FIELD

The present description relates generally to systems and methods for ion sequestration in environmental matrices.

BACKGROUND AND SUMMARY

Remediation of contaminated environmental media may be costly and demanding of both time and energy. For example, soil may be infiltrated with materials that form cations, such as lead, and/or anions, such as arsenic, when dissolved in soil. Contaminant ions, e.g., cation and anions, present in soil may dissolve in water, thereby increasing mobility and allowing the contaminant ions to enter residential waterways which may lead to widespread health issues. Thus, rapid and effective removal of the contaminant ions or irreversible sequestration is highly desirable.

Conventional treatment of contaminated soils may include physical removal of the soil and replacement with clean soil, which may be slow, expensive, and inefficient and may adversely affect an ecology of a source site of the clean soil. Direct remediation of the soil, either in situ or ex situ, narrows an effect of the treatment to a contaminated medium. For example, a mobility of lead may be decreased by increasing soil pH to promote conversion of lead to a solid phase, such as lead carbonate. However, upon entering a digestive system of an organism, a bioavailability of lead from lead carbonate may remain high due to an increased solubility of lead carbonate when subjected to low stomach pH. Other techniques include lead absorption using materials such as organic matter, clays, metals which similarly reduce mobility but do not sufficiently decrease bioavailability. Phosphate amendments may provide more effective results, driving formation of a lead-phosphate mineral known as pyromorphite. Pyromorphite, however, is sensitive to environmental conditions such as pH, organic matter content, mineral content, and ability of lead to interact with phosphate. As such, results of phosphate amendments demonstrate widely variable results, e.g., from 0-50% reduction in lead bioavailability. Furthermore, excess use of phosphate may drive accumulation of phosphates in waterways which may cause eutrophication. In addition, phosphate amendments do not address removal of other contaminant ions, such as arsenic anions, radionuclides, etc.

In one example, the issues described above may be addressed by a method for treating a contaminated environmental medium, comprising adding a salt to the contaminated environmental medium to form a slurry and heating the slurry to expedite an irreversible precipitation of a jarosite-group mineral incorporating contaminant cations and contaminant anions into a structure of the jarosite-group mineral. In this way, a bioavailability of more than one contaminant ion may be simultaneously minimized via a simple, effective, and low cost process.

It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.

