Geopolymerization of coal fly ash in the presence of electric arc furnace dust

• Published in: Minerals engineering Vol. 49; pp. 24 - 32
• Main Authors: Nikolić, I., Đurović, D., Blečić, D., Zejak, R., Karanović, Lj, Mitsche, S., Radmilović, V.R.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.08.2013
• Subjects: Coal fly ash; Electric arc furnace dust; Geopolymerization; Hazardous metals; Leachability; Coal fly ash; Geopolymerization; Leachability; Electric arc furnace dust; Hazardous metals
• ISSN: 0892-6875; 1872-9444
• DOI: 10.1016/j.mineng.2013.04.007

•Electric arc furnace dust can be immobilized in the fly ash based geopolymers.•Efficiency of immobilization is influenced by the alkaline dosage.•Immobilization of Zn occurs by chemical and physical retention.•Geopolymers contaminated with electric arc furnace dust are mesoporous materials. The results of synthesis of fly ash based geopolymers and the experimental investigations of the geopolymerization of fly ash in the presence of eclectic arc furnace dust were presented. The electric arc furnace dust (EAFD) is a hazardous solid waste formed during remelting processes of iron and steel scrap in an electric arc furnace. In this work, the possibility of immobilization of Zn (as a most abundant toxic metal in EAFD) from EAFD and the influence of EAFD addition and alkaline dosage on the mechanical and microstructural properties of fly ash based geopolymers was investigated. Our result show that the best mechanical properties of FA and FE geopolymers were obtained using 10M NaOH and 10wt.% EAFD. The X-ray phase analysis confirmed the presence of aluminosilicate and oxide phases in investigated samples of FA, EAFD, as well as FA and FE geopolymers. SEM–EDS results have revealed the presence of Zn in an amorphous aluminosilicate phase. This material is considered as mesoporous and the change of porosity is greatly dependent on the alkaline dosage. The efficiency of immobilization of Zn from EAFD was evaluated using TCLP, EN 12457-2 and EPA Method 1313 leaching tests. Results of TCLP and EN 12457-2 tests have shown that the increase of alkaline dosage leads to the more effective immobilization of Zn and other toxic metals present in EAFD. On the other hand, the results of EPA method 1313-pH dependent leaching test have indicated that FE geopolymers are relatively stable in neutral and alkali environment while in a pH range 2–5.5, solubility of Zn and Pb is a concern for this type of materials.