Sorption and Desorption of Red 5 and Yellow 6 by a Fe-Zeolitic Tuff

摘要

The capacity of an iron-modified zeolite was evaluated for the removal of two dyes (red 5 and yellow 6) use in foodstuff; the regeneration of the dye-saturated materials was also considered. The zeolitic material (clynoptilolite type) was treated with sodium chloride (Na-Ze) and then with ferric chloride (Fe-Ze). The sorption kinetics and isotherms were evaluated, considering the effect of pH on the sorption processes. Sorption-regeneration cycles using iron-modified zeolitic material were performed. The sorption kinetics showed that the sodium-modified zeolitic material removed neither red 5 nor yellow 6 dyes, while the iron-modified zeolitic material removed both dyes; the equilibrium time was reached in 48 h for yellow 6, and it was almost reached in the same time for red 5, the removal percentage for red 5 was 89.4 % and for yellow 6 was 96.7 %. The experimental data showed best adjustment to the pseudo-first-order model (Lagergren), which is based on a superficial reaction. The sorption capacities obtained by the sorption isotherms were 1.6 and 1.7 mg/g for red 5 and yellow 6, respectively. The experimental data were best adjusted to the Langmuir-Freundlich model which indicates that the sorption takes place on a heterogeneous material. It was also observed that the sorption capacities increase as the pH decreases. The results on the desorption processes showed that the best regenerator agent was Fenton's reagent; the capacities increased in each sorption-regeneration cycle using this reagent; for the red 5, the sorption percentage was 73.6 % in the first cycle and 96.3 % in the third cycle and for yellow 6, the removal percentage was 66.7 % in the first cycle and 80.5 % in the second.