Excellent adsorption of toxic Cd (II) ions from water with effective antibacterial activity by novel GO-ZnO-curcumin...

A significant health risk arises from the bioaccumulation of harmful Cd (II) in drinking water. Here, we report the unique Cd (II) remediation from drinking water by using novel GO-ZnO-curcumin composite. The composites were tailored by varying the ratio of GO-ZnO and curcumin. The composites followed Langmuir adsorption isotherm and pseudo-second-order kinetics. ZnO nano-rods were more effective in Cd (II) than ZnO nano-disks. A maximum adsorption capacity of 4580 ± 40 mg/gm was achieved for 21G-B with a removal efficiency of 87.5% at neutral pH under optimized conditions. The removal process was governed by ion exchange and electrostatic attraction, followed by cation exchange capacity (CEC). The lattice parameter increase was detected after adsorption of Cd (II) ions. The regeneration and reusability of the composite was studied. Also, the effect of presence of dyes such as methylene blue on Cd (II) adsorption was noted. The latter had negligible effect on Cd (II) removal efficiency from water. The composite showed high antibacterial activity against B. subtilis and P. aeruginosa with minimum inhibitory concentration (MIC) of 10 ± 0.75 µg/ml and 5 ± 1 µg/ml respectively due to the presence of zinc. Composite stability was confirmed through leaching and thermal gravimetric analysis (TGA) analysis. The study establishes the nanocomposite as a potential material for remediation of hazardous Cd (II) ions from real water samples under neutral conditions.