Yüzer Hayrettin, Kara Mustafa, Sabah Eyüp, Celik Mehmet Sabri
Materials and Chemical Technologies Research Institute, Tubitak-Marmara Research Centre, 41470 Gebze, Turkey.
J Hazard Mater. 2008 Feb 28;151(1):33-7. doi: 10.1016/j.jhazmat.2007.05.052. Epub 2007 May 21.
Contribution of metal ion precipitation to the adsorption of Co2+ ions from aqueous solutions onto sepiolite has been analyzed as a function of pH. Abstraction and precipitation isotherms are constructed to isolate the precipitation of cobalt from the real adsorption. The contribution of all cobalt species against pH is calculated from the available solubility products or acid constants. It is found that at pH 8.2, which is the onset of cobalt hydroxide precipitation, the distribution of adsorbed cobalt species is as follows: 92% Co2+, 7% CoOH+ and 1% Co(OH)2. The experimental values are in accord with the calculated uptake of cobalt species onto sepiolite. Adsorption of cobalt ions onto sepiolite before precipitation of cobalt is governed by ion exchange between the released Mg2+ ions from sepiolite matrix and those adsorbed Co2+ ions; this behavior differs from typical oxide (titanium dioxide) and silicate (quartz) minerals. However, adsorption of cobalt onto the same materials including sepiolite follows the same trend after the region of cobalt precipitation despite distinct differences in their charge profiles.
已分析了金属离子沉淀对海泡石从水溶液中吸附Co²⁺离子的贡献，并将其作为pH的函数。构建了提取和沉淀等温线，以从实际吸附中分离出钴的沉淀。根据可用的溶解度积或酸常数计算了所有钴物种对pH的贡献。发现在pH 8.2（即氢氧化钴沉淀开始时），吸附的钴物种分布如下：92% Co²⁺、7% CoOH⁺和1% Co(OH)₂。实验值与计算得出的钴物种在海泡石上的吸附量一致。在钴沉淀之前，钴离子在海泡石上的吸附受海泡石基质中释放的Mg²⁺离子与吸附的Co²⁺离子之间的离子交换控制；这种行为不同于典型的氧化物（二氧化钛）和硅酸盐（石英）矿物。然而，尽管钴沉淀区域后它们的电荷分布存在明显差异，但钴在包括海泡石在内的相同材料上的吸附遵循相同趋势。
