Leaching behavior and kinetics of arsenic’s leaching from arsenic-antimony dust in H2SO4-H3PO4-H2O system

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In response to the challenges of low rates of leaching of arsenic and poor separation of arsenic and antimony in arsenic-antimony dust using acidic leaching, the present study proposed a selective leaching approach for arsenic from arsenic-antimony dust using a mixed acid of H2SO4 and H3PO4. The leaching mechanism of arsenic-antimony dust in the H2SO4-H3PO4-H2O system was elucidated through the characterization of the solution and the leaching residue, identifying the effects of various parameters such as the concentration of phosphoric acid and temperature on the separation efficiency of arsenic and antimony, and clarifying the leaching kinetics of arsenic-antimony dust. The results indicated that the introduction of PO43- into the reaction system promoted the formation of SbPO4 precipitate, effectively inhibiting the leaching of antimony and preventing the formation of AsSbO3 and (Sb,As)2O3, as well as enabling efficient leaching of arsenic. Under the H3PO4 concentration of 0.97 mol/L, reaction temperature of 90 ℃, liquid-to-solid ratio of 30:1, and leaching duration of 3 h, the rate of leaching of arsenic reached 99.53 %, with the corresponding value of only 5.13 % for antimony. The arsenic content in the leaching residue was reduced to 0.98 %, while the antimony content was as high as 65.34 %, indicating a preliminary separation of arsenic and antimony. The results for the leaching kinetics indicated that the leaching process of arsenic was governed by the diffusion control model within the Avrami model, with an apparent activation energy (Ea) of 74.863 kJ/mol. Last but not the least, the results showed that reducing the particle size or disrupting the product layer coating resulted in enhanced leaching of arsenic.