Synthesis and characterization of SnO2/rGO nanocomposite for an efficient photocatalytic degradation of pharmaceutical pollutant: Kinetics, mechanism and recyclability

Photocatalytic removal of some selected antibiotics in polluted water system by graphitic carbon nitride-enhanced vanadium ferrite (VFe2O4@g-C3N4)

Antibiotics such as sulfamethoxazole (SUF), ciprofloxacin (CIP) and erythromycin (ERY) are frequently detected in water systems without being efficiently removed during water treatment. This study synthesized a graphitic carbon nitride-enhanced vanadium ferrite (VFe2O4@g-C3N4) as a photocatalyst for degrading SUF, CIP and ERY in an aqueous solution. VFe2O4@g-C3N4 was characterized with X-ray diffractometry (XRD), thermogravimetry analysis (TGA), ultraviolet (UV)-visible spectrophotometry, scanning electron microscope (SEM) and transmission electron microscope (TEM). The XRD characterization of VFe2O4@g-C3N4 revealed diffraction patterns with a crystallite size of 22.45 nm and a bandgap energy of 1.94 eV. The SEM image revealed the surface to be rough with irregular particle shape and size. The TEM image showed an average particle size of 92.47 nm. VFe2O4@g-C3N4 exhibited a degradation efficiency, which showed complete removal of SUF (100 %) from solution while the efficiency towards CIP is 94 ± 0.60 % and 90 ± 0.8 % towards ERY. The best photocatalytic performance was achieved with 0.12 g L-1 of VFe2O4@g-C3N4 and pH = 7.0 as the optimal conditions for achieving complete removal of SUF, CIP and ERY at a concentration lower than 10.00 mg L-1 under visible-light irradiation. The photodegradation of SUF, CIP and ERY by VFe2O4@g-C3N4 was found to be promoted by ROS with ˙OH and SO4˙- radicals playing a significant role. VFe2O4@g-C3N4 demonstrated a regeneration capacity that is above 90 % at the 10th cycle of regeneration treatment, suggesting it to be stable and reusable with the X-ray diffraction pattern remaining unchanged and no leaching of VFe2O4@g-C3N4 into solution. The result from the study reveals VFe2O4@g-C3N4 as a promising photocatalyst for removing antibiotics from an aqueous solution.

Enhanced photocatalytic activity of tin oxide-doped molybdenum disulfide nanohybrids under visible light irradiation: Antibiotics elimination, heavy metal reduction and antibacterial behavior

Nano-heterojunction photocatalytic can operate removal of pollutants, which is basic for the sustainable development of a clean environment. Herein, we propose a novel MoS2/SnO2 (MS) S-scheme heterojunction by a facile hydrothermal process, which is cheap, easily available, highly visible-light response, and good stability. The MS nano-heterojunction suggested superior performance with the photocatalytic degradation of 97.6% within 100 min for ciprofloxacin (CIP) removal, which was 5.74 and 4.88 folds higher than that of pristine MoS2 and SnO2, respectively. The fabricated MS photocatalysts displayed outstanding photocatalytic efficiency toward Cr (VI) reduction. The removal capability of Cr (VI) reached up to 92.5% within 60 min. The photodegradation efficiency was 5.2 folds that of pristine MoS2. In addition, the antibacterial performance approximately approached 100% for E. coli within 10 min, which was more apparent than the others. A series of excellent results implied that MS nano-heterojunction had a high ultraviolet and visible light absorbance, larger specific surface area, outstanding electron-hole pairs migration and higher capability of photo-response electrons and holes separation rate. This system offers a novel window into the evolution of nano-heterojunction for wastewater treatment and solar energy harvesting applications.

Graphene-based photocatalysts for degradation of organic pollution

Compared with the traditional wastewater treatment technology, semiconductor photocatalysis is a rapidly emerging environment-friendly and efficient Advanced Oxidation Process for degradation of refractory organic contaminants. Single-component semiconductor photocatalysts exhibit poor photocatalytic performance and cannot meet the requirements of wastewater treatment. The combination of semiconductor photocatalysts and Graphene can effectively improve the photocatalytic activity and stability of semiconductor photocatalysts. This review focuses on the synergistic effect of several types of semiconductors with Graphene for photocatalytic degradation of organic pollutants. After a brief introduction of the photodegradation mechanism of semiconductor materials and the basic description of Graphene, the synthesis, characterization and degradation performance of various Graphene-based semiconductor photocatalysts are emphatically introduced.

A novel tungsten diselenide nanoparticles for enhanced photocatalytic performance of Cr (VI) reduction and ciprofloxacin (CIP)

Nanoparticles (NPs) fabrication is a significant approach to enhance the visible light response of photocatalysts, to realize inexpensive and more harmful compound removal, at larger scale. The poor electrons and holes separation capability and low light activity of bulk materials can be notably enhanced through developing NPs. From photocatalytic investigation, better performance was received in the tungsten diselenide (WSe2) NPs than that in bare WSe2, exhibiting the action of restrained recombination of charge carriers in the NPs. The photocatalytic Cr(VI) reduction efficiency of WSe2 NPs is 2.7 folds greater than that by bare WSe2. On the other hand, the photocatalytic efficiency follows the order of nano WSe2-3 > nano WSe2-2 > nano WSe2-1 > bare WSe2, nano WSe2-3 is nearly 2.7 folds greater than that of bare WSe2. The results imply the fabrication of WSe2 NPs and it possesses improved visible light utilization. The proposed WSe2 NPs have merged with the three aspects of photocatalytic capability including the visible light activity, the valid separation of photo-response charge carriers and enough surface active sites owing to the nanoscale formed. This research endows conduct on the potential style of NPs for photo-response water environmental remediation.

ZnWO4 nanorod-colloidal SnO2 quantum dots core@shell heterostructures: Efficient solar-light-driven photocatalytic degradation of tetracycline

Zinc tungsten oxide (ZW) and colloidal SnO₂ quantum dots (CS) were synthesized individually by hydrothermal and wet chemical methods. ZW-CS core@shell nanorods were prepared using a sonochemical method for the enhanced photocatalytic activity of tetracycline (TC) degradation. ZW-CS core@shell nanorods were systematically characterized by structural, morphological mapping and optical techniques. All characterization techniques were synchronized to confirm the construction of core@shell nanorods. Optical absorption studies indicate an increased light-capturing efficiency along with a reduced bandgap from 3.56 to 3.23 eV, which is further supported by photoluminescence. Mapping analysis from SEM and HR-TEM evidence the presence of elements as well as a core@shell nanostructure. The optimized sample of ZW-CS 1.0 shows improved photocatalytic degradation of TC under stimulated solar light. The TC degradation efficiency by ZW-CS 1.0 core@shell nanorods was about 97% within 2 h. The formation of core@shell nanorod structure might be the reason for the better photocatalytic tetracycline degradation performance.