Development of oxidized sodium alginate/silica hybrid as efficient adsorbent for anionic and cationic dyes: mechanism and thermodynamic studies

A sodium alginate/silica–containing amine group hybrid was successfully prepared by a sodium alginate oxidation process
followed by a simple sol − gel method. Dialdehyde alginate was prepared through the selective oxidation process using sodium
periodate. 3–aminopropyltriethoxysilane (APTES) was added to dialdehyde alginate to produce a functionalized alginate/
silica hybrid with excellent adsorption performance. As a result of APTES functionalization, the material’s characteristics
were significantly altered. The chemical properties of alginate, oxidized alginate, and alginate/silica hybrid were investigated
utilizing different techniques such as FT-IR, TGA, XRD, and SEM/EDX. The alginate/silica hybrid efficiently removed cationic
and anionic dyes thanks to its numerous functional surface groups. The adsorption of methylene blue (MB) and methyl
orange (MO) is mainly driven by electrostatic interactions, though other mechanisms may also contribute to the process. The
adsorption process of an oxidized alginate/silica hybrid followed the Langmuir model, and the maximum adsorption exhibited
178.6 and 192.7 mg/g for MB and MO, respectively. Thermodynamic analysis indicated that the adsorption method is
endothermic and spontaneous, with improved efficiency at higher temperatures. The oxidized alginate/silica hybrid showed
excellent reusability, retaining significant adsorption capacity after multiple cycles. This study highlights the potential of
the alginate/silica hybrid as an economical and sustainable adsorbent for water purification applications, particularly in the
removal of organic dye pollutants.