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61.
The chromium(VI) biosorption onto guava seeds, as an alternative method for Cr6+ removal from aqueous solutions, was investigated. The parameters affecting kinetics and equilibrium of Cr6+ adsorption onto guava seeds were studied. An external mass-transfer diffusion coefficient k and intra-particle diffusion coefficient ki were determined to measure the rate-limiting step of adsorption. A single external mass-transfer diffusion model and intra-particle diffusion models were used. The effects of initial pH, sorbent mass, and initial Cr6+ concentrations on mass-transfer coefficients were investigated. The external mass-transfer coefficient has an average value of 7.2×10-3 cm s-1, while the intra-particle mass-transfer diffusion coefficient was 0.34 mg g-1 min-0.5. This indicates that external diffusion to the guava seeds surface and intra-particle diffusion are both involved in the sorption process. The isotherm equilibrium data were well fitted by the Langmuir and Freundlich models with an average correlation coefficient R2=0.98. The maximum removal of Cr6+ was obtained at pH 1 (about 100% for adsorbent dose of 15 g l-1 and 25 mg l-1 initial concentration of Cr6+). The results indicated that the guava seeds exhibit acceptable sorption capacity. 相似文献
62.
Highly activated carbon from the seed husk of Casuarina Casuarinas equisetifolia, a worldwide famous plant, have been prepared and tested for the removal of toxic Cr(VI) from its aqueous solution. The adsorbent was investigated for influences of initial chromium concentration (75, 100, 125, and 150 mg l-1), pH, contact time, and quantity of carbon on removal of Cr(VI) from aqueous solution at room temperature (25±2 °C). The adsorption kinetic of Cr(VI) was studied, and the rates of sorption were found to conform to pseudo-second-order kinetics with a good correlation (R2≥0.99). The Langmuir and Freundlich models fit the isotherm data well. Furthermore, the Gibbs free energy was obtained for each system and was found to be-5.29 kJ mol-1 for removal of Cr(IV). The negative value of Δ G° indicates the feasibility and spontaneous nature of adsorption. The results indicate that acidic pH (1.05) supported the adsorption of Cr(IV) on activated carbon. The maximum adsorption capacity of Cr(VI) on activated carbon was about 172.4 mg g-1 at pH 1.05. 相似文献
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铬、砷离子吸附剂的制备及其吸附性能的研究 总被引:3,自引:0,他引:3
通过对沸石的改性,在沸石表面形成了一层纳米态的二氧化锰,而纳米态的二氧化锰及沸石都对水中重金属有强烈的吸附性能,从而达到对铬、砷离子的吸附作用。通过沸石与二氧化锰的配比、吸附溶液的pH值、吸附时间、改性沸石的用量对其去除效果的影响,探讨了吸附作用机理。通过吸附测定,改性沸石的最佳配比沸石:MnO2为2:1;改性沸石对As(III)的最佳吸附pH和时间为5.0和30 min;对Cr(VI)的最佳吸附pH和时间为7.0和30 min的条件下吸附效果最佳。 相似文献
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F. Galgani J. F. Chiffoleau P. LE Gall Y. Pichot B. Andral C. Martin 《Chemistry and Ecology》2013,29(2):133-141
We experimented with caging the Mediterranean mussel (Mytilus galloprovincialis) at various depths for 69 d to measure basic physiological parameters, histological response and bio-accumulation of contaminants in a deep-sea contaminated area. In preliminary experiments, we demonstrated, under artificial pressure conditions, the ability of mussels Mytilus galloprovincialis to tolerate rapid immersion (at a speed of up to 120 m min?1). In situ experiments were performed using submerged lines enabling mussels to be maintained at depths ranging of 40–1550 m with survival rates ranging from 80 to 38%, respectively. No significant differences in condition indexes were observed between treated and control specimens. However, histological observations demonstrated a clear reduction in thickness of the digestive epithelium with increasing depth exposure. By determining the contaminants in caged mussels, we found the following values for chromium accumulation: 27.4 μg g?1 dry weight at 580 m depth and 9.8 μg g?1 dry weight at 1550 m. Selected stations were located downstream of an industrial effluent at 420 m. The biological and environmental consequences of deep-sea contamination demonstrate the suitability of caged mussels for monitoring contaminant accumulation. 相似文献
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Brent Finley Paul K. Scott Meghan E. Glynn Dennis Paustenbach Kerry A. Thuett 《毒物与环境化学》2017,99(1):48-64
The objective of this study was to determine the valence state of chromium (Cr) in the blood of individuals with Cr-containing metal hip implants. Serum and red blood cell (RBC) Cr concentrations from 52 patients with Cr-containing total hip arthroplasties were measured preoperatively and at 3, 12, and 24 months postoperatively. Geometric mean and median pre-surgery serum Cr concentrations were consistently below 0.2 µg/L, while geometric mean and median pre-op RBC Cr concentrations were typically about four- to six-fold higher than the serum values. A significant 5- to 13-fold increase was found in the mean and median serum Cr concentrations three months post-surgery, with an 8- to 18-fold rise at 12 and 24 months, respectively. Steady-state serum concentrations were reached between 3 and 12 months. In contrast, there were no marked differences in mean and median RBC Cr concentrations pre- and post-surgery. Slope regression analysis for our data was similar to those reported for Cr(III) in spiked blood samples. The analysis showed that Cr released from hip implants preferentially distributed into serum and not RBC, indicating that the form of Cr present in blood of hip implant patients was in the form of non-toxic Cr(III). Our findings indicate that blood Cr concentrations Cr(III) associated with metal implants do not pose an adverse health risk to patients, which is in agreement with findings published by most investigators. 相似文献
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在研究RH大孔吸附树脂吸附和解吸性能的基础上,以RH树脂处理炼油厂的碱渣进行了试验。结果表明,RH树脂可用于碱渣脱酚,在一定条件下,树脂的吸酚量可达130mg/ml,吸附饱和后的树脂,解吸后可重复使用,碱渣中的硫不会树脂中毒而降低吸酚量。 相似文献