Lead removal from crude antimony in the pyrometallurgical refining process by using NaPO₃

In order to solve the problem of lead removal from crude antimony in the traditional antimony refining process,NaPO₃ was introduced as a lead elimination reagent to generate phosphate slag and the slag was removed by floating on the surface of liquid antimony. The reaction mechanisms were clarified by thermogravimetric-differential thermal analysis and X-ray diffraction analysis and removal of Pb from crude Sb was investigated by condition experiment. It is found that PbO and NaPO₃ begin an endothermic reaction at 590℃ and mainly form NaPb₄(PO₄)₃ and NaPbPO₄ below 850℃ and above 850℃,respectively. The reaction products of the mixture of PbO,Sb₂O₃ and NaPO₃ show that NaPO₃ preferentially reacts with PbO when NaPO₃ is insufficient,and amorphous antimony glass will generate only with enough NaPO₃. Single-factor experiments were taken with NaNO₃ as an oxidizing agent under nitrogen.Reaction time,temperature,NaPO₃ and NaNO₃ amounts were considered for smelting results. Under the optimal condition,the content of lead in refined antimony is 0. 047% and 98. 90% of lead is removed.