In-Situ Synthesis of ZnO Nanoparticles using Gum Arabic Based Hydrogels as a Self-template for Effective Malachite Green Dye Adsorption

The current study focused on the use of gum Arabic grafted polyacrylamide (GA-cl-PAM) hydrogel as a self-template for the in situ synthesize of zinc oxide nanoparticles (ZnO NPs) and the application of synthesized nanocomposite as a potential adsorbent to remove synthetic dyes especially malachite green (MG) from aqueous solution. Different characterization techniques supported in situ synthesis of ZnO NPs onto polymer matrix. The gum Arabic-crosslinked-poly(acrylamide)/zinc oxide nanocomposites (i.e., GA-cl-PAM/ZnO nanocomposite) exhibited much better surface properties as compared to the parental hydrogel matrix. The swelling abilities of the GA-cl-PAM/ZnO nanocomposites with different concentrations of acrylamide were also checked and the nanocomposite with 7.03 × 10–⁴ mol/L of acrylamide exhibited maximum swelling capacity of 2354%. The nanocomposite adsorbed approximately 99% MG dye with 0.4 g/L adsorbent dose at neutral pH. Adsorption kinetics and isotherm followed pseudo-second-order and Langmuir isotherm models, respectively with the high adsorption capacity of 766.52 mgd/gₐdₛ at 25 °C. It was observed that the dye molecules were adsorbed onto GA-cl-PAM/ZnO nanocomposite mostly via electrostatic interactions, hydrogen-bonding and pore-diffusion mechanisms. Diffusion of dye molecules within the internal structure of GA-cl-PAM/ZnO nanocomposite followed the combination of both liquid film as well as intraparticle diffusion mechanisms. Furthermore, nanocomposite was applied ten times consecutively to adsorb MG dye from aqueous solution. Therefore, GA-cl-PAM hydrogel have capability to be used for the in situ ZnO NPs synthesis and thus synthesized nanocomposite can be used effectively to treat dyes polluted wastewater.