Production of synthetic zeolites from lignite - calcareous Greek fly ashes and their potential for metals and metalloids retention

Abstract

The current state of the art focuses on the production of synthetic zeolites from lignite -calcareous fly ashes. The synthetic minerals are produced by the hydrothermal treatment of Greek fly ashes originating from Ptolemais and Megalopolis Power Plants in Greece. The products are examined in terms of their mineralogical composition, for the formation of known zeolites, morphology, thermal behavior, cation exchange capacity, pH, porosity and specific surface area. Zeolitic products, along with untreated fly ash, are investigated for their potential of retaining heavy metals from liquid wastes. The mechanisms of metal retention by zeolites in artificial solutions including lead, zinc, copper, arsenic and cadmium were examined. Solutions including the same pollutants, mobilized from a contaminated soil, utilizing selected solvents were produced. Results revealed the capability of zeolitic materials and fly ashes to retain metals in significant concentrations. Furthermore, a number of different retention mechanisms are developed, including ion exchange, surface adsorption and precipitation of metals.

Removal of heavy metals from wastewater using CFB-coal fly ash zeolitic materials

“…zeolites) [13][14][15][16]. Therefore, NaOH solutions present higher conversion efficiency than the respective KOH under the same temperature, as it is also concluded from the vast body [3][4][5][6][7][8][10][11][12] of previous research studies.…”

“…The classical alkaline conversion of fly ash is based on the combination of different activation solution/FA ratios, with temperature, pressure and reaction time to obtain different zeolitic types. The methodologies developed on this field aim at the dissolution of Al-Si bearing phases of the FA and the subsequent precipitation of the zeolitic material [5,6]. NaOH or KOH solutions with different molarities, at atmospheric and water vapor pressure, from 80 to 200 • C and 3 to 96 h have been combined to synthesize many different types of zeolites.…”

Radiocesium Adsorption By Zeolitic Materials Synthesized From Coal Fly Ash

“…The classical alkaline conversion of fly ash (FA) is based on the combination of different [activation solution]/ [fly ash] ratios. The methodologies developed on this field aim at the dissolution of Al-Si bearing phases of the FA and the subsequent precipitation of the zeolitic material (BLISSETT and ROWSON, 2012;AHMARUZZAMAN, 2010;HUI and CHAO, 2006;MOUTSATSOU and PROTONOTARIOS, 2006;QUEROL, 2002;IYER and SCOTT, 2001;HOLLMAN, 1999;AMRHEIN et al, 1996;SHIGEMOTO et al, 1993).…”