Efficient transformation and elimination of roxarsone and its metabolites by a new Α-FeOOH@GCA activating persulfate system under UV irradiation with subsequent As(V) recovery

Roxarsone (ROX) is extensively used as a feed additive which tends to leave toxic inorganic arsenic (As) in the natural environment. A composite of reduced graphene oxide and carbon nanotubes was impregnated with goethite designated as α-FeOOH@GCA and tested as an integrated catalyst and adsorbent for ROX decontamination. Nearly 100% of the ROX was transformed in α-FeOOH@GCA activating persulfate (PS) under UV₃₆₅ irradiation system at relatively low dosage of the α-FeOOH@GCA catalyst (250 mg L⁻¹) in 120 min. The As(V) released in the ROX oxidation was simultaneously adsorbed onto the surface of the α-FeOOH@GCA. A possible ROX transformation pathway is proposed. The As(V) adsorbed on catalyst was recovered and used to form an efficient Ag₃AsO₄ photocatalyst. This work further extends the oxidation-adsorption technology in solving organoarsenical contamination without producing secondary pollution.