Efficient tetracycline adsorptive removal using tricaprylmethylammonium chloride conjugated chitosan hydrogel beads: Mechanism, kinetic, isotherms and thermodynamic study

In the present study, novel ionic liquid-impregnated chitosan hydrogel beads (CS-TCMA) were fabricated via the reaction of tricaprylmethylammonium chloride (TCMA, Aliquat-336) with the chitosan's amino groups. They were used for the fast adsorption of Tetracycline (TC), as a pharmaceutical compound model, from aqueous solution. It was found that the impregnation of TCMA greatly improved the adsorption behaviour of chitosan toward TC. The optimum adsorbent was determined to be 3 mg/ L in a wide pH range of 5–11. It was a fast process, with a 90% removal efficiency in <45 min. The adsorption kinetic of TC on the CS-TCMA was well described by the pseudo-first-order model and intra-particle diffusion model. The adsorption also obeyed the Langmuir adsorption isotherm model and the maximum adsorption capacity obtained was 22.42 mg/g at 45 °C. The thermodynamic study also revealed the endothermic nature of the process. The adsorption mechanism was also studied.