Selective Separation of Antimony and Preparation of Sodium Antimonate by Sodium Salt Leaching-Synergistic Oxidation from High Arsenic Antimony Residue

In this study, the catalytic air oxidation method was used to selectively form sodium antimonate from an antimony residue Na₂S-NaOH leaching solution of a high arsenic copper anode slime. In the first stage, the leaching process with Na₂S and NaOH media resulted in more than 98% leaching of antimony. The synergistic oxidation method was used to selectively separate antimony in the second stage. In this study, the oxidation rate of antimony was greater than 98% at the NaOH concentration of 50 g·L⁻¹ and a combined oxidation concentration of 0.75 g·L⁻¹ catechol + 0.75 g·L⁻¹ KMnO₄, under the air flow rates of 1.415 m³·min⁻¹ at 75 °C for 8 h. The pH of the crude sodium antimonate product was adjusted; subsequently, it was redissolved and precipitated to prepare refined sodium antimonate that meets the secondary product standard of China’s non-ferrous metal industry, which recommends an antimony recovery rate of >95.60%. After neutralisation, the liquid contains [As] < 0.10 g·L⁻¹, [Sb] = 0.16–0.38 g·L⁻¹, which can be reused in the composite leaching process. The apparent activation energy (Ea) of the catalytic oxidation reaction was 6.47 kJ·mol⁻¹; the results suggested that the reaction process was diffusion controlled. <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo>−</mo><mstyle scriptlevel="0" displaystyle="false"><mfrac><mrow><mi>d</mi><mfenced open="[" close="]" separators="|"><mrow><mi>S</mi><mi>b</mi></mrow></mfenced></mrow><mrow><mi>d</mi><mi>t</mi></mrow></mfrac></mstyle><mo>=</mo><mn>8.86</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>5</mn></mrow></msup><mo>×</mo><msup><mrow><mi>e</mi></mrow><mrow><mstyle scriptlevel="0" displaystyle="false"><mfrac><mrow><mo>−</mo><mn>778.44</mn></mrow><mrow><mi>T</mi></mrow></mfrac></mstyle></mrow></msup><mo>×</mo><msup><mrow><mfenced open="[" close="]" separators="|"><mrow><mi>S</mi><mi>b</mi></mrow></mfenced></mrow><mrow><mn>0.4906</mn></mrow></msup><mo>×</mo><msup><mrow><mo>[</mo><mi>N</mi><mi>a</mi><mi>O</mi><mi>H</mi><mo>]</mo></mrow><mrow><mn>1.190</mn></mrow></msup></mrow></semantics></math></inline-formula>.