Efficient Desulfurizer Recycling during Spent Lead-Acid Batteries Paste Disposal by Zero-Carbon Precursor Hypothermic Smelting.

Recycling of spent lead-acid batteries (LABs) is extremely urgent in view of environmental protection and resources reuse. The current challenge is to reduce high consumption of chemical reagents. Herein, a closed-loop spent LABs paste (SLBP) recovery strategy is demonstrated through Na2MoO4 consumption-regeneration-reuse. Experimental and DFT calculations verify that MoO4 2- competes Pb/Ca ions and weakens the metal-oxygen bond of PbSO4/CaSO4.2H2O in SLBP, facilitating PbMoO4/CaMoO4 formation and 99.13 wt% of SO4 2- elimination. Pb of 99.97 wt% is obtained as zero-carbon precursors (PbO2 and PbMoO4) by green leaching coupled with re-crystallization. The regeneration of Na2MoO4 is realized at 600 ℃ using LABs polypropylene shells and NaOH as reagents. Compared with the traditional smelting technologies, the temperature is reduced from ＞1000 to 600 °C. The extraction of Na2MoO4 require only water, and satisfactory re-used desulfurization efficiency (98.67 wt%) is achieved. For the residual Na2MoO4 after first SLBP desulfurization, the desulfurization efficiency remains above 97.36 wt% after adding fresh reagents for two running cycles. The new principle enables the reuse of 99.83 wt% of Na2MoO4 and the recycling of 95.27 wt% of Pb without generating wastewater and slags. The techno-economic analysis indicates this strategy is efficient, economical, and environmentally-friendly.