Mathematically, bleaching or purification process follows the Freundlich adsorption isotherm. Adsorption isotherm is the equilibrium relationships between the concentration in the fluid phase and the concentration in the adsorbent particles at a given temperature. For the cases involving liquids, the concentration is often expressed in mass units such as part per million (ppm). The concentration of adsorbate on the solid is given as mass adsorbed per unit mass of original adsorbent.