The impacts of temperature, soil-water ratio, and background multiplied inorganic anions on the degradation of organophosphorus flame retardants in soil by peroxydisulfate-based advanced oxidation processes

Soil contamination by triphenyl phosphate (TPHP) has posed a potential threat to human health. In this study, the degradation of TPHP by different chemical oxidation methods, including H 2 O 2 , persulfate (PS), peroxymonosulfate (PMS), ferrous ions (Fe 2+ ) activated H 2 O 2 , Fe 2+ activated PS, heat activated PS (heat-PS), and heat activated PMS, was compared. Heat input could promote the activation of PS to generate highly reactive species (HRS) and the aqueous availability of TPHP for more efficient degradation of TPHP in soil than other methods. As reaction temperature rose to melting point of TPHP (50 o C), the degradation rate sharply increased. The activation energy ( Ea ) of TPHP degradation in soil was caculated to be 115.57 kJ mol -1 . The oxidation capacity per unit PS was about 22.0 M -1 . Sulfate radicals (SO 4 •− ) and hydroxyl radicals (•OH) were the major HRS for TPHP degradation in heat-PS system. With increasing of soil-water ratio, the inhibitory effect of soil organic matter (SOM) on TPHP degradation was significantly enhanced. The degradation efficiency was highest under weakly acidic conditions (pH ≈ 4.8). Cl − significantly inhibited the degradation of TPHP in heat-PS system, while HCO 3 − and H 2 PO 4 − had little effects on the degradation of TPHP. After reaction, TPHP in soil could be degraded to be less toxic para -hydroxy triphenyl phosphate ( p -OH-TPHP), diphenyl phosphate (DPHP), and phosphate ions (PO 4 3− ). This study discloses a sustainable strategy for the remediation of OPFRs-contaminated soil by utilizing heat-PS method.