Direct preparation of sodium stannate from lead refining dross after NaOH roasting-water leaching

[Display omitted] •Sodium stannate powder was effectively prepared from lead refining dross.•More than 93% Sn could be selectively extracted from lead refining dross.•Sodium stannate product has a dense massive structure with good crystallinity.•Antimony was separated into the leaching residue which contained 31.32% Sb. Sodium stannate (Na2SnO3·3H2O) has been widely applied in the field of electroplating and flame retardants preparation. In general, Na2SnO3·3H2O is mainly prepared from cassiterite or metallic tin, which has the problems of high production costs and natural mineral shortage. This study investigated a combined process of roasting, leaching, purification, and evaporating-crystallizing to prepare Na2SnO3·3H2O directly from lead refining dross. The effects of roasting process parameters (NaOH dosage, roasting temperature, and time) and leaching process parameters (leaching temperature, leaching time, liquid-to-solid ratio, and stirring speed) on the leaching efficiency of tin were detailly investigated. The results showed that about 93.5% of tin was converted into sodium stannate after NaOH roasting and thus could be leached out by water leaching. The optimized conditions have been established as: mass ratio of NaOH to the dross of 1.4 during roasting at 450 °C for 60 min and leaching at 75 °C for 90 min with 10 mL/g liquid-to-solid ratio and 300 r/min stirring speed. Meanwhile, the antimony was separated into the leaching residue, in which the content of antimony reached 31.32%. Thereafter, the leachate was purified by sulfide precipitation with Na2S. The purified solution was then subjected to an evaporating and crystallizing process for the preparation of Na2SnO3·3H2O.