Determination of adsorption isotherms of aniline and 4-chloroaniline on halloysite adsorbent by inverse liquid chromatography

• FT-IR, XRF, and XRD methods were used to investigate the composition of Hal.
• The high levels of iron and titanium oxide are observed for the Hal samples.
• The FTIR spectra indicate incorporation of aniline and 4-chloroaniline to Hal samples.
• The division peak method was adapted in inverse liquid chromatography.
• This method was used for aniline adsorption measurements on halloysite.

Infrared spectroscopy (ATR FT-IR), X-ray fluorescence (WDXRF), and X-ray powder diffraction (XRPD) methods were used to investigate the structure and composition of halloysite mineral. On the basis of the results, we found that the chemical composition of Hal samples is typical as regards clay minerals with the exception of the high levels of iron and titanium oxides. The FTIR spectra of halloysite samples, before and after modifying, with aniline and 4-chloroaniline indicate successive incorporation of these compounds to the halloysite sample. Inverse chromatography is a quick and accurate method to determine adsorption equilibrium constants. The division peak method used previously to inverse gas chromatography was adapted in inverse liquid chromatography. Inverse liquid chromatography was used for aniline and 4-chloroaniline adsorption measurements on halloysite, which was an applying method of division peak. Both adsorption isotherms and enthalpy were determined. Physical significance of adsorption enthalpy was checked by the Boudart's criterion of entropy. In this paper proved that the division peak method of inverse liquid chromatography is useful because adsorption equilibrium constant can be determined with a single adsorbate dosage.