Novel Hybrid Polymer Materials with Magnetic Properties for Effective Purification of Aqueous Environments

A series of pectin/polyethylenimine (Pectin-PEI) composites was developed in combination with other components such as Fe₃O₄, activated carbon, complexing metal ions, and HCl to optimize the removal of methyl orange (MO) from aqueous solutions. The PEI content in the samples ranged from 35 to 53 wt %. The morphology of the obtained samples was analyzed by using SEM images, and their composition was determined through elemental analysis, EDX spectra, and acid-base titration. The adsorption capacity for methyl orange was studied, which for the initial (nonprotonated) samples was 814-1460 mg/g. A significant increase in affinity for MO was observed for protonated samples (1516-2470 mg/g), as well as for composites loaded with metal ions like Cu²⁺, Zn²⁺, and Fe³⁺ (1246-3015 mg/g). According to the diffuse reflectance spectra of samples with adsorbed MO, the formation of H- and J-aggregates of MO was confirmed. The most effective sorbent was the sample containing PEI with a molecular weight of 0.61 × 10⁶ Da at a pectin-to-PEI weight ratio of 1:2. Based on this, magnetic composites with Fe₃O₄ and activated carbon were produced. The materials were prepared both by solid-phase dispersion of mixtures of Pectin-PEI, activated carbon (AC), and Fe₃O₄ and by direct formation of a cross-linked Pectin-PEI product in a mixture of AC and Fe₃O₄. The highest efficiency was demonstrated by samples with Pectin-PEI:AC:Fe₃O₄ ratios of 36:54:10 and 45:45:10. To examine the adsorption characteristics, the composite samples were prepared as hydrochloride and metal complexes with Cu²⁺, Zn²⁺, Cd²⁺, Hg²⁺, Pb²⁺, and Fe²⁺. The kinetics of methyl orange adsorption from aqueous solutions were analyzed using various models, including pseudo-first-order, pseudo-second-order, intraparticle (Weber-Morris), and film-diffusion models.