Removal of Paracetamol, Amoxicillin and Triclosan from Synthetic Solutions and Wastewater Using Hazelnut Shell and Biochar: From Batch Adsorption to Fixed-Bed Application

This study evaluated the adsorption performance of hazelnut shells and their derived biochar for removing paracetamol (PCM), amoxicillin (AMX), and triclosan (TCS) from synthetic solutions and wastewater matrices. Batch and fixed-bed experiments were conducted using hazelnut shell/biochar mixtures (0–100%), a combination rarely examined in continuous systems. The materials were characterized by XPS, SEM-EDS, FTIR, and TPD-MS. In batch tests, hazelnut shell kinetics were empirically better described by the pseudo-second-order than the pseudo-first-order model (R2 = 0.78–0.98). Pyrolysis of the raw biomass increased the adsorption capacity by up to 113-fold. In fixed-bed experiments with synthetic solutions, the best performance was achieved with biochar at the top of the column, lower hydraulic rates, and higher packing heights. Thomas and Bohart–Adams models described most breakthrough profiles (R2 = 0.638–0.996), and fitted bed capacities increased with biochar content. Combining hazelnut shells with biochar did not improve adsorption compared with biochar alone. In wastewater, capacities decreased by up to 4.8-fold because of matrix complexity, while PCM retained higher capacities than AMX. Biochar retained 85% of its initial PCM adsorption capacity after three ethanol regeneration cycles without drying. These results identify biochar as the main adsorbent, while hazelnut shells may provide structural and operational support in fixed-bed applications.