Nowadays, many industries use dyes in various processes and the resulting wastewater is a major source of environmental pollution. A part of these dyes are resistant to degradation and due to their toxicity are harmful to humans and to aquatic organisms. Tartrazine is an anionic dye that is commonly used, as coloring agent, in a variety of foods. This is also used to color capsules used in medicines, cosmetics, vitamins and syrups. In order to reduce its impact on the environment, different treatment methods are used (e.g. adsorption, coagulation, flocculation, ozonation, photocatalysis). Among the methods used to retain dyes, it was found that adsorption is the most efficient and with promising results. In addition, adsorption is considered an attractive process because it involves easy operation and simplicity in process. Various materials have been tested for removal of dyes from wastewater, the most widely used being activated carbon. Recently, nanomaterials have emerged as a strong competitor of conventional adsorbent materials due to their unique properties, such as large surface / volume ratio, chemical stability etc. The application of nanomaterials based on carbon, such as carbon nanotubes (CNT), for the adsorption of dyes from wastewater is one of the new trends in this field. CNT are characterized by high adsorption surface and relatively easy attachment of functional groups that give them interesting adsorption properties. The present investigations concern the application of magnetic nanocomposites CNT-COOH/Fe3O4 and CNTCOOH/ Fe3O4/NiO as adsorbents for the removal of tartrazine, a hazardous dye, from aqueous solutions. In order to establish the conditions for optimal retention of tartrazine, the influence of some physico-chemical parameters on the adsorption process was evaluated, such as: initial pH of the dye solution, temperature, adsorbent dose, contact time and the initial concentration of dye. The best degree of removal of tartrazine was obtained with CNT-COOH/Fe3O4/NiO.