Abstract:

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.

Key words: copper smelting dust, ultrasound wave, selective leaching, separation, kinetics, interface, oxidation

摘要：

采用超声辅助Na₂S-NaOH浸取体系对铜冶炼烟灰进行研究，在NaOH、Na₂S与烟灰质量比0.4：1，液固比20：1，反应温度75℃，反应时间5 min，超声功率80 W，搅拌速率400 r·min^-1条件下，As浸出率为88.81%，Cu浸出率为0.025%，实现了Cu和As的有效分离。采用该方法处理后，与单独碱浸相比，As浸出率提高9.21%，烟灰中As含量由0.85%降至0.58%，Cu含量由2.21%增至2.30%，且As浸出毒性浓度由12.66 mg·L^-1降至2.84 mg·L^-1，为烟灰的资源化利用创造了条件。超声辅助碱浸除砷动力学满足收缩核混合反应控制模型，表观活化能0.114 kJ·mol^-1。XRD、XPS和重金属形态分析结果表明，超声空化作用可使As（Ⅲ）氧化为As（Ⅴ），有利于As浸出，故超声过程强化有利于Cu和As在碱浸体系中的选择性分离。

关键词: 铜冶炼烟灰, 超声波, 选择性浸出, 分离, 动力学, 界面, 氧化