This study systematically elucidates the distinct responses of two representative anionic collectors—sodium oleate (NaOl) and cetyl phosphate (CP)—to variations in pH and dissolved Ca²⁺/Mg²⁺ concentrations. Dynamic foam analysis combined with surface tension measurements demonstrated that both collectors exhibited optimal yet fundamentally different pH-dependent foaming behaviors. CP generated highly stable foam under near-neutral conditions (pH ≈ 8), whereas severe foam destabilization occurred above pH 10 owing to enhanced electrostatic repulsion between fully ionized phosphate headgroups. In contrast, NaOl maintained excellent foam stability under alkaline conditions but lost foaming ability below pH 7.7 due to protonation of the carboxylate groups. The presence of divalent cations exerted pronounced detrimental effects, with significant ion-specific and collector-dependent characteristics. CP foamability was almost completely suppressed by trace Ca²⁺ concentrations as low as 1 ppm, whereas NaOl maintains favourable foaming performance at Ca²⁺ levels up to 10 ppm, which is likely associated with electrical double-layer compression. Low Mg²⁺ concentrations (≤5 ppm) slightly enhanced CP foam stability, whereas higher concentrations (≥10 ppm) significantly deteriorated the foam properties of both collectors. Compared with Mg²⁺, Ca²⁺ exhibited a substantially stronger destabilizing effect, this difference can be tentatively attributed to the relatively lower hydration energy of Ca²⁺ as well as its comparatively higher tendency to form complexes with anionic surfactant headgroups. These findings provide important mechanistic insights into how solution chemistry regulates collector foam behavior in magnesite flotation systems. Future investigations combining dynamic foam analysis with batch flotation tests are required to quantitatively establish the relationship between bubble properties and flotation performance.