Hydrochar-derived adsorbent for the removal of diclofenac from aqueous solution

The characteristics and diclofenac adsorption properties of a carbon adsorbent prepared from palm kernel shells were studied. The adsorbent prepared via hydrothermal carbonization followed by an activation in nitrogen flow had a mesoporous structure with homogenous pore distribution and the specific surface area of 131 m2g−1. The Raman spectra showed a formation of graphene or graphite structures in the material during activation with small number of defects based on its ID/IG ratio of about 0.5. The FTIR analysis showed both a qualitative and quantitative decrease in the functional groups of the raw material after activation. The developed adsorbent was found to be effective in the removal of diclofenac with 95% maximum removal at pH 2, adsorbent dose of 15 gL−1 and adsorbate dose of 50 mgL−1. Diclofenac adsorption followed the Langmuir isotherm model with correlation coefficient R2 > 0.98. The adsorption kinetics was explained by the second-order kinetic model with rate constant (K2) 0.869 min−1. The interaction via aromatic π–π stacking and hydrogen bonding between -OH groups of phenol and carboxylic acid groups of DCF are leading to a good adsorption efficiency despite of the low surface area of the adsorbent.