Wang Kaijun, Xing Baoshan
Department of Plant and Soil Sciences, Stockbridge Hall, University of Massachusetts, P.O. Box 37245, Amherst, MA 01003-7245, USA.
Chemosphere. 2002 Aug;48(7):665-70. doi: 10.1016/s0045-6535(02)00167-4.
The adsorption of Cd by oxides or soils have been extensively studied, however, the desorption has received relatively limited attention, especially in the presence of phosphate. In this study, a batch equilibration method was used to investigate Cd sorption and desorption by goethite pretreated with phosphate. Phosphate not only enhanced Cd adsorption, but also accelerated the adsorption process. Compared with Cd adsorption by goethite alone, phosphate substantially moved the adsorption curves (edges) to lower pH range, indicative of enhancement of Cd sorption. The Cd adsorption by the pretreated goethite reached apparent equilibrium within 24 h at 20 degrees C, while such equilibrium was not observed after 4 weeks in the absence of phosphate. Cadmium was more readily released from phosphate-treated goethite. It is believed that phosphate blocked the pores on goethite surface, which lead to the fast adsorption kinetics and high extraction percentage. These results provided strong support for the diffusion of Cd into goethite particles.
氧化物或土壤对镉的吸附已得到广泛研究，然而，解吸受到的关注相对有限，尤其是在磷酸盐存在的情况下。本研究采用批量平衡法研究了经磷酸盐预处理的针铁矿对镉的吸附和解吸。磷酸盐不仅增强了镉的吸附，还加速了吸附过程。与单独的针铁矿对镉的吸附相比，磷酸盐使吸附曲线（边界）显著向较低pH范围移动，表明镉吸附增强。在20℃下，经预处理的针铁矿对镉的吸附在24小时内达到明显平衡，而在没有磷酸盐的情况下，4周后仍未观察到这种平衡。镉更容易从经磷酸盐处理的针铁矿中释放出来。据信，磷酸盐堵塞了针铁矿表面的孔隙，这导致了快速的吸附动力学和高提取率。这些结果为镉扩散到针铁矿颗粒中提供了有力支持。
