Cd(II) Sorption by Nanomagnetic Aerogels Modified with Bentonite and Activated Carbon

In this study, magnetic alginate beads (MABs) were prepared as adsorption materials by adding Fe3O4 nanoparticles to sodium alginate (SA) matrix through in situ cross-linking and freeze drying. To improve adsorption performance, bentonite (BE) and activated carbon (AC) were also used to create composite BE–MABs and AC–MABs, respectively. Furthermore, Fourier transform infrared spectroscopy, scanning electron microscopy, and X-ray diffractometry were used to characterize the magnetic beads before and after Cd(II) adsorption. BE and AC were successfully compounded with SA, which not only enhanced the compressive properties of SA but also exploited the adsorption capacities of BE and AC for cadmium. Batch adsorption experiments revealed that the optimum adsorbent dosage, pH, and contact time were 0.2 g, 5, and 1,440 min, respectively. The adsorption kinetics of the MABs and AC–MABs obeyed the pseudo-second-order model, suggesting that chemical reactions are involved in Cd(II) adsorption. The experimental adsorption–equilibrium isotherm data are consistent with the Langmuir model, which reveals that the process involves monolayer surface adsorption. The results show that magnetic bead materials with BE or AC can be used to treat cadmium-contaminated wastewater with similar efficiencies.