Preparation of reusable hydrogel spheres based on sodium alginate/Fe3O4 modified with carboxymethyl Huangshui polysaccharide and the efficient adsorption performance for methylene blue.

This study successfully constructed a novel multifunctional bio-adsorbent using sodium alginate (SA), ferroferric oxide (FFO), and carboxymethyl Huangshui polysaccharide (CMHSP) with rapid separation, pH sensitivity, efficient adsorption, and reusability for enhancing the removal of methylene blue (MB) in wastewater. FTIR, XRD, SEM, and VSM results indicated CMHSP improved the porosity of the hydrogel spheres, thus significantly enhancing the MB adsorption capacity with the rate-limiting controlled by chemical adsorption, intraparticle diffusion, and film diffusion. The maximum adsorption capacity obtained from Langmuir model of SA-FFO-CMHSP (186.57 mg/g) was obviously higher than that of SA-FFO (178.82 mg/g). Thermodynamic results showed that the MB adsorption process was endothermic, spontaneous, and favorable, and physical adsorption was dominant. Remarkably, MB adsorption maintained 87% ∼ 95% of the initial after four adsorption-desorption cycles, and proper carboxymethylation was conducive to MB adsorption over a broader range pH. These findings provided reference for designing new efficient bio-adsorbents and the recyclable utilization of Huangshui by-products, which was of great value.

Synthesis, characterization, and methylene blue adsorption of multiple-responsive hydrogels loaded with Huangshui polysaccharides, polyvinyl alcohol, and sodium carboxyl methyl cellulose.

Huangshui (HS), a typical by-product of traditional Chinese Baijiu, has attracted more and more attention since its rich resources of polysaccharides. However, there's little information on hydrogels preparation by Huangshui polysaccharides (HSPs). A series of novel HSP-loaded hydrogels were synthesized using crude HSP (cHSP), polyvinyl alcohol (PVA), sodium carboxyl methyl cellulose (CMC), and in situ incorporation of Fe3O4 for methylene blue (MB) adsorption for the first time. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM) and texture tests indicated the paramagnetic hydrogels with porous structure were formed via physical crosslinking, and cHSP had no effect on hydrogel texture. Notably, cHSP enhanced the swelling capacity and MB adsorption ability of the hydrogels, and the corresponding maximum value was 38.67 g/g and 71.07 mg/g, respectively, when the additive amount of cHSP to the hydrogels was 2 % at 25°Ð¡. In addition, the swelling kinetics of hydrogels followed the Schott's second-order kinetics model, while MB adsorption fitted well with the Freundlich isotherm and pseudo-second-order model. Furthermore, intraparticle and film diffusion-controlled MB adsorption process. Significantly, cHSP amount could counteract the negative influence of high temperature on MB adsorption, and the prepared hydrogels could be reusable, demonstrating cHSP effectively promoted the properties of hydrogels and had potential application in MB removal. The adsorption mechanism of MB onto the hydrogels involved ion-exchange, hydrogen bonding, electrostatic interaction, and chemical reaction according to the above results together with the analysis by X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray (EDX) characterizations, thermodynamic, etc.