Efficiency of Coffee Ground Biochar in the Adsorption of Diclofenac

The increasing presence of pharmaceutical compounds in aquatic environments triggers significant environmental challenges. Traditional water treatment systems struggle in fully removing such pollutants, leading to their environmental release and long-term impacts on aquatic ecosystems and public health. This study investigates the effectiveness of biochar derived from coffee grounds (CGB) to remove diclofenac from aqueous solutions. The capacity of diclofenac retention of this biochar was evaluated using a dynamic approach, simulating a 2-D barrier with three-layer columns under controlled conditions. The hydrodynamic properties of these biochar columns were characterized using as a non-reactive tracer. The retention of diclofenac was then characterized along with its mobility at a realistic water flow. The results showed a good reproducibility of the experiments and a low to moderate retention of diclofenac by the tested CGB, with distribution coefficients ranging between 8.30 and 12.97 cm3 g-1. Without process optimization, removal efficiency was calculated to be 40% (± 14%), with a short contact time of around 7h. The breakthrough curves of both the tracer and diclofenac were fitted with the convection-dispersion equation (CDE model) and with its CDE-2SS and CDE-MIM versions. Results were well represented with the convection dispersion approach, giving consistent reactive transport parameters, suggesting that CGB effectively adsorbed diclofenac, with retardation factors eight times larger than on KBr. Altogether, our results suggest that, although not optimized, CGB offers a promising approach for removing pharmaceuticals such as diclofenac from water. Further investigations are needed to improve both biochar reactivity and transfer conditions in columns.