Synthesis and characterization of novel pectin-based copper oxide nanocomposite and its application for removal and photocatalytic degradation of methylene blue from aqueous solution

The pectin-modified hydrogel-copper oxide nanocomposite (PMH@CuO) has been successfully synthesized using free radical polymerization method by incorporating CuO nanoparticles into pectin-modified hydrogel (PMH) network. The target of this work was to examine the usage of PMH@CuO nanocomposite for eliminating methylene blue (MB) dye from aqueous solutions. The CuO nanoparticles (NPs) as well as PMH@CuO nanocomposite have been characterized by several techniques, viz., UV–visible and FTIR spectroscopies, TGA, ΔpH_pzc, XRD, and SEM analyses. The percentage removal of MB dye has been found to be 98.41% at pH of 7 during 30 min with dye concentration of 50 mg/L, and dosage of adsorbent 1.2 g/L, at 25°C. The adsorption kinetics has been found to fit perfectly with pseudo-second-order kinetic model. The adsorption data fit appreciably with Langmuir isotherm model, representing monolayer adsorption with maximum adsorption capacity (q_e) of 132.27 mg/g at 25℃. A thermodynamic analysis revealed that the MB dye adsorption was a spontaneous and exothermic process and resulted in lowering of entropy. The photocatalytic activity of the PMH@CuO nanocomposite has been found to be quite notable as the degradation of 80.20% of MB dye was observed within 60 min under visible light. Moreover, the synthesized nanocomposite was reusable up to five adsorption and desorption cycles with 86.8% of adsorption and 85.4% of desorption in fifth cycle.