Silver nano-prisms (Ag NPrs) exhibit high sensitivity to specific ions in solution, which makes them effective colorimetric sensors for ion detection. However, the conventional synthesis of Ag NPrs in a nitrate system leads to the generation of nitrate wastewater. Additionally, the presence of nitrate ions can destabilize triangular Ag NPrs. To avoid the drawbacks of the nitrate system, this study successfully synthesized Ag NPrs in an acetate system using the previously developed electrosynthesis-chemical reduction (ES-CR) process. This approach not only completely eliminates the generation of nitrate pollution but also yields Ag NPrs with a higher proportion of triangular particles. This, in turn, enhances the sensitivity of Ag NPrs for colorimetric detection. For the detection of Cl− and Hg2+, the linear detection limits were as low as 5 μM and 3 nM, respectively. Therefore, the synthesis of Ag NPrs in the acetate system offers a promising alternative to the conventional nitrate system, providing both environmental and performance benefits.