Waste derived starch and activated carbon biocomposite hydrogel as a green and reusable adsorbent for tetracycline removal

Tetracycline is an emerging environmental threat, as its presence in water may contribute to antibiotic resistance in microorganisms. In this study, starch and activated carbon were extracted from potato peels and subsequently modified via free-radical polymerization using acrylic acid to develop a novel, green composite hydrogel for efficient tetracycline removal. Various adsorption parameters were optimized using the Taguchi method, including initial contaminant concentration, pH, adsorbent dosage, and contact time. The optimal conditions for tetracycline adsorption by the starch-acrylic acid/activated carbon biocomposite hydrogel identified were an initial concentration of 10 mg/L, a pH of 7, an adsorbent dosage of 2.5 g/L, and a contact time of 80 min. The incorporation of activated carbon significantly enhanced the adsorption capacity from 29.58 mg/g (for the starch-acrylic acid hydrogel) to 52.63 mg/g (for the starch-acrylic acid/activated carbon biocomposite hydrogel). Adsorption equilibrium was best described by the Temkin isotherm model, while kinetic studies confirmed that the process follows the pseudo-second-order model for starch-acrylic acid/activated carbon biocomposite hydrogel. Additionally, thermodynamic evaluations indicated that the process was both spontaneous and exothermic. Despite a moderate loss in efficiency over 8 reuse cycles from 99.99% to 58.06%, the developed starch-acrylic acid/activated carbon biocomposite hydrogel demonstrates a highly favorable adsorption capacity compared to previously reported green adsorbents, establishing it as a promising candidate for sustainable tetracycline removal.