Abstract The effects of pH (5.0, 6.0 and 7.0) and reaction time (2 h–60 d) on sorption/desorption of Si by a Si-deficient soil were investigated. Sorption isotherms for Si were linear indicating that with increasing surface coverage precipitation reactions were occurring on the sorption surfaces. Sorption of Si was increased as pH was increased from 5.0 to 7.0. Increasing the pH also resulted in a decrease in the percentage of sorbed Si that was subsequently desorbed over 10 desorption cycles. Similarly, increasing the pH during desorption (from 5.0 to 7.0) decreased the percentage Si desorbed as well as the percentage of Si that was released during the first desorption cycle. Thus, increasing pH not only increased the magnitude of sorption but the Si that was sorbed was held more strongly than at lower pH values. Increasing the period of sorption (up to 60 d) resulted in increased Si sorption thus demonstrating the existence of slow reactions between added Si and soil surfaces. Increasing contact time also decreased the percentage sorbed Si that could be desorbed over 12 desorption cycles and the percentage of total Si that was desorbed during the first desorption cycle. As the period of contact during sorption is increased subsequent desorption involves reversal of slow reactions and it is apparent that these are not easily or rapidly reversible. After a 60 d sorption period, only 49% of sorbed Si was desorbed over 12 desorption cycles. It was concluded that over a period of several months sorption can become a process by which Si is sequestered into a non-mobile form so that it cannot be regarded as simply a retention mechanism.

中文翻译：

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缺硅土壤对硅酸盐的吸附和解吸 - pH 值和接触时间的影响

摘要 研究了 pH（5.0、6.0 和 7.0）和反应时间（2 h–60 d）对缺硅土壤对硅的吸附/解吸的影响。Si 的吸附等温线是线性的，表明随着表面覆盖率的增加，吸附表面上发生了沉淀反应。随着 pH 从 5.0 增加到 7.0，Si 的吸附增加。提高 pH 值还导致吸附的 Si 百分比降低，随后在 10 个解吸循环中解吸。类似地，在解吸过程中增加 pH 值（从 5.0 到 7.0）会降低解吸的硅百分比以及在第一次解吸循环期间释放的硅百分比。因此，增加 pH 值不仅增加了吸附量，而且比在较低 pH 值下吸附的 Si 更牢固。增加吸附时间（最多 60 天）导致 Si 吸附增加，从而证明添加的 Si 和土壤表面之间存在缓慢的反应。增加接触时间还降低了在 12 个解吸循环中可以解吸的吸附硅百分比和在第一个解吸周期中解吸的总硅百分比。随着吸附过程中接触时间的增加，随后的解吸涉及缓慢反应的逆转，很明显，这些反应不容易或快速逆转。在 60 天的吸附期后，在 12 个解吸循环中只有 49% 的吸附硅被解吸。得出的结论是，在几个月的时间里，吸附可以成为一个过程，通过这个过程，Si 被隔离成非移动形式，因此不能简单地将其视为一种保留机制。