In this research work, surface of graphene oxide was functionalized by zirconium and phosphate to form graphene oxide−zirconium phosphate (GO−Zr-P) nanocomposite, which is used for the removal of heavy metals from aqueous solutions. The GO−Zr-P nanocomposite was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), X-ray photoelectron spectroscopy (XPS), and zetapotential analysis. The sheets of GO−Zr-P was found to be strongly wrinkled, and the flat and layered structure of GO varied significantly after treatments with zirconium and phosphate. The effects of pH, contact time, and initial concentrations on the removal of heavy metals were studied. The results of batch experiments indicated that, at pH 6, maximum adsorption capacity can be achieved for Pb(II), Cd(II), Cu(II), and Zn(II), as 363.42, 232.36, 328.56, and 251.58 mg g −1 , respectively. A removal efficiency of ∼99% was obtained after 20 min, via the dispersion of 150 mg of GO−Zr-P nanocomposite in 100 mL of 50 ppm heavy metals. The pseudo-second-order kinetic model provided excellent kinetic data fitting (R 2 > 0.99) and data were fitted to both the Langmuir (R 2 > 0.97) and Freundlich isotherm models (R 2 > 0.99). The XPS results confirmed that the adsorption mechanism of zirconium and phosphate on the GO, as well as adsorption of metal ions onto the GO−Zr-P nanocomposite, was chemisorption, mainly through surface complexation. The results confirmed that GO−Zr-P nanocomposite could be a potential sorbent for effective and regenerable removal of heavy metals from aqueous solutions.

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A nonenzymatic glucose sensor based on a disposable pencil graphite electrode (PGE) modified by copper nanoparticles [Cu(NP)] was prepared for the first time. The prepared Cu(NP) exhibited an absorption peak centered at ∼562 nm using UV-visible spectrophotometry and an almost homogenous spherical shape by scanning electron microscopy. Cyclic voltammetry of Cu(NP)-PGE showed an adsorption controlled charge transfer process up to 90.0 mVs. The sensor was applied for the determination of glucose using an amperometry technique with a detection limit of [0.44 (±0.01) μM] and concentration sensitivity of [1467.5 (±1.3) μA/mMcm]. The preparation of the Cu(NP)-PGE sensor was reproducible (relative standard deviation = 2.10%, n = 10), very simple, fast, and inexpensive, and the Cu(NP)-PGE is suitable to be used as a disposable glucose sensor.

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