Sorption of azo dyes onto a Mexican surfactant-modified clinoptilolite-rich tuff

The selectivity of a Mexican surfactant-modified clinoptilolite-rich tuff to retain azo dyes (red-40, yellow-5 and a mixture of them) from aqueous solutions has been investigated. The zeolitic material was modified with hexadecyltrimethylammonium bromide and then left in contact with azo dyes. The uptake was determined at different contact times and concentrations of dyes solutions. First order Elovich, and pseudo second order models as well as the lineal, Langmuir, and Freundlich isotherms were used to describe the experimental data. It was found that in single and binary solutions, under the experimental conditions, the modified zeolitic material retain preferentially the dye red-40 in comparison to yellow-5. The best models to describe the reaction rate and the sorption of azo dyes red-40 and yellow-5 by Mexican surfactant modified clinoptilolite-rich tuff were pseudo-second order and Langmuir models, respectively. These results show that surfactant modified clinoptilolite-rich tuff from Villa de Reyes (San Luis Potosi, Mexico) could be considered as a potential adsorbent of azo dyes from aqueous solutions.