Eco‐Friendly Schiff Base Cellulosic Adsorbent for Selective Removal of Cationic Dyes from Petroleum Wastewater: Synthesis, Characterization, and Application

ABSTRACT Our investigation explores the exclusion of two health‐risk cationic dyes (e.g., Methylene Blue (MB) and Malachite Green (MG)) using a novel hydrazone‐modified cellulose (HMC) adsorbent synthesized via a Schiff base reaction. The HMC is fully characterized by XRD, FT‐IR, SEM/EDX, BET, and TGA, confirming successful functionalization with enhanced surface area (2.489 m 2 g − 1 ) and mesoporous structure. Batch adsorption experiments optimized the key parameters, including the pH suitable for the adsorption process, the amount of adsorbent, the contact time needed for complete adsorption, and temperature. The results revealed maximum removal efficiencies of 97.5% for MG (pH 5) and 92.3% for MB (pH 8) at equilibrium (120 min). Adsorption followed the Langmuir isotherm, indicating monolayer coverage with capacities of 160.86 mg g − 1 (MG) and 137.88 mg g − 1 (MB). Thermodynamic analysis confirmed spontaneous, exothermic adsorption (Δ G < 0, ΔH < 0), with decreased disorder (ΔS < 0). The HMC exhibited excellent reusability, retaining high efficiency over multiple cycles. These findings highlight HMC as a low‐cost, eco‐friendly adsorbent for dye‐laden petroleum treatment, offering high selectivity and scalability for industrial applications.