<p>To address the prevalent limitations of narrow applicable pH ranges and poor structural stability in existing Cd²⁺ adsorbents, this study innovatively introduces the rare earth element Lanthanum (La)—characterized by high adsorption capacity and broad pH adaptability—to synthesize two Layered Double Hydroxides (MgLa-LDH and CaLa-LDH). The study investigates the influence of different divalent cations on Cd²⁺ adsorption performance. Within a broad pH range of 4–7 and at a dosage of 0.5&#xa0;g/L, both materials exhibited efficient and stable Cd²⁺ removal performance. Notably, CaLa-LDH achieved a maximum removal efficiency of 99.8% ± 0.089%, attributed to the superior ionic radius matching between Ca²⁺ and Cd²⁺. The adsorption behavior follows a non-monolayer model dominated by chemisorption. Mechanism analysis indicates that both adsorbents sequester Cd²⁺ primarily through ion exchange and precipitation; however, CaLa-LDH exhibits an additional, unique complexation mechanism. By rationally regulating the metal composition of the LDH layers, this study significantly broadens the operational pH window and enhances adsorption performance from the perspective of crystallochemical matching. These findings provide a novel design strategy and theoretical basis for developing efficient, stable La-based adsorbents suitable for treating complex, real-world cadmium-containing wastewater.</p> Graphical Abstract <p></p>