Browsing by Author "Sanchez, Julio"
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- ItemAnalysis of a constant-volume diafiltration system with the ability to remove lithium cations when using poly(2-acrylamido-2-methyl-1-propanesulfonic acid) in water(2024) Tapiero, Yesid; Sanchez, JulioThis study describes the synthesis of a poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPS) and its application for the removal of Li+ in water using a constant-volume diafiltration system. PAMPS with molecular weights exceeding 100 kDa (88 % w/w), polymerisation yields of 97 % and high acidity was obtained. A block experimental design characterized the diafiltration system reporting: Regenerated cellulose (RC) and polyethersulfone (PES) ultrafiltration membranes with a molecular cut-off of 100 kDa can retain up to 1 % Li+ ions through surface charges. But when PAMPS 2000 kDa was used, 89 % of Li+ was removed (%R). Permeate flux (J(s)) decreases with increasing PAMPS:Li+ ratio, whereas the %R value increases. The filtration process is controlled by diffusion mechanisms according to the Peclet dimensionless number. Using PAMPS 100 kDa with a PAMPS:Li+ ratio (20:1), %R decreases to 76 %, whereas J(s) increases slightly. PAMPS can be reused 3 consecutive times, maintaining a Li+ cation rejection efficiency of >60 %. Additionally, it was found that the percentage of Li+ rejection capacity exercised with PAMPS is reduced to 60 % when Ca2+, K+, Mg2+ and Na+ cations are present.
- ItemCopolymeric 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.
- ItemInvestigating micelle formation in systems with benzethonium chloride and n-lauroyl sarcosine sodium salt: The impact of thermal effects and ethyl lactate concentration using volumetric, statistical, acoustic, and molecular dynamic methods(2024) Fatma, Ishrat; Cantero-Lopez, Plinio; Sharma, Vivek; Yanez, Osvaldo; Correa, Cristian; Sanchez, Julio; Thakur, Ramesh Chand; Kumar, AshishSurface active agents (SAAs) are versatile molecules that possess the ability to serve as multifunctional ingredients in a wide range of consumer products across various industrial sectors. These molecules can act as wetting and dispersion agents, emulsifiers, foaming and anti-foaming agents, lubricants, and more. The objective of this study was to evaluate the effect of temperature, and ethyl lactate concentration on micelle formation in systems containing benzethonium chloride (BC) and N-lauroyl sarcosine sodium salt (NLSS). The experimental measurements were conducted at three equidistant temperatures i.e., 298.15 K to 318.15 K and pressure, P=0.1 =0.1 MPa. Several volumetric as well as compressibility parameters including apparent molar properties ( V phi , K phi , S ), partial molar properties (V degrees phi , V degrees phi , K degrees phi, S ), transport properties ( Delta tr V degrees phi , Delta tr K degrees phi, S ), hydration number, etc. have been evaluated. A Bayesian two-factor design with uninformative priors was used to analyze the values of V degrees phi , and K degrees phi,S. S . It was possible to determine that the temperature factors, and the ethyl lactate (EL) addition significantly influence the results for V degrees phi while for K degrees phi, S it is not appreciable at 5and 10% in EL concentration when BC and NLSS systems is compared. The simulations of the micellization process show the impact of temperature, particularly in the presence of ethyl lactate, is evident in the structural and dynamic changes observed in the micelles. Specifically, as the temperature rises from 298.15 K to 318.15 K, the self-assembly process becomes more spontaneous and accelerated, leading to larger and more spherical micelles. These alterations in micelle size, shape, and orientation enhance their capacity to effectively solubilize hydrophobic substances. The computational simulations demonstrated that BC molecules exhibit spontaneous aggregation at the interface of polarnonpolar systems, resulting in the formation of a monolayer. In this monolayer, the heads of the molecules are oriented towards the polar phase, while the hydrophobic tails are in the nonpolar phase. Similarly, the NLSS system exhibits a continuous and gradual process of self-organization over a period of 120 ns, where NLSS molecules naturally come together to create a single layer arrangement at the zigzag-shaped boundary.
- ItemLignin and functional polymer-based materials: Synthesis, characterization and application for Cr (VI) and As (V) removal from aqueous media(2024) Salfate, Gabriel; Negrete-Vergara, Camila; Azocar, Laura; Xiao, Ling-Ping; Sun, Run-Cang; Sanchez, JulioIn this study, lignin derived from corncobs was chemically modified by substituting the hydroxyl groups present in its structure with methacrylate groups through a catalytic reaction using methacrylic anhydride, resulting in methacrylated lignin (ML). These MLs were incorporated in polymerization reaction of the monomer 2-[(acryloyloxy)ethyl trimethylammonium] chloride (Cl-AETA) and Cl-AETA, Cl-AETA/ML polymers were obtained, characterized (spectroscopic, thermal and microscopic analysis), and evaluated for removing Cr (VI) and As (V) from aqueous media in function of pH, contact time, initial metal concentrations and adsorbent amount. The Cl-AETA/ML polymers followed the Langmuir adsorption model for the evaluated metal anions and were able to remove up to 91 % of Cr (VI) with a qmax (maximum adsorption capacity) of 201 mg/g, while for As (V), up to 60 % could be removed with a qmax of 58 mg/g. The results demonstrate that simple modifications in lignin enhance its functionalization and properties, making it suitable for removing contaminants from aqueous media, showing promising results for potential future applications.
- ItemNano-composites based on ligno-sulfonate and titanium oxide to study methylene blue removal and photo-degradation(2024) Boulett, Andres; Roa, Karina; Pizarro, Guadalupe; Sanchez, JulioThe 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.
- ItemNature of host-guest interaction of cyclic alcohols in β-Cyclodextrin: A molecular view of its structural features(2025) Cantero-Lopez, Plinio; Sanchez, Julio; Meza, Manuel S. Paez; Garcia-Negrete, C. A.; Bustos, Daniel; Yanez, OsvaldoHost- guest complexes are commonly found in several disciplines such as biochemistry, cosmetics, food, pharmaceuticals, and the environment. Studying the relationships between host and guest is essential in this context to understand their physicochemical behavior. This study aimed to examine the intermolecular interactions of cyclic alcohols within n- cyclodextrin (n- CD). The experimental spectroscopic results demonstrated the formation of the studied complexes. In this work, two orientations were used: orientation A (hydroxyl group toward the primary hydroxyl of n- CD) and orientation B (hydroxyl group toward the secondary hydroxyl of n- CD). The results indicate that regardless of the orientation used, the profile energy is thermodynamically favorable. However, there are differences in terms of greater or less stability in terms of the thermodynamic parameters studied. Physicochemical properties demonstrate that the host-guest complex forms spontaneously, and exothermic mode. The interaction between cyclic alcohols and n- CD in orientation A promotes a more pronounced deformation of the secondary edge of n- CD. Moreover, the arrangement of molecules demonstrates that intramolecular hydrogen bonds are less stable between the glycosidic units of n- CD. This arrangement may help or hinder the development of intermolecular hydrogen bonds.
- ItemPolycaprolactone and poly-β-cyclodextrin polymer blend: a Biopolymers composite film for drug release(2022) Antonella Sepulveda, Francesca; Sanchez, Julio; Oyarzun, Diego P.; Rodriguez-Gonzalez, Fidel E.; Tundidor-Camba, Alain; Garcia-Herrera, Claudio; Zapata, Paula A.; Pizarro, Guadalupe del C.; Martin-Trasanco, RudyNowadays, biomedical films containing drug carriers are preferred over conventional ones, since the protection of the injury and the therapy is joined within a single device. In the current work, we prepared polycaprolactone (PCL) composite films with beta-cyclodextrin (beta CD) or its epichlorohydrin crosslinked polymer (beta CDP) as ibuprofen (Ibu) drug carrier. The composite films were prepared at different PCL/additive ratios (2, 5, 10 and 20 wt%). ATR-FTIR spectroscopy and water contact angle (WCA) measurements indicated a scarce presence of the additives on the surface. Cross-section scanning electron micrographs showed the presence of aggregates corresponding to beta CD and beta CDP in the inner regions of the films. The incorporation of beta CD and beta CDP into the PCL films did not affect their thermal properties as was determined from differential scanning calorimetry (DSC). PCL-films with 10 wt% of the inclusion complexes Ibu@beta CD and Ibu@beta CDP were prepared and the release studies were performed. At pH = 7.2, PCL-Ibu@beta CDP composite film released 55% of Ibu within the first six hours; eight times the amount released by PCL-Ibu@beta CD within the same time interval. A plausible mechanism for ibuprofen release is discussed based on the cross-section SEM micrographs of composite films.
- ItemSodium lignosulfonate as an extracting agent of methylene blue dye using a polymer-enhanced ultrafiltration technique(2024) Sotelo, Sebastian; Oyarce, Estefania; Roa, Karina; Boulett, Andres; Pizarro, Guadalupe; Sanchez, JulioThe purpose of this research was to evaluate the efficacy of sodium lignosulfonate (LS) as a dye adsorbent in the removal of methylene blue (MB) from water by polymer-enhanced ultrafiltration. Various parameters were evaluated, such as membrane molecular weight cut-off, pH, LS dose, MB concentration, applied pressure, and the effect of interfering ions. The results showed that the use of LS generated a significant increase in MB removal, reaching an elimination of up to 98.0 % with 50.0 mg LS and 100 mg L-1 MB. The maximum MB removal capacity was 21 g g-1 using the enrichment method. In addition, LS was reusable for up to four consecutive cycles of dye removal-elution. The removal test in a simulated liquid industrial waste from the textile industry was also effective, with a MB removal of 97.2 %. These findings indicate that LS is highly effective in removing high concentrations of MB dye, suggesting new prospects for its application in water treatment processes.