Evaluation of natural and cationic surfactant modified pumice for congo red removal in batch mode: Kinetic, equilibrium, and thermodynamic studies

Present study focused on the adsorption of congo red onto natural pumice (NP) and cetyltrimethyl ammonium bromide modified pumice (SMP) from aqueous solution in batch experiments. The effects of contact time, solution pH, adsorbent dosage, initial dye concentration, and temperature on the removal of CR were studied. Characterization of natural and modified pumice has been accomplished by XRF, SEM, BET, and FTIR analysis. The experimental data were fitted by three isotherm models, and the results showed that the adsorption isotherm data were fitted well to the Langmuir and Temkin isotherms for NP and SMP, respectively, and the measured maximum adsorption capacities calculated according to linear and non-linear forms of the Langmuir isotherm were 3.87 mg/g, 4.42 mg/g and 27.32 mg/g, 18.81 mg/g for NP and SMP at 25 °C, respectively. The adsorption kinetic data for both adsorbents were better described by the pseudo-second order kinetic model. Weber-Morris intra-particle diffusion equation was applied to determination of rate limiting stage. Besides, the thermodynamic parameters, such as ΔG°, ΔH° and ΔS°, were also calculated. It was resulted that surfactant modified pumice was a promising route to prepare a potential geo-material and showed better adsorption capacity for CR removal, compared to natural pumice.