Factors Influencing Adsorption of solutes from solutions
The amount of solute adsorbed by a solid from the solution depends on the following factors.
1. Effect of temperature
A rise in temperature increases the kinetic energies of solute particles and hence these particles leave the surfaces and thereby lowering the extent of adsorption.
Frendlich adsorption equation is found suitable to explain the effect of concentration.
If a graph is drawn between log x/m Vs log c, a straight line is obtained for small changes of concentrations.
i) when the solute is adsorbed by an adsorbent it is called positive adsorption.
ii) But of the solvent is taken up by the adsorbent it is called negative adsorption.
a. Negative adsorption
Adsorption of substance from the solution decrease with rise in temperature and decrease in concentration of solution. This type of adsorption is known as negative adsorption.
Ex. Adsorption of water
From the dilute solution of KCl, charcoal adsorbs water, thereby the concentration gets increased.
b. Positive adsorption
Adsorption of substance from solution increases with decreases in temperature and in concentration of solution. This type of adsorption is concentration of solution. This type of adsorption is known as positive adsorption.
Ex. Adsorption of salt (KCl)
Charcoal adsorbs KCl rather than water thereby salt concentration gets decreased.
i) The nature of the solute adsorbed
The extent of adsorption is usually greater when the molecular weight of the solute is high.
ii) Effect of surface area
If the surface area of the adsorbent is increased, adsorption also increases.
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