Adsorption isotherms for tetracycline removal from water using carbon-mineral composites determined by inverse liquid chromatography

This work describes the use of inverse liquid chromatography (ILC) to assess the adsorption process for tetracycline removal from water using carbon-mineral composites. Adsorption parameters, including adsorption constants and adsorbent maximum capacities of the adsorption determination were determined using the Breakthrough Curves Inverse Liquid Chromatography (BC ILC), while the adsorption isotherms were using the Peak Division method (PD ILC). The tetracycline adsorption process was conducted on three different carbon-mineral composites, in which raw halloysite (HS), halloysite nanotubes (HNT) and kaolinite (KT) served as mineral carriers, while fruit pomace was used as the carbon precursor. The composites differed in structure, which influenced their adsorption properties. Our results showed that the C-HNT material had the highest specific surface area (77.71 m 2 /g). However, as confirmed by BC ILC method results, the highest amount of tetracycline adsorbed (19.1 mg g -1 ) and the highest adsorption equilibrium constant (0.027) were observed for raw halloysite (HS). The adsorption equilibrium equations indicated that the n-center adsorption model without dissociation model provided the best fit for tetracycline adsorption on the three studied carbon-mineral composites, suggesting a similar adsorption mechanism for the tested materials. We showed that the ILC method enables a quantitative descriptions of elution profiles under various conditions, improving the understanding of adsorption process in dynamic systems. The synthesized carbon-mineral adsorbent, derived from apple pomace and halloysite and kaolinite was used for adsorption of tetracycline from water. The Breakthrough Curves Inverse Liquid Chromatography (BC ILC) method and Peak Division method (PD ILC) is useful for adsorption investigation.