RESUMEN
The prevalence of emerging organic contaminants (EOCs) in ground and surface water has sparked the search for more effective methods to remove EOCs from the environment. In pursuit of a solution for this environmental concern, herein we present the development of reusable films based on cellulose nanofibers (CNFs) and the block copolymer, poly(4-vinylpyridine-b-ethylene oxide) (P4VP-PEO) to adsorb sulfamethoxazole (SMX) as an EOC model compound. We hypothesize that the adsorption of SMX was achieved mainly by π-π interactions between the pyridine functionalities of the block copolymer and the electron deficient phenyl group of the SMX. Preceding preparation of the films, CNFs were modified with the alkoxysilane trimethoxy(2-phenylethyl)silane (TMPES) to increase their stability in aqueous solution. After the addition of P4VP-PEO, the process was completed by filtration followed by oven-drying. XPS and FTIR were employed to confirm the addition of TMPES and P4VP-PEO, respectively. Adsorption batch experiments were performed in aqueous solutions of SMX at a neutral pH, obtaining adsorptions of up to 0.014 mmol/g in a moderate time of 60 min. For the reusability tests, films were immersed in ethanol 95 wt.% to elude the adsorbed SMX, rinsed with deionized (DI) water, and dried at room temperature to be reused in a new adsorption cycle. We found that this new composite material could be reused several times with negligible loss of adsorption capacity. The films presented have been shown to be of substantial importance for water remediation as they find direct application in the adsorption of electron deficient aromatic compounds and are reusable.
RESUMEN
The prevalence of pharmaceutical compounds in surface and groundwater presents a rising threat to human health. As such, the search for novel materials that serve to avoid their release into the environment or for the remediation once in the water effluent is of utmost importance. The present work describes the fabrication of a cellulose acetate membrane modified with the block copolymer poly(4-vinylpyridine-b-ethylene oxide) (P4VP-b-PEO) crafted for the specific targeting and adsorption of electron-deficient pharmaceuticals (EDPs). The EDPs under study were sulfamethoxazole, sulfadiazine, and omeprazole. The results as part of this work present a thorough characterization of the prepared membranes by FTIR, contact angle measurement, and SEM images. Moreover, results show that the adsorptive character of the membrane correlates with the relative electron deficiency and spatial orientation of the contaminant. Interestingly, the addition of nominal 1% P4VP-b-PEO to the cellulose matrix helps to increase the adsorption efficiency of the membranes by at least 2-fold in most cases. For the compounds studied, the prepared membrane has a higher efficiency toward omeprazole followed by sulfamethoxazole and sulfadiazine. This work may serve to inspire the design and fabrication of selective soft materials for the adsorption and remediation of contaminants of emerging concern.
RESUMEN
The occurrence of contaminants of emerging concern (CECs) in water is an environmental issue that must be addressed to avoid damage to ecosystems and human health. Inspired by this current issue, in this work, we fabricated nanocellulose (NC) particles grafted with the block copolymer Jeffamine ED 600 (NC-Jeffamine) capable of adsorbing acetaminophen, sulfamethoxazole, and N,N-diethyl-meta-toluamide (DEET) from aqueous solution by electrostatic interactions. NC-Jeffamine composites were prepared by carboxylation of the NC surface via 2,2,6,6-tetramethyl-1-piperidinyloxy oxidation followed by the covalent attachment of Jeffamine using the N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide/N-hydroxysulfosuccinimide sodium salt reaction. The reaction was followed and confirmed by Fourier transform infrared and conductometric titration. The physical characterization was performed by thermogravimetric analysis, Brunauer-Emmett-Teller analysis, scanning electron microscopy, dynamic light scattering, and Z-potential analysis. This material was used to study the adsorption profile of three CECs in deionized water, namely, acetaminophen, sulfamethoxazole, and DEET. The adsorption isotherms were obtained at pH 3, 7, and 9, where the best adsorption results corresponded to pH 9 because of the uniform dispersion of the adsorbate in solution. A computational study based on the density functional theory determined that the possible interactions of the CECs with the adsorbent material were related to hydrogen bonds and/or van der Waals forces. The calculated binding energies were used as a descriptor to characterize the optimum adsorption site of CECs onto NC-Jeffamine.