Browsing by Author "Roa, Karina"

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    Copolymeric hydrogels with high capacities of hydration and methylene blue adsorption in water
    (2024) Oyarce, Estefania; Diaz, Hector; Boulett, Andres; Roa, Karina; Sanchez, Julio; Marambio, Oscar G.; Pizarro, Guadalupe del C.
    Copolymers based on monomethyl hydrogen itaconate (beta HI) with 2-hydroxyethyl methacrylate (HEMA) and beta HI with 2-hydroxypropyl methacrylate (HPMA) were prepared in different monomer molar ratios. The reactivity parameters of copolymerization (r1 and r2) were determined. The values obtained for r1 and r2 indicate that P (beta HI-co-HEMA) exhibits a high tendency towards alternate copolymerization. Structural characterization of the copolymeric hydrogels was carried out using Fourier transform infrared (FTIR) and 1H NMR spectroscopies, where the characteristic signals of the constituent functional groups were observed. The typical thermal stability of the polymeric systems was observed by thermogravimetric analysis (TGA). In addition, the swelling capacity in water was evaluated, and a swelling percentage over 655 % and 1249 % presented P(beta HI-co-HEMA) and P (beta HI-co-HPMA) respectively, in a period of 15 days at pH 10, and presence of 0.05 M NaNO3. Additionally, methylene blue (MB) adsorption capacity was studied in batch mode by varying different experimental parameters. MB adsorption capacity of 122.79 mg g- 1 and 112.24 mg g- 1 were achieved for P(beta HIco-HEMA) and P(beta HI-co-HPMA), respectively. The data obtained were fitted to the Elovich kinetic model and to a Redlich-Peterson isotherm. The thermodynamic parameters indicated that the adsorption phenomenon is spontaneous, endothermic and with a high probability of occurrence. The adsorption efficiency decreases by approximately 60 % in the presence of interfering ions (Na+, K+, Ca2+ and Cl-). The adsorbents are reusable and achieve high MB adsorption efficiency (90 % and 80 % for P(beta HI-co-HEMA) and P(beta HI-co-HPMA) respectively) in a textile-simulated wastewater. Based on the results obtained, it is concluded that P(beta HI-co-HEMA) and P(beta HI-coHPMA) show great potential for use in adsorption of water molecules, for MB retention and purification of simulated effluents from the textile industry.
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    Nano-composites based on ligno-sulfonate and titanium oxide to study methylene blue removal and photo-degradation
    (2024) Boulett, Andres; Roa, Karina; Pizarro, Guadalupe; Sanchez, Julio
    The dyes in minimum concentrations are toxic, cause visual and photosynthetic contamination in natural waters. For this reason, in this study, methylene blue (MB) adsorbent nano-composites were prepared based on variable percentages of sodium ligno-sulfonate (LS) (0.00-30.0 wt%) and titanium oxide nanoparticles (Np TiO2) (0.00-10.0 wt%) in sodium poly (4-styrene sulfonate) (P(SSNa)). Chemical, morphological, and thermal techniques corroborated the presence of the main functional groups of the nano-composites, with surfaces formed by macro-pores, and that of Np TiO2 showed an increase in the thermal stability of the material. On the other hand, from studies of hydration of the nano-composites, percentages higher than 4000% were obtained with low dependence on pH effects, which could benefit the diffusion of the pollutant to the adsorbent in its adsorption. In relation to this, the MB retention capacity was evaluated by experimental parameters, such as % LS, % Np TiO2, pH, presence of ionic strength, contact time, MB concentration and amount of nano-composites. A maximum MB adsorption efficiency of 94.8 % and a capacity of 2886 mg g- 1 were obtained using the P(SSNa)-based system with 20% LS and 10% Np TiO2. The obtained results were fitted to the pseudo-second order kinetic model and Langmuir and Redlich-Peterson isotherm models. In addition, through the synergistic effect of adsorption and photo-degradation, 97.5% of the MB was removed within 1 h of irradiation.