Commercial flakes of graphite were prepared into functionalized graphene oxide (GO) by chemical treatment. After the exfoliation and intercalation of graphene into functionalized graphene oxide that formed stable colloidal dispersion in polar aprotic solvent, the reduction process was undertaken by continuous stirring with hydrazine hydrate. The reduced material was characterized by X-ray diffraction (XRD), attenuated total reflectance (ATR) FT-IR, ultraviolet visible (UV-vis), atomic force microscopy (AFM) and Raman spectroscopy which confirm the oxidation of graphite and reduction of graphene oxide into graphene sheet.

No abstract

No abstract

The adsorption properties of layered double hydroxide (Mg/Al-CO3) for the removal of Congo Red (CR) dye from aqueous solution were studied. The layered double hydroxide was synthesized by co-precipitation method and characterized by X-ray diffraction (XRD), Fourier Transform Infrared spectroscopic (FTIR) and Energy-Dispersive X-ray Spectroscopic (EDX). The effects of various experimental parameters such as contact time, dye concentrations and temperature variation were investigated. The results show that the amount of Congo Red adsorbed increases with increase in temperature but decreases with increase in initial dye concentration and contact time. The data were also fitted to several kinetic models: zero-order kinetic model, first-order kinetic model, second-order kinetic model, pseudo-second-order kinetic model and third-order kinetic model respectively. The adsorption process was best defined by zero-order-kinetic model (R 2 = 1). Langmuir, Freundich, Temkin and Dubinin-kaganer-Radushkevich (DPK) adsorption isotherm models were applied to analyze adsorption data with Temkin isotherm being the most applicable to the adsorption process. Thermodynamic parameters e.g. ∆G o , ∆S o , ∆H o and ∆Hx of the adsorption process were found to be endothermic, spontaneous and feasible.

No abstract

No abstract

Plain polyvinyl alcohol (PVA) nanofibres and novel polyvinyl alcohol benzene tetracarboxylate nanofibres incorporated with strontium, lanthanum and antimony ((PVA/Sr-TBC), (PVA/La-TBC) and (PVA/Sb-TBC)), respectively, where TBC is benzene 1,2,4,5-tetracarboxylate adsorbents, were fabricated by electrospinning. The as-prepared electrospun nanofibres were characterized by scanning electron microscope (SEM), Fourier transform infrared (FTIR) and thermogravimetric analysis (TGA). Only plain PVA nanofibres followed the Freundlich isotherm with a correlation coefficient of 0.9814, while novel nanofibres (PVA/Sb-TBC, PVA/Sr-TBC and PVA/La-TBC) followed the Langmuir isotherm with correlation coefficients of 0.9999, 0.9994 and 0.9947, respectively. The sorption process of all nanofibres followed a pseudo second-order kinetic model. Adsorption capacity of novel nanofibres was twofold and more compared to that of plain PVA nanofibres. The thermodynamic studies: apparent enthalpy (ΔH°) and entropy (ΔS°), showed that the adsorption of Pb(II) onto nanofibres was spontaneous and exothermic. The novel nanofibres exhibited higher potential removal of Pb(II) ions than plain PVA nanofibres. Ubiquitous cations adsorption test was also investigated and studied.Electronic supplementary materialThe online version of this article (doi:10.1186/s11671-016-1631-2) contains supplementary material, which is available to authorized users.

Graphene oxide (GO) was functionalized using two silanes ((3‐aminopropyl)‐triethoxysilane and (3‐mercaptopropyl)‐triethoxysilane) to obtain, separately, the eco‐friendly amine‐functionalized GO (GONH) and thiol‐functionalized GO (GOSH). Both silanes were also used together to obtain the amine–thiol dual‐functionalized GO (GOSN). Various physicochemical characterizations were obtained including spectra from using Fourier‐transform infrared (FTIR) spectrometer, thermogravimetric analyzer, and X‐ray diffractometer. The adsorbents were used for a comparative study of Cr adsorption from aqueous solution. The obtained data were fitted to pseudo‐first order (PFO) and pseudo‐second order (PSO) models, the homogeneous fractal pseudo‐second order (FPSO), and the Weber–Morris intraparticle diffusion (IPD) kinetics models. Model parameters of the Langmuir and Freundlich adsorption isotherm models, as well as the thermodynamics, were calculated. Characterization results showed successful functionalizations. The GONH, GOSH, and GOSN exhibited alkaline, acidic, and neutral pH, respectively, in water. Amine and thiol functional groups were observed in the new adsorbents, as well as reduced orderliness. The adsorbents had higher density per unit weight and better thermal stability than pristine GO. Equilibrium Cr adsorption was attained within 60 min for all adsorbents. The PSO and FPSO described the rate data better. The Cr adsorption decreased as solution pH increased; optimum adsorption was recorded at pH 2. Equilibrium adsorption data fitted the Langmuir adsorption isotherm model for the GONH, while it fitted the Freundlich for both GOSH and GOSN. The adsorption process was theoretically exothermic process that was spontaneous processes. The Cr adsorption capacities of these adsorbents are 114, 89.6, and 173 mg/g for GONH, GOSH, and GOSN, respectively, and these were better than several reported graphene‐based adsorbents and suggest the potential of these adsorbents for water treatment.Practitioner points Graphene oxide was mono and dual‐functionalized with amine and thiol groups for Cr adsorption. The adsorption capacities of these adsorbents were better than several earlier reported. These adsorbents may be used for real contaminated water treatment.