414 induced a transition to a Face-Face (F-F) orientation, where Mnt particles overlapped face-toface, forming denser aggregates. Additionally, Mnt aggregation was observed attached to CaCO3 particles. Figure 4 – FE-SEM images of (a) pristine Mnt and (b)Mnt+CaCO3 3.2 Removal performance of Mnt with CaCO₃ In the batch experiments, distinct removal behaviors were observed for arsenite [As(III)] and arsenate [As(V)]. Pristine Mnt showed limited sorption capacities for both species, while the addition of CaCO3 significantly enhanced the removal performance for As(V). The removal efficiency of As(V) increased proportionally with the CaCO₃ dosage. In contrast, the enhancement of As(III) removal was limited under the same conditions, indicating no significant correlation with increased CaCO₃ dosage. Investigation of arsenic removal efficiency as a function of Mnt and CaCO₃ dosages confirmed that a 1 g/L Mnt suspension alone had limited capacity; however, the coexistence of CaCO₃ resulted in a remarkable performance enhancement. Specifically, the combination of 1 g/L Mnt and 100 g/L CaCO₃ achieved a substantial reduction in residual arsenic concentration. These results indicate that effective arsenic treatment is feasible with low Mnt dosages in the presence of sufficient CaCO₃, suggesting a significant synergistic effect between the two minerals. Table 1 – Amount of adsorbed As and Ca concentration in Mnt-CaCO3 systems (a) pristine Mnt (b) Mnt (1 g/L) + CaCO3 (100 g/L) The dosed CaCO3 (g/L) Mnt dosage (g/L) Adsorbed As (mg/g-Mnt) Ca dissolution (mg/L) for As(Ⅲ) for As(V) for As(Ⅲ) for As(V) 0 1.0 0.003 0.008 - - 5.0 0.000 0.004 - - 0.5 1.0 0.019 0.048 85.0 90.6 5.0 0.007 0.025 54.2 62.9 0.1 µm 1 µm
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