Browsing by Author "Abad Delgado, Alex David"

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Adsorción de ciprofloxacina y diclofenaco sobre arcillas naturales e hidrolizadas usando vasos agitados
(Universidad de Cuenca, 2023-02-14) Abad Delgado, Alex David; Ponce Montalvo, Jonathan Daniel; Peñafiel Tenorio, María Eulalia
Emerging contaminants such as ciprofloxacin and diclofenac are not adequately removed in wastewater treatment plants, affecting the environment. These drugs are of particular interest as they appear on the EU watch list. Several processes, such as adsorption on carbonaceous materials and agricultural waste, have been successfully tested. Against this background, the objective of this work was to find environmental, economical, and effective solutions for the removal of contaminants such as ciprofloxacin and diclofenac on clays in stirred vessel adsorption processes. The clays were characterized by determining the zero-charge point, functional groups, specific surface area, and adsorption capacity. In addition, acid hydrolysis was performed to increase their specific surface area and adsorption capacity, especially in the removal of DCF, which increased by 40 to 60%. All clays adsorbed ciprofloxacin up to 270 mg/g. Acid treatment did not significantly increase the adsorption capacity of this drug. Instead, hydrolyzed clays achieved the adsorption of diclofenac, which natural clays were unable to adsorb, indicating that ciprofloxacin has a greater affinity with clays than diclofenac. Finally, it was shown that the adsorption kinetics for all clays in the removal of CPX and DCF fit the pseudo-second-order model, indicating rapid adsorption. The equilibrium model that best fit for CPX was Freundlich, which suggests multi-layer adsorption, and for DCF was Langmuir, indicating monolayer adsorption.
Removal of ciprofloxacin from an aqueous medium by adsorption on natural and hydrolyzed bentonites
(2023) Menéndez, Miguel; Abad Delgado, Alex David; Jara Cobos, Lourdes Elizabeth; Peñafiel Tenorio, María Eulalia; Ponce Montalvo, Jonathan Daniel
Two bentonites (sodic bentonite, BSN, and calcic bentonite, BCN) were treated with nitric acid to improve the adsorption capacities using ciprofloxacin (CIP) as an adsorbate. The results demonstrated that nitric acid treatment enhances the specific area and increases the pore volume of both bentonites. The mechanism of adsorption of CIP was investigated using a kinetic model, isotherms, and pH influence. The adsorption capacity for BSN increased from 294.1 mg.g−1 to 416.6 mg.g−1 after acid treatment, while the increase in the adsorption capacity of BCN was minor. The increase in CIP removal may be due to an increase in the specific area and the presence of acidic surface functional groups. The adsorption mechanism of CIP on all adsorbents was governed by external diffusion, internal diffusion, and adsorption to reach equilibrium. The adjustment of strong adsorbents to the BET model indicated multilayer adsorption. The best adsorbent is sodic bentonite with nitric acid treatment. The study of the pH effect showed that the mechanism of CIP adsorption is hydrogen bonds and electrostatic interaction. Therefore, the acid treatment was found promising to improve the adsorbent characteristic of clays for removing CIP from water.