Selective leaching of arsenic and copper in copper smelting dust was investigated by Na2S-NaOH leaching process with assistance of ultrasound method. The results showed that ultrasound wave could enhance alkaline leaching capacity and separation of arsenic and copper. The corresponding leaching ratios of arsenic and copper reached to 88.81% and 0.025% at the condition of 5 min discharge time

80 W discharge power

mass ratio of Na2S

NaOH to ash 0.4:1

liquid-solid ratio 20:1

temperature 75℃ and stirring speed 400 r·min-1. The leaching process with Na2S-NaOH assistant with ultrasound reduced arsenic and increase copper content in soot from 0.85% to 0.58% and from 2.21% to 2.30%

and the leaching rate of As increased 9.21%

the leaching toxicity concentration of As was reduced from 12.66 mg·L-1to 2.84 mg·L-1

compared with alkaline leaching

respectively. Kinetics of alkaline assisted with ultrasound leaching of arsenic in copper smelting dust was controlled by hybrid reaction and its leaching kinetic equation followed the reacted shrinking core model

its apparent activation energy was 0.114 kJ·mol-1

and the reaction system was balanced within 5 min. XPS

XRD and speciation analysis of heavy metals indicated that ultrasound wave was able to oxidize As(Ⅲ) to As(Ⅴ)

which was propitious to leaching of arsenic. In conclusion

ultrasound wave assisted Na2S-NaOH leaching process proved to be an efficient way of removing both arsenic and copper from soot

so the soot could be further utilized after toxic content reduction.