Treatment of Organophosphorus Esters Waste by CeO₂: Efficient Degradation with Simultaneous Phosphorus Immobilization

Abstract

Organophosphorus esters (OPEs) are important chemicals functioning as extractants, plasticizers, flame retardants, solvents, additives, etc., and are also recognized as hazardous organic liquids generated from industrial processes. Herein, we developed a CeO2-catalyzed degradation with simultaneous phosphorus immobilization technology to treat typical OPE solvents. Under the investigated reaction conditions of a temperature of 180 °C, a reaction time of 3 h, and a dosage of ball-milled CeO2 of 19.8 g mL–1 of the OPE, the model pollutant of tributyl phosphate (TBP) was efficiently degraded with phosphorus immobilization efficiency near 100%. Meanwhile, the mineralization efficiency of TBP was also as high as 98%, which was reflected by the chemical oxygen demand change of liquid products. Gaseous products generated from CeO2-catalyzed TBP degradation could also fulfill the requirements of an environmental standard. Further mechanism studies indicated that the surface oxygen vacancy in CeO2 induced the in situ formation of superoxide radicals, which dominated TBP degradation. During catalytic degradation, the P-containing species were mainly immobilized as cerium phosphate, while the hydrocarbon chains of TBP were degraded into small molecules and finally mineralized into inorganic species. The developed CeO2-catalyzed OPE degradation approach was also applicable to aromatic and halogenated OPEs, i.e., tricresyl phosphate and tris­(2-chloroethyl) phosphate. This study provided a possible alternative for waste treatment of the waste of OPEs with low environmental risks.