Process for regenerating sodium sulphide from the sodium sulphate which forms in treating lead paste from exhausted batteries

A process for treating lead paste from exhausted batteries, comprising the steps of:

• (a) reacting elemental sulfur with an aqueous lime suspension in accordance with the reaction:
• 3Ca(OH).sub.2 +4S.degree..fwdarw.2CaS+CaS.sub.2 O.sub.3 +3H.sub.2 O(1)
• to form calcium sulphide and calcium thiosulphate;
• (b) reacting the calcium salts formed in step (a) with sodium sulphate in accordance with the reaction:
• 2CaS+CaS.sub.2 O.sub.3 +3Na.sub.2 SO.sub.4 .fwdarw.2Na.sub.2 S.sub.2 +Na.sub.2 S.sub.2 O.sub.3 +3CaSO.sub.4 ( 2)
• (c) separating the calcium sulphate formed in step (b), by filtration, to obtain a solution containing sodium sulphide and thiosulphate which is suitable for treating said lead paste;
• and
• (d) suspending said lead paste in water, and reacting the sodium sulphide and thiosulphate solution obtained in step (b) with said lead paste suspended in water, to produce PbS and Na.sub.2 SO.sub.4, in accordance with the reactions
• PbSO.sub.4 +Na.sub.2 S.sub.2 O.sub.3 +H.sub.2 O.fwdarw.PbS+Na.sub.2 SO.sub.4 +2H.sub.2 SO.sub.4 ( 3)
• PbO+Na.sub.2 S.sub.2 O.sub.3 .fwdarw.PbS+Na.sub.2 SO.sub.4 ( 4)
• 4PbO.sub.2 +5Na.sub.2 S.sub.2 O.sub.3 +H.sub.2 O.fwdarw.4PbS+5Na.sub.2 SO.sub.4 +H.sub.2 SO.sub.4 ( 5).