To improve adsorption capabilities, varios activation methods are used. Activation is any process where the treated material’s adsorption capabilities are improved, i.e. its mean surface area, porosity and adsorption capacity. Activation is also physical and chemical treatment of a mineral.
Activation is performed physically, chemically or in a combined process. Physical method come to do thermal treatment of sorbents, processing them in a colloid mill in vacuum and at high temperature, high pressure and temperature (hydrothermal treatment), as well as treatment with ultrasonic waves, radiation, high frequency current, and energetic particles.
Chemical treatment involves mineral or organic acids, alkali, soluble or insoluble salts, surfactants, water-soluble electrolytes etc.
Mineral acids are the least expensive and the most efficient activators, which deeply influence the chemical composition and structure of silicates. The nature, concentration and the amount of the acid used, process temperature and duration, the degree of crystallization, dispersion and mineral composition of the adsorbent defines the rate and results of the activation.
The variety of crystal and mineral structure of natural clays and their varying chemical composition require research of the acidic method to identify the optimal process parameters to improve the adsorption capabilities.
The method involves thermal treatment of the mineral before acidic activation for 1.5-2.0 hours at 720-750oС. This method can be successfully applied to activate natural sorbents.
Other activation methods
One of the promising methods of improving silicate adsorption capability is processing with various organic chemicals.