Equilibrium, thermodynamic, and kinetic study of Co-ZIF-67 for adsorptive removal of fipronil from aqueous system

Abstract The BET specific area (S BET ), total pore volume and micropore volume were calculated to be 1319.36 m 2 g −1 , 0.686 cm 3 g −1 , and 0.636 cm 3 g −1 , respectively. ZIF-67 shows a type I isotherm for N 2 adsorption-desorption. The ZIF-67 have particle size 614.9 nm with zeta potential equal to 5.52 mV (neutral surface) at pH 7, which indicates possibility of hydrophobic and π-π interaction between fipronil and ZIF-67. Fipronil adsorption with ZIF-67 was found to be monolayer and favourable, as evidenced by the Langmuir adsorption isotherm and endothermic and chemisorption process, as indicated by Pseudo second order (Ps.Sec.Ord.) kinetic model. The endothermic temper of adsorption was also concluded from the value of ∆H o and ∆S i.e. 17.19 kJ mol −1 and 0.063 kJ mol −1 K −1 , respectively. The ∆G o for adsorption of fipronil were found to be −1.293, −2.749, and −3.818 kJ mol −1 for 303, 318, and 333 K, respectively. Negative value of ∆G o shows feasibility and spontaneous nature of adsorption process. Under optimised conditions, ZIF-67 achieved 68.2% maximum removal of fipronil (20 mg L −1 ). Results obtained from the reusability studies suggested that ZIF-67 can be recycled by washing it five times with DMF and heating at 50 °C.