A sustainable bioadsorbent approach for tetracycline adsorption from aqueous solutions using calcined chicken bone waste: Optimization via response surface methodology

Abstract

Pharmaceutical pollutants, particularly tetracycline (TC), are of growing concern due to their persistence in the environment and toxicity, which pose significant risks to both aquatic ecosystems and human health. This novel study investigates the potential of chicken bone waste (CBW) as a bioadsorbent for TC removal from aqueous solutions, presenting a sustainable and cost-effective alternative to traditional methods. CBW was dried at 100 °C and subsequently calcined at 500 °C and 900 °C to enhance its surface properties, porosity, and crystallinity. Characterization techniques, including thermogravimetry (TGA), X-ray diffraction (XRD), Fourier-ransform infrared (FTIR) spectroscopy, and BET/BJH analysis, revealed notable enhancements in the surface area, porosity, and crystallinity of CBW. Specifically, calcination increased the specific surface area from 16.47 ² to 32.90 ² Optimization of the adsorption process was achieved using a Central Composite Design (CCD) based on Response Surface Methodology (RSM). The optimal conditions for TC removal were pH 6.34, TC concentration of 73.76 mg/L, CBW-900 dosage of 2.65 g/L, and temperature of 45 °C, resulting in a 94 % removal efficiency. Adsorption isotherms and kinetics indicated a complex physisorption mechanism, best described by the modified Langmuir-Freundlich isotherm and pseudo-first-order kinetics. DFT, BET/BJH, and FTIR analyses further suggested that TC interacts with the CBW-900 surface via donor-acceptor mechanisms, hydrogen bonding, π-π stacking, and pore filling. CBW-900 exhibited excellent recyclability, maintaining over 70% removal efficiency after ten adsorption-desorption cycles. These findings highlight CBW as an