Equilibrium and kinetic study of the adsorption of reactive blue, red, and yellow dyes onto activated carbon and barley husk

Batch adsorption of reactive blue H3R (B), red 3BF (R), and yellow FG (Y) dyes onto activated carbon (AC) and barley husk (BH) was studied. Various experiments were carried out to find the effect of initial dye concentration (5-100 mg/l), adsorbent dosage (0.1-1 g), contact time (15-420 min), pH solution (2.5-8.5), and temperature 30 degrees C. The experimental data showed that the increasing uptake at decreasing pH with respect to (AC) was with B and R dyes while in comparison with (BH) was showed increased uptake at pH increasing for all dyes. Adsorption capacity increased with increasing initial concentration of all dyes with (AC) and (BH). The experimental data were analyzed using Langmuir, Freundlich, and Sips isotherm models. The adsorption of B, R, and Y dyes with (AC) was well fitted with all above models with R-2 (0.925-1), while adsorption onto (BH) for B dye showed R-2 (0.87-0.96) for above models, while for other dyes showed low R-2 values. Pseudo-first-order, pseudosecond- order kinetic, and intraparticle diffusion models were used to analyze the kinetic data. The data were well fitted at dye concentration 10ppm with the pseudo-first order when R-2 values for B, R, and Y dyes were (0.88, 0.97, and 0.982) and (0.98, 0.947, and 943) for (AC) and (BH), respectively, while intraparticle models with R-2 values were (0.97, 0.9, and 0.818) and (0.932, 0.8, and 0.947) for each of (AC) and (BH), respectively. Pseudo-second-order model showed well fitting for (AC), when R-2 values were (0.77, 0.965, and 0.998) for B, R, and Y dyes, respectively.