In the present study, a novel pH-sensitive hydrogel composite of pectin-grafted-poly (acrylic acid-co-itaconic acid)/MWCNTs- COOH was prepared by using graft copolymerization of acrylic acid and itaconic acid on pectin backbone with incorporation of MWCNTS- COOH. The prepared hydrogel composite has been employed for the adsorption and controlled release of the diclofenac sodium (DS) drug. The hydrogel composite was characterized by the analysis methods: FTIR, XRD, SEM, and TGA to analyze structural characteristics before and after DS drug adsorption. The swelling ratio of the hydrogel composite was investigated at different pH values from pH 1.2 to 10. According to the results, the swelling ratio of the hydrogel composite was found 4195% at pH 7.4. Adsorption process parameters such as pH, contact time, adsorbent dose, and temperature were investigated and found to have a significant influence on DS drug adsorption. The maximum DS drug loading through adsorption of 91% was obtained at pH 3, adsorbent dose of 0.05 g, contact time of 150 min, and temperature of 15 °C. The adsorption isotherm and kinetic results were well-fitted to Freundlich and second-order models. Thermodynamic parameters including changes in Gibb’s free energy, enthalpy, and entropy suggested that the adsorption of DS drug onto hydrogel composite was a spontaneous and exothermic process. The in vitro drug release experiment showed that the cumulative release of DS drug from hydrogel composite after 35 h was significantly higher in simulated intestinal fluid at pH 7.4 than in simulated gastric fluid at pH 1.2.

Preparation and characterization of a novel pH-sensitive pectin-grafted-poly (acrylic acid-co-itaconic acid)MWCNTs-COOH hydrogel composite for adsorption and controlled release of diclofenac sodium
    Abstract
        Graphical abstract
    1 Introduction
    2 Methodology
        2.1 Chemicals
        2.2 Preparation of Pectin-g-poly(AA-co-IA) MWCNTs-COOH hydrogel composite
        2.3 Characterization
        2.4 pH dependence of the swelling ratio
        2.5 Point zero charge measurement
        2.6 Adsorption studies
        2.7 Adsorption kinetics
        2.8 Adsorption isotherms
        2.9 Thermodynamic studies
        2.10 In vitro drug release study
    3 Results and Discussion
        3.1 FTIR spectra analysis
        3.2 SEM analysis
        3.3 XRD analysis
        3.4 TGA analysis
        3.5 Effect of pH on swelling behavior
        3.6 Point zero charge of hydrogel composite
    4 Optimization of adsorption conditions
        4.1 Effect of solution pH
        4.2 Effect of adsorbent dosage
        4.3 The effect of contact time
        4.4 Effect of temperature
    5 Kinetic studies
    6 Adsorption isotherm
    7 Thermodynamics studies
    8 Adsorption mechanism
    9 In vitro release of DS drug
    10 Conclusion
    Acknowledgements 
    References

• Wissam L. Penyan(Department of Chemistry, College of Education, University of Al-Qadisiyah, Thi‑Qar City, Iraq) Corresponding author
• Layth S. Jasim(Department of Chemistry, College of Education, University of Al-Qadisiyah, Diwaniya City, Iraq) Corresponding author