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In the present work, the modified bentonites were prepared by the modification of bentonite with cetyltrimethylammonium bromide (CTAB), both cetyltrimethylammonium bromide and hydroxy-Fe cations and both cetyltrimethylammonium bromide and hydroxy-Al cations. X-ray diffraction (XRD), thermal analysis (TG-DTA), infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and nitrogen adsorption/desorption isotherms were utilized to characterize the resultant modified bentonites. The modified bentonites were employed for the removal of phenol red dye from aqueous solution. Phenol red adsorption agreed well with the pseudo-second-order kinetic model. The equilibrium data were analyzed on the basis of various adsorption isotherm models, namely, Langmuir, Freundlich, and Dubinin‒Radushkevich models. The highest monolayer adsorption capacity of phenol red at 30°C derived from the Langmuir equation was 166.7 mg·g−1, 125.0 mg·g−1, and 100.0 mg·g−1 for CTAB‒bentonite, Al‒CTAB‒bentonite, and Fe‒CTAB‒bentonite, respectively. Different thermodynamic parameters were calculated, and it was concluded that the adsorption was spontaneous (∆G° < 0) and endothermic (∆H° > 0), with increased entropy (∆S° > 0) in all the investigated temperature ranges.

The synthesis of magnetic iron oxide/reduced graphene oxide (Fe 3 O 4 /rGO) and its application to the electrochemical determination of paracetamol using Fe 3 O 4 /rGO modified electrode were demonstrated. The obtained materials were characterized by means of X-ray diffraction (XRD), nitrogen adsorption/desorption isotherms, X-ray photoelectron spectroscopy (XPS), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR), and magnetic measurement. The results showed that Fe 3 O 4 /rGO composite exhibited high specific surface area, and its morphology consists of very fine spherical particles of Fe 3 O 4 in nanoscales. Fe 3 O 4 /rGO was used as an electrode modifier for the determination of paracetamol by differential pulseanodic stripping voltammetry (DP-ASV). The preparation of Fe 3 O 4 /rGO-based electrode and some factors affecting voltammetric responses were investigated. The results showed that Fe 3 O 4 /rGO is a potential electrode modifier for paracetamol detection by DP-ASV with a low limit of detection. The interfering effect of uric acid, ascorbic acid, and dopamine on the current response of paracetamol has been reported. The repeatability, reproducibility, linear range, and limit of detection were also addressed. The proposed method could be applied to the real samples with satisfactory results.

The synthesis of reduced graphene oxide modified by magnetic iron oxide (Fe3O4/rGO) and its application for heavy metals removal were demonstrated. The obtained samples were characterized by X-ray diffraction (XRD), nitrogen adsorption/desorption isotherms, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), and magnetic measurement. The results showed that the obtained graphene oxide (GO) contains a small part of initial graphite as well as reduced oxide graphene. GO exhibits very high surface area in comparison with initial graphite. The morphology of Fe3O4/rGO consists of very fine spherical iron nanooxide particles in nanoscale. The formal kinetics and adsorption isotherms of As(V), Ni(II), and Pb(II) over obtained Fe3O4/rGO have been investigated. Fe3O4/rGO exhibits excellent heavy metal ions adsorption indicating that it is a potential adsorbent for water sources contaminated by heavy metals.

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