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Dissolution Kinetics of Synthetic Zeolite NaP1 and Its Implication to Zeolite Treatment of Contaminated Waters

Department of Geological and Environmental Sciences, Ben-Gurion University of the Negev, Be'er Sheva`, Southern District, Israel
Environmental Science and Technology (Impact Factor: 5.48). 08/2005; 39(13):4871-7. DOI: 10.1021/es0500512
Source: PubMed

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.

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    • "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 [21] [22], (ii) as an effective technique in metal retention processes in contaminated soils [23] [24] and, (iii) for the treatment of acid mine drainage [25] [26]. Recently, Soong et al. [15] 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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