Activating natural bentonite as a cost-effective adsorbent for removal of Congo-red in wastewater

The bentonite is a widely available and abundant natural mineral, and can be a low cost adsorbent for water and wastewater treatment. This study reported here was directed towards identifying a cost-effective activation protocol for enhancing the adsorption capacity of Australian bentonite for removal of toxic contaminants in wastewater. We investigated three protocols including thermal activation (TA), acid activation (AA), and combined acid and thermal activation (ATA). The results showed that these activation protocols under designed conditions can enhance the surface area and porosity of the raw bentonite. The best ATA protocol considered here brought a 70% increase in the surface area compared to 65% and 20% for the best AA and TA protocols, respectively. The optimal ATA protocol identified in the study leads to approximately 25% increase in the Congo-red adsorption capacity of the activated bentonite. This activation method could be a cost-effective approach to enhance the adsorption capacity, applicability and selectivity of natural clay materials, making them as promising and low cost adsorbents for wastewater treatment.