In case chemisorption, why adsorption first increase and then decrease with temperature ?

Explanation

Chemical adsorption involves a chemical reaction between adsorbent and adsorbate. As we know, the rate of a chemical reaction always increases with increase in temperature, because the heat added provides the activation energy. This explains why rate of chemical adsorption first increases with increase in temperature. Desorption involves breaking of bonds and breaking of bonds requires energy. As the temperature rises furthers the additional amount of heat added is used for breaking the bonds first formed leading to desorption its (desorption is reverse of adsorption), an increase in the rate of desorption with increase in temperature lowers the rate of adsorption.