<p>The effective removal of toxic Cr(VI) from wastewater remains a significant environmental challenge. To address this, a novel composite adsorbent was developed by incorporating amino-functionalized mesoporous silica (NH₂-SBA-15) into a sodium alginate (SA) matrix, with its network density and mechanical strength further enhanced by crosslinking with polyethylenimine (PEI) and carboxymethyl cellulose (CMC). The obtained NH₂-SBA-15/SA/CMC composite beads exhibited an exceptional Cr(VI) adsorption capacity of up to 931.25 mg/g and a robust tensile strength of 73.48 kPa, alongside excellent recyclability over five consecutive adsorption–desorption cycles. Characterization techniques including scanning electron microscopy (SEM) and transmission electron microscopy (TEM) confirmed the uniform dispersion of NH₂-SBA-15 particles within a highly cross-linked, porous polymer network, which facilitated efficient mass transfer and access to active sites. The adsorption process was found to follow the pseudo-second-order kinetic model, indicating that chemisorption was the rate-controlling step. Equilibrium data were best described by the Langmuir isotherm, suggesting a monolayer adsorption mechanism. The high adsorption capacity is attributed to a synergistic mechanism involving electrostatic attraction between protonated amine groups and Cr(VI) oxyanions, followed by reduction to less toxic Cr(III). This study demonstrates that the strategic integration of functional mesoporous silica into a reinforced biopolymer hydrogel presents a highly promising and feasible solution for the remediation of Cr(VI)-contaminated water.</p> Graphical abstract <p></p>