Ecofriendly magnetic gels beads based on carboxymethylcellulose and iron oxides for diclofenac adsorption

Abstract

This work presents the development of eco-friendly ferrogel beads that can effectively remove emerging pollutant diclofenac (DFC) from wastewater. These beads are composed of natural polysaccharide/iron oxide. The structure and properties of the ferrogel beads were studied using various techniques. Scanning electron microscopy images revealed porosity nature of hydrogel and ferrogel beads due to the incorporation of magnetic nanoparticles (MNPs). TEM images indicates the diameter size of MNPs around 8.3 ± 2 nm. The addition of MNPs resulted in enhanced porosity and visible MNP agglomerates. Fourier-transform infrared spectroscopy confirmed interactions between the polymer (carboxymethyl cellulose, CMC) and iron oxide nanoparticles, as indicated by characteristic peaks associated with both compounds. X-ray diffraction patterns indicated that MNPs had a crystalline nature (appears the characteristic peaks at 35.6°, 43.3° and 53.7° were corresponding to the (3 1 1), (4 0 0), (4 2 2)) while CMC hydrogel exhibited an amorphous structure.The behavior of fresh and dried beads was compared, revealing that drying increased crosslinking, particularly in the presence of MNPs. This led to a reduction in the swelling percentage of ferrogels (154% at 23 °C in water) when compared to hydrogels (581% at 23 °C in water). Magnetic properties analysis using a vibrating sample magnetometer demonstrated a Langevin-type response for NMPs dispersions, they showed no coercivity, and the saturation magnetization was 47(3) emu/g, in the case of ferrogels beads, the saturation magnetization is 3.8(2) emu/g, indicating a proportion of 8% p/p of nanoparticles relative to the dried beads.Adsorption studies showed that DCF is slowly adsorbed into the beads after 500 min, reaching 50% in the lowest DFC concentration (10 mg/L), 75% in 20 mg/L, 83% in 30 mg/L and 30% in the highest DFC concentration solution (2000 mg/L), the kinetics of DFC adsorption onto ferrogel beads followed a pseudo-second-order and intraparticle diffusion model, indicating physical and chemical interactions as the controlling factor. Adsorption isotherm studies provided insights into the adsorption mechanism and capacity, which are crucial for optimizing adsorbent performance. It was found that the Temkin isotherm shows a better fit.Overall, these findings suggest that ferrogel beads have great potential for environmental applications in pollutant removal due to their high DFC adsorption capacity (qe = 666.7 mg/g), sustainability through reusability, and promising magnetic recovery post-adsorption capabilities.