Treatment of Organics in Wastewater Derived from Submerged Comminution of Lithium-Ion Batteries

Submerged comminution of lithium-ion batteries (LIB) has been developed as a pretreatment in the recycling process. Wastewater treatment is necessary in this process because electrolyte used in LIBs is mixed into the water bath. Especially, carbonate esters which are used as the typical solvents in LIBs must be removed to decrease the chemical oxygen demand (COD). In this paper, the removal of organics derived from the solvents was discussed for the development of the submerged comminution process in lime water. It is generally known that in alkaline solutions such as lime water, carbonate esters are readily hydrolyzed to alcohols. Therefore, the hydrolysis behaviors of the carbonate esters used as the solvents were investigated in detail. As a result, the carbonate esters with high solubilities were almost completely hydrolyzed, though one that hardly dissolves in water, such as diethyl carbonate, was not hydrolyzed enough. In addition to the investigation of the hydrolysis, the removal of the alcohols generated in the hydrolysis is important to decrease the COD of the wastewater. Ozonation was employed as a removal method of the alcohols in this work. It was confirmed that the alcohols formed in the hydrolysis of the carbonate esters could be removed in the ozonation.