Nanocrystalline CaO as Adsorbent to Remove COD from Paper Mill Effluent

Porous nanocrystalline CaO has been prepared by the solution combustion process using calcium nitrate as oxidizer and glycine as a fuel. As prepared calcium oxide has been characterized using powder X-Ray Diffraction (XRD), BET surface area, and Scanning Electron Microscopy (SEM). The powder XRD pattern confirms the crystallinity and phase purity of the powder. The particle size of the powder obtained from Scherrer's formula lies in the range of 37–53 nm. The particles are loosely agglomerated and spherical in shape as observed by SEM. The specific surface area of the powder is 18.5 m²/g and the average pore diameter obtained from N₂-desorption isotherm is ∼5.2 nm. Batch shaking process was performed using CaO as adsorbent with effluent collected from pulp and paper mill to remove chemical oxygen demand (COD). The COD removal capacity of the CaO is ∼93%.