<p>Dye pollution from industrial wastewater has emerged as a major environmental issue due to its persistence and toxicity. In this study, a chitosan-glutaraldehyde/zeolite X (CSZ) bio-composite was synthesized using zeolite X (ZX) derived from rice husk ash (RHA) as a low-cost and sustainable adsorbent for crystal violet (CV) removal from aqueous solutions. The effects of key synthesis parameters, including the chitosan:ZX weight ratio and glutaraldehyde concentration, were investigated to obtain an optimal composite. The CV adsorption performance was examined across various operating conditions, such as material dosage, initial CV concentration, contact time, coexisting ions, and others (types of dyes, pH, ionic strength, and water matrices). The equilibrium data was well described by the Sips isotherm with the maximum adsorption capacity (AC) according to the Sips model (422.674&#xa0;mg/g). Thermodynamic studies revealed that the adsorption was spontaneous and exothermic. Based on model fitting and post-adsorption composite characterizations, the main adsorption mechanisms on CSZ composite were attributed to electrostatic interaction, π–π interaction, hydrogen bonding, and pore filling. The CSZ composite also showed good stability and reusability, retaining approximately 85% after five adsorption–desorption cycles. In addition, the CSZ composite exhibited effective adsorption of various dyes, including both cationic and anionic dyes. The integration of biopolymer-derived chitosan with RHA-derived ZX underscored a sustainable route to develop high-performance adsorbents from agricultural waste.</p> Graphical abstract <p></p>