Adsorption and Regeneration Characteristics of Granular Adsorbent Based on Coal Fly Ash for Methylene Blue Removal

In a previous work, a granular adsorbent based on coal fly ash (GAF) has been prepared and the adsorption amount of methylene blue (MB) reached 278.55mg/g, which is comparable with granular activated carbon. To study its adsorption and regeneration characteristics for MB removal, influencing factors on adsorption, regeneration efficiency, adsorption kinetics and thermodynamics characteristics were investigated. The results indicate that the adsorption amount of MB increased with the increasing of contact time, initial concentration and adsorption temperature, while the initial pH has no significant influence. After 4 times regeneration cycles the regeneration efficiency remains 92% indicating that GAF has desirable regeneration ability. Isothermal studies show that Langmuir and Temkin isothermal models fit the adsorption processes well, indicating that the adsorption should be monolayer adsorption and may existing ion-exchange. Intraparticle diffusion describes the adsorption kinetics processes best. Thermodynamics research reveals the spontaneous and endothermic nature of the adsorption processes.