Rational design of anti-interference Fe/Co MOF-coupled PMS process for As(III) removal in DOM-rich groundwater: 1O2-dominated As(III) oxidation and chemisorption of As(V)

Dissolved organic matter (DOM) extensively exists in high-arsenic groundwater with relatively high concentration, which could not only compete with arsenic for adsorption sites, but also depress As(III) oxidation in persulfate-based advanced processes (PS-AOPs) through scavenging free radicals (SO 4 • − and •OH). In order to effectively avoid the negative effect of DOM , an Fe/Co bimetallic metal–organic framework (Fe/Co MOF)-coupled peroxymonosulfate (Fe/Co MOF-PMS) system was rationally constructed for non-radical-dominated As(III) oxidation and chemisorption-driven As(V) adsorption. Results showed that the Fe/Co MOF-PMS system did realize anti-interference As(III) immobilization in DOM-rich high-arsenic groundwater, which was evidenced by no difference in As(III) immobilization efficiencies in the absence and presence of 20 mg/L humic acid (HA). During the oxidation process, 1 O 2 dominated As(III) oxidation while O 2 • − dominated HA oxidation, and the presence of HA significantly promoted the generation of 1 O 2 besides SO 4 • − and •OH. During the adsorption process, chemical adsorption mainly drove As(V) adsorption such as forming M-O-As (M = Fe, Co) bond, while physical adsorption forces played a major role in HA adsorption, such as π-π interaction, hydrogen bonding, and electrostatic attraction. The synergism of oxidation and adsorption processes made the anti-interference As(III) immobilization in DOM-rich high-arsenic groundwater in Fe/Co MOF-PMS system come true. This work is believed to shed light on the highly efficient purification of DOM-rich high-arsenic groundwater.