Monitoring and optimization of diclofenac removal by adsorption technique using in-line potentiometric analyzer

Abstract

Diclofenac (DICLO) is one of the most prescribed non-steroidal anti-inflammatory drugs worldwide. The presence of DICLO residues in aquatic environment either from industrial or hospital wastewater has harmful effects on many organisms. In this contribution, the adsorption of DICLO on granulated active carbon and mesoporous silica nanoparticles was optimized in order to remove those residues from water. The tracking of DICLO was done using in-line potentiometric ion-selective electrodes (ISE) through the whole experiments. The constructed electrode allows tracking of DICLO residues in real time. A central composite design was applied, inspecting the pH, initial concentration, adsorbent loading concentration and adsorbent type effects on the adsorption process, the results showed that the pH effect was most significant; pH 5 gave best results. The adsorption kinetics of these adsorbents have been investigated and the results indicated that the adsorption process followed the pseudo-second-order kinetic model. The adsorption isotherm data were analyzed by both Langmuir and Freundlich models and later provides better fit of the experimental data. The removal efficiency was about ~89% upon applying the optimum set of experimental conditions in time < 60 min. In-line monitoring is considered a green protocol, that should be carried out also at the pharmaceutical industry scale due to the high selectivity, lack of harmful waste generation and minimal solvent use.