The recyclingRecycling of under-recycled wastesUnder-recycled wastes with low economic value and limited recoveryRecovery infrastructure, such as spent lithiumLithium iron phosphate batteries, has become increasingly important for sustainable materials management. Although hydrometallurgical processes effectively extract lithium, they often generate significant wastewaterWastewater, limiting environmental and economic viability. This study highlights recent advances in closed-loop hydrometallurgyHydrometallurgy with an emphasis on wastewater reuse strategies for low-value battery materials. Lixiviant systems, comprising inorganic acids, salt-based oxidizers, alkaline solutions, and organic media, are classified by their compatibility with wastewaterWastewater regeneration. Process-level techno-economic simulations show that reusing leachates from the second cycle onward can lower operating costs and deliver net-positive profit within four to five reuse cycles, especially in regions with favorable electricity and labor conditions. However, challenges such as impurity buildup, reagent degradation, and limited multi-cycle validation persist. This review identifies current limitations and proposes future directions for advancing closed-loop hydrometallurgical recyclingRecycling in line with green chemistry and circular economyCircular economy principles.