Sono-activation of persulfate by Fe-expanded perlite catalyst for oxidative degradation of Orange G: synergy study, influence of parameters and phytotoxicity tests

Iron-coated expanded perlite (Fe-EP) was prepared as a heterogeneous catalyst for activating persulfate (PS) to degrade Orange G (OG) under ultrasonic irradiation (US). The expanded perlite (EP) and Fe-expanded perlite (Fe-EP) catalyst were characterized by several techniques. X-ray diffraction analysis showed that the Fe-EP catalyst mainly consists of SiO 2 , Fe 2 O 3, and Al 2 O 3 crystallites. The BJH average pore diameter of the prepared catalyst is found to be 15.39 nm. The catalytic performance of the Fe-EP was tested by the discoloration of OG in US/Fe-EP/PS system. The effect of factors influencing the percentage of degradation was analyzed. At optimal conditions (1.2 mmol/L of S 2 O 8 2− , 40 mg/L of initial OG concentration, and pH = 5), the treatment efficiency of OG attains 94% after 40 min. Also, the effects of the addition of iron (III) and H 2 O 2 on the degradation efficiency were determined. The reaction process of OG discoloration was followed by UV–Vis technique. The negligible iron leaching and the possibility of reuse indicated satisfactory stability of prepared catalyst. Phytotoxicity tests towards the broad bean plant ( Vicia faba L.) confirmed that the OG dye is phytotoxic.