UTILIZATION OF CHEMICALLY ACTIVATED WATERMELON PEELS FOR THE ADSORPTIVE DECONTAMINATION OF WATER CONTAINING COPPER AND CADMIUM

In this study, watermelon peels an abundant agro-industrial byproduct, were transformed into a cost-effective activated carbon through chemical impregnation with 1 M H₂SO₄ followed by thermal activation at 300 °C. The adsorbent exhibits bulk density 0.36 g/cm³, pH 6.72, moisture 1.82%, ash 18.7%, and electrical conductivity 32.4 µS/cm. Batch experiments (20–40 min, 50–140 mg/L, 1–3 g adsorbent) demonstrate maximum removal efficiencies of 99.98% for Cu²⁺ and 99.90% for Cd²⁺. The equilibrium data were well described by the Langmuir isotherm (R² > 0.99), with calculated monolayer adsorption capacities of 151.5 mg/g for Cu²⁺ and 115.0 mg/g for Cd²⁺. The kinetic profiles conform to the pseudo-second-order model (R² > 0.98), suggesting that chemisorption governs the rate-limiting step. Regeneration with 0.1 M HNO₃ retains 94.1% capacity after three cycles. These results position sulphuric-acid activated watermelon peel as a competitive, sustainable sorbent for dual heavy-metal remediation in wastewater.