François Zagabe Zabene^{1, 2}, Simplice Koudjina^{3, 2,}, Alidor Mbaya Shikika¹, Ferdinand Goudjo², Nafiou Egbeola Chitou², Jean Wilfried Hounfodji², Etienne Sagbo², Fabrice Amisi Muvundja¹, Waris Kewouyemi Chouti²

Heavy metal and drug residues in the environmental have become serious pollutants to be addressed. Grey waters from municipalities, hospitals and chemical industries may be loaded with these chemicals and end up into the environment, especially in water springs, rivers and lakes. Moreover, the pre-treatment measures for these wastewaters are needed to ensure the treated water is environmentally safe and unpolluted. Therefore, we aimed in this work to optimize the physicochemical conditions that favour their adsorption onto Beninese Kaolinite geopolymer from Ketou. Moreover, a quantum chemical mechanistic modeling showed that the adsorption of copper and paracetamol is exothermic according to a single mode for copper with an energy of -139.15 kJ.mol^-1 while that of paracetamol is in two modes, namely the horizontal mode having a high energy of -159.40 kJ.mol^-1, and the vertical mode of -91.10 kJ.mol^-1. By heating the kaolinite that had adsorbed these pollutants, it can release them at 435 K and 750 K respectively. Under these conditions, the geopolymer eliminates about 90% of the Cu²⁺ ions and 72% of the paracetamol. This adsorption process does not cause any disorder in its structure (∆S < 0), as follow the Pseudo-second order model with R² > 0.99 and its isotherms are well simulated by Langmuir model. Application to hospital wastewater gave reduction rates in copper of 90.5 ± 2.1% and in paracetamol of 88.5 ± 3.65%. Kaolinite was found to be an effective adsorbent for treating industrial wastewater before its discharge into the environment.

Adsorption, Kaolinite, Copper, Paracetamol, Wastewater