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Removal of a Mixture of Blue BF-5G and Chocolate Brown Textile Dyes Through Adsorption and Degradation: an Assessment of the Individual and Combined Processes

Abstract:

This work analyzes the removal of reactive blue BF-5G and chocolate brown textile dyes from an aqueous mixture by using adsorption, advanced oxidative processes (AOP), and the combination of these two processes. The adsorbent used was obtained by calcinating chicken eggshells at 1073 K. The carbonization led to an increase in the surface area, diameter, and volume of the pores, the presence of hydroxyl, carboxyl, and carbonyl groups on the surface of the material, which became positively charged. The operational conditions of the adsorptive process that produced the highest percentages of removal were pH 5.5, 2 g L−1, and 200 rpm. The kinetic evolution was rapid in the first minutes and was best described by the pseudo-first order (PFO) model, while the equilibrium was attained in 60 min and was best described by the Langmuir model. The AOP that attained the greatest degradation was the photo-Fenton process using pH 3.5, along with iron and hydrogen peroxide concentrations of 3 mg L−1 and 80 mg L−1, respectively, with UV-C radiation. In the kinetic study, the system stabilization occurred after 90 min and had PFOAOP behavior. The adsorption and AOP processes proved to be efficient in removing the dyes. However, the combined processes (AOP followed by adsorption) attained the best results. The use of the combined process significantly contributed to the reduction in the toxicity of the solutions. The use of the AOP process followed by adsorption is, therefore, a viable alternative for the treatment of textile dyes.