University of Kashan Journal of Nanostructures 2251-7871 15 4 2025 10 01 Structural and Functional Investigation of Sodium Alginate-Grafted-Poly (Methacrylic Acid-co-Crotonic Acid)/Functionalized Single-Walled Carbon Nanotube Hydrogel for Organic Dye Decontamination 1795 1814 115043 10.22052/JNS.2025.04.023 EN Khudhair M. Mahdi Department of Chemistry, University of Sumer, College of Education, Thi-Qar, Iraq Wissam L. Penyan Ministry of Education, Thi-Qar Education Directorate, Iraq‬‏ Salam H. Alwan Department of Chemistry, College of Education for Pure Sciences, University of Karbala, Karbala, Iraq Layth S. Jasim Department of Chemistry, College of Education, University of Al-Qadisiyah, Diwaniyah, Iraq Journal Article 2025 06 12 polysaccharide through the copolymerization of methacrylic acid (MAA) and crotonic acid (CA) monomers via free-radical grafting in the presence of functionalized single-walled carbon nanotubes (SWCNTs-COOH). The resulting hydrogel composite, designated as SA-g-poly(MAA-co-CA)/SWCNTs-COOH, was prepared using N,[N′-methylene bis-acrylamide (MBA) as the crosslinker and potassium persulfate (KPS) as the initiator. The primary objective was to develop a novel adsorbent exhibiting enhanced adsorption capacity, superior swelling behavior, and improved reusability for the efficient removal of Safranin-O dye from aqueous solutions. The structural and surface characteristics of the composite, along with its adsorption interactions, were systematically analyzed using FTIR, XRD, FESEM, and TGA. The composite exhibited a point of zero charge (pHpzc) of 3.4 and a swelling capacity of up to 3950% at neutral pH (pH 7). The influence of various operational parameters—including adsorbent dosage, pH, temperature, contact time, and ionic strength—was thoroughly investigated at an initial dye concentration of 200 mg/L. Under optimal conditions (30 °C, pH 7, 0.05 g adsorbent, and 90 min equilibrium time), the hydrogel achieved a maximum removal efficiency of 99.20%. Increasing ionic strength was found to reduce adsorption efficiency. The adsorption process followed the Freundlich isotherm model and was best described by pseudo-second-order kinetics, with the maximum adsorption capacity determined as 366.34 mg/g. Thermodynamic studies indicated that the adsorption was spontaneous and endothermic in nature. Furthermore, the hydrogel composite demonstrated excellent reusability, maintaining an adsorption efficiency above 81.4% after five successive cycles. https://jns.kashanu.ac.ir/article_115043_6cd3444a60a3569dfb7e92110fe8f336.pdf