Adsorption Behavior of Acid Dyestuffs on the Surface of Fly Ash

The adsorption behavior of two acid dyes, AOII and ARBG, on the surface of fly ash was investigated. The results disclosed that the adsorption isotherms of AOII and ARBG on the fly ash at 20 degrees C followed the Langmuir adsorption equation. The saturated adsorptive amount of ARBG and AOII on the fly ash was 3.15 and 1.10mg/g at 20 degrees C, respectively, indicating that the adsorption capacity of ARBG was larger than that of AOII. Based on the Langmuir adsorption equation, the adsorption isotherm equation of ARBG can be shown as: [image omitted], and that of AOII can be shown as: [image omitted]. The adsorption kinetics of AOII and ARBG on the fly ash could be described with pseudo-secondary adsorption rate equation. The adsorption equilibrium of ARBG could reach in 1.5 hours, faster than that of AOII. The adsorption of acid dyes increased the potential of fly ash obviously. As a result, the coagulation of fly ash would be retarded, which would further benefit the adsorption of acid dyes. Compared with AOII, ARBG increased the potential of fly ash more efficiently.