Multi-mechanistic modeling and experimental validation for pharmaceutical removal through novel clew-shaped ZnO: diclofenac removal from aqueous environment

A modified ZnO adsorbent, named clew-shaped ZnO (CSZN), was introduced as a highly effective material for removing diclofenac (DCF). Compared to smooth ZnO (SZN), CSZN showed a more than 250% increase in adsorption capacity under the same experimental conditions. This improvement was assigned to more active adsorption sites and a larger effective surface area. The study investigated various operating parameters and their effects on DCF adsorption onto SZN and CSZN. To optimize the adsorption model, both kinetic and isotherm models were evaluated. Two multi-mechanism isotherm models were employed to improve the predictive accuracy of the adsorption process. The nonlinear multi-mechanism model showed that the Lan-Lan model provided the best predictive capability, having a significantly lower Sum of Squares Error (SSE) of 1735, compared to 5505 for a single isotherm model. This finding emphasized the better accuracy of the multi-mechanistic approach, particularly the Lan-Lan model, in predicting DCF adsorption behavior onto CSZN. Overall, the study confirms that CSZN can be considered as a highly efficient adsorbent for DCF removal from wastewater as well as the power of the multi-mechanistic approach for offering better models.