Optimizing the preparation of carbonaceous adsorbents for the selective removal of textile dyes by using Taguchi methodology

The pyrolysis of vegetal wastes obtained from fruit industry (pine nut shell, pecan shell, peach stone and pistachio shell) was studied using the L16 orthogonal array of Taguchi method with the purpose to found the best conditions of preparation of efficient activated carbons for the removal of acid, basic and reactive dyes. Sixteen different samples of carbon were prepared and they were characterized using FT-IR spectroscopy, SEM/EDX analysis, nitrogen adsorption isotherms at 77 K and elemental analysis. The adsorbed amount of reactive black 5 (RB5), reactive red 2 (RR2), acid orange 7 (AO7), acid blue 74 (AB74), basic blue 41 (BB41) and basic blue 9 (BB9) was used a response variable of Taguchi methodology. The results are indicating that is possible to obtain activated carbons with high dye adsorption capacity using a chemical–physical activation with FePO4 or CaHPO4 in CO2 atmosphere. Particularly, the adsorbed amount of RR5 (256.26 mg g−1), RR2 (326.72 mg g−1), AO7 (537.18 mg g−1), AB74 (485.02 mg g−1), BB41 (440.67 mg g−1) and BB9 (561.92 mg g−1), using the sample S-5 was very high and in many cases it values are higher than the results reported in the literature for carbonaceous adsorbents.