Figure 1 – Location of bentonite deposits in Boa Vista, Paraíba, Brazil. 2.1.1 Clay preparation Raw bentonite samples (Bofe and Chocolate) were crushed, ground, and sieved to ensure 100% of particles passed through a 0.053 mm mesh. They were then dispersed in deionized water and ultrasonicated in a BRANSON 450 (400 W) with a 102-C converter, ½ in. tapped Bio Horn, and ½ in. extension probe. Ultrasonication parameters: 3 min total time, 50% amplitude, pulse on = 1.0 s, pulse off = 5.0 s, no temperature control. After sonication, the suspension settled for 24 h, and the supernatant (<2 µm particles) was collected. The volume was reduced to 1.5 L by drying at 55 °C for 24 h (HAUBER DMS-G-EG oven), followed by lyophilization (LioTOP L101) [Lima ET AL., 2019]. 2.1.2 Organo Clay modification The surface modification of clays was performed using cetyltrimethylammonium bromide (CTAB – C₁₉H₄₂BrN, molar mass = 364.45 g mol⁻¹), a cationic surfactant with a C-16 hydrocarbon tail. Organoclays were prepared via cation exchange reaction, assuming a cation exchange capacity (CEC) of 100 meq/100 g for each clay type [Middea et al., 2018]. 20 g of each clay were dispersed in 500 mL deionized water (4 wt% solids) and ultrasonicated (1 cm probe, Branson Inc.) for 2 × 3 min cycles at 50% amplitude. The suspension was left to stand for 24 h at room temperature for complete hydration. Then, 7.289 g CTAB (≈ 1.0 × CEC) were slowly added to avoid micelle formation [Zhuang et al., 2016]. The mixture was transferred to an ultrasonic bath (Thornton INPEC Electronic) for 8 h to promote intercalation. After sonication, the suspension was mechanically stirred for 3 h to ensure homogeneous coverage of clay lamellae. The organoclay was washed with deionized water, centrifuged at 5,000 rpm for 15 min (Cientec CT-6000), and dried at 60 °C for 48 h. Figure 2 illustrates the organophilization process of montmorillonites. Figure 2 – Schematic representation of montmorillonite organophilization with CTAB (C₁₉H₄₂BrN), illustrating interlayer spacing expansion: d₁ < d₂ < d₃. 2.2 Biocomposites preparation 2.2.1 Casting Biofilms were prepared by casting as previously described [Lima ET AL., 2019]. PLA (8 g) was dissolved in 36 mL chloroform (Vetec) for 2 h with magnetic stirring. For composites, 0.08 g
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