Chakir Achraf, Bessiere Jacques, Kacemi Kacem E L, Marouf Bouchaïb
Département de Chimie, Faculté des Sciences, Université Mohamed V, Avenue Ibn Batouta, Rabat, Morocco.
J Hazard Mater. 2002 Nov 11;95(1-2):29-46. doi: 10.1016/s0304-3894(01)00382-x.
Local bentonite and expanded perlite (Morocco) have been characterised and used for the removal of trivalent chromium from aqueous solutions. The kinetic study had showed that the uptake of Cr(III) by bentonite is very rapid compared to expanded perlite. To calculate the sorption capacities of the two sorbents, at different pH, the experimental data points have been fitted to the Freundlich and Langmuir models, respectively, for bentonite and expanded perlite. For both sorbents the sorption capacity increases with increasing the pH of the suspensions. The removal efficiency has been calculated for both sorbents resulting that bentonite (96% of Cr(III) was removed) is more effective in removing trivalent chromium from aqueous solution than expanded perlite (40% of Cr(III) was removed). In the absence of Cr(III) ions, both bentonite and expanded perlite samples yield negative zeta potential in the pH range of 2-11. The changes of expanded perlite charge, from negative to positive, observed after contact with trivalent chromium(III) solutions was related to Cr(III) sorption on the surface of the solid. Thus, it was concluded that surface complexation plays an important role in the sorption of Cr(III) species on expanded perlite. In the case of bentonite, cation-exchange is the predominate mechanism for sorption of trivalent chromium ions, wherefore no net changes of zeta potential was observed after Cr(III) sorption. X-ray photoelectron spectroscopy measurements, at different pH values, were also made to corroborate the zeta potential results.
对当地膨润土和膨胀珍珠岩（摩洛哥产）进行了表征，并将其用于去除水溶液中的三价铬。动力学研究表明，与膨胀珍珠岩相比，膨润土对Cr(III)的吸附非常迅速。为了计算两种吸附剂在不同pH值下的吸附容量，分别将膨润土和膨胀珍珠岩的实验数据点拟合到Freundlich模型和Langmuir模型。对于两种吸附剂，吸附容量均随悬浮液pH值的升高而增加。计算了两种吸附剂的去除效率，结果表明膨润土（去除了96%的Cr(III)）在从水溶液中去除三价铬方面比膨胀珍珠岩（去除了40%的Cr(III)）更有效。在不存在Cr(III)离子的情况下，膨润土和膨胀珍珠岩样品在2-11的pH范围内均产生负的zeta电位。与三价铬(III)溶液接触后，观察到膨胀珍珠岩的电荷从负变为正，这与Cr(III)在固体表面的吸附有关。因此，可以得出结论，表面络合在Cr(III)物种在膨胀珍珠岩上的吸附中起重要作用。在膨润土的情况下，阳离子交换是三价铬离子吸附的主要机制，因此在Cr(III)吸附后未观察到zeta电位的净变化。还在不同pH值下进行了X射线光电子能谱测量，以证实zeta电位结果。
