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

Abstract

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 Ce5ZSM-5, Ce10ZSM-5, Ce15ZSM-5, Ce20ZSM-5, Ce25ZSM-5 and Ce30ZSM-5 respectively. The modified zeolite was characterized with XRD, N2-adsorption, HRTEM, FESEM, EDS and XPS techniques. The metal-modified zeolite Ce25ZSM-5 was proved to be a capable adsorbent for efficient removal of FIP from aqueous solution (>90% FIP removal). The batch adsorption experiments were carried out to study various parameters like pH (2−10), temperature (25–40 °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 Ce25ZSM-5. The maximum adsorption capacity of 598.80 mg/g was found for Ce25ZSM-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 (ΔG°), (ΔH°) and (ΔS°) predicted the exothermic nature, randomness, spontaneity and feasibility of the adsorption process.