Preparation of filter by alkali activation of blast furnace slag and its application for dye removal

• Published in: Journal of environmental chemical engineering 2022-02, Vol.10 (1), p.107051, Article 107051
• Main Authors: Bhuyan, M.A.H., Gebre, R.K., Finnilä, M.A.J., Illikainen, M., Luukkonen, T.
• Format: Article
• Language: English
• Subjects: Adsorption; Filter design; Methylene blue; Regeneration; Wastewater treatment
• ISSN: 2213-3437; 2213-3437
• DOI: 10.1016/j.jece.2021.107051

This study demonstrates a high-value valorization of blast furnace slag in foamed alkali-activated filters for adsorption applications, using methylene blue as a model compound. The filters were prepared by combining alkali activation of blast furnace slag with direct foaming, followed by curing at 60 °C for 4 h. Five different surfactants were compared for the stabilization of foams. Based on an initial screening, the Triton X-405 surfactant was selected for further studies. The dosages of selected surfactant and H2O2 were optimized to obtain compressive strength of 2.59 MPa and specific surface area of 83.3 m2/g for powdered material and 78.31 m2/g for foam pieces. Porosity was determined as 64%, 65%, or 50% by using gas pycnometry, Archimedes method, or X-ray microtomography, respectively. The optimized filter mix design was applied for methylene blue removal in continuous column experiments at two influent concentrations (5 and 10 ppm) by using constant empty-bed contact time of ~9 min (flowrate of ~1 L/h). After 6 h, for both influent concentrations, the dye removal was still 74%, with the initial removal of ~100%. The saturated filter could be regenerated by a thermal treatment resulting improved adsorption performance. When the material was employed as powder, the maximum adsorption capacity was 60.35 mg/g according to the Langmuir isotherm (R2 = 0.99) and adsorption kinetics followed the pseudo-second order model. The results demonstrate preliminarily that porous filters prepared in this study have potential to be used in industrial wastewater treatment. [Display omitted] •Alkali-activated foams were developed from high Ca-containing blast furnace slag.•Among the five surfactants, Triton X-405 yielded the highest compressive strength.•The optimized foam was used as a filter for methylene blue (MB) adsorption.•After 6 h, MB removal was 74% with initial removal of approximately 100%.•Dye removal by using blast furnace slag-based filter assures waste valorization.