LAUSR

Abstract This paper explored the effect of trace Cu(Ⅱ) (5 μM) on the degradation of Orange Ⅱ by Fe(Ⅱ)/Hydroxylamine (HA)/Persulfate (PS) system. The results showed that the addition of trace Cu(Ⅱ) not only improved the degradation efficiency of Fe(Ⅱ)/HA/PS system, but also broadened the pH range of Fe(Ⅱ)/HA/PS degradation Orange Ⅱ (2-10). Increasing the dosage of Fe(Ⅱ), Cu(Ⅱ) and PS will promote the degradation of Orange Ⅱ by the Cu(Ⅱ)/Fe(Ⅱ)/HA/PS system. However, the optimal dosage of HA is 0.03 mM. Lower or excessive HA dosage is not conducive to the degradation of Orange Ⅱ by the Cu(Ⅱ)/Fe(Ⅱ)/HA/PS system. Scavenger experiments show that SO4·- is the main reactive oxygen species (ROS) in the Cu(Ⅱ)/Fe(Ⅱ)/HA/PS system. In both acidic and alkaline environments, Cu(Ⅰ) reduced by hydroxylamine can promote the conversion of Fe(Ⅲ) to Fe(Ⅱ). In acidic environment, Fe(Ⅱ) reduced by Cu(Ⅰ) is the reason why trace Cu(Ⅱ) can enhance the efficiency of Fe(Ⅱ)/HA/PS system to degrade Orange Ⅱ. However, in alkaline environment, Cu(I) reduced by hydroxylamine is the main participant in the production of SO4·- by activating persulfate, which is also the main reason for broadening the applicable pH of Fe(Ⅱ)/HA/PS for Orange Ⅱ degradation to alkaline environment.