MINERALOGICAL INVESTIGATIONS OF CATHODIC REGIONS OF DISPOSABLE SPENT ALKALINE BATTERIES

Spent alkaline batteries are a global waste stream with many geologic connections. Few details are known regarding the nature of materials in spent alkaline batteries and this is a critical gap in our knowledge for understanding the role these materials play in landfill leachate and for improving recycling methods. Several Duracell type D cell batteries collected from Virginia, Ohio and tourist locations in the Yucatan were investigated to assess the nature of mineralogy of the cathodic portion of these batteries. Cathodic material in approximately 90% of batteries is poorly crystalline Mn-oxides and cathodic material in approximately 10% of spent batteries is dominantly hetaerolite, a zinc manganese spinel. Transmission electron microscopy (TEM) investigation indicates that poorly crystalline Mn-oxide particles are anhedral and irregular in shape and the diameters of particles vary between 50 nanometers and 3 micrometers, Chemical composition varies for poorly crystalline Mn-oxide particles with concentrations being SiO₂ (0.00-1.52 wt %), TiO₂ (0.49-4.58 wt%), MnO (65.85-92.06 wt%), ZnO (1.00-7.53 wt%), K₂O (4.97-20.48 wt%) and SO₃ (0.43-2.21 wt%). Elemental mapping of poorly crystalline oxides indicates that spatial distribution of elements is reasonably uniform. Common, but minor amounts of zinc and titanium crystals occur. Zinc crystals are elongated and vary from a maximum of approximately 0.8 micrometers long x 0.15 micrometers, to 100 nanometers long x 20 nanometers wide. Titanium metal particles are rounded and are 100 to 200 nanometers in diameter. Hetaerolite crystals are subhedral to euhedral octahedra, commonly 50 to 200 nm in diameter and are uniform in chemical composition. Textures consistent with either gas bubble formation or bacterial-related mineralization are common in hetaerolite rich material.

Results of this investigation provide constraints for understanding interactions of spent alkaline batteries with landfill leachate and provide insight into potential recycling methods using industrial mineral approaches.