Sepiolite clay: A review of its applications to immobilize toxic metals in contaminated soils and its implications in soil-plant system

Abstract High reactivity, reliable properties and positive environmental impacts of sepiolite clay in environment make it an important adsorbent for soil and water applications. Present review critically evaluates the applications of sepiolite in contaminated soils to adsorb toxic metals with an emphasis on cadmium (Cd) and lead (Pb). Research data has been compiled from about 140 publications reporting lab simulation studies, greenhouse experiments, and field trials. First section of this review describes the properties of sepiolite due to their role in dictating the efficiency of this mineral. In the next sections, we evaluate research advancements on the use of sepiolite for soil decontamination with a brief description about the underlying mechanisms. The properties and remediation efficiency of sepiolite can be tuned by its modification by physical or chemical strategies. In addition to its prominent metal adsorption capacity, sepiolite has the potential to increase soil pH which reduces the metal availability in soils and uptake by plants. The impacts of sepiolite on soil properties and plant growth are illustrated in soil-plant system. This extensive review highlights the strong remediation potential of sepiolite in metal-contaminated soils and positive impacts on soil-plant systems. Future studies need to focus on finding suitable methods to modify sepiolite and to explore its use in composite amendments for an improved efficiency under field conditions.