Comparision of fly ash and metakaolin based geopolymer properties for heavy metal adsorption

Abstract

This work aims to evaluate the effectiveness of fly ash and metakaolin based geopolymer powder and fly ash and metakaolin based geopolymer composite fiber as an adsorbent for removal of heavy metal ions from aqueous solution. The fly ash and metakaolin used as raw materials in this research was from Thailand. Fly ash based geopolymer (FAG) was synthesized by mix with an alkali solution. After that, the geopolymerization process was occurred and then cured geopolymer samples at 60oC for 24 h and left at 25 oC for 6 days. The fly ash based geopolymer was ground, washed and sieved through 100 mesh to obtain geopolymer powder. The process of metakaolin based geopolymer (MKG) powder was synthesized as same as that of fly ash based geopolymer powder. In addition, the geopolymer composite fiber was fabricated by mixing geopolymer powder with Polyethersulfone (PES)/ N-Methyl-2-pyrrolidone (NMP) solution and then being extruded through a nozzle to coagulation bath. The geopolymer composite fiber was formed to be fiber by phase inversion method. After synthesis of geopolymer powder and fabrication of geopolymer composite fiber, the effect of contact time, adsorbent amount, pH of a solution, temperature and initial concentration of solution on the adsorption efficiency were studied. Furthermore, the multi- and mono- Pb2+, Cd2+, Cu2+ and Ni2+ solutions were demonstrated to compare the efficiency of each metal ions. The adsorption isotherm and kinetics study were also studied. The results showed that the geopolymer powder had the semi-crystalline phases and mainly composed of silica and alumina. The surface area of FAG powder, MKG powder, FAG composite fiber and MKG composite fiber were 85.31, 20.36, 71.67 and 53.11 m2/g, respectively. The results showed that metal ions in aqueous solution are effectively removed by geopolymer powder and geopolymer composite fiber.