Adsorption of a textile dye onto activated sepiolite

Adsorption of Remazol red B (RRB) on thermal activated sepiolite (TAS) and acid activated sepiolite (AAS) from aqueous solutions was investigated at different parameters, such as, adsorbent type, temperature, contact time and solution pH. Then, the obtained results were compared for all the parameters. According to the results, the equilibrium time, optimum pH and adsorbent type were found to be 120 min., 2–3 ≈ pH and AAS, respectively, and it was found that the adsorption capacity of AAS samples was higher than that of TAS. The kinetic data for both sepiolite samples support the pseudo-second-order model (r2 > 0.99), and intra-particle model (r2 > 0.92) but the first order kinetic model did not adequately fit to experiment values (r2 < 0.87). The equilibrium adsorption data were interpreted using Langmuir and Freundlich models. The adsorption of RRB was better represented by the Langmuir equation (r2 > 0.99). In addition, the thermodynamic parameters, ΔHo, ΔSo, ΔGo, and Ea were also calculated for RRB adsorption onto both TAS and AAS. In order to reveal the adsorptive characteristic of sepiolite samples, surface area, SEM, XRD and FT-IR spectra analyses were carried out. The results show that AAS samples can be an alternative low-cost adsorbent for removing dye from wastewater.