Structure and properties of forming adsorbents prepared from different particle sizes of coal fly ash

In this paper, different particle sizes of coal fly ash FA-R (D50 = 15.75 μm), FA-A (D50 = 3.61 μm) and FA-B (D50 = 1.73 μm) were treated with NaOH solution to prepare the forming adsorbents FFA-R, FFA-A and FFA-B. The structure and adsorption properties of the forming adsorbents for methylene blue (MB) from aqueous solution were examined. The results showed that the specific surface areas and adsorption capacities of the forming adsorbent for MB increased with decreasing particle size of raw coal fly ashes. The adsorption kinetic data of MB on FFA-R, FFA-A and FFA-B fitted the second-order kinetic model very well with the rate constants (k2) of 3.15 × 10− 2, 3.84 × 10− 2 and 6.27 × 10− 2 g·mg− 1·min− 1, respectively. The adsorption process was not only controlled by intra-particle diffusion. The isotherms of MB on FFA-R, FFA-A and FFA-B can be described by the Langmuir isotherm and the Freundlich isotherm, and the adsorption processes were spontaneous and exothermic.

Graphical AbstractSEM of coal fly ash and forming adsorbents.Figure optionsDownload as PowerPoint slide