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: Carlos Alberto Rios[Show abstract] [Hide abstract]
ABSTRACT: This paper studies the reactivity of kaolinite and metakaolin in a fluori-nated medium under hydrothermal conditions. This path of conventional zeolite synthesis did not yield promising results, although traces of different zeotypes did crystallize, such as the crystal structures Linde type Y (LTY), zeolite Na-P1 (GIS), chabazite-ca (CHA), sodalite (SOD), cancrinite (CAN) and Linde type A (LTA). Other zeolites reported in this study were zeolite ZSM-5 (MFI type structure) and zeolite ITQ (ISV type structure). The non-reacting starting material and the synthesized products where characterized by x-ray diffraction, scanning electron microscopy, infrared spectroscopy by Fourier transform and thermogravimetric analysis. The products of the synthesis are of interest because they can be used in different industrial applications.06/2013; 17(1):183-203.
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ABSTRACT: A zeolite (ZFA) was synthesized from coal fly ash and then modified using hexadecyltrimethylammonium. The surfactant modified ZFA (SMZFA) was evaluated for its versatility to sequester multiple classes of pollutants from water. The target pollutants include ionic inorganic pollutants (ammonium and phosphate), ionic organic pollutants (methylene blue and humic acid), ionizable organic pollutants (bisphenol A, ρ-chlorophenol and phenol, with different pKa), and electrically neutral organic pollutants (aniline, nitrobenzene, and naphthalene, with different hydrophobicity). The SMZFA showed high potential for the retention of ammonium and phosphate, being comparable with ZFA. While the negative charge in the internal pores of zeolite was responsible for the retention of ammonium, the oxides of CaO, Al2O3 and Fe2O3 in the non-zeolite fraction, which originated from coal fly ash but received modification during zeolite synthesis, accounted for the removal of phosphate. Results also showed that while ZFA had little affinity for humic acid, the ionizable, and the electrically neutral organic compounds, SMZFA exhibited greatly enhanced adsorption capacity. Thus, the surfactant modified external surface, which formed a bilayer micelle of zeolite, imparts a hydrophobic characteristic that enables the uptake of the organic pollutants. We showed that SMZFA is a promising versatile sorbent for water treatment.Science China Technological Sciences 07/2013; 56(7). DOI:10.1007/s11431-013-5232-3 · 1.11 Impact Factor
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ABSTRACT: Since the first successful synthesis of zeolite from coal fly ash (ZFA) in 1985, the preparation and application of ZFA has been intensively investigated to recycle the solid waste. However, problems arising from the waste alkaline solution have rarely been addressed to date. This study initiated a novel method to synthesize ZFA/Al2O3 hybrid material by introducing a reaction step involving the neutralization of the waste alkaline solution with soluble Al salts into the traditional ZFA synthesis route. When compared with ZFA, ZFA/Al2O3 was found to have a significantly higher CEC. The increases of the BET surface area and phosphate-immobilization capacity were even more dramatic, with the former increasing by 2–4 times and the latter increasing by 2–3 times. The hybrid material had a significantly lower alkalinity than ZFA. The results also showed that the effluent from the production of the hybrid material could be much more environmentally friendly.Industrial & Engineering Chemistry Research 10/2013; 52(42):14890–14897. DOI:10.1021/ie4021396 · 2.24 Impact Factor