Water pollution has widely impacted our lives in the recent years. Water-borne diseases are on an exponential rise. Many prominent studies have shown that millions lose their lives due to the consumption of contaminated water each year. Water pollution due to the industrial effluents is at its peak due to the global industrialization, spillage of oil in the ocean, radioactive waste, and so on. Industrial effluents that are discarded into water bodies generally contain organic dyes and heavy metal ions. In this alarming situation, wastewater treatment and desalination to provide clean and toxin-free drinking water becomes of high priority. Various techniques and materials are employed for this purpose, among which graphene and its derivatives fulfill this purpose excellently. Polymeric matrices serve as bulk carriers for the immobilized nanomaterial, which helps limit their release into the environment during application processes and makes clean-up easier. In other instances, the composite's polymeric component functions cooperatively to improve the remediation techniques. This book chapter provides a systematic anthology of various graphene oxide–synthetic polymer-based nanocomposites (GO–Polymer) for wastewater treatment involving the removal of textile dyes, metal ions, oil–water separation, and desalination.
Graphene oxide and reduced graphene oxide (r-GO) were synthesized by wet chemistry and the effect of r-GO in PS–PVME blends was investigated here with respect to phase miscibility, intermolecular cooperativity in the glass transition region and concentration fluctuation variance by shear rheology and dielectric spectroscopy. The spinodal decomposition temperature (Ts) and correlation length were evaluated from isochronal temperature scans in shear rheology. The r-GO is shown to induce miscibility in the blends, which may lead to increased local heterogeneity in the blends, though the length of cooperatively re-arranged regions (ξ) at Tg is more or less unaltered. The evolution of the phase morphology as a function of temperature was assessed using polarized optical microscopy (POM). In the case of the 60/40 PS–PVME blends with 0.25 wt% r-GO, apart from significant refinement in the morphology, retention of the interconnected ligaments of PVME was observed, even in the late stages of phase separation suggesting that the coarsening of the phase morphology has been slowed down in the presence of r-GO. This phenomenon was also supported by AFM. Surface enrichment of PVME, owing to its lower surface tension, in the demixed samples was supported by XPS scans. The interconnected network of PVME has resulted in significantly higher permittivity in the bi-phasic blends, although the concentration of r-GO is below the percolation threshold.
In the present work, we report on the development of a highly sensitive electrochemical sensor for the rapid detection of dopamine, and acetaminophen molecules based on barium titanate nanocubes deposited on a glassy carbon electrode. The as-synthesized barium titanate nanocubes were characterized using X-ray diffraction measurements, field emission scanning electron microscopy, and UV–vis diffuse reflectance spectroscopy. The electrochemical performances of the as synthesised nanomaterials were investigated by cyclic voltammetry and differential pulse voltammetry. A linear response was exhibited by the modified electrode for both dopamine, and acetaminophen in the range 10–100 μ M, and the detection limit (S/N=3) was calculated to be 0.35 μ M, 0.23 μ M respectively. Under the optimised conditions, highly stable, sensitive, selective, and reproducible performances were exhibited by the electrochemical sensor. Furthermore, the as developed sensor also showed acceptable recoveries for the analysis of real samples.
Crystallization-induced phase separation and segmental relaxations in poly(vinylidene fluoride)/poly(methyl methacrylate) (PVDF/PMMA) blends was systematically investigated by melt-rheology and broadband dielectric spectroscopy in the presence of multiwall carbon nanotubes (MWNTs). Different functionalized MWNTs (amine, -NH2; acid, -COOH) were incorporated in the blends by melt-mixing above the melting temperature of PVDF, where the blends are miscible, and the crystallization induced phase separation was probed in situ by shear rheology. Interestingly, only -NH2 functionalized MWNTs (a-MWNTs) aided in the formation of β-phase (trans-trans) crystals in PVDF, whereas both the neat blends and the blends with -COOH functionalized MWNTs (c-MWNTs) showed only α-phase (trans-gauche-trans-gauche') crystals as inferred from wide-angle X-ray diffraction (WXRD) and Fourier transform infrared (FTIR). Furthermore, blends with only a-MWNTs facilitated in heterogeneous nucleation in the blends manifesting in an increase in the calorimetric crystallization temperature and hence, augmented the rheologically determined crystallization induced phase separation temperature. The dielectric relaxations associated with the crystalline phase of PVDF (αc) was completely absent in the blends with a-MWNTs in contrast to neat blends and the blends with c-MWNTs in the dielectric loss spectra. The relaxations in the blends investigated here appeared to follow Havriliak-Negami (HN) empirical equations, and, more interestingly, the dynamic heterogeneity in the system could be mapped by an extra relaxation at higher frequency at the crystallization-induced phase separation temperature. The mean relaxation time (τHN) was evaluated and observed to be delayed in the presence of MWNTs in the blends, more prominently in the case of blends with a-MWNTs. The latter also showed a significant increase in the dielectric relaxation strength (Δε). Electron microscopy and selective etching was used to confirm the localization of MWNTs in the amorphous phases of the interspherulitic regions as observed from scanning electron microscopy (SEM). The evolved crystalline morphology, during crystallization-induced phase separation, was observed to have a strong influence on the charge transport processes in the blends. These observations were further supported by the specific interactions (like dipole induced dipole interaction) between a-MWNTs and PVDF, as inferred from FTIR, and the differences in the crystalline morphology as observed from WXRD and polarized optical microscopy (POM).
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