Síntesis de materiales adsorbentes obtenidos a partir de desechos para la eliminación de surfactantes vertidos en aguas residuales

Abstract

Decontamination of emerging pollutants such as surfactants in aqueous sources is one of the main challenges facing wastewater treatment. Surfactants are difficult contaminants to deal with due to their wide variety and uses. There is a wide variety of surfactants depending on their application. These molecules have a negative impact on the environment due to the inadequate treatment of their waste, where most of these are deposited in water sources, such as rivers and seas affecting wildlife and the ecosystem, due to their marked biological activity. Surfactants are amphiphilic molecules that have a hydrophilic part (head) and a hydrophobic part (tail) and are compounds that modify the surface tension at the interface. When their concentration is less than the critical micellar concentration (CMC) they are in solution in the form of monomers, while when their concentration is greater than the CMC they form micelles. For this reason, they are used as detergents, emulsifiers, disinfectants, and humectants. Although there is a wide range of technologies for the removal, destruction, transformation, or use of liquid waste, conventional treatment systems are currently inadequate to completely remove surfactants from wastewater. More effective treatments are required to reduce the environmental impact of the effluents and comply with the legislative regulations that are increasingly strict. One of these alternative processes is adsorption on activated carbons, due to its low costs and specificity. Activated carbon is an adsorbent that can be obtained from waste materials, such as tire waste or lignocellulosic waste, which can adsorb various substances, together with great ease and speed of removal from the treated medium and the ability to be regenerated for reuse, allowing efficient and economical treatment in various applications. For this reason, this research project focuses on the development of porous materials that efficiently remove surfactants present in an aqueous solution. For this, activated carbons were prepared from two different residues: waste tire and coconut shell. The treatment of the raw material was carried out, using two-particle sizes 0.3mm and 5.0mm and the activated carbons were prepared using physics activation with carbon dioxide and chemical activation with potassium hydroxide and phosphoric acid at 10, 20, 30, and 40% wt.%, at a heating rate of 2 °C. Min-1, with a total flow of 100mL.min-1 and using two final carbonization temperatures 700 and 900 °C. A total of 65 solids carbons were obtained, which were characterized from a structural, textural, and chemical perspective. Taking into account these characterization results and carrying out an experimental design by Minitab, 32 samples were chosen which were further evaluated in adsorption and kinetic studies with three different surfactants: anionic, cationic, and non-ionic.