Efficient degradation of disodium adenosine triphosphate by Ca–Al-LDH-supported Fe-activated persulfate and in situ adsorption of the phosphate products

Abstract

To efficiently treat organophosphorus pollutants and synchronously recover phosphorus resources, Fe-loaded layered double metal hydroxides (Fex/Ca–Al-LDHs) were successfully prepared via coprecipitation and impregnation. The effects of the Fex/Ca–Al-LDHs on the degradation of disodium adenosine triphosphate (5-ATP-Na2) in water and in situ separation of the oxidation product, PO43−, were analyzed. The amount of Fe impregnated into the Fex/Ca–Al-LDHs considerably influenced the capacity of the composite for the oxidative separation of 5-ATP-Na2. A 5-ATP-Na2 removal rate of 94.43% was achieved at pH 3 when the Fe content of the Fe0.4-LDHs, catalyst dosage, and potassium persulfate (PS) concentration were 0.4 mol L−1, 0.6 g L−1, and 0.8 mmol L−1, respectively. The removal rate of the Fex-LDHs/PS system was maintained at 71.81% after three oxidation adsorption−desorption cycles. The system was effective for the removal of other organophosphorus species and practical treatment of various sewage types. The activity of the catalyst is derived from the active Fe species (FeCl3, Fe(OH)2, and Fe2O3), which promoted the cyclic conversion of Fe(II) and Fe(III). An increase in the Fe(II) content promoted the activation of PS, enabling rapid pollutant degradation. The main pathway for 5-ATP-Na2 degradation involved oxidation by SO• 4− and •OH; the generated PO43− was primarily removed by adsorption on the Ca–Al-LDHs. The novel Fe-LDHs/PS catalytic adsorption system prepared in this study is an innovative platform for the efficient catalytic degradation of organophosphorus and simultaneous adsorption of the oxidation product, PO43−.