Preparation of a novel composite geopolymer based on calcium carbide slag-fly ash and its characterization, mechanism and adsorption properties

Abstract

In this study, a mixed precursor system of fly ash (50 wt%) and calcium carbide slag (50 wt%) was used to prepare a geopolymer, and the hydration and hardening mechanism of the whole system and the microscopic characterization of the calcium carbide-fly ash based polymer were investigated after the addition of calcium carbide slag. Ca(OH)2 in calcium carbide slag can effectively excite the volcanic ash activity of fly ash, which leads to a more adequate geopolymerization reaction and produces more hydrated calcium silicate (C-S-H) gels. These gels have very high specific surface area and surface adsorption energy. The results showed that the specific surface area of geopolymer was as high as 79.76 m2/g, and through the study of its adsorption capacity of Cu(II) in aqueous solution, the results showed that its removal efficiency of Cu(II) was 97.63% and its adsorption capacity was 58.58 mg/g. By using fly ash and calcium carbide slag as the auxiliary raw materials for the preparation of geopolymer, it not only can promote the reaction of proceeding, but can also act as an excellent adsorption material, and also as an effective way to utilize industrial waste resources. HIGHLIGHTS A fly ash-calcium carbide slag-based geopolymer was used as adsorbent for the first time.; The surface area of the fly ash-calcium carbide slag-based geopolymer is as high as 79.76 m2/g.; The composite material has a high removal efficiency of 97.63% for heavy metal ions.; The geopolymer could be an eco-friendly substitute material.;

Keywords

• adsorption
• calcium carbide slag
• composite materials
• fly ash
• geopolymer