Importance of reagent addition order in contaminant degradation in an Fe(II)/PMS system

Addition order of reagents in the Acid Orange 7 (AO7) degradation process was investigated by varying the concentration of Fe(II), the Fe(II)/peroxymonosulfate (PMS) molar ratio and stepwise addition of Fe(II) and PMS. The importance of addition order of reagents was confirmed and an order of Fe(II)–PMS to improve the oxidation efficiency was recommended.