−1 and the detection limit was 6.4 µg L−1. The MRT-SPE allows selective Pb(II) extraction from complex ion-rich matrices, which is difficult with other techniques. Interference from common matrix ions such as Fe2+, Ni2+, Cu2+ or Co2+ is minimized. [...]
EN
Background: To evaluate whether salivary lead can be used as a surrogate for blood lead, and if so, over what concentration range. Methodology: Three saliva devices were evaluated and one chosen to undertake this project. Paired saliva and blood samples were collected from 89 UK lead workers. Lead concentrations were determined using ICP-MS. In addition, haemoglobin and ZPP levels were determined in the blood samples and albumin was determined in the saliva samples to investigate standardisation using protein adjustments. Results: The chosen saliva device gave low but consistent recoveries for lead in saliva and the blank levels were low. The mean +/- SD blood lead level was 19.9 +/- 14 μg/dl; the mean +/- SD saliva lead level was 19.1 +/- 32.5 μg/l for 89 workers. Log10-transformed data showed correlation of r=0.69. The protein adjustments did not improve the blood-saliva correlation. Conclusions: This study has demonstrated that salivary lead measurement is feasible and correlated with blood lead levels, at least at occupational exposure levels, and may have value as a screening technique. Correlation may improve at environmental levels where exposures are generally more consistent and chronic, although this needs to be demonstrated in a genuine environmental population.
EN
A plant waste, rubber (Hevea brasiliensis) leaf powder was modified with carbon disulfide (xanthation) for the purpose of introducing sulfur groups, and the adsorbent performance in removing Pb(II) ion was evaluated. Pb(II) adsorption was confirmed by spectroscopic analysis, which involved Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The amount of Pb(II) adsorbed increased with increasing pH, contact time and concentration but slightly decreased with increasing ionic strength. Adsorption equilibrium was achieved in less than 60 min and followed the pseudo-second order model. The isotherm data indicated that Pb(II) adsorption on xanthated rubber leaf (XRL) fitted well with Langmuir isotherm model. The maximum adsorption capacity computed from the Langmuir isotherm model was 166.7 mg/g. Pb(II) adsorption occurred via ion-exchange and complexation mechanisms.
EN
This paper describes the potential application of a freely suspended cyanobacterial biomass of Microcystis aeruginosa as a sorption material for toxic metals, cadmium (Cd) and lead (Pb) from aqueous solutions. In order to identify the most suitable conditions for removal of these elements (concentration range: 1–20 mg L−1), the laboratory experiments were carried out during different incubation times (1–48 h) and under various temperatures (10–40°C), pH (5–9) and with or without light irradiance. Competitive biosorption of Cd and Pb was also investigated. We found that M. aeruginosa demonstrates high efficiency in removing both of the studied metals from aqueous solutions. Sorption of Pb occurred, however, more rapidly and effectively, and was less disturbed by changes in physico-chemical conditions. Under pH=7, 25°C and light, the removal rates after 3 h and 6 h of incubation, were 90–100% for Pb and 79.5–100% for Cd, respectively. The co-occurrence of the metals decreased the rate of metal biosorption. Pb was sequestered preferentially over Cd. From the results we conclude that freely suspended M. aeruginosa can constitute a promising low-cost, easy-producible biosorbent material for toxic metals in contaminated wastewater.
EN
Two series of activated carbon have been prepared by chemical activation of Amygdalus Scoparia shell with phosphoric acid or zinc chloride for the removal of Pb(II) ions from aqueous solutions. Several methods were employed to characterize the active carbon produced. The surface area was calculated using the standard Brunauer-Emmet-Teller method. The microstructures of the resultant activated carbon were observed by scanning electron microscopy. The chemical composition of the surface resultant activated carbon was determined by Fourier transform infrared spectroscopy. In the batch tests, the effect of pH, initial concentration, and contact time on the adsorption were studied. The data were fitted with Langmuir and Freundlich equations to describe the equilibrium isotherms. The maximum adsorption capacity of Pb(II) on the resultant activated carbon was 36.63 mg g−1 with H3PO4 and 28.74 mg g−1 with ZnCl2. To regenerate the spent adsorbents, desorption experiments were performed using 0.25 mol L−1 HCl. Here we propose that the activated carbon produced from Amygdalus Scoparia shell is an alternative low-cost adsorbent for Pb(II) adsorption.
EN
Determination of cadmium, lead, chromium and nickel in soil samples by slurry sampling graphite furnace atomic absorption spectrometry (GFAAS) was presented. Optimization of determination conditions, stability test for slurries and metal partitioning between solid and liquid phase was investigated. The method was successfully tested by the analysis of certified reference materials.
11
Content available remote

Surface diffusion of Pb on clean Si surfaces

63%
EN
Pb diffusion on clean Si(111), (100), and (110) surfaces was studied by Auger electron spectroscopy and low energy electron diffraction in the temperature range from 100 to 300°C. It is shown that lead transport along sillicon surfaces takes place via the mechanism of solid-phase spreading with a sharp moving boundary. The temperature dependence of the Pb diffusion coefficients on Si(111), (100) and (110) surfaces have been obtained. A Si(110)-4×2-Pb surface structure has been observed for the first time.
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