1. Repositorio Bibliotecas UdeC

Buscar por Autor Waste management, especially in wastewater treatment, is a growing challenge due to urban development and the release of heavy metals into aquatic environments caused by industrial activities, poses a threat to ecosystems and human health. Extracellular Polymeric Substances (EPS) have unique properties that make them effective adsorbents for heavy metals, making them an attractive alternative in the search for sustainable and economically viable solutions for metal removal. This thesis focused on optimizing a process for the efficient extraction of EPS from sludges of Wastewater Treatment Plants (WWTPs) to maximize the yield and their capacity for copper (Cu2+) adsorption, through experimental design as a statistical technique. The extraction method used was alkaline hydrolysis, varying four factors: reagent concentration, temperature, percentage by mass of sludge in the sludge-reagent mixture, and type of alkaline reagent. Although the optimal conditions were not achieved, it was identified that at 20ºC, 10% w/w sludge, and using 1M NaOH, extraction yields and adsorption capacity of EPS were maximized (465 mg EPS/g SV and 46.5 mg Cu(II) ads/g EPS, respectively). Additionally, it was determined that temperature and sludge percentage are the most influential variables on the extraction yield, while reagent concentration and sludge percentage are the most influential on the adsorption capacity. Characterization of extracts revealed a higher presence of proteins than polysaccharides, especially in trials with high concentrations of alkaline reagents. Unlike what is published in the literature, apparently increasing the temperature in the extraction does not increase the amount of EPS; however, what is observed in this study is the result of two effects, one of them being the degradation of macromolecules caused by temperature and the other due to the loss of molecular components of lower weight during the dialysis stages prior to adsorption tests. Better adsorption capacities were observed using Na2CO3 instead of NaOH as the alkaline reagent, as the lower alkalinity allowed better maintenance of the structural integrity of the EPS, thus maintaining the activity of the functional groups on its surface, favoring the adsorption of metal ions. On the other hand, Z potential assays indicated that electrostatic interaction does not fully explain the behavior of EPS in adsorption processes, thus requiring further investigation of the mechanisms involved in this process. The main limitation of this study was the first-order regression model used in the experimental design, which did not allow for complete optimization. It is recommended to carry out an experimental design with a second-order regression model, with the Central Composite Design or the Box-Behnken Design being suitable for this purpose.