Characterization and Utilization of Wood Ash in Geopolymers Production and Pb+2 Removal from an Aqueous Solution

The main goal of this work is to characterize wood ash as a waste product from tree trunks burning and utilize it for geopolymer production. The geopolymerization was achieved by a chemical reaction between calcined kaolin and different ratios of wood ash in an alkali solution of sodium silicate (Na2SiO3) and sodium hydroxide (NaOH). The produced geopolymers' physical, chemical, and microstructural characteristics were investigated. The synthesized geopolymer with 50% wood ash showed lower density, higher water absorbability, and higher porosity than the free wood ash geopolymer. The microstructural analysis indicated the formation of zeolitic and amorphous phases that were causing an increase in micropores and a high specific surface area, as revealed by XRD, SEM, and BET analyses. Therefore, the potential use of the developed geopolymer for Pb+2 removal from an aqueous solution was investigated. It was found that the generated geopolymer has a higher removal efficiency than the raw materials. The studied adsorption isotherms showed that the Langmuir isotherm model explains the experimental results well than the Freundlich model.