Synthesis of zeolites from residual diatomite using a microwave-assisted hydrothermal method

Synthesis of Zeolites from Fine-Grained Perlite and Their Application as Sorbents

“…The synthesis of high-quality LTA-zeolite as well as other commercially available zeolites, is often done with expensive chemical grade silicon (colloidal silica, precipitated silica or fumed silica) and alumina (gibbsite, aluminate salts or metal powder) compounds [27,28]. Alternative synthesis routes for zeolite production may also use a variety of natural raw materials of comparatively low price, including kaolinite [29,30], pumice [31], diatomite [32] and fly ash [19,33], while the use of natural reagents over commercial ones has economic benefits, the complex chemical composition of natural materials increases the risk of zeolitic products formation with variable composition and purity [34]. For these reasons, the production of, e.g., LTA-zeolites for commercial water treatment applications is still limited caused by (i) the complexity of the synthesis process, (ii) the involvement of seeds of high costs in the synthesis, (iii) difficulties to obtain reproducible and defect-free (pure) products, (iv) the unsuitable performance of most zeolites under acidic conditions, (v) the fragile structure and the corresponding low mechanical stability of most zeolites under corrosive conditions and (vi) technical challenges to manufacture porous zeolite membranes [28].…”

Zeolitization of Diatomite Residues by a Simple Method

“…The holed structural pattern of diatomite gives it very interesting physical properties, which has led this material to be commonly used in different industrial processes as an absorbent, filter medium, thermal insulator, filler, catalyst carrier, among others [1,2]. Accordingly, diatomite has been exploited for more than a century and is used in large quantities due to its low cost [3,4]. Among other applications, diatomite is used in the agri-food industry as a filter medium in the production of wine and beer, generating large quantities of waste rich in this material, in this case saturated in organic matter.…”

“…Among other applications, diatomite is used in the agri-food industry as a filter medium in the production of wine and beer, generating large quantities of waste rich in this material, in this case saturated in organic matter. From an environmental and economic perspective, different strategies are being considered to valorize these wastes, not only to obtain new products with added value, but also to reduce their potential hazardousness [3,4].…”

“…Due to their nanostructure, zeolites can be considered advanced materials whose application is very wide as a catalyst in chemical processes, adsorbent of cations and organic molecules, desalination processes, gas separation, etc. [4,5]. There are several publications that cover the study of the synthesis of zeolites from (fundamentally natural) diatomites, some of which are summarized below.…”

“…As a result, the authors obtained ZSM-5 zeolites of good quality. In a relatively recent study, Stafin et al [4] used diatomaceous earth wastes from beer filtration. Apart from distilled water, the diatomite was mixed with NaOH and Al(NO 3 ) 3 •9H 2 O as aluminum source.…”