Leaching behavior of copper and arsenic in collaborative leaching system of copper-smelting dust and waste acid

The harmless treatment of hazardous wastes, such as dust and waste acid from copper smelting process and comprehensive recovery of valuable metals, are important environmental problems to be solved in copper smelting industry. In this study, the free acid in waste acid was used to high efficiently leaching of valuable metals from copper smelting dust with the ideal of treatment of waste by waste. The collaborative leaching of copper-smelting dust and waste acid was conducted, and the influence of key parameters on the leaching rate of copper and arsenic, and the dissolution, precipitation, and mineral phase transformation behavior of complex arsenic phases were intensively studied. The results show that, under the conditions of reaction temperature of 80 ℃, liquid-solid ratio of 8: 1, reaction time of 1 h, stirring speed of 300 r/min, and the equivalent sodium sulfite addition of 1, the leaching rate of copper is as high as 99%, and the leaching rate of arsenic is 80%, and the enrichment rates of lead, silver, bismuth in the leaching slag are more than 99%. Because of the formation of insoluble arsenate, such as bismuth arsenate and iron arsenate in the collaborative leaching process, the efficient leaching of arsenic is inhibited. The reaction temperature has a significant effect on the reduction of As(Ⅴ) and the oxidation of As(Ⅲ), which becomes the main factor affecting the precipitation and dissolution of arsenic. When the leaching temperature is lower than 90 ℃, As(Ⅴ) and Bi(Ⅲ) converte to crystalline bismuth arsenate (BiAsO4), and its thermodynamic advantage zone increases with the increase of the reaction temperature. When the reaction temperature is higher than 90 ℃, As(Ⅴ) and Fe(Ⅲ) form a small amount of amorphous iron arsenate (FeAsO4), and the higher the temperature, the more favorable the formation of amorphous iron arsenate. The system's oxidation-reduction potential should be reduced by shortening the reaction time or adding sodium sulfite (Na2SO3) reductant, and it can inhibit the formation of bismuth arsenate (BiAsO4). © 2022, China Science Publishing & Media Ltd. All right reserved.