A sample of phonolite was treated by cold plasma and hydrochloric acid diluted in water to study the change of its structure and acid properties. The phonolite and treated samples were analysed by XRD, elemental analysis XRF, specific surface area BET, TPD-NH 3 and FT-IR spectroscopy. They were also tested in the adsorption of Ca, K, Mg, P and Na impurities present in waste cooking oil. Plasma treated sample presented almost the same structure with some surface differences respect to the original phonolite. However, acid treated sample presented bigger total surface compared to the other samples, different structure, composition and acid properties.