What does the term “sorption” stand for?
Sorption is a collective term for adsorptive and absorptive processes. Adsorption describes the attachment of molecules of a fluid phase onto the surface of a solid or liquid. In the course of absorption, there is an additional diffusion of fluid molecules into the stationary phase. The reversal process of both sorption processes is the desorption, describing the removal of previously sorbed molecules and the return into the fluid phase. The corresponding nomenclature will be explained by the example of adsorption in the figure on the left side. According to this, the molecules to be adsorbed are called adsorptives. The solid on which the molecules are adsorbed is called adsorbent. In addition, the term adsorbate stands for already adsorbed molecules. In case of an adsorption of different fluid molecules, it is called a coadsorption.
How are sorption processes used on industrial scale?
Corresponding sorption processes are used for example, in pressure swing adsorption plants for the treatment of biogas. In general, the adsorption capacity of sorbents increases with increasing pressure within the sorptive gas phase. This property is used in a PSA plants for biogas purification, i.e. for the separation of CO2 and CH4. In this process, an adsorber filled with a carbon molecular sieve or zeolite, is flown through with biogas under increased gas pressure. Such sorbent materials exhibit a defined pore size distribution. Due to the different molecular diameters of the individual gas components, smaller gas molecules, such as those of carbon dioxide, are being increasingly adsorbed. In this way, a methane-rich product stream is generated. After achieving maximum capacity of sorbent material, the adsorber can be regenerated under reducing gas pressure. A batch operation of up to 6 adsorbers enables a constant generation of pure biomethane.
How can sorption processes be measured?
Knowledge of sorption behavior of used sorbent materials is of great importance for the design of such PSA systems. For this reason, the accurate measurement of sorption capacity is of particular interest. This is often described by means of sorption isotherms. For performing of such sorption measurements, Rubolab offers various instruments of the RuboSORP product line. The Magnetic Suspension Balance is currently the most accurate measurement method for sorption measurement on smallest sample masses and within extreme measuring conditions. Volumetric measurement instruments of the RuboSORP MPA series are the perfect instrument for performing screenings, i.e. the time-saving characterization of several sample materials. Using of RuboSORP BTC / PSA series measuring instruments is suitable for a realistic study of dynamic adsorption processes.