Batch and bulk removal of hazardous colouring agent Rose Bengal by adsorption techniques using bottom ash as adsorbent

Abstract

Rose Bengal is a halogen-containing fluorescein water soluble dye, which is widely used for medical purposes. The dye, however, is highly toxic and can cause irritation, itching etc. to the human skin and eyes. It is therefore considered worthwhile to develop a systematic method for the removal of Rose Bengal by adsorption processes. The present investigation is devoted to batch as well as bulk removal of Rose Bengal. Under preliminary batch studies, adsorption isotherm measurements and kinetic studies were carried out, while for the bulk removal, a glass column was used as a fixed bed adsorber made up of Bottom Ash. Attempts were also made for the recovery of the dye from the exhausted Bottom Ash column by eluting dilute NaOH. The paper also presents a detailed procedure for activating Bottom Ash and its chemical and physical analysis. Rose Bengal showed a decrease in adsorption with increasing pH and conversely, increases in concentration, temperature, amount of adsorbent and sieve size increased the adsorption. Langmuir, Freundlich, Tempkin and D–R adsorption isotherm models were also verified, and on the basis of Langmuir constants thermodynamic parameters such as the Gibb's free energy, enthalpy and entropy of the adsorption were also calculated. A pseudo-second order process was found to operate during the adsorption. During column operations various parameters like fractional capacity of the column, mass flow rate, percentage saturation of column etc. were calculated. Desorption from the exhausted column gave almost 91% of dye recovery.