Compósitos quitosana-ferrita de cobalto para remoção do surfactante dodecilbenzenossulfonato de sódio de meios aquosos

Abstract

Anionic surfactants, such as sodium dodecylbenzenesulfonate (SDBS), are widely employed in industrial and domestic formulations. However, their presence in aqueous effluents may cause environmental impacts of considerable magnitude. In this context, natural adsorbent materials modified through the incorporation of inorganic components have attracted increasing interest as sustainable alternatives for the treatment of waters contaminated with surfactants. The present work aimed at the development and evaluation of composites based on cobalt ferrite and chitosan crosslinked with glutaraldehyde for the removal of SDBS from aqueous media. Cobalt ferrite (CoFe₂O₄), obtained by the coprecipitation method, was used in the preparation of two composites with chitosan-to-CoFe₂O₄ mass ratios of 2:1 and 4:1, designated as C21 and C41, respectively. A material composed only of crosslinked chitosan (QT), without the addition of CoFe₂O₄, was synthesized for comparison. The materials were characterized by Fouriertransform infrared spectroscopy (FTIR), scanning electron microscopy coupled with energydispersive spectroscopy (SEM/EDS), vibrating sample magnetometry (VSM), thermal analyses, and determination of the point of zero charge (pHPZC). In the adsorption assays, the maximum adsorption capacities (qmax) achieved were 670,5 mg g⁻¹ (C21) and 667,2 mg g⁻¹ (QT), obtained under natural pH conditions, without NaCl addition, [SDBS]initial = 800 mg L⁻¹, adsorbent dosage = 1,0 g L⁻¹, and contact time = 48 h. The satisfactory fit to the Elovich and Freundlich models suggested the presence of heterogeneous surfaces and the predominance of hydrophobic interactions. The application of the intraparticle diffusion model evidenced the occurrence of pore transport, whereas SDBS concentrations above the critical micelle concentration (cmc) indicated the possibility of micelle adsorption. Reuse assays confirmed the stability of the composites, which maintained efficiencies above 97% after three consecutive cycles, with emphasis on C21, which enabled rapid separation under magnetic field application. The results highlight the high potential of these materials as sustainable and reusable adsorbents for the treatment of effluents containing anionic surfactants.