Hydrothermal synthesis of sodalite on alkali-activated coal fly ash for removal of lead ions

Sodalite was prepared by Alkali fusion-desilication-hydrothermal method using fly ash as raw material and characterized by X ray diffraction and scanning electron microscope. In addition, the adsorption characteristics of Pb2+ on the sodalite under different conditions were investigatedand the adsorption mechanism was studied by IRspectrum analysis. The results showed thatthe sodalitewith high crystallinity was prepared at the basicity of 2mol/L, crystallization time of 12 hours, and crystallization temperature of 90 degrees C; The adsorption performance of sodalitehad significantly improved than the original fly ash, andit could effectively remove the Pb2+ with considerably lower dosage; When initial concentration was 100 mg/L and the dosage was 2g/L, the removal rate could exceed 99%; The improvement of the initial concentration were in favor of the increase of theadsorption capacity, but we should regulate the relationship between adsorptioncapacity and adsorption rateby adjusting the ratio of solid to liquid; The adsorption capacity was increased with the increase of temperature and pH; Increasing ionic strength would inhibit the adsorption behavior; The maximum adsorption capacity of 157.2 mg/g was obtained by the Langmuir equation. Through infrared analysis, it can be inferred that the adsorption ofsyntheticsodalite is a physical adsorption. Now, research shows that thesodalite from fly ash has a remarkable removal effect on Pb2+. So, it can be used as an effective adsorbent for heavy metal disposal. (C) 2016 The Authors. Published by Elsevier B.V.