Organic Ligand-Assisted Fe(II)-Activated Persulfate for Enhanced Degradation of Chlorinated Aromatic Contaminants in Soil Remediation

Chlorinated aromatic compounds are extremely dangerous, transmittable, and bioaccumulative. Ferrous-based persulfate stimulation methods are a potential approach for soil restoration, however they have limitations with ferrous accumulation. Citrate (CA) and ethylenediaminetetraacetic acid (EDTA) were used in the current investigation to enhance the efficiency of Fe(II)-activated persulfate (PS) reactions in the decomposition of 4-chlorophenol (4-CP) and 3-chlorobenzoic acid (3-CB) in soil. The combination of organic ligands with Fe(II) increased the overall iron content in the organic ligands/Fe(II)/PS systems and inhibited Fe(II) accumulation. Organic ligands absorbed Fe oxides in soil and facilitated to stimulate persulfate. The optimal concentration of organic ligands/Fe(II)/PS is 50:50:50, and around 74.11%, 70.05%, and 77.67%, 72.92% of the 4-CP and 3-CB were decomposed within 30   minutes, in contrast to 34.14% and 38.14% in the Fe(II)/PS system. The degradation percentage of 4-CP and 3-CB raised with increasing PS and Fe(II) levels, whereas high PS and Fe(II) concentrations prevented 4-CP and 3-CB degradation, most likely because of sulfate radical absorption. Furthermore, the 4-CP and 3-CB decomposition mediated by the citrate/Fe(II)/PS and EDTA/Fe(II)/PS systems were effective over a wide range of pH values (2.0–10). The organic ligands combined with Fe(II) catalyzed PS degradation showed a strong ability on enduring the effects of HCO3, Cl, and HA anions in soil on 4-CP and 3-CB decontamination. In addition, SO4 •- and OH • produced from citrate/Fe(II)/PS and EDTA/Fe(II)/PS systems were identified as the primary reactive oxygen species for 4-CP and 3-CB degradation. In conclusion, the organic ligands coupled with Fe(II) stimulated PS activation are potentially useful technique for the restoration of 4-CP and 3-CB contaminated soils.