Punica granatum (pomegranate) carpellary membrane and its modified form used as adsorbent for removal of cadmium (II) ions from aqueous solution

Abstract

Punica granatum carpellary membrane (PGCM) has been chemically modified with 2,4 dinitrophenylhydrazine by one step reaction process. Pristine PGCM and modified Punica granatum carpellary membrane (MPGCM) have been employed as adsorbents for removal of cadmium (II) ions from aqueous solution. Modification on the surface of PGCM was characterized by Fourier transform infrared, scanning electron microscope, energy dispersive X-ray spectroscopy and X-ray diffraction techniques. Removal of Cd (II) ions was carried out at various optimized conditions i.e. adsorbent dose (20 mg/l), pH (7), contact time (2 h), and temperature (303 K). The Langmuir isotherm model was the best fit with a high value of regression coefficient (R 2 = 0.991–0.999) compared with the Freundlich and Temkin models. Langmuir maximum adsorption capacity for cadmium was found to be 111.11 mg/g for PGCM and 142.85 mg/g for MPGCM. Kinetics of adsorption of cadmium onto MPGCM was best described by pseudo-second-order kinetics model compared with pseudo-first-order. The negative value of free energy change showed that adsorption was highly spontaneous and favorable. Also the positive value of entropy and enthalpy showed that the process of adsorption was associated with increased randomness and endothermic in nature. Mechanism of removal of cadmium ions from water by MPGCM has also been explicated.