Adsorption of Organic Acids on Blast Furnace Sludge

A. Radjenovic and J. Malina

Abstract
This paper describes the adsorption of two organic (acetic and citric) acids on the blast furnace sludge, a representative by-product of the steelmaking industry. By PIXE, XRD, BETand SEM methods, it was shown that blast furnace sludge is a complex heterogeneous material with a specific surface area of s = 31.46 m2 g–1, composed mainly of amorphous phase (w = 76.2 %), calcite (w = 9.9 %), magnetite (w = 6.3 %) and kaolinite (w = 2.2 %). Chemically, blast furnace sludge is dominated by O (w = 42.23 %) and C (w = 31.74 %). The adsorption process is analyzed using the theories of Freundlich and Langmuir. The experimental data were better fitted to the Langmuir isotherm. The negative Gibbs energy values indicate the spontaneous nature of adsorption. After adsorption the surface image changes in the BFS were observed, and BETsurface area increased when acetic acid was adsorbed. Contrarily, blast furnace sludge became almost non-porous in the case of citric acid adsorption and BETsurface area decreased significantly.

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Keywords
Blast furnace sludge, organic acids, adsorption