Remediation of artificially Arsenic Contaminated clay Soil (Sepiolite) by extraction and its effect on soil properties

Soil properties such as particle size distribution, plasticity, compressibility, or strength of the soil always affect the geotechnical design in construction. The knowledge of contaminants and their extraction on natural adsorbents (clay soils) with various treatments, and extractants is essential for geo-environmental engineering applications. To address these challenges, sepiolite as a widely used environmental natural resource (which is a native and non-expansive clay soil with high cation exchange capacity), was subjected to a study of the effect of arsenic (As) contamination and extraction using the different solutions on its characteristics in two incubations period (7 and 28 days curing). After incubation, various physical and mechanical tests were performed on As contaminated and extracted clay soil to investigate the effect of anionic contaminant on the clay soil properties and to evaluate how the properties of the contaminated soil change after extraction, as well. The optimal extractant for arsenic extraction from sepiolite was determined by hydrochloric acid and nitric acid, respectively. The results revealed improvements in some soil characteristics. Arsenic extraction by acid after contamination caused changes in the properties of clay soil specimens, including a decrease in pH, plastic index, and fine particles content which reduced the permeability coefficient in the soil. The overall results showed that the environmental and engineering properties of clay mineral are suitable for use as clay liners in pounds containing anionic leachates with improving workability.