Microporous nanohybrids of carbon xerogels and multi-walled carbon nanotubes for removal of rhodamine B dye

Abstract

In the current paper, microporous nanohybrids of carbon xerogel and multi-walled carbon nanotubes (CX/MWCNTs) with different loadings of MWCNTs (1, 2 and 4 g/L) were synthesized. Scanning electron microscope (SEM) and transmission electron microscope (TEM) assessed the decoration of microspheres of carbon particles in CX matrix with bundles of MWCNTs. Nitrogen adsorption at −196 °C revealed that the N2 uptake was enhanced when CX was decorated with MWCNTs and the specific surface area (SBET) increased from 192 to 643 m2/g. The resulting hybrids are mainly microporous materials. Rising the amount of MWCNTs from 1 to 4 g/L led to a decrease in the SBET from 643 to 515 m2/g (i.e. decreased approximately 20%). Fourier transform infrared spectra (FTIR) and Boehm's titration showed that both acidic and basic oxygen functional groups were equally distributed while carboxylic groups were increased considerably by increasing the amount of MWCNTs. The efficiency of adsorption and catalytic oxidation properties of CX/MWCNTs nanohybrids towards removal of rhodamine B (RB) was examined. Adsorption equilibrium data were analyzed using five different adsorption isotherms, i.e. Langmuir, Freundlich, Flory-Huggins, Halsey and Elovich models. The equilibrium adsorption results proved that adsorption of RB dye onto these nanohybrids can be well-fitted using Langmuir and Halsey isotherms. These nanohybrids exhibited considerable adsorption capacities that varied from 154 to 256 mg/g. The catalytic performance indicated that the investigated nanohybrids could eventually be used for the removal of RB dye in presence of H2O2 and visible light within 60 min, affirming that the CX/MWCNTs obtained are effective materials in liquid-phase applications for treating dye-contaminated industrial wastewater.