Modification of Bentonite Clay for Adsorption Enhancement for Congo Red Dye Removal from Textile Waste Water

No Thumbnail Available



Journal Title

Journal ISSN

Volume Title


Addis Ababa University


Bentonite clays are considered as low cost adsorbents due to their local and abundant availability, non-toxicity, and potential for ion exchange and can easily undergo modification to increase their surface area and adsorption capacity. The present study includes the preparation, characterization and performance testing of a set of adsorbents, prepared by the acid activation of bentonite clay obtained from Gewane, Afar regional state of Ethiopia. The acid activation experiments were carried out by sulfuric acid solutions of various concentrations in the range of (0.05-0.5 M) at different temperatures (30, 60, 90 oC) for 3hours.The result revealed that bentonite activated with 0.1M sulfuric acid at 30 oC showed a higher efficiency in removing congo red dye from aqueous solution and was selected for further investigation. The raw and acid activated bentonite materials were characterized using several techniques such as wet-chemical /complete silicate analysis , Scanning electron microscopy (SEM with EDS), Fourier-transform infrared spectroscopy (FTIR) and XRD. The results of the analysis by complete silicate analysis and Energy Dispersive Spectroscopy (EDS), showed that the presence of silica and alumina as major constituents with a very small amount of iron, calcium, magnesium, sodium, potassium, and titanium as a form of impurities. The results of the XRD showed that the raw bentonite was composed of montmorillonite, quartz, hematite, feldspar, and cristobalite. The microscopic images obtained through SEM showed that the structure of the activated bentonite was different from the raw bentonite clay indicating the formation of perforation /vacant sites. A general full factorial experimental design was employed to correlate the effect of key operational parameters, such as contact time, initial dye concentration and, pH on the adsorption of congo red dye onto bentonite activated with 0.1 M sulfuric acid were experimentally studied using a batch adsorption process. The result showed that the optimum condition for the percentage dye removal was 95.74% at the time of 6 hr. a dye concentration100.58 mg/l and pH 5.03 .The isotherm data for adsorption of congo red dye on AA bentonite were analyzed using Langmuir and Freundlich adsorption isotherms. Freundlich isotherm model was found more representative. Further to understand the adsorption kinetics the adsorption data were analyzed by pseudo first-order and pseudo second-order kinetics. The results revealed that adsorption kinetics was adequately described by pseudo second-order kinetics.



Raw bentonite, Acid activation, congo red dye, Adsorption