Nickel is a toxic heavy metal among trace elements which has a detrimental impact on living organisms. There is growing need of finding an economic and effective solution for Ni(Ⅱ) immobilization in environments. Chi...Nickel is a toxic heavy metal among trace elements which has a detrimental impact on living organisms. There is growing need of finding an economic and effective solution for Ni(Ⅱ) immobilization in environments. Chinese loess was selected as adsorbent to remove Ni(Ⅱ) from aqueous solution. Adsorbent dosage, reaction time, solute concentration, temperature, and solution p H also have influences on efficiency of Ni(Ⅱ) removal. The monolayer adsorption capacity of loess towards Ni(Ⅱ) is determined to be about 15.61 mg/g. High temperature and p H favor the removal of Ni(Ⅱ) using Chinese loess soil and the optimal dosage of loess is determined to be 10 g/L. The kinetics and adsorption isotherms of the adsorption process can be best-fitted with the pseudo second order kinetics and Langmuir isothermal model, respectively. The thermodynamic analysis reveals that the adsorption process is spontaneous, endothermic and the system disorder increases with duration. Nickel ions can be removed with the removal efficiency of 98.5% at p H greater than or equal to 9.7. Further studies on loess and Ni(Ⅱ) laden loess(using X-Ray diffraction, Fourier transform infrared spectroscopy) and Ni(Ⅱ) species distribution at various p H have been conducted to discuss the adsorption mechanism. Loess soils in China have proven to be a potential adsorbent for Ni(Ⅱ) removal from aqueous solutions.展开更多
The frequency effects on the velocities and attenuations of the bulk waves in a saturated porous medium are numerically studied in the cases of considering and neglecting the compressibility of solid grain, respective...The frequency effects on the velocities and attenuations of the bulk waves in a saturated porous medium are numerically studied in the cases of considering and neglecting the compressibility of solid grain, respectively. The results show that the whole frequency can be divided into three parts, i.e., low frequency band, medium frequency band, and high frequency band, according to the variation curves and the characteristic frequency. The compressibility of the solid grain affects the P1 wave distinctively, the S wave tiny, and the P2 wave little. The effects of the porosity and Poisson＇s ratio on the bulk waves are numerically analyzed. It is found that both the porosity and Poisson＇s ratio have obvious effects on the bulk waves. Compared with the results in the case of neglecting the porosity-moduli relation, the results in the case of considering the porosity-moduli relation are more reasonable. The results in the case of considering the porosity-moduli relation can be degenerated into the results of elastic solid and pure fluid, while the results in the case of neglecting the porosity-moduli relation cannot be degenerated into the results of elastic solid and pure fluid. Therefore, the porosity-moduli relation must be considered in the parametric study for a certain porous medium.展开更多
基金Projects(5117916851308310)supported by the National Natural Science Foundation of ChinaProject(LQ13E080007)supported by Zhejiang Provincial Natural Science Foundation of China
文摘Nickel is a toxic heavy metal among trace elements which has a detrimental impact on living organisms. There is growing need of finding an economic and effective solution for Ni(Ⅱ) immobilization in environments. Chinese loess was selected as adsorbent to remove Ni(Ⅱ) from aqueous solution. Adsorbent dosage, reaction time, solute concentration, temperature, and solution p H also have influences on efficiency of Ni(Ⅱ) removal. The monolayer adsorption capacity of loess towards Ni(Ⅱ) is determined to be about 15.61 mg/g. High temperature and p H favor the removal of Ni(Ⅱ) using Chinese loess soil and the optimal dosage of loess is determined to be 10 g/L. The kinetics and adsorption isotherms of the adsorption process can be best-fitted with the pseudo second order kinetics and Langmuir isothermal model, respectively. The thermodynamic analysis reveals that the adsorption process is spontaneous, endothermic and the system disorder increases with duration. Nickel ions can be removed with the removal efficiency of 98.5% at p H greater than or equal to 9.7. Further studies on loess and Ni(Ⅱ) laden loess(using X-Ray diffraction, Fourier transform infrared spectroscopy) and Ni(Ⅱ) species distribution at various p H have been conducted to discuss the adsorption mechanism. Loess soils in China have proven to be a potential adsorbent for Ni(Ⅱ) removal from aqueous solutions.
基金Project supported by the National Natural Science Foundation of China(Nos.U1234204 and 51378463)
文摘The frequency effects on the velocities and attenuations of the bulk waves in a saturated porous medium are numerically studied in the cases of considering and neglecting the compressibility of solid grain, respectively. The results show that the whole frequency can be divided into three parts, i.e., low frequency band, medium frequency band, and high frequency band, according to the variation curves and the characteristic frequency. The compressibility of the solid grain affects the P1 wave distinctively, the S wave tiny, and the P2 wave little. The effects of the porosity and Poisson＇s ratio on the bulk waves are numerically analyzed. It is found that both the porosity and Poisson＇s ratio have obvious effects on the bulk waves. Compared with the results in the case of neglecting the porosity-moduli relation, the results in the case of considering the porosity-moduli relation are more reasonable. The results in the case of considering the porosity-moduli relation can be degenerated into the results of elastic solid and pure fluid, while the results in the case of neglecting the porosity-moduli relation cannot be degenerated into the results of elastic solid and pure fluid. Therefore, the porosity-moduli relation must be considered in the parametric study for a certain porous medium.
