Zeolite was synthesized via alkaline fusion from the tailings dam sediments of a sand mine in southern Brazil. The sediments are composed of a mixture of illite, kaolinite, vermiculite, quartz and K-feldspar yielding a silty-loam texture. The extent of zeolite synthesis was tested under varied NaOH:sediment ratio, temperature and fusion time. At the NaOH:sediment ratio of 8:5 and fusion temperature of 600 °C, all minerals were dissolved and converted in faujasite, except a quartz residue of less than 5 wt%. The synthetic faujasite shows intergrown octahedral habit, grain size < 2 µm, specific surface area of 760 m² g⁻¹ and cation exchange capacity of 4.6 cmol kg⁻¹. Experiments at lower NaOH:sediment ratio produced lower amounts of zeolite from 6:5 to 5:5 and 4:5, faujasite fraction declined from 73 to 50 wt%. At an NaOH:sediment ratio of 3:5, the faujasite fraction dropped to 0.7 wt%, below which no faujasite was formed. By decreasing temperature from 550 to 250 °C, a smooth decrease in faujasite formation was observed, from 64 to 29 wt%. A synthetic analogous of ferrierite appeared in the runs at 300 and 250 °C. Experiments using prolonged heating (up to 12 h) at low temperatures (300, 200 °C) and low NaOH:sediment ratio (3:5) did not enhance zeolite formation. Kaolinite and vermiculite were dissolved in all runs, while residual illite was ubiquitous and residual quartz was present in all experiments.

中文翻译：

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尾矿坝沉积物中碱性熔融合成沸石的程度

沸石是通过碱性熔融从巴西南部某砂矿的尾矿坝沉积物中合成的。沉积物由伊利石，高岭石，ver石，石英和钾长石的混合物组成，产生粉质壤土质感。在不同的NaOH：沉降比，温度和熔融时间下测试了沸石的合成程度。在8：5的NaOH：沉泥比和600°C的熔融温度下，除了石英残留量少于5 wt％之外，所有矿物均被溶解并转化为八面沸石。合成八面沸石显示出混杂的八面体习性，晶粒度小于2 µm，比表面积为760 m ²  g ^-1，阳离子交换容量为4.6 cmol kg ^-1。在较低的NaOH：沉降比下进行的实验产生的沸石量从6：5降至5：5和4：5，八面沸石的含量从73wt％降低至50wt％。在3：5的NaOH：沉渣比下，八面沸石的含量下降至0.7重量％，在此以下没有八面沸石的形成。通过将温度从550降低至250℃，观察到八面沸石的形成从64重量％降低至29重量％。合成的镁碱沸石出现在300和250°C的运行中。在低温（300，200°C）和低NaOH：沉积比（3：5）下长时间加热（长达12小时）的实验不会增加沸石的形成。高岭石和ver石在所有运行中均溶解，而残余伊利石普遍存在，并且在所有实验中均存在残余石英。