Surface functionalization of multi-walled carbon nanotubes by ozone and the enhancement of their environmental applications

Controlled synthesis of MWCNTs/V2O5 nanocomposite by hydrothermal approach for adsorption and photodegradation processes

The current paper outlines the synthesis of pristine multi-wall carbon nanotubes (PMWCNTs)/Vanadium pentoxide V2O5 and functionalized multi-wall carbon nanotubes (FMWCNTs)/V2O5 nanocomposite for photocatalytic applications. The FMWCNTs were obtained by the oxidizing agents (H2SO4 and HNO3) to introduce the oxygenated functional groups. The samples were synthesized by hydrothermal approach and investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy analysis (EDX), and Fourier transform infrared spectroscopy (FTIR). The photocatalytic activity of multi-wall carbon nanotubes (MWCNTs), FMWCNTs/V2O5, and PMWCNTs/V2O5 nanocomposites was assessed via methylene blue (MB) degradation from water under visible light. The results demonstrated that the removal efficiency of MB by PMWCNTs, FMWCNTs/V2O5, and PMWCNTs/V2O5 could reach 90.4, 98.9, and 94.9%, respectively. It was noticed that MB adsorption and photodegradation tend to follow pseudo-second-order kinetics. The mechanism of MB photodegradation by FMWCNTs/V2O5 nanoparticles was explained. MWCNTs/V2O5 nanocomposites will allow further applications to remove other dyes and contaminants from wastewater.

Structural control of V2O5 nanoparticles via a thermal decomposition method for prospective photocatalytic applications

Background

Recently, transition-metal oxides have represented an exciting research topic, especially their fundamental and technological aspects. Here, vanadium pentoxide nanoparticles (V2O5-NPs) were synthesized through the thermal decomposition of ammonium meta-vanadate. In the current study, we investigated the photocatalytic activity of V2O5-NPs to develop and regulate the V2O5 structure for adsorption applications.

Results

The obtained nanoparticles were inspected by X-ray diffraction, scanning electron microscope, transmission electron microscope, and differential thermogravimetric analysis, which proved the formation of the nanorod structure. The ultraviolet–visible absorption spectra revealed a 2.26 eV band gap for V2O5-NPs that correlates with indirect optical transitions. The photocatalytic activity of the V2O5-NPs was investigated by methylene blue (MB) degradation in aqueous solutions. An initial concentration of 25 ppm, a temperature of 40 °C, 40 mg of adsorbent mass, and 1 h of contact time were the optimal conditions for the efficient removal of MB that could reach up to 92.4%. The mechanism of MB photocatalytic degradation by V2O5-NPs is explained.

Conclusions

The photodegradation data better fit with the Langmuir isotherm model. The thermodynamic parameters indicated that the adsorption was spontaneous and endothermic. The reaction kinetics followed the pseudo-second-order model. Thermally prepared V2O5-NPs offer a simple and efficient approach for selective MB removal from an aqueous medium.

Graphical abstract

Toxicological assessment of functional polymer with single-walled carbon nanotubes in zebrafish embryos and its gill cell line

Carbon nanotubes (CNTs) have been widely used in developing polymer hybrid coatings for anticorrosive application. In the present study, poly [(3,5-dimethyl-lH-pyrazole-1-yl) methyl methacrylate-co-glycidyl methacrylate] (PyM) was prepared by solution polymerization. Single-wall carbon nanotubes (SWCNT) were incorporated in the PyM by solution blending technique at different proportions. The PyM and its SWCNT (PyM-SWCNT) nanocomposites were characterized by FT-IR spectroscopy, X-Ray Diffraction, FE-SEM and HR-TEM. Different concentrations of PyM or PyM-SWCNT prepared in the present study were assessed separately for their toxicity by in vivo and in vitro assays using zebrafish embryos and gill cell line of zebrafish (DrG), respectively. The nanocomposites at the concentration of 400 μg ml^-1 of PyM in 1.0% of SWCNT was found to be non-toxic and recommended for anticorrosive application whereas the nanocomposites with above 1% of SWCNT was found to be toxic. The nanocomposites with 1.5% of SWCNT delayed the hatching rate of eggs, decreased survival rate and heart beat in zebrafish embryos, and induced the morphological changes in DrG cells. Gene expression studies revealed that PyM-SWCNT with high concentration of SWCNT induced oxidative stress by activating ROS generations in zebrafish embryos and DrG cells. The immersion study of uncoated and coated with recommended concentration of PyM-SWCNT on mild steel (MS) in sea water was studied using FE-SEM and EDS, and the results showed effective corrosion protection without leaching behaviour. The nanocomposites with novel polymer in the present study may be used in the industry for anticorrosive purpose.