Cyanide-Impacted Soil: Evaluating Ex-Situ Thermal Treatment

Ex-situ thermal remediation treats material after excavation. A treatment pile may be constructed at the original site; the term does not require transport to an offsite facility.

Conceptual ex-situ treatment pile from GEO’s cyanide white paper, showing heating, extraction, and aboveground equipment.

GEO's cyanide white paper describes a batch-pile approach using heater wells, vapor extraction, and aboveground vapor and water treatment. Its proposed treatment sequence depends on the material and contaminants present.

Cyanide occurs in different chemical forms, and their responses to heating can differ. A treatment assessment therefore needs the cyanide species, soil properties, target concentrations, and an appropriate treatability test. A single temperature range cannot establish complete detoxification for every cyanide-bearing material.

The process also requires evaluation of potentially hazardous gases, condensate, and residual water. Confirmation sampling must demonstrate whether the treated material meets the project's specified criteria.

This article summarizes a treatment approach described in GEO's technical materials. It is not a completed-project case study or a guarantee of a particular removal percentage, duration, or regulatory outcome.