Foam-Porous Alginate-Bentonite Beads Coated with Gamma-Irradiated Chitosan for Selective Chlorophyll Removal with Preservation of Plant Bioactives

Excess chlorophyll in plant ethanol extracts can compromise analytical accuracy and restrict industrial applications in food, herbal, and cosmetic formulations. This study developed foam-porous alginate-bentonite beads coated with gamma-irradiated chitosan (FP-Alg/Bent-gCS) as a selective, reusable biocomposite adsorbent for chlorophyll removal while preserving plant bioactives. The beads were created using CO₂ foaming, cross-linked with CaCl₂, reinforced with bentonite, and coated with gamma-irradiated chitosan (0.5%, pH 5.5). The resulting beads demonstrated a high surface area (75.6 m²·g^-1) and pore volume (0.096 cm³·g^-1), as confirmed by BET analysis. FTIR spectra indicated the presence of hydrogen bonding and electrostatic interactions among hydroxyl, carboxyl, and amino groups. Additionally, XRD and HRTEM confirmed the formation of a semicrystalline foam-like structure. When applied to kale extract in 50% ethanol (25 mL), the beads achieved an impressive 88.4% total chlorophyll removal in just 30 min at a dosage of 5 g. This process followed pseudo-second-order kinetics, suggesting chemisorption via electrostatic attraction between -NH₃ ⁺ groups and chlorophyll molecules. Colorimetric assays for total phenolic content (TPC) and total flavonoid content (TFC) revealed no significant reduction in polyphenols or flavonoids, confirming that the removal of pigments was selective and did not lead to loss of bioactives. The beads maintained over 85% removal efficiency through five reuse cycles, with only minor surface deformation observed after the sixth cycle, consistent with XRD and EDS analyses that showed structural stability. In conclusion, the FP-Alg/Bent-gCS beads represent a low-cost, environmentally friendly, and sustainable method for selectively removing chlorophyll while preserving bioactives. They present a promising material for green extraction and purification processes in the food, herbal, and cosmetic industries.