Surface modification with cold plasma application on kaolin and its effects on the adsorption of methylene blue

•Cold plasma treatment was applied for the surface modification of kaolin.•The maximum adsorption capacity of MB increased from 19.60 to 51.02 mg/g.•SEM, FT-IR and pHpzc measurements indicated the change in functional groups.•The modified kaolin exhibited potential application for removal of MB.

In this study, cold plasma treatment was applied for the surface modification of kaolin adsorbent to improve the removal of methylene blue (MB) from aqueous solution. To achieve the aim, the conditions for adsorption, including cold plasma application time, initial dye concentration, and pH were investigated with respect to the removal efficiency of MB. The changes of the surface property before and after cold plasma treatment were discussed. The maximum adsorption capacity of MB compared with untreated raw kaolin increased from 19.60 to 51.02 mg/g (up to approximately 2, 5-fold) after modification by cold plasma. The experimental data were analyzed using pseudo first-order and second-order kinetic models. The surface properties of kaolin treated with cold plasma were investigated with scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and point of zero charge (pzc) measurements to understand the adsorption mechanism.