The use of a modified fly ash as an adsorbent for lead

Abstract

Coal fly ash was modified by hydrothermal treatment with NaOH solutions of varying concentrations. During the modification the zeolites, Na-P1 and hydroxysodalite, were synthesised. Increasing base concentration led to hydroxysodalite being the preferred product. Elemental analysis revealed that the modification treatment preferentially leached Si from the fly ash at low base concentrations. Elevated base concentrations, however, resulted in Al also being leached as well as the inclusion of Nain the zeolitic product. The modification activated the fly ash significantly with respect to specific surface area (SSA) and cation exchange capacity (CEC). SSA increased from 1.0 m2·g-1 to a maximum of 62.7 m2·g-1 while CEC rose from 25 mmol/100 g to a maximum of 300 mmol/100 g. Metal sorption studies were performed with lead as the metal of choice. Adsorption experiments at pH = 5, revealed that all modified ash samples adsorbed significantly more Pb than the raw ash. The best adsorption was obtained for ash, modified with 3M NaOH.

Authors

Categories