Column, kinetic and isotherm studies of PAH (phenanthrene) and dye (acid red) on kaolin modified with 1-hexyl, 3-decahexyl imidazolium ionic liquid

• Synthesis and characterization of 1-hexyl, 3-decahexyl imidazolium ionic liquid.
• Ionic liquid modified kaolin efficient for removal of phenanthrene and acid red dye.
• An adsorption capacity of 842.7 mg g−1 was obtained for acid red dye.
• An adsorption capacity of 188.9 mg g−1 was obtained for phenanthrene.

Adsorption studies were carried out to determine the efficiency of kaolin modified with a novel long chain ionic liquid (IL) 1-hexyl, 3-decahexyl imidazolium. Synthesis of IL was carried out and characterised with NMR and fourier transform infrared (FT-IR) spectroscopy. Kaolin was modified with IL to form hydrophobic kaolin (modified–kaolin) by adding IL in excess of the cation exchange capacity of kaolin. Modified–kaolin was characterised using FT-IR, x-ray diffraction (XRD), Brunauer−Emmett−Teller (BET), thermal gravimetric analysis (TGA), and scanning electron microscopy (SEM). Modified–kaolin was used in column and batch adsorption studies for phenanthrene and acid red dye. Modified–kaolin was an efficient material for the removal of phenanthrene and acid red dye. For column studies, the adsorption capacity, depth of exchange zone, time required for the pollutant to move through the exchange zone which is the height of the adsorbent in the column and adsorption rates were investigated using the Adams-Bohart, Yoon-Nelson model flow and Thomas sorption model. Column adsorption capacity at the same flow rate (5.0 mL min−1) and different concentrations (50, 100 and 200 mg L−1) for phenanthrene were 222.9, 611.8 and 1093.5 mg g−1, while that of acid red dye were 877.0, 1337.4 and 1350.7 mg g−1, respectively. Thomas and Yoon–Nelson models best explained the column studies. Data from both batch studies fitted well to pseudo-second order. The Langmuir isotherm had the best fit with an adsorption capacity of 842.7 mg g−1 for dye and the Freundlich isotherm best described phenanthrene with an adsorption capacity of 188.9 mg g−1.