Biosorption of Tetracycline and Cephalexin onto Surfactant?Modified Waste Biomass Using Response Surface Methodology and Ecotoxicological Assessment: Phytotoxicity and Biotoxicity Studies

Waste hazelnut shell was modified using hexadecyltrimethylammonium (HDTMA) to remove tetracycline and cephalexin from water and minimize the residual antimicrobial activity of tetracycline and cephalexin. Response surface methodology (RSM) was used to determine the effect of solution pH (3.0–6.0–9.0), initial pollutant concentration (5–52.5–100 mg/L), contact time (5–92.5–180 min), and temperature (20–35–50°C) on the removal efficiency of tetracycline and cephalexin. Comparison between model results and experimental data gave a high coefficient of determination (R2 TC 0.94, R2 CPX 0.99). The predicted removal efficiency of tetracycline and cephalexin by the RSM design was 37.34% and 83.07%, respectively. Langmuir, Freundlich, D-R, and Temkin isotherm were applied to equilibrium data. The Qo values for tetracycline and cephalexin were 6.97 and 47.77, respectively. Acute tests were performed before and after biosorption using Lepidium sativum and Daphnia magna. IC50, LC50, and toxic unit were determined. IC50 values for root and shoot for tetracycline and cephalexin were 50 mg/L, 50 mg/L, 140 mg/L, and 270 mg/L, respectively. LC50 values of tetracycline and cephalexin were 58 mg/L and 37 mg/L for 48 h, respectively. There was a large decrease in mortality (%) after biosorption. This biosorbent was effective in the biosorption of tetracycline and cephalexin and in reducing toxicity.