In the earliest civilizations, man transformed raw materials in order to obtain the materials he needed to make tools and equipment in general. Among the most abundant, universal and accessible raw materials, clay is undoubtedly a particularly interesting example. In fact, it is used in an extremely wide range of applications, from the most traditional, such as construction, to sophisticated materials such as certain heterogeneous catalysts, illustrating the real utility and great versatility of this family of silicates.
It's no commonplace to assert that a raw material as simple as clay can have so-called "advanced" applications. In fact, it can be transformed into a wide variety of materials - even functional nano-materials. In order to illustrate these concepts, we will consider various examples that constitute a concise review of functional materials based on clays, which have been the subject of studies in our group over the last few years. Today, these materials are of great interest in a wide range of applications: special adsorbents, specific catalysts, anti-pollution materials, electrical and electrochemical components and devices, selective membranes, photo-active systems or even in the preparation of latest-generation adjuvants for vaccines.
Among the most recent examples, clays have been the basis for the preparation of new multi-functional materials, such as magnetic adsorbents or supported graphenes. Lamellar clays, such as montmorillonite, or fibrous clays, such as sepiolite, treated with ferrofluids are transformed into superparamagnetic materials capable of absorbing organic species very efficiently and exchanging cations in solution. Their superparamagnetic nature facilitates the capture of the material by the action of a magnetic field, enabling the sequestration and removal of pollutants from water without the need for complex recovery processes such as filtration, centrifugation or membrane processes. In addition, clay-supported graphene has been produced by the controlled carbonization of absolutely harmless organic compounds, such as caramel or gelatin. This is a new process for preparing graphenoid-type materials by a "soft route", leading to carbon-clay compounds with properties simultaneously characteristic of both components, i.e. adsorption and electrical conductivity.
