Preparation, characterization, and dye adsorption potential of quaternized cellulose materials

<p class="MsoNormal" style="margin-bottom:0cm;text-align:justify;line-height:115%"><span lang="EN-US" style="font-size:10pt;line-height:115%;font-family:&#39;times new roman&#39; , serif">Cellulose-based adsorbents are
attractive candidates for water treatment, yet their performance is governed
not only by surface functionalization but also by the structural accessibility
of adsorption sites. In this work, we establish structure-adsorption
relationships in cellulose materials by correlating pretreatment-controlled
morphology, textural properties, and various quaternization routes with dye
uptake behavior. Microcrystalline cellulose was subjected to sulfuric acid
hydrolysis and ultrasonication, followed by freeze-drying to generate porous
cellulose precursors, which were subsequently quaternized appropriately with
glycidyltrimethylammonium chloride or related reagents with different alkyl
chain lengths. The synthesis was optimized to obtain a reproducible precursor
with a well-developed architecture, and the resulting materials were subjected
to physicochemical characterisation. The most favourable precursor was a
material with substantially enhanced specific surface area and pore volume
relative to the starting microcrystalline cellulose. Quaternization effectively
altered the surface chemistry and morphology, with a visible decrease in
specific surface area and pore volume. Adsorption experiments with methyl
orange, Congo Red, and methylene blue revealed a dependence of adsorption
performance on both dye chemistry and adsorbent structure. No meaningful
adsorption was observed for methyl orange. Hydrogels were ineffective for all
dyes examined. Congo Red was adsorbed only to a limited extent by microcrystalline
cellulose and the quaternized aerogel, whereas methylene blue exhibited high
uptake exclusively on quaternized aerogel, consistent with a heterogeneous
adsorption surface and multiple interaction pathways. Altogether, these
findings show that adsorption in quaternized cellulose systems is dictated by
the interplay between pore architecture, surface functionality, specific
interactions, rather than by cationization alone. </span><span lang="EN-US" style="font-size:10pt;line-height:115%"></span></p>