A new desulfation process of spent lead paste via cyclic utilization of CO2–NH3·H2O

The costly desulfation processes have severely restricted the development and industrial application of hydrometallurgy lead recovery process. In this work, new high efficiency and value-added desulfation method of the spent lead paste is proposed. The new route consists of three sections as follows: (1) Desulfation of spent lead paste by ammonium carbonate; (2) Regeneration of ammonium carbonate through calcium hydroxide sulfuration and ammonia carbonation ; (3) Lead carbonate decomposition to obtain the product lead oxide and CO 2 to construct a high efficiency and value-added desulfation method of the spent lead paste. The regenerated ammonium carbonate filtrate is re-used in the next batch desulfation process in order to realize a green and sustainable process. For the tests of 5 cycles, the optimal average conversion rate of calcium hydroxide sulfation is up to 88.2% and the desulfation rate of lead paste is above 98.7% as well ammonium ions concentration maintains stable all the way. This work put forwards calcium hydroxide as an inexpensive desulfurizer via “ex-situ nucleation process (ESNP)” and “CO 2 –NH 3 ·H 2 O” strategy, providing a cleaner and more economical routes to recover PbO from lead-acid batteries. The cost calculation and technical analysis indicate this new strategy is economical, efficient, and high value-added. • Hydrated lime is proposed as the value-added desulfurizer for spent lead paste. • A new ex-situ nucleation process realizes the high utilization rate of hydrated lime. • The desulfation rate of spent lead paste is up to 98.7%. • The optimal average conversion rate of hydrated lime sulfuration is 88.2%.