Treatment of Contaminated Soil with NORM of Oilfields by Chemical Extraction Method

Abstract

Contamination of soil with naturally occurring radioactive material (NORM) is a common problem in oilfields leading to costly remediation and disposal programs, where ²²⁶Ra and ²²⁸Ra are the most important radionuclides. This study focuses on treatment of the contaminated soil with NORM to reduce the activity concentration within the allowable limits, that reflect to minimize the risk to workers, the public, and the environment. The study investigated the chemical treatment of two soil samples by a leaching batch test using single and sequential methods with diluted organic and inorganic acids (HNO₃, HCl, C₆H₈O₇, C₂H₄O₂, EDTA, and H₂SO₄). The initial activity concentrations of the two soil samples were measured for ²²⁶Ra and ²²⁸Ra using a gamma spectroscopy with a high-purity germanium (HPGe) detector, where they were; 59674.7 ± 2731.2 and 7058.2 ± 451.07Bq.kg^-1 respectively for the first sample, whereas 7666.6 ± 615.4 and 826.4 ±143.4 Bq.kg^-1 for the second. The sequential extraction is done in three successive steps (pH moderation, inion exchanging, and leaching with the final solvent). It found that single leaching appeared poor results of radium isotopes extraction from the soil samples with diluted acids, whereas the sequential extraction was the best, where the most effective solvent was 2M acetic acid (C₂H₄O₂) with a liquid-to-solid ratio L:S of 5 mL.g^-1 at a temperature of 40˚C for the first sample, where, 78.4% and 80.6% of ²²⁶Ra and ²²⁸Ra were removed from the soil and converted to the aqueous phase, whereas 87.9% and 89.8% were removed using 2M HNO₃ for the second sample at the same conditions.

Received 16/10/2023

Revised 23/02/2024

Accepted 25/02/2024

Published Online First 20/08/2024