Synthesis and adsorption property of zeolite FAU/LTA from lithium slag with utilization of mother liquid

Co-crystalline zeolite FAU/LTA-0 was synthesized by hydrothermal method from lithium slag. To make the most of excess silicon and alkali sources in mother liquid derived from FAU/LTA-0, zeolite FAU/LTA-1b was synthesized in the same method with the use of mother liquid by adding a certain amount of aluminum source. Influences of different adding ways of aluminum source and recycling dosages of mother liquid on synthesis of zeolites FAU/LTA with mother liquid were investigated. The phase, microstructure and thermostability of FAU/LTA-0 and FAU/LTA-1b were characterized by XRD, SEM and TG-DTA. The calcium and magnesium cation exchange capacities (CECs) of the zeolites were determined. The results have shown that co-crystalline zeolite can be synthesized with the use of mother liquid by adding aluminum source after 2 h of reaction. Compared with FAU/LTA-0, the crystal twinning structure of FAU/LTA-1b became weaker, the grain size was smaller, and the thermostability was better. With a lower dosage of mother liquid, the content of P-type impurity in product decreased significantly, and the content of LTA phase increased. The reuse rate of mother liquid can reach 48%. The CECs of FAU/LTA-1b-150 can reach 343 mg CaCO3·g− 1 and 180 mg MgCO3·g− 1, showing more excellent adsorption capacities than FAU/LTA-0 and commercial zeolite 4A. The full recycling use of mother liquid to synthesize zeolite FAU/LTA which can be applied for detergent not only improves resource utilization but also reduces production cost.

Graphical abstractMother liquid was used in the synthesis of Co-crystalline zeolite by hydrothermal method with lithium slag and NaOH as start materials. Adding ways of aluminum source and dosages of mother liquid have a great influence on structure and performance of co-crystalline zeolite. Zeolite FAU/LTA-1b-150 synthesized with utilization of mother liquid show excellent adsorption capacities for calcium and magnesium which can reach 343 mg CaCO3/g and 180 mg MgCO3/g. The utilization rate of mother liquid can reach 48% which can both save raw materials and reduce pollution of environment. So zeolite FAU/LTA synthesized from lithium slag with utilization of mother liquid has an excellent application prospect for replacing 4A as a detergent builder.Figure optionsDownload full-size imageDownload as PowerPoint slide