Peld Merike, Tõnsuaadu Kaia, Bender Villem
Departments of Chemistry, Chemical Engineering, and Physics, Tallinn University of Technology, 19086 Tallinn, Estonia.
Environ Sci Technol. 2004 Nov 1;38(21):5626-31. doi: 10.1021/es049831l.
As a low-soluble phosphate mineral capable of binding various metal ions, apatite can be used to immobilize toxic metals in soils and waters. In the present research the factors affecting sorption and desorption of Cd2+ and Zn2+ ions on/from apatites are investigated. Batch experiments were carried out using synthetic hydroxy-, fluoride-, and carbonate-substituted apatites having various specific surface area (SSA). Apatite sorption capacity was found to depend mainly on its SSA, ranging from 16 to 78 and from 11 to 79 mmol per 100 g of apatite for Cd2+ and Zn2+, respectively. The solution composition (pH, and presence of Cl- and NO3- ions) had no essential impact on sorption. Desorption of bound cations depended both on the sorption level and solution composition. The amount of desorbed Cd2+ and Zn2+ increased proportionally to the amount of sorbed cations. However, apatites having higher sorption capacity release relatively less sorbed cations. Desorption increases with increasing Ca2+ concentration in the solution, reaching 8-20% of sorbed Cd2+ in 0.002 M, 10-35% in 0.01 M, and 33-45% in 0.05 M Ca(NO3)2 solution. Compared to nitrate solutions, the presence of Cl- ions in the solution promotes the release of bound cations. Desorption of Zn2+ is slightly higher than that of Cd2+. The desorption mechanism was assumed to include both ion-exchange and adsorption of Ca2+ ions on apatite surface.
作为一种能够结合各种金属离子的低溶性磷酸盐矿物，磷灰石可用于固定土壤和水中的有毒金属。在本研究中，研究了影响镉离子（Cd2+）和锌离子（Zn2+）在磷灰石上吸附和解吸的因素。使用具有不同比表面积（SSA）的合成羟基取代、氟取代和碳酸根取代的磷灰石进行了批量实验。发现磷灰石的吸附容量主要取决于其比表面积，对于Cd2+和Zn2+，每100克磷灰石的吸附容量分别为16至78毫摩尔和11至79毫摩尔。溶液组成（pH值以及Cl-和NO3-离子的存在）对吸附没有实质性影响。结合阳离子的解吸既取决于吸附水平，也取决于溶液组成。解吸的Cd2+和Zn2+的量与吸附阳离子的量成比例增加。然而，具有较高吸附容量的磷灰石释放出的吸附阳离子相对较少。解吸随着溶液中Ca2+浓度的增加而增加，在0.002M的Ca(NO3)2溶液中，解吸的Cd2+达到吸附量的8 - 20%，在0.01M中为10 -
35%，在0.
