Application of pyrrolidinomethylcalix[4]arene coated silica adsorbent for the removal of Chicago sky blue 6B dye from water samples: Equilibrium and computational modelling studies

ABSTRACT In this study, silica surface has been coated using pyrrolidinomethylcalix[4]arene through the chemical modification of silanol groups. The pyrrolidinomethylcalix[4]arene-coated silica (PCS) adsorbent was characterized using the Fourier transform infrared and scanning electron microscopic technique. The adsorptive removal efficiency of PCS adsorbent was checked through batch studies with various effective parameters such adsorbent dose, pH, and temperature. During experiments, it has been observed that maximum adsorption was achieved in acidic to neutral pH and 25 mg.L−1 of PCS dose, while the kinetic models demonstrates that the pseudo 2nd order equation was the best fit (R2 0.99). The thermodynamic experiments described that the reaction is exothermic and spontaneous. Furthermore, equilibrium models were applied on experimental data and it has been noticed that the equilibrium data was best-fitted with Langmuir isotherm model (R2 0.99). The DFT analysis of dye molecule is helpful to examine the chemical interaction sites of absorbent and adsorbent using B3LYP/LANL2DZ/6-311++G (d,p) level using G09W software. Graphical Abstract