This study explores the removal of the emerging contaminant diclofenac using pristine biochar and iron-impregnated biochar derived from anoxic sewage sludge. A biochar ensemble was prepared at varying pyrolysis temperatures (350 °C to 950 °C) and residence times (30 to 240 min). The iron-modified material was synthesized by incorporating FeCl3 with the precursor at 950 °C for 30 min. A comprehensive characterization based on the morphology, crystallinity, and functional groups confirmed the structural and chemical modifications in the pristine and modified biochar of interest. Adsorption experiments demonstrated that iron-modified biochar exhibited superior adsorption capacity for diclofenac (18.958±0.417 mg/g) compared to pristine biochar (0.814±0.001 mg/g), attributable to its larger surface area and more active sites. The adsorption mechanisms were identified as a combination of electrostatic interactions, hydrogen bonding, and complexation, with significant Fe3+ to Fe2+ reduction indicating electron transfer processes. Adsorption kinetics followed the Elovich model, and equilibrium studies fitted best to the Redlich-Peterson model for the iron-amended biochar. The study also assessed the reusability of the adsorbents, with pristine and iron-impregnated biochar maintaining around 70 % removal efficiency up to 3 and 5 cycles, respectively. Consequently, both the biochar serve as potentially efficient adsorbents for diclofenac removal from aqueous solutions.