A laboratory trial was performed to test the sequestration capacity of two minerals (bentonite and zeolite) at three initial concentrations (2.5, 5 and 10%) in order to counter water-soluble nickel (Ni) exceeding the Italian legal limit (10 μg L-1) in carbonation lime disposed of in a field and sampled for an 85-day lab study. The results show a noticeable reduction in water-soluble and bioavailable Ni in lime after the addition of sequestrants, especially at the dose of 5% bentonite or zeolite, thereby indicating a "ceiling effect" of the sequestrant, i.e., an increasing dose could reduce the adsorption capacity and be less effective. The alkaline pH and the presence of organic matter could be the main factors affecting the good performance of sequestrant addition, causing an increase in the negative charge of the organic and mineral colloids and the formation of unavailable Ni precipitates. The 85-day experiment seems to be sufficient to reach an adsorption equilibrium for water-soluble nickel, while for the bioavailable form a longer period appears to be necessary.

中文翻译：

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来自糖业的碳酸钙中的沸石和膨润土作为镍螯合剂。

进行了一项实验室试验，以测试三种初始浓度（2.5％，5％和10％）下两种矿物（膨润土和沸石）的螯合能力，以抵消超过意大利法定限量（10μgL）的水溶性镍（Ni） -1）在现场处置的碳酸钙中取样并进行85天的实验室研究。结果表明，添加螯合剂后，石灰中水溶性镍和生物利用度Ni明显降低，尤其是在5％膨润土或沸石的剂量下，从而表明螯合剂具有“天花板效应”，即增加剂量可以降低吸附能力较差。碱性pH和有机物的存在可能是影响螯合剂添加性能良好的主要因素，导致有机和矿物胶体的负电荷增加，并形成不可用的镍沉淀。85天的实验似乎足以达到水溶性镍的吸附平衡，而对于生物利用形式，则似乎需要更长的时间。