In situ interface oxidation-adsorption by ferrate (VI)/PMS self-excitation: Unique dual-reaction platform for phenylarsonic acid degradation and immobilization.

• First report of PAA oxidize by Fe(VI)/PMS and As(V) adsorb by in situ Fe(III) oxides. • The TOC removal efficiency was >45% and the total-As removal efficiency was >95%. • Oxidation of PAA is dominated by non-free radical pathways. • Fe(VI)/PMS could effectively oxidize PAA and remove total-As in authentic waters. In this study, we dexterously constructed a unique in situ interface oxidation–adsorption dual-reaction platform through the self-excitation of ferrate (Fe(VI))/peroxymonosulfate (PMS) for phenylarsonic acid (PAA) and inorganic As(V) removal. When the molar ratio of Fe(VI)/PMS was 1:2, 80% degradation of PAA could be achieved within 180 min and the apparent constant value of the reaction rate (k obs) would reach up to 0.185 min−1. 1O 2 and Fe(IV) were the main active species for degradation of PAA in Fe(VI)/PMS reaction system. In addition, we explored the possible degradation intermediates and pathway of PAA. In situ Fe(III) oxides generated from Fe(VI) decomposition could adsorb arsenic pollutants through ligand exchange with inorganic As(V) through surface hydroxyl groups to form Fe-O-As bonds. The effect of coexisting anions on the removal performance of the system was investigated, and the results showed that the presence of PO 4 3− and CO 3 2− promoted the oxidative degradation of PAA owing to the activation of PMS by PO 4 3− and CO 3 2−, but Cl− can inhibit the PAA degradation through a free radical scavenging mechanism. PO 4 3− and SiO 3 2− affected the adsorption and removal of the released inorganic As(V) due to their competitive adsorption of in situ Fe(III) oxides. Density functional theory (DFT) calculations indicated an obvious electron transfer (1.83 e) between the in situ Fe(III) oxides and inorganic As(V) with a high adsorption energy of −10.30 eV. These results indicate that the combination of Fe(VI) and PMS can effectively control the total arsenic (total-As) in water bodies. [ABSTRACT FROM AUTHOR]