C-S-H凝胶对K^+和Na^+的吸附作用

Adsorption of K^+ and Na^+ by C-S-H gel

为了探讨水化硅酸钙(C-S-H)凝胶对K^+和Na^+的吸附性能,采用3CaO·SiO_2(C3S)和纳米SiO_2制备了不同钙硅物质的量之比(Ca/Si比)的C-S-H凝胶,着重研究浸泡溶液浓度和不同Ca/Si比C-S-H凝胶固体试样加入量对K^+和Na^+吸附能力的影响以及吸附态的K^+和Na^+的解吸行为。结果表明:C-S-H凝胶对K^+和Na^+的吸附能力随着Ca/Si比的降低而增高;对于相同Ca/Si比的C-S-H凝胶,随着浸泡溶液浓度的增大,K^+和Na^+吸附量逐渐增大,随着固体试样用量的增加,K^+和Na^+的吸附量降低而吸附率增高。C-S-H凝胶对K^+和Na^+的吸附不仅与其比表面积有关,而且与溶液中Ca2+浓度(浸泡溶液的p H值有关)有关。在溶液低p H值或高Ca2+浓度体系中,K^+和Na^+的吸附会被溶液中高浓度Ca2+所抑制。脱附实验证实了在碱溶液浓度<0.5 mol/L时,K^+和Na^+在C-S-H凝胶上吸附是可逆的。

To investigate adsorption of K＋ and Na＋ by calcium silicate hydrate（C-S-H） gel, C- S-H gels with different n（ Ca）/n（ Si） were prepared by hydration of 3CaO · SiO2（ C3S） incorporated with different substitution levels of nano-SiO2.Effects of alkali solution concentration and solid content on the K＋ and Na＋ adsorption were studied. Results showed that adsorption capacity of K＋ and Na＋ increased with the decrease of n （Ca）/n（Si） ratio. For a given n （Ca） /n（Si ） , with the alkali solution concentration and solid content increased, the adsorption capacity of K＋ and Na＋increased,while the K＋ and Na＋adsorption content by C- S-H gel decreased with the increase of solid content. K＋ and Na＋ adsorption capacity of C- S- H gel was affected not only by the specific surface area,but also by the concentration of Ca2＋changed by pH value of the solution.At high C^Si ratio or low pH value,alkali adsorption was suppressed by higher Ca2＋ concentration. Desorption test demonstrated that adsorption of K＋ and Na＋ on C- S-H gel was reversible,when the alkali solution concentration was lower than 0. 5 mol/L.