In this research, active groups of biguanide were grafted to the surface of graphene oxide sheets through covalent functionalization and combined with magnetic nanoparticles to produce a magnetic graphene-based composite (MMGO). Then, the fabricated MMGO hybrid was introduced into the polyethersulfone (PES) polymer through phase inversion induced by immersion precipitation method. The prepared MMGO embedded PES membranes were examined for pure water flux permeability, salt rejection, antifouling, copper removal, and dye retention capability. The effect of MMGO hybrid on the cross-sectional morphology, hydrophilicity, and roughness of the PES membrane was investigated as well. Embedding MMGO hybrid was eventuated in a significant increase in the pure water flux because of changes in surface roughness and hydrophilicity of the membranes. Besides, the copper and dye removal capability of the prepared membranes remarkably raised due to the presence of hydrophilic functional groups on the surface of MMGO hybrid. The fabricated nanofiltration membrane with 0.5 wt % MMGO hybrid had the highest affinity for copper ions removal (92%). Dye rejection of the MMGO embedded PES membranes at different concentrations of MMGO hybrid was almost the same (about 99%) while the value of the bare PES membrane was 91%. Flux reduction of the MMGO embedded PES membranes was lower than that of the bare PES membrane during repeated filtration.

Modified graphene oxide by acetic acid moiety (GO/COOH) was synthesized and employed in the ultrasoundassisted oxidative-adsorptive desulfurization processes. The modified graphene oxide was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy The fabricated material was applied to simultaneous oxidation and adsorption of dibenzothiophene (DBT) from model fuel. Adsorption studies were carried out to evaluate its potential for DBT removal. The effects of contact time, initial DBT concentration, and temperature on the removal efficiency of the catalyst-adsorbent were investigated. The equilibrium adsorption results was well-described by the Freundlich isotherm model (at room temperature) and oxidation-adsorption of DBT were achieved by GO/COOH with an outstanding adsorption capacity of 370 mg g−1. The adsorption process followed a pseudo-first-order kinetic model and the adsorption kinetic data suggests that physical interactions are mainly involved on the entire adsorption process (Ea < 40 kJ mol−1). The initial sulfur content of 1000 ppm was reduced to<50 ppm within 300 min, achieving a sulfur removal of about 95%. As a whole, a model fuel with ultra-low sulfur content was obtained by the developed procedure and GO/COOH shows a high potential for effective desulfurization of diesel fuel as a catalyst-adsorbent.

A sulfonated magnetic graphene oxide (SMGO) hybrid was successfully synthesized via the nucleophilic substitution reaction and characterized. The removal of chromate by SMGO was investigated. The effects of contact time, initial pH of the solution, and initial chromate concentration on the removal efficiency were investigated. The optimal experimental conditions for enhanced chromate removal were found to be a contact time of 60 min at an initial solution pH of 3. The observed data were fitted with Lagergren pseudo-second-order kinetic model, indicating that chromate adsorption on SMGO was a chemical interaction in nature. The Langmuir model was also used to describe the adsorption processes and the adsorption capacity was found to be 222.22 mg g À1. Thermodynamic studies (DG < 0, DH > 0, DS > 0) revealed that the adsorption process was exothermic and spontaneous. SMGO has potential to be applied several times after desorption in wastewater treatment.

Lewis or Brønsted acidic methylimidazolium ionic liquid-functionalized Fe 3 O 4 @SiO 2 nanoparticles were fabricated and applied as an efficient magnetic heterogeneous catalyst for dibenzothiophene (DBT) oxidation in a biphasic system using H 2 O 2 as the oxidant. The structures of catalysts were characterized by SEM, TEM, XRD, TGA, FT-IR, VSM and EDX techniques. The magnetic catalysts showed high catalytic performance in the oxidation of DBT in an n-hexane/acetonitrile biphasic system using H 2 O 2 , and high conversions were obtained. The effects of contact time, temperature, amount of H 2 O 2 and amount of catalyst on the DBT oxidative removal efficiency were investigated. The contact time of 60 min, 0.1 g catalyst, and 4 mL H 2 O 2 at 313 K were found as optimal experimental conditions for an improved DBT oxidative removal process. The sulfur level could be lowered from 100 ppm to less than 7, 5, and 2 ppm under optimal conditions for Fe 3 O 4 @SiO 2 -Mim-BF 4 , Fe 3 O 4 @SiO 2 -Mim-HSO 4 , and Fe 3 O 4 @SiO 2 -Mim-FeCl 4 , respectively. These nanomagnetic heterogeneous catalysts could be easily separated from the reaction mixture by applying an external magnetic field and recycled several times.Scheme 1 Preparation of Fe 3 O 4 @SiO 2 -methylimidazolium chloride. This journal isScheme 2 Schematic illustration of Fe 3 O 4 @SiO 2 -methylimidazolium chloride nanoparticles anion exchange. 34976 | RSC Adv., 2017, 7, 34972-34983 This journal isFig. 6 Energy dispersive X-ray spectroscopy of (a) Fe 3 O 4 @SiO 2 -Mim-BF 4 (b) Fe 3 O 4 @SiO 2 -Mim-HSO 4 and (c) Fe 3 O 4 @SiO 2 -Mim-FeCl 4 . This journal is Scheme 4 The suggested mechanism of DBT oxidation by Fe 3 O 4 @SiO 2 -Mim-BF 4 . This journal is Scheme 5 The suggested mechanism of DBT oxidation by Fe 3 O 4 @SiO 2 -Mim-HSO 4 . 34980 | RSC Adv., 2017, 7, 34972-34983 This journal is