Hidrogeles compuestos a base de microfibras de celulosa y quitosano para la recuperación de cobre en soluciones acuosas

Abstract

Copper is one of the metals that is often found exceeding permissible limits due to anthropogenic factors, making it a risk for human health and the environment. In this context, the development of polymeric materials for the removal of metal ions is a priority in the field of chemical engineering. The objective of this study was to evaluate the potential of cellulose microfibers (CMF) and hydrogels composed of chitosan modified with citric acid and polyethyleneimine (CS/PEI and CS/CMF/CA/PEI) for the recovery of copper in aqueous solutions. The CMF were obtained from dried banana rachis after a delignification, bleaching and hydrolyzing process, resulting in cellulose microfibers, while CS/PEI began with the dilution of chitosan (CS) in acetic acid to later be homogenized with a polyethyleneimine (PEI) solution, then bound with sodium hydroxide for cross-linking; On the other hand, the CS/CMF/CA/PEI material was chemically modified with the carboxyl groups of citric acid (CA) and then mixed with the CS and PEI solution, similar to that described above. The characterization was carried out using FTIR spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), zero charge potential (pHpzc), swelling percentage and water retention percentage. While for the pH adsorption study, conditions of 3, 4 and 5 were used. The characterization analyses showed that the CS/PEI and CS/CMF/CA/PEI materials have a high swelling capacity and the water retention times were very similar. The X-ray patterns reveal important information such as the crystallinity index, with CS/PEI having a much lower index than the rest of the materials. SEM images provide information on the size of the microfibers in the case of CMF, but in CS/PEI and CS/CMF/CA/PEI, fibers in nanometers were obtained. FTIR spectroscopy of the adsorbent materials revealed the presence of functional groups such as OH, C-H and C-N-C stretching, C-O-C vibrations, C=O bonds and CH2 deformation. Finally, the pH adsorption study indicated that the CS/PEI material has the maximum adsorption percentage of 94%, starting from an initial concentration of 50 ppm at a pH of 5. These developed materials present a promising, sustainable and biodegradable alternative for the remediation of copper-contaminated waters, being a potential for their application in industrial effluent treatments.