Adsorptive removal of fipronil from its aqueous solution by modified zeolite HZSM-5: Equilibrium, kinetic and thermodynamic study

Fipronil (FIP), an endocrine disrupter pesticide is a hazardous broad spectrum insecticide which needs to eliminate from wastewater effluent. The present investigation explores the performance of cerium-modified H-ZSM-5 zeolite as adsorbent for removal of FIP from its aqueous solution. The H-ZSM-5 zeolite was modified with ceric ammonium nitrate salt by a simple refluxing method. The zeolite was modified with 5%, 10%, 15%, 20%, 25% and 30% (wt%) of cerium nitrate solution are designated as Ce(5)ZSM-5, Ce(10)ZSM-5, Ce(15)ZSM-5, Ce(20)ZSM-5, Ce(25)ZSM-5 and Ce(30)ZSM-5 respectively. The modified zeolite was characterized with XRD, N-2-adsorption, HRTEM, FESEM, EDS and XPS techniques. The metal-modified zeolite Ce(25)ZSM-5 was proved to be a capable adsorbent for efficient removal of FIP from aqueous solution (>90% HP removal). The batch adsorption experiments were carried out to study various parameters like pH (2-10), temperature (25-40 degrees C), adsorbent amount (0.5-4 g/L), stirring speed (50-300 rpm) and initial adsorbate concentration (400-900 mg/L) for elimination of FIP by Ce(25)ZSM-5. The maximum adsorption capacity of 598.80 mg/g was found for Ce(25)ZSM-5 sample in 120 min. The Langmuir isotherm model fitted well to the experimental data whereas the adsorption process obeyed pseudo-second order kinetics. Thermodynamic parameters (Delta G degrees), (Delta H degrees) and (Delta S degrees) predicted the exothermic nature, randomness, spontaneity and feasibility of the adsorption process. (C) 2019 Elsevier B.V. All rights reserved.