<p>This study investigates the removal of methylene blue (MB) dye from water using a cost-effective, reusable, and efficient iron oxide-doped Xanthan-gum xanthate-based hydrogel nanocomposite (XNH@Fe₃O₄ NC). The nanocomposite was synthesized by doping optimized Xanthan-gum xanthate-based hydrogel (XNH; synthesised via free radical polymerization method) with Fe₃O₄ nanoparticles. Four synthesized hydrogel grades (XNH-1, XNH-2, XNH-3, and XNH-4) were evaluated based on their swelling ratio (SR), water retention percentage (%WRR), and point of zero charge (∆pHpzc) to identify the optimal grade for dye adsorption. XNH-3 exhibited the highest SR (268.19 g/g) and %WRR (92.03% at 65 °C) in distilled water, along with a negatively charged surface over a wider pH range, making it the most suitable for adsorption of MB dye. Consequently, XNH-3 was used to synthesise XNH-3@Fe₃O₄ NCs via the sol-gel method. The selectivity of Fe₃O₄ nanoparticles (NPs) is attributed to their magnetic properties, which allow for easy separation from the solution using an external magnetic field. Additionally, Fe₃O₄ NPs exhibit a low band gap between the valence band (VB) and conduction band (CB), facilitating electron transfer, thereby acting as a competent photocatalyst for the degradation of dye. The nanocomposite achieved a maximum MB removal of 97.9 (±1.0) % under optimal conditions i.e. (pH 7, temperature 25 °C, contact time 30 min, adsorbent dose 0.5 g/L and initial MB concentration 100 mg/L). The absorption process followed Langmuir isotherm model with adsorption capacity of 208.33 (±1.76) mg/g. Furthermore, the XNH-3@Fe₃O₄ NC demonstrated 87.56% degradation of MB dye under visible light photocatalysis.</p><p></p>