Clofibric acid removal by ion exchange using a magnetic ion exchange resin: equilibrium, kinetics, reusability and characterisation

Abstract

In this study, a commercial magnetic ion exchange (MIEX) resin was used for the removal of clofibric acid (CA), one of the most persistent pharmaceutical active compounds (PhACs) in the environment, from aqueous solutions. As a result of batch experiments, optimum conditions were determined as pH = 4-7, equilibrium time = 240 min., and resin dosage = 26 mL/L for the removal of CA with MIEX resin. Freundlich isotherm model and pseudo-second order kinetic model showed the best fit for the sorption data with correlation coefficients higher than 0.99. Thermodynamic calculations indicated that the ion exchange process betweenMIEX resin and CA was a thermodynamically feasible and spontaneous process. Regeneration studies showed that the repeated use of MIEX resin is possible. The effect of all coexistent anions (chloride, carbonate and sulphate) was found to be close to each other for molar ratios of CA:coexisting anion = 1-3. Fourier transform infrared (FTIR) spectrum and environmental scanning electron microscopy (ESEM) images were used to examine the interactions of resins with CA and to see the changes that could occur in the resins after regeneration. The most obvious changes in MIEX resin due to CA sorption are found in the 1712 cm(-1), 1480 cm(-1), 1238 cm(-1)and 963 cm(-1)bands. This study revealed that the mechanism of removal of the CA by MIEX resin is ion exchange and is reversible.