The status of SWNT purification sciences within the last two decades are reviewed. Over the years, the aggressive search for effective and efficient post-synthetic purification technique has given rise to the development of numerous methods. Unfortunately, most of these methods do not possess the potentials of being selective, scalable, nor effective. On the other hand, the mechanisms behind the promising separation methods are yet to be fully understood. For such techniques, it is recommended that interest should now lie more on investigating the underpinning mass transfer kinetics and equilibrium thermodynamics with a view to making them more efficient.

Removal of ciprofloxacin (CIP) pollutant from wastewater using conventional process is particularly challenging due to poor removal efficiency. In this work, CIP was photocatalytically degraded using a porous ZnO/SnS2 photocatalyst prepared via microwaves. The influence of process parameters (e.g., pH, catalyst mass and initial CIP concentration) and radical scavengers on visible-light induced degradation of CIP on the catalyst was investigated. From the study, it was found that visible-light induced degradation of CIP on ZnO/SnS2 is a surface-mediated process and the reaction kinetics followed the Langmuir-Hinshelwood first-order kinetics. It was found that the optimum condition for CIP degradation was at pH of 6.1 and catalyst dosage of 500 mg L−1. Higher catalyst dosage however led to a decline in reaction rate due to light scattering effect and reduction in light penetration.

Porous ZnO/SnS2nanocomposites with adjustable SnS2contents were prepared via microwave-assisted heating of different aqueous solutions of SnS2precursors in the presence of fixed amount of ZnCO3nanoparticles at pH 7. The structures, compositions, BET specific surface areas, and optical properties of the as-prepared products were characterized by X-ray diffraction, energy dispersive X-ray spectroscopy, transmission electron microscopy, N2adsorption, and UV-Vis absorption spectra. Photocatalytic activities of the samples were tested by the removal of aqueous ciprofloxacin,CrVI, and methylene blue under visible-light (λ>420 nm) irradiation. The experimental results reveal that the as-prepared heterogeneous nanostructures exhibit much higher visible-light-driven photocatalytic activity for the degradation of the pollutants than pure SnS2nanocrystals. The photocatalytic degradation ratesCt/C0of the pollutants for the most active heterogeneous nanostructure are about 10, 49, and 9 times higher than that of pure SnS2. The enhanced photocatalytic activities exhibited by the heterojunctions could be ascribed to the synergetic effect of enhanced absorption in the visible region and the reduced rate of charge carrier recombination because of efficient separation and electron transfer from the SnS2to ZnO nanoparticles.

The unique physicochemical properties of carbon quantum dot-(CQD)-based photocatalysts, notably their exceptionally good light absorption in the UV and near-visible region, tunable photoluminescence, extraordinary upconversion photoluminescence, outstanding electron affinity, and photoinduced electron transfer, and electron mobility, have attracted considerable attention in different photocatalytic applications. In this review, we summarized the fundamental mechanism and thermodynamics of heterogeneous photocatalysis of aqueous pollutants and the fundamental multifaceted roles of CQDs in photoredox process. Furthermore, we discussed the recent developments in the use of CQD-based materials as visiblelight active photocatalysts in water purification. Finally, the challenges and future direction of CQD-based materials as photocatalytic materials for environmental decontamination were highlighted.

A series of CdS/TiO2nanocomposites with different Cd to Ti molar ratio were synthesized from P25-TiO2nanopowder using microwave-assisted hydrothermal method. The as-produced powders were characterized by XRD, electron microscopy, EDX, and UV-Vis diffuse reflectance spectroscopy. The adsorption capacity and photocatalytic activity of the samples were investigated using methylene blue as a model pollutant. Sorption tests revealed that the adsorption of MB onto the samples obeys the Freundlich-Langmuir isotherm model. The sorption capacity decreased as follows:TiO2>TCd2>TCd1>TCd3>TCd4. The results of the photocatalytic tests under high-intensity discharge (HID) lamp revealed that CdS/TiO2powders with low Cd to Ti molar ratios exhibited much higher activities than P25-TiO2. The CdS/TiO2sample with 20% CdS/(TCd2) showed the most activity among all these samples. The results also show that the Cd to Ti molar ratio of the nanocomposite has a significant effect on the photodegradation of MB and the enhanced activities exhibited by the nanocomposites are because of the low rate of electron-hole recombination.