Journal of Applied Chemical Science International

This study aimed at the valorization of African star apple (Chrysophyllum albidum) seed shell into activated carbon as a sustainable, cost-effective adsorbent for Basic red 9 (BR9) dye removal from aqueous solutions. Chrysophylum albidum seed shell activated carbon (CASSAC) was synthesized after washing and drying the seed shell, it was carbonized and chemically activated with phosphoric acid. The adsorbent was characterized using BET, SEM, XRD, and pHpzc analyses, and batch adsorption experiments were conducted to evaluate the influence of pH, adsorbent dosage, initial dye concentration, contact time, and temperature of adsorption of the adsorbate onto the adsorbent. The prepared adsorbent had a surface area of 329.46 m²/g with a heterogeneous structure with irregular patterns of pore and achieved maximum BR9 dye removal efficiency of 96% at a pH of 8. Adsorption followed a pseudo-second-order kinetic model (R² = 0.983) and fitted the Freundlich isotherm (R² = 0.9513), suggesting multilayer chemisorption on a heterogeneous surface. Thermodynamic studies gave a positive ΔH (24.99 kJ/mol), and ΔS (55.89 J/mol·K) and negative Gibb’s free energy values at all studied temperature [-18.03 kJ/mol (323 K), -18.59 kJ/mol (333K), -19.15 kJ/mol (343 K), and -19.71 kJ/mol (353 K)], revealing spontaneous and endothermic adsorption process. Compared to other adsorbents, CASSAC provides a cost-effective solution, supporting the valorization of agricultural waste.