Speech: A Speech On Manorbents And Obsorption Process
1295 Words6 Pages
Adsorbents and adsorption process
Most adsorbents are highly porous materials, and adsorption takes place primarily on the walls of the pores or at specific sites inside the particle. Because the pores are generally very small, the internal surface area is often in the range of 500 to 1000 m^2/g. Separation occurs because differences in molecular weights, shape or polarity cause some molecules to be held more strongly on the surface than others or because the pores are too small to admit the larger molecules. In many cases, the adsorbing component(or adsorbate) is held strongly enough to permit complete removal of that component from the fluid with very little adsorption of other components. Regeneration of the adsorbent can then be carried out to obtain the adsorbate in…show more content… Transport of adsorbate from the bulk of the solution to the exterior film surrounding the adsorbent particle;
2. Movement of adsorbate across the external liquid film to the external surface sites on the adsorbent particle (film diffusion);
3. Migration of adsorbate within the pores of the adsorbent by intraparticle diffusion (pore diffusion);
4. Adsorption of adsorbate at internal surface sites.
All these processes play a role in the overall sorption within the pores of the adsorbent. In a rapidly stirred, well mixed batch adsorption, mass transport from the bulk solution to the external surface of the adsorbent is usually fast. Therefore, the resistance for the transport of the adsorbate from the bulk of the solution to the exterior film surrounding the adsorbent may be small and can be neglected.
Adsorption Isotherms:
The process of Adsorption is usually studied through graphs know as adsorption isotherm. It is the graph that express the amount of adsorbate adsorbed on the surface of adsorbent as a function of its pressure (if gas) or concentration (if liquid) at constant temperature.
Where, Q= Adsorbate Loading C= Conc in fluid
Isotherm Equation
Freundlich q_e=K_F