Abstract: Germanium (Ge) is critical for infrared optics, photovoltaic cells and optical fiber communication, but its low crustal abundance demands efficient enrichment methods. The tannic acid (TA) precipitation method is widely used; however, TA tends to self-associate in solution, limiting the number of active sites available for Ge coordination and causing high TA consumption. In this work, sodium bisulfite (NaHSO₃) was used to modify TA via sulfonation to suppress self-association and enhance Ge precipitation. The sulfonated TA (SMTA) was characterized by SEM–EDS, FTIR, DLS, XPS and sulfur quantification. A physical mixture control experiment confirmed that –SO3Na groups are covalently grafted onto the TA backbone. Sulfonation reduced the Z‑average particle size of TA by 23.6% and lowered the polydispersity index, indicating suppressed self‑association. Under optimized conditions (60 °C, 30 min, pH 2.5, SMTA/Ge mass ratio=18), SMTA achieved a Ge precipitation efficiency of 99.81% in pure solution (residual Ge 0.38 mg/L) and 92.39% in real smelter leachate, outperforming unmodified TA. Co‑precipitation of Zn2+ and Fe2+ remained below 0.3% and 0.2%, respectively. Kinetic and isotherm studies suggest a chemisorption‑dominated monolayer process, with a maximum adsorption capacity of 55.52 mg/g at 333 K. These results demonstrate that sulfonation of TA with NaHSO3 is an effective strategy for germanium enrichment by suppressing TA self‑association and increasing the availability of active sites.