Direct Synthesis of Zeolites from a Natural Clay, Attapulgite

Abstract

Presently, chemical Si/Al sources are predominantly used as raw materials for the synthesis of zeolites in spite of their high cost. Here, we report for the first time the direct synthesis of a ZSM-5 zeolite by using a natural clay, attapulgite (ATP), as the lowcost and environmentally benign Si/Al source through a vaporinduced transformation (VIT) method, in which the vapor diffuses into ATP and interacts with the framework. In a crystallization recipe, ATP is well present with a pristine crystal structure, and the yield of zeolite reaches 96%. The resultant zeolite exhibits welldefined crystallinity and porosity, which are comparable to the counterpart synthesized from traditional chemical Si/Al sources. In the synthetic process, the formation of Si−F species plays an important role, which promotes the transformation of an ATP crystal to a zeolite crystal. Meanwhile, the metal elements (e.g., Al, Fe, and Mg) of ATP exist in the zeolite products, and at least part of them are located in the zeolite framework, which endows the zeolite with excellent catalytic activity. Direct synthesis of various zeolite crystals including TON, MOR, and *BEA from ATP is also realized via the VIT method. Our work provides a green and economic alternative for the synthesis of zeolites using natural clays instead of chemical raw materials.

Formation of Palygorskite Clay from Treated Diatomite and its Application for the Removal of Heavy Metals from Aqueous Solution

“…However, the amount of silica increased to 78.83% after using HCl solution. These results of XRF analysis are in agreement with those reported by Li and coauthors, although the diatomite was from different sources containing mainly SiO 2 with percentage ranging from 62.8 to 90.1% [20].…”

Supramolecular Organization in Confined Nanospaces

“…Taking inspiration from Blue Maya, the indigo molecule was recently encapsulated into zeolite L microcrystals yielding an exceptionally robust colorant: the insight from simulations was instrumental for the successful blockage of the crystal terminations. An atomistic knowledge of natural host matrices is also important for their use in environmental protection (e. g., absorption of organic pollutants by layered hydroxides,, sequestration of trace uranium in multiphase iron minerals) and in the realization of new materials via sustainable fabrication approaches; for instance, using a vapor‐induced approach, a direct synthesis of zeolites starting from clay minerals has been recently performed …”

Comprehensive Understanding of the Eco‐Friendly Synthesis of Zeolites: Needs of 21st Century Sustainable Chemical Industries

“…[48e] Recently, the natural clay attapulgite has been employed for the fabrication of different zeolites (BEA, MFI, and MOR) by using vapor induced transformation method (Table 1, en-tries 39-41). [49] In the clay-based synthesis strategy, the dissolution of activated or not activated clays in the basic medium produce the Si and Al monomeric species, which upon aging forms secondary building units depending on the Si/Al ratio and NaOH concentration, and in the nucleation step it forms the seed of a particular zeolite (with or without a template), which is followed by the crystal growth to form the zeolites (Figure 2b). The main problem of this synthesis strategy is the incorporation of impurity metal ions (Fe, Mg, etc) present in the clay matrix.…”