Synthetic dyes are widely used around the world, and big volumes of coloured effluents end up being discharged into water bodies.Allura Red and Tartrazine are azo dyes with a broad use spectrum mainly in food and textile industries and their removal from the aquatic ecosystems, is a challenge.In the last decades, several methods have emerged to find a solution of this environmental problem, among them, adsorption using agro-industrial by-products stands out as a high efficient and low cost metodology for the removal of dyes, both individual and in mixture.Thus, the aim of this work was to confirm the reliability of spectrophotometric techniques for quantifying coloured compounds and then to evaluate the adsorption process of the mixture Allura Red -Tartrazine through a 2 3 full factorial design with a central point.The Lambert-Beer law allows to quantify with errors lower than 2.0%.The best percentage of adsorption of the azo dyes mixture, in order of 94.92%, was achieved with a dosage of 20 g/L and concentrations of 20 ppm for both dyes.These results show that adsorption using agricultural wastes is a promising alternative for treating mixtures of dyes in solution.