Hydrochar-derived adsorbent for the removal of diclofenac from aqueous solution
Velma Beri Kimbi Yaah, Mohamed Zbair, Sérgio Botelho de Oliveira, Satu Ojala
Abstract
Abstract 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 m 2 g −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 I D /I G 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 R 2 > 0.98. The adsorption kinetics was explained by the second-order kinetic model with rate constant (K 2 ) 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. Graphic abstract