锂矿渣制备FAU/LTA共晶分子筛的表征及性能

Characterization and Performance of FAU/LTA Co-Crystalline Zeolite Synthesized by Lithium Slag

以锂矿渣为原料,采用水热合成法制备了3种不同FAU/LTA质量比的FAU/LTA共晶分子筛(FAU/LTA-1、FAU/LTA-2、FAU/LTA-3),并利用XRD、SEM和TG-DTA等手段对其物相、晶体形貌和热稳定性进行了表征,测定了它们对钙、镁离子的交换能力。结果表明,制备的3种FAU/LTA共晶分子筛具有FAU和LTA分子筛典型的晶相,且无其他杂质。FAU/LTA-3中,LTA分子筛占82%,呈立方体;FAU分子筛占18%,呈八面体,伴有孪晶;在800℃下骨架结构未发生坍塌,具有良好的热稳定性。制备的FAU/LTA共晶分子筛对钙离子的交换能力高于X型分子筛,对镁离子的交换能力优于4A分子筛;FAU/LTA-3对钙、镁离子的交换能力分别为324 mg CaCO_3/g和177 mg MgCO_3/g。以锂矿渣为原料制备FAU/LTA共晶分子筛替代4A分子筛作为洗涤剂助剂将具有良好的应用前景。

Three FAU/LTA co-crystalline zeolites with different mass proportions of FAU to LTA （FAU/LTA-1, FAU/LTA-2, FAU/LTA-3） were synthesized by hydrothermal method with lithium slag as Si and A1 sources. The crystalline phases, morphology and thermostability of synthesized FAU/LTA were characterized by XRD, SEM and TG-DTA. The cation （Ca2＋ and Mgz＋） exchange capacities of synthesized FAU/LTA were determined. The results indicated that the synthesized FAU/LTA co-crystalline zeolites had complete crystallization of FAU and LTA zeolite without other crystal types. The main crystalline phase of FAU/LTA-3, in which crystal twinning existed, was LTA-type zeolite of cubic shape with the mass fraction of 82%, while there was a small amount of FAU-type zeolite, only 18%. The skeleton structure of FAU/LTA-3 did not collapse under 800＂C. The Caz＋ exchange capacity of FAU/LTA-3 reached 324 mg CaCO3/g, higher than that of commercial X zeolite. The Mgz＋ exchange capacity of FAU/LTA-3 reached 177 mg MgCOa/g, which had an obvious advantage over commercial 4A zeolite. As a result, FAU/ LTA co-crystalline zeolite synthesized by lithium slag have an excellent application prospect for replacing 4A as detergent builder.