Efficient removal of Congo red using curcumin conjugated zinc oxide nanoparticles as new adsorbent complex

Congo red is one of the common organic dyes that is found in water as waste of the industrial work. The use of congo red has long been of great concern, primarily because of its carcinogenic properties. Congo red can be isolated and removed from water by adsorption using nanoparticles. The use of zinc curcumin oxide, also known as curcumin conjugated zinc oxide, nanoparticles was elaborated for the first time in this work for this purpose. The optimization of the synthesis reaction of zinc curcumin oxide nanoparticles was established by modifying the flow rate of KOH, pH of the medium, different temperature, and in the presence or absence of chitosan polymer. These nanoparticles were characterized through SEM, UV-Visible absorption Spectroscopy, fluorescence spectroscopy, TGA, and XRD. It is found that during synthesis, addition of KOH dropwise in alkaline media improved the stability of the formed nanoparticles. Similarly, addition of chitosan has further increased their stability with only 10% mass loss. The importance of the formed nanoparticles was investigated by analyzing their efficiency in the adsorption of congo red where Zn(Cur)O had an adsorption capacity equal to 89.85 mg/g, which is one of the highest reported in literature, following the pseudo second order model. Nevertheless, negative surface charge of congo red and positive surface charge of Zn(Cur)O may also get supported by π-π interaction between curcumin and congo red that encourages adsorption in zinc curcumin oxide which is obstructed in the presence of chitosan.