Potential Scrubbing via Coal Fly Ash of Wastes From the Quarries Industry

Nir Roy Lieberman, Institute of Environmental Assessment and Water Research (IDAEA), Consejo Superior de Investigaciones Cientificas (CSIC), Barcelona, Spain
Oriol Font, Institute of Environmental Assessment and Water Research (IDAEA), Consejo Superior de Investigaciones Cientificas (CSIC), Barcelona, Spain
Yaakov Anker, 4. Research and Development Center of Samaria, Ariel, Israel
Yaniv Knop, Civil Engineering, Ariel University, Ariel, Israel
Xavier Querol, Institute of Environmental Assessment and Water Research (IDAEA), Consejo Superior de Investigaciones Cientificas (CSIC), Barcelona, Spain
Yitzhak Mastai, Chemistry and the Institute of Nanotechnology, Bar Ilan University, Ramat-Gan, Israel
Haim Cohen, Biological Chemistry, Ariel University, Ariel, Israel

Coal power plants in Israel produce ~1.3Mtons of coal fly ash and ~100ktons of bottom ash every year as a waste. As a result of strict environmental regulations in Israel the coal imported undergoes beneficiation process in order to reduce its mineral content, thus it is very low in sulfur, and contains highly basic content (~9.9% CaO in South African Fly Ash (SAFA); ~5% in Columbian Fly Ash (COFA)), hence the fly ash is Type F (Highly basic upon immersion in water- pH 12.5 in SAFA; pH 10 in COFA). The bottom ash fines have the same composition as the fly ash.

Recently it has been found that class F fly ash can act as an excellent scrubber and fixation reagent for acidic wastes, from the phosphate and oil regeneration industries. Thus, we have decided to study the potential of using these fly ashes (SAFA and COFA) as scrubbing reagents for fine wastes from the Quarries industry of the Israel and the West Bank (The Palestinian Authority).

The investigations have shown that both fly ashes can serve as encapsulation reagents for the sludge and that the scrubbed product can be used as a partial substitute in the mixture for concrete production. Leaching experiments using the European Directive (EN 12457-2) have proved that the aggregate product as well as the concrete produced are with the compliance test for leaching and the leached is within the D.L. standards in Israel and below the hazardous limits of the European Directive. Furthermore the concretes produced have better mechanical properties than regular concretes.

Keywords: fly ash, query sludge, chemical scrubber, trace elements, concretes