Congo Red removal using Fesdis soil: kinetic, equilibrium and thermodynamic studies.

The removal of Congo Red dye from an aqueous solution using the soil from Fesdis (FS) area (Batna, Algeria) was studied. The soil was characterised using ATR, BET, SEM and XRF techniques. The characterisation results showed the existence of clay, carbonate and quartz in this soil. The adsorption results demonstrated that the CR dye adsorption onto the Fesdis soil is dependent on the different investigated parameters as the biosorbent concentrations, the pH, the initial dyes concentrations, temperature and the ionic strength effect. The results show that the dye removal was increased with the raise of the reaction temperature, adsorbent dose, and dye initial concentration. The efficiency dye removal increased to 96% and achieved the value 99% when CaCl2 was added. The optimum conditions determined at room temperature were [dye] = 50 mg/L, [adsorbent] = 12 g/L, neutral pH with a maximum adsorption capacity (qmax) was around 6.693 mg.g−1. Equilibrium isotherms were analysed by the Langmuir model, Freundlich model, and the Dubinin–Radushkevich models. The pseudo-first-order, the pseudo-second-order and intraparticle diffusion models were used for kinetic analysis. The thermodynamic study reveals that CR dye adsorption onto the Fesdis soil is a spontaneous, physical and endothermic process. [ABSTRACT FROM AUTHOR]