Somerset V S, Petrik L F, White R A, Klink M J, Key D, Iwuoha E
Inorganic Porous Media Group, University of the Western Cape, Private Bag X17, Bellville 7535, South Africa.
Talanta. 2004 Sep 8;64(1):109-14. doi: 10.1016/j.talanta.2003.10.059.
The use and application of synthetic zeolites for ion exchange, adsorption and catalysis has shown enormous potential in industry. In this study, X-ray fluorescence (XRF) analysis was used to determine Si and Al in fly ash (FA) precipitates. The Si and Al contents of the fly ash precipitates were used as indices for the alkaline hydrothermal conversion of the fly ash compounds into zeolites. Precipitates were collected by using a co-disposal reaction wherein fly ash is reacted with acid mine drainage (AMD). These co-disposal precipitates were then analysed by XRF spectrometry for quantitative determination of SiO(2) and Al(2)O(3). The [SiO(2)]/[Al(2)O(3)] ratio obtained in the precipitates range from 1.4 to 2.5. The [SiO(2)]/[Al(2)O(3)] ratio was used to predict whether the fly ash precipitates could successfully be converted to faujasite zeolitic material by the synthetic method of [J. Haz. Mat. B 77 (2000) 123]. If the [SiO(2)]/[Al(2)O(3)] ratio is higher than 1.5 in the fly ash precipitates, it favours the formation of faujasite. The zeolite synthesis included an alkaline hydrothermal conversion of the co-disposal precipitates, followed by aging for 8h and crystallization at 100 degrees C. Different factors were investigated during the synthesis of zeolite to ascertain their influence on the end product. The factors included the amount of water in the starting material, composition of fly ash related starting material and the FA:NaOH ratio used for fusing the starting material. The mineralogical and physical analysis of the zeolitic material produced was performed by X-ray diffraction (XRD) and nitrogen Brunauer-Emmett-Teller (N(2) BET) surface analysis. Scanning electron microscopy (SEM) was used to determine the morphology of the zeolites, while inductively coupled mass spectrometry (ICP-MS), Fourier transformed infrared spectrometry (FT-IR) and Cation exchange capacity (CEC) [Report to Water Research Commission, RSA (2003) 15] techniques were used for chemical characterisation. The heavy and trace metal concentrations of the zeolite products were compared to that of the post-synthesis filtrate and of the precipitate materials used as Si and Al feed stock for zeolite formation, in order to determine the trends (increase or decrease) and ultimate fate of any toxic metals incorporated in the co-disposed precipitated residues.
合成沸石在离子交换、吸附和催化方面的应用在工业中已显示出巨大潜力。在本研究中，采用X射线荧光（XRF）分析来测定粉煤灰（FA）沉淀物中的硅和铝。粉煤灰沉淀物中的硅和铝含量被用作将粉煤灰化合物碱性水热转化为沸石的指标。通过共处置反应收集沉淀物，其中粉煤灰与酸性矿山排水（AMD）反应。然后用XRF光谱法对这些共处置沉淀物进行分析，以定量测定SiO₂和Al₂O₃。沉淀物中获得的[SiO₂]/[Al₂O₃]比值范围为1.4至2.5。[SiO₂]/[Al₂O₃]比值用于预测粉煤灰沉淀物是否能通过[J. Haz. Mat. B 77 (2000) 123]的合成方法成功转化为八面沸石沸石材料。如果粉煤灰沉淀物中的[SiO₂]/[Al₂O₃]比值高于1.5，则有利于八面沸石的形成。沸石合成包括对共处置沉淀物进行碱性水热转化，然后老化8小时并在100℃下结晶。在沸石合成过程中研究了不同因素，以确定它们对最终产物的影响。这些因素包括起始原料中的水量、与粉煤灰相关的起始原料组成以及用于熔融起始原料的FA:NaOH比值。通过X射线衍射（XRD）和氮布鲁诺尔-埃米特-泰勒（N₂ BET）表面分析对所生产的沸石材料进行矿物学和物理分析。扫描电子显微镜（SEM）用于确定沸石的形态，而电感耦合质谱（ICP-MS）、傅里叶变换红外光谱（FT-IR）和阳离子交换容量（CEC）[提交给水研究委员会，南非共和国（2003）15]技术用于化学表征。将沸石产物中的重金属和痕量金属浓度与合成后滤液以及用作沸石形成的硅和铝原料的沉淀材料的浓度进行比较，以确定共处置沉淀残渣中所含任何有毒金属的趋势（增加或减少）和最终归宿。
