Effect of heavy metal contamination on the plasticity of kaolin-bentonite clay mixtures and an illite-smectite rich natural clay

Abstract

The behaviour of soil is complex in a natural environment. Contamination of soil with organic and inorganic contaminants may change the properties of soil. Recent studies have shown that the heavy metal contaminants affect the plasticity and consolidation behaviours. However, little is known about the effects of heavy metals on the behaviour of different types of clay, especially how clay behaves when multiple heavy metals are present in clay. The paper will present results from tests on the effect of three different heavy metal ions used separately, and mixed together in combinations, on the liquid limit (wL), plastic limit (wP) and plasticity index (PI) of kaolin, bentonite, mixtures of kaolin and bentonite and reconstituted Lucera clay. It is found that plasticity index of bentonite is reduced significantly with the addition of heavy metals while PI increases slightly in kaolin. A 1:1 clay mixture of kaolin and bentonite showed significant reduction, while reconstituted Lucera clay has shown small reduction with the addition of heavy metals. It is found that at higher concentrations of copper and zinc cations, the effect takes reverse trend on the liquid limit of kaolin and similar behaviour was observed on the bentonite at higher concentrations of lead ion. Interestingly, lead ion exhibited a significant effect on the plasticity of bentonite when tested with NaCl solution as pore fluid.

Effect of Bentonite on the Early Growth Characteristics of Teak Seedlings Planted in Sandy Soil in Northeast Thailand—A Pilot Study

“…In contrast, application of bentonite improves the fertility of sandy soil owing to its high CEC value. A particle of bentonite is charged negatively, and bind various kind of cations [28]. As a result, bentonite has high capacity of nutrient retention, and plants efficiently absorb cations bound a surface of bentonite [29].…”

Characterisation of clays from Alicante province (SE Spain) for use in the recovery of degraded soils

“…Regarding the water holding capacity, it was not affected by the presence of lime or kaolinite in several samples, despite the smaller interlayer space in kaolinite compared to illite. This can be due to the absorption of Ca by kaolinite, which increases its interlayer space (Miranda-Treviño and Cole, 2003;Muththalib and Baudet, 2019). Maybe other properties related to soil water as the wilting point or the rate of water loss would be more adequate to understand the differences in water dynamics in clays and degraded soils.…”

“…On the contrary, 1:1 clay minerals such as kaolinite show lower CEC values. However, the adsorption of divalent metals in kaolinite improves properties such as flocculation, plasticity, porosity and the hydraulic conductivity of the clay, and increases metal retention (Miranda-Treviño and Cole, 2003;Muththalib and Baudet, 2019). This effect has also been observed in 2:1 clays.…”

Activating Illite kaolinite clay with CTAB for adsorbing Methylene blue: Isotherms, Kinetics, and thermodynamics studies

“…Depending on the pH of the solution, the surface of IKaol has a continuous structurally negative charge due to the isomorphous substitution of Si 4+ by Al 3+ in the silica layer [24], which is an active adsorption site for the removal of colours from wastewater [25]. IKaol has recently been used in a few studies as an adsorbent for removing water pollutants such as dyes [26] and heavy metal ions [27]. However, the direct application of pure IKaol clay is ineffective in efficiently removing anionic dyes, such as MB, from aqueous solutions.…”