4.2.8. Miscellaneous industrial wastes as adsorbents
Namasivayam and Yamuna explored waste biogas residual slurry for Cr(III) removal from aqueous solutions. The maximum adsorption potential of biogas residual slurry for Cr(III) was found 7.8 mg/g at pH 2.5.
Solid wastes from the distiller waste (DW), which is the byproduct of the ammonia-soda process for the production of soda ash, has been used as an alternative adsorbent for removing the anionic dyes from aqueous medium. The results indicated that adsorption was strongly pH dependent. The typical dependence of dye uptake on temperature and the kinetics of adsorption indicated the process to be chemisorption. The results showed that as the pH increased, extent of dye uptake increased and Ca(OH)2 particles precipitated at higher pHs were mainly responsible for the removal of anionic Procion Crimson H-EXL (reactive red 231) dye. The required time to reach the equilibrium was found to be less than 2 min. Dye uptake process followed the pseudo-secondorder rate expression. The Freundlich isotherm best fitted for the adsorption of the dye.