Removal of Alizarin Red Dye Using Calcium Hydroxide as a Low-cost Adsorbent

Calcium ions have very strong affinity and binds effectively to alizarin red dye during staining of biomaterials. This promotes us to choose calcium hydroxide as a low cost adsorbent for the removal of alizarin red dye. Various parameters such as pH, concentration, dose of adsorbent, time, and temperature have been investigated. In addition, enthalpy, entropy, free energy and activation energy have been estimated. Different types of isotherms have been evaluated to understand the nature adsorption and its kinetics. It has been found that the adsorption equilibrium can be obtained after 120 minutes. The adsorption of alizarin red dye on calcium hydroxide is endothermic in nature and occurs spontaneously. It has been found that the adsorption is effective at pH = 12 (60 oC) and the kinetic parameters indicate that the adsorption phenomena is of monolayer type and fits well for the pseudo-second order rate equation.