Abstract Tartrazine, (CI 19140) is an azo dye widely used in pharmaceuticals, cosmetics and foodstuff, as well as for coloring the textiles, hence it can be easily found in municipal wastewaters or wastewaters originating from textile, food, drugs and cosmetic industry. In this work, the capacity of a Romanian soil to retain Tartrazine from aqueous solution by sorption onto soil particles of different size has been investigated. The sorption kinetics was studied by applying five kinetic models aiming at establishing the model that best describes the sorption of the azo dyes onto the particles of soils of different size.