Sustainable Adsorbent Development: Tartrazine Dye Uptake by Banana-Peel-Activated Carbon

The excessive use of dyes by Brazilian industries has increased the generation of dye-containing effluents, highlighting the need for efficient treatment technologies. This study evaluated the removal of the food dye tartrazine using activated carbon produced from Cavendish banana peel chemically activated with H3PO4. The precursor and activated carbon were characterized by proximate analysis, pHPZC, N2 adsorption/desorption, SEM, EDS, FTIR, XPS, XRD, Raman spectroscopy, and TGA. The influence of pH was investigated before kinetic, equilibrium, and thermodynamic evaluations. The precursor exhibited high volatile-matter content, favoring mesoporous carbon production. The activated carbon showed a pHPZC of 5.89, a specific surface area of 1052 m2 g−1, a mesoporous structure, and an average pore diameter of 4.29 nm. Surface analyses confirmed tartrazine adsorption after treatment. FTIR, EDS, and XPS verified dye retention, whereas XRD and Raman spectroscopy indicated an amorphous structure. TGA demonstrated improved thermal stability after phosphoric acid activation. Maximum adsorption occurred at pH 2, reaching 159.7 mg g−1. Modeling indicated simultaneous physisorption and chemisorption in a spontaneous (ΔG° = −15.42 kJ mol−1) and endothermic (ΔH° = 10.06 kJ mol−1) process. The maximum adsorption capacity reached 165.28 mg g−1 at 30 °C, evidencing banana peel’s high tartrazine adsorption efficiency and its organic pollutant removal potential.