Experimentally and theoretically approaches for Congo red dye adsorption on novel kaolinite-alga nano-composite

Abstract

ABSTRACT A comprehensive study combining experimental, computational, and field experiments was conducted to find out the most suitable catalysis method to assist industries using Congo red dye to get rid of this waste from industrial wastewater in Beni-Suef area. The adsorption potential of kaolinite, Liagora farinose (Egyptian marine macroalgae) and kaolinite modified by Liagora farinose macroalgae assessed for the removal of Congo red dye from aqueous solutions. The kaolinite/alga nano-composite with a crystal size of 40 nm was fabricated using a wet impregnation technique. Our results indicate that surface modification of kaolin with Liagora farinose results in an obvious increase in adsorption of toxic dye for nano-composite than individuals. Batch experiments were applied and both kinetics and isotherms of Congo red dye adsorption were also explored in order to find out the influence of different experimental factors. Congo red removal percentage is highly affected by adsorbent dose, working temperature, and pH value. The best temperature for Congo red adsorption onto kaolinite/alga nano-composite is 40°C at pH > 7. The maximum adsorption capacities were found to be 5.0, 7.0 and 10 mg/g for kaolinite, alga and kaolinite/alga nano-composite, respectively. Computational simulations studies have shown that the adsorption of the Congo red molecule on Kaolinite surfaces is exothermic, energetically favourable and spontaneous. Congo red adsorption on kaolinite/alga nano-composite is well handled with the first-order diffusion model, while kaolin and Liagora farinose follow two different kinetic adsorption models depending on the Congo red dye concentration. Finally, the field tests showed optimistic results with nearly 94% efficiency for kaolinite/alga nano-composite in removing mixed dyes from industrial wastewater, which in turn verified the foundation of new eco-friendly nano-adsorbents to help reuse industrial wastewater.