Effect of Acidic Conditions on Surface Properties and Metal Binding Capacity of Clay Minerals

Abstract

Clays are one of the most abundant minerals on the Earth's surface, and they play a significant role in global trace element cycling because of their ability to adsorb and incorporate a range of metal cations. However, to what extent clay surface reactivities are affected by changes in pH of the surrounding environment remains poorly understood. To address this uncertainty, we investigated three common clay minerals (kaolinite, illite, and montmorillonite) and compared their surface properties and metal binding capacity prior to and after acidic treatment (pH ranges from 0 to 7). We report that (1) the morphologies and crystal structures of the three studied clay minerals do not differ markedly after exposure to an acidic solution, (2) all three clays display increases in surface area after the pH 0 acidic treatment, and (3) cadmium adsorption to all three clays decreased after the pH 0 acidic treatment. Our results suggest that the variation in metal adsorption capacity is related to acidic modification of clay surface properties. Importantly, this work shows the relevance of acidic environments on surface-controlled reactions of trace metals to clay minerals.

The kaolinite shuttle links the Great Oxidation and Lomagundi events

“…This link is well developed in modern settings, with extensive kaolinite formation in soils developed on organic and pyrite-rich lithologies such as black shales 22,23 . Despite still constituting an important part of the clay fraction, clay minerals more characteristic of moderate terrestrial weathering conditions (e.g., smectites) are more rapidly dissolved in acidic environments 21,[24][25][26] .…”

Trace Elemental Partitioning on Clays Derived From Hydrothermal Muds of the El Tatio Geyser Field, Chile

“…For instance, Hao, Pudasainee, et al. (2019) showed significant increases in the surface areas of clay minerals (kaolinite, illite, and montmorillonite) after exposure to acidic solutions (pH ∼ 0–4), as well as decreased cadmium (Cd) adsorption. Similarly, Jeon and Nam (2019) showed that acidic treatment can decrease the surface functional group density and the proton binding constants of montmorillonite.…”

Spectroscopic and Modeling Investigation of Sorption of Pb(II) to ZSM-5 Zeolites

“…Heavy metals that are released into the environment are a major public health concern due to their toxic nature and persistence, and lead (Pb) is among the most common. − A wide range of remediation methods have been investigated to remove heavy metals from water and wastewater, including surface precipitation, ion exchange, electrochemical processes, adsorption, , and a combination of these methods . Of the methods described above, adsorption is considered to be an efficient and economic method of metal remediation, and zeolites are some of the most widely used and low-cost adsorbents .…”