Covalent modification of reduced graphene oxide with piperazine as a novel nanoadsorbent for removal of H2S gas

In the present research, piperazine grafted-reduced graphene oxide RGO-N-(piperazine) was synthesized through a three-step reaction and employed as a highly efficient nanoadsorbent for H2S gas removal. Temperature optimization within the range of 30–90 °C was set which significantly improved the adsorption capacity of the nanoadsorbent. The operational conditions including the initial concentration of H2S (60,000 ppm) with CH4 (15 vol%), H2O (10 vol%), O2 (3 vol%) and the rest by helium gas and gas hour space velocity (GHSV) 4000–6000 h−1 were examined on adsorption capacity. The results of the removal of H2S after 180 min by RGO-N-(piperazine), reduced graphene oxide (RGO), and graphene oxide (GO) were reported as 99.71, 99.18, and 99.38, respectively. Also, the output concentration of H2S after 180 min by RGO-N-(piperazine), RGO, and GO was found to be 170, 488, and 369 ppm, respectively. Both chemisorption and physisorption are suggested as mechanism in which the chemisorption is based on an acid–base reaction between H2S and amine, epoxy, hydroxyl functional groups on the surface of RGO-N-(piperazine), GO, and RGO. The piperazine augmentation of removal percentage can be attributed to the presence of amine functional groups in the case of RGO-N-(piperazine) versus RGO and GO. Finally, analyses of the equilibrium models used to describe the experimental data showed that the three-parameter isotherm equations Toth and Sips provided slightly better fits compared to the three-parameter isotherms

Covalent Modification of Graphene Oxide with Vitamin B1: Preparation, Characterization, and Catalytic Reactivity for Synthesis of Benzimidazole Derivatives

The GO-VB1 catalyst has successfully synthesized in current research with strong covalent bonds between GO and VB1. This catalyst with covalent bonds has a higher thermal stability in different reaction conditions as compared to the other catalysts with nonspecific adsorption to the substrate. GO-VB1 catalyst showed high catalytic activities in benzimidazole synthesis and could be recycled and reused several times without noticeable loss of activity. GO-VB1 is proper for high-yielding preparations and could be used for more catalytic applications. The morphology and chemical structure of GO-VB1 were characterized by X-ray diffraction, Fourier transform infrared spectra, scanning electron microscopy, energy dispersive X-ray spectroscopy, atomic force microscopy, and thermogravimetric analyses