Decolorization of Wastewater from Pulp and Paper Industry by Adsorption on Talc

This study focuses on the elimination of residual dyes from industrial wastewater using talc as an adsorbent. Talc is an easily available, ecological, and inexpensive adsorbent. The adsorption process was tested on two model dye samples (Ecozol Blue LR Liquid and Cartasol Yellow 3GF Direct Yellow 132), and two samples of real wastewater from the pulp and paper industry (PM and TP). Kinetic studies revealed that the adsorption of Ecozol Blue LR Liquid followed pseudo-second-order kinetics, while the other tested samples followed pseudo-first-order kinetics. Langmuir, Freundlich, and Dubinin-Radushkevich adsorption isotherm models were also evaluated. The Langmuir isotherm model best fitted the experimental data for the adsorption of model dye solutions and wastewater sample TP onto talc. For wastewater sample PM, the Dubinin-Radushkevich isotherm model provided the best fit to the experimental data. The results of the adsorption isotherms indicated that the adsorption of all tested systems was favorable and primarily involved physical adsorption. The adsorption efficiency for the model solutions exceeded 90 %. For real wastewater samples, the monitored adsorption efficiency in the COD pollution indicator was less efficient, ranging from 43 to 51 %. The lower efficiency of COD may have resulted from the adsorption of residual dyes with lower specific COD values before the adsorption of other organics.