Treatment of polychlorinated dibenzo-p-dioxins and dibenzofurans contaminated soil using S₂O₈ ²⁻ with ferrous ion and heat as activating methods

The uses of Fe²⁺ and thermal energy as S₂O₈ ²⁻ activating methods for the treatment of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) contaminated soil using S₂O₈ ²⁻ were simultaneously studied for the first time. PCDD/Fs degradation was conducted using S₂O₈ ²⁻ with and without the Fe²⁺ addition at 25 °C, 40 °C, and 60 °C, and the process of S₂O₈ ²⁻ without Fe²⁺ showed the best performance, 99.0% removal efficiency of 17 PCDD/Fs in 72 h. The SO₄ ^[rad]− based process is effective for the degradation of PCDD/Fs. The presence of Fe²⁺ greatly influenced the soil pH development during the process, but the pH change showed an insignificant effect on PCDD/Fs degradation by the SO₄ ^[rad]− based process. The performances of several options implied that the direct interactions of Fe²⁺, heat, and S₂O₈ ²⁻ on PCDD/Fs are very few, and interestingly, the combination of Fe²⁺ and thermal energy did not always show a clear advantage over the individual use of Fe²⁺ or thermal energy. The behaviours of PCDD/Fs in S₂O₈ ²⁻ based process is consistent regardless of an activating method. The lower-chlorinated PCDD/Fs were easier to be degraded than higher ones, and in most cases, more PCDFs were degraded than PCDDs in the case of same chlorine numbers.