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Cobalt and nickel have become important strategic resources because they are widely used for renewable energy technologies and rechargeable battery production. Cementation, an electrochemical deposition of noble metal ions using a less noble metal as an electron donor, is an important option to recover Co and Ni from dilute aqueous solutions of these metal ions. In this study, cementation experiments for recovering Co²⁺ and Ni²⁺ from sulfate and chloride solutions (pH = 4) were conducted at 298 K using Al powder as electron donor, and the effects of additives such as activated carbon (AC), TiO₂, and SiO₂ powders on the cementation efficiency were investigated. Without additives, cementation efficiencies of Co²⁺ and Ni²⁺ were almost zero in both sulfate and chloride solutions, mainly because of the presence of an aluminum oxide layer (Al₂O₃) on an Al surface, which inhibits electron transfer from Al to the metal ions. Addition of nonconductor (SiO₂) did not affect the cementation efficiencies of Co²⁺ and Ni²⁺ using Al as electron donor, while addition of (semi)conductors such as AC or TiO₂ enhanced the cementation efficiencies significantly. The results of surface analysis (Auger electron spectroscopy) for the cementation products when using TiO₂/Al mixture showed that Co and Ni were deposited on TiO₂ particles attached on the Al surface. This result suggests that conductors such as TiO₂ act as an electron pathway from Al to Co²⁺ and Ni²⁺, even when an Al oxide layer covered on an Al surface.