Porous carbon materials are currently subjected to strong research efforts mainly due to their excellent performances in energy storage devices. A sustainable process to obtain them is hydrothermal carbonization (HTC), in which the decomposition of biomass precursors generates solid products called hydrochars, together with liquid and gaseous products. Hydrochars have a high C content and are rich with oxygen-containing functional groups, which is important for subsequent activation. Orange pomace and orange peels are considered wastes and then have been investigated as possible feedstocks for hydrochars production. On the contrary, orange juice was treated by HTC only to obtain carbon quantum dots. In the present study, pure orange juice was hydrothermally carbonized and the resulting hydrochar was filtered and washed, and graphitized/activated by KOH in nitrogen atmosphere at 800 °C. The resulting material was studied by transmission and scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and nitrogen sorption isotherms. We found porous microspheres with some degree of graphitization and high nitrogen content, a specific surface of 1725 m²/g, and a pore size distribution that make them good candidates for supercapacitor electrodes.

In this study, we propose a novel approach to prepare few-layer graphene (FLG) dispersions, which is realized by exfoliating natural graphite flakes in a surfactant aqueous solution under hydrothermal treatment and liquid-phase exfoliation. In order to obtain stable and well-dispersed FLG dispersions, pristine graphite is hydrothermally expanded in a hexadecyltrimethylammonium bromide (CTAB) aqueous solution at 180 °C for 15 h, followed by sonication up to 3 h. In comparison to long-time sonication methods, the present method is significantly efficient, and most importantly, does not involve the use of an oxidizing agent and hazardous media, which will make it more competent in the scalable production of graphene.

The present paper reports the in situ hydrothermal synthesis of a composite mordenite membrane. In this process, mordenite forms at the surface and within the pores of a porous ceramic alumina support by nucleation and crystallization from a mixture containing alumina and silica species. The structure and texture of the composite membrane were identified by XRD and SEM, as well as by single gas permeation at room temperature with H₂, N₂, O₂, Ar, CO, He and CH₄. The permeation resulting as a function of transmembrane pressure revealed a small viscous flow contribution for gas transport through the MOR composite membrane. Furthermore, these preliminary results (order of gas permeance and ideal selectivities) suggest that Knudsen diffusion is the dominant transport mechanism for the investigated series of gases, although an ideal selectivity slightly higher than the Knudsen selectivity was obtained, namely α = 1.6 at Δp = 0.6 bar for CH₄/N₂.