Dissolution Kinetics of Synthetic Zeolite NaP1 and Its Implication to Zeolite Treatment of Contaminated Waters
ABSTRACT The effect of pH on the dissolution kinetics of NaP1 zeolite, which was produced from the alkaline treatment of coal fly ash and may be used for decontamination of acid mine waters, is studied. The sample contains considerable amounts of accessory phases that partly dissolve during the experiment. Therefore, the dissolution rate was estimated during a stage in which the Al/Si ratio was equal to that of NaP1 (0.6). The release rate of these elements is controlled by the dissolution of the zeolite itself during this stage. The dissolution rate of NaP1 slows down with increasing pH in the acidic range, becomes constant at an intermediate pH, and increases with increasing pH in the basic range. The observed changes in rates were described using a rate law based on a surface speciation model. Using this rate law, we calculated the half-life of NaP1 to be about 2 years at near neutral pH and less than 10 days at pH below 3. For the utilization of NaP1 in the treatment of wastewaters or acid mine waters, these short half-lives bear two implications: (1) The treated waters must be kept at near neutral pH, and NaP1 should be added periodically to the treated waters in order to compensate for zeolite loss. (2) In water treatment applications that require a relatively short reaction time, the zeolite removed from the effluents should be kept dry in order to avoid its decomposition and the consequent release of the adsorbed metal to the environment.
- SourceAvailable from: François Renard
- "At present, numerous investigations are focused on the search of new applications for this residue. Three main research lines use fly-ash: (i) to synthesize zeolites used as filter material in water decontamination and gas retention  , (ii) as an effective technique in metal retention processes in contaminated soils   and, (iii) for the treatment of acid mine drainage  . Recently, Soong et al.  propose the use of coal combustion fly-ash and brine solutions (waste from oil and gas production) to sequester CO 2 via aqueous mineral carbonation . "
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ABSTRACT: Fly ash obtained from a coal combustion thermal electric power plant was reacted with NaOH at 100 °C for 24 h to synthesize zeolite. Shaker flasks experiments were conducted to assess whether fly ash or fly ash zeolite (FAZ) could be used to treat acidic mine water. The FAZ was used to treat the mine water at doses of 5–60 g/L; the FAZ increased pH from 2.76 to as high as 7.51 and removed most of the Ca and Mg hardness and acidity from the mine water, though it did not affect sulphate concentrations. The cation exchange capacity of the FAZ was regenerated using NaCl. After six regeneration/reuse cycles, the FAZ was less effective but still capable of increasing pH and removing substantial hardness. In contrast, fly ash was not effective in removing hardness or acidity, and instead released ions into the mine water.Mine Water and the Environment 06/2013; 32(2). DOI:10.1007/s10230-013-0222-z · 1.20 Impact Factor
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ABSTRACT: This work reviews the availability and the potential of the carbon capture and storage (CCS) technology using coal fly ash (FA). Because the technology can be effectively applied on-site to coal fired power plants and as FA contains sufficient alkali components, the technology may be another option of CCS technology to a limited extent.The technology can be divided into wet and dry processes. In the former, the available components for CCS in FA are leached into solution by the solvent where they are subsequently consumed for carbonation to store CO2. Particularly, the CO2 storage capacity of CaO-enriched FA solution mixed with brine under high pressure may be equal to or greater than the true CO2 emission reduction achieved by applying FA as a cement additive.In the dry process, FA can be used as a direct support or as the raw material of the sorbent supports for CO2 capture. The dry process is effectively applied for CO2 capture rather than storage because the sorbents should be regenerated. Another advantage of the technology is the stabilization of the harmful components present in FA, which are mostly co-precipitated with carbonated FA during the process.Applied Energy 06/2013; 106:143–151. DOI:10.1016/j.apenergy.2013.01.062 · 5.61 Impact Factor