Solvothermal synthesis of WO3 /TiO2 /carbon fiber composite photocatalysts for enhanced performance under sunlight illumination

Enhanced photocatalytic activity and charge carrier separation of CNT/TiO2/WO3/CdS catalyst for the visible-light photodegradation of reactive blue 19

The novel quaternary CNT/TiO₂/WO₃/CdS nanostructure was fabricated to be employed in the photocatalytic degradation of reactive blue 19 (RB19) under the visible light irradiation. The physicochemical properties of the pure TiO₂, CNT/TiO₂, CNT/TiO₂/WO₃, and CNT/TiO₂/WO₃/CdS were characterized using XRD, FTIR, FESEM, EDX, DRS, PL, and BET analyses. The photodegradation results showed that the optimum weight percentage of CNT, WO₃, and CdS was 4%, 35%, and 5%, respectively. The highest RB19 degradation efficiency of CNT/TiO₂/WO₃/CdS was achieved 97%. Besides, the central composite design was applied to model and optimize the photocatalytic activity of CNT/TiO₂/WO₃/CdS nanocatalyst and assess the effects of processing variables including RB19 concentration, catalyst concentration, pH, and irradiation time on the response. RB19 concentration and pH had the most and the second most significant role in the removal efficiency. While increasing the catalyst concentration and irradiation time positively enhanced the removal efficiency to more than 82%, increasing the pH and dye concentration showed the remarkable hindering effects on the removal efficiency by about 45% reduction. The reusability of the synthesized catalysts was studied under the optimum conditions as follows: [RB19] = 25 mg/L, [catalyst] = 1 g/L, pH of 4, and irradiation time = 2 h. The COD and TOC analyses were also conducted during photodegradation process. The COD and TOC removal efficiencies were achieved about 67% and 62%, respectively.

Photodegradation assessment of RB5 dye by utilizing WO3/TiO2 nanocomposite: a cytotoxicity study

Textile dyeing wastewater becomes one of the root causes of environmental pollution. Titanium dioxide (TiO₂) is one of the photocatalysts that shows prominent organic dye photodegradation ability. In this study, a porous tungsten oxide (WO₃)/TiO₂ composite was prepared through ultrasonic-assisted solvothermal technique with varying amounts of WO₃ ranging from 0.25 to 5 weight % (wt.%). The prepared 0.50 wt.% WO₃/TiO₂ (0.50WTi) composite exhibited the highest photodegradation activity (4.39 × 10^-2 min^-1) and complete mineralization in chemical oxygen demand (COD) reading towards 30 mg.L^-1 of Reactive Black 5 (RB5) dye under 60 min of light irradiation. Effects of large surface area, small crystallite size, high pore volume and size, and low electron-hole pair recombination rate attributed to the superiority of 0.50WTi. Besides, 0.50WTi could be reused, showing 86.50% of RB5 photodegradation at the fifth cycle. Scavenger study demonstrated that photogenerated hole (h⁺) was the main active species of 0.50WTi to initiate the RB5 photodegradation. Cytotoxicity assessment determined the readings of half-maximal inhibitory concentration (IC₅₀) were 1 mg.mL^-1 and 0.61 mg.mL^-1 (24 and 72 h of incubations) for the 0.50WTi composite.

Titanium dioxide based nanocomposites - Current trends and emerging strategies for the photocatalytic degradation of ruinous environmental pollutants

Many ruinous pollutants are omnipresent in the environment and among them; pesticides are xenobiotic and pose to be a bio-recalcitrance. Their detrimental ecological and environmental impacts attract attention of environmental excerpts and the surge of stringent regulations have endows the need of a technically feasible treatment. This critical review emphasizes about the occurrence, abundance and fate of structurally distinct pesticides in different environment. The practiced remedial strategies and in particular, the advanced oxidation processes (AOPs) those utilize the photo-catalytic properties of nano-composites for the degradation of pollutants are critically discussed. Photo-catalytic degradation utilizes many composite materials at nano-scale level, wherein synthesis of nano-composites with appropriate precursors and other adjoining functional moieties are of prime importance. Therefore, suitable starter materials along with the reaction conditions are prerequisite for effectively tailoring the nano-composites. The aforementioned aspects and their customized applications are critically discussed. The associated challenges, opportunities and process economics of degradation using photo-catalytic AOP techniques are highlighted and in addition, the review tries to explain how best the photo-degradation can be a stand-alone tool with a societal importance. Conclusively, the future prospects for undertaking new researches in photo-catalytic breakdown of pollutants that can be judiciously sustainable.

Preparation of TiO2/WO3/C/N Composite Nanofibers by Electrospinning Using Precursors Soluble in Water and Their Photocatalytic Activity in Visible Light

Extending the absorption range of TiO₂ nanofibers to visible light is a great improvement of the photocatalytic property of TiO₂. In this study, TiO₂/WO₃/C/N nanofibers were prepared by electrospinning using precursors soluble in water then annealing in argon. Titanium(IV) bis(ammonium lactato)dihydroxide (TiBALDH) and ammonium metatungstate (AMT) were used as the precursor for TiO₂ and WO₃ respectively. Different volume ratios of the precursors were added to a solution of PVP before electrospinning. The fibers were studied by XPS, SEM-EDX, TEM, FTIR, XRD, Raman spectroscopy and UV–VIS diffuse reflectance spectroscopy (DRS). The photocatalytic degradation of methylene blue by the fibers in visible light was investigated. The fibers had anatase TiO₂ and monoclinic WO₃. Based on UV–VIS DRS and Kubelka-Munk function the fibers could absorb visible light. Moreover, 100% TiBALDH had an indirect band gap of 2.9 eV, and the band gap decreased with increase in AMT, i.e., for 0% TiBALDH, band gap was 2.4 eV. The fibers degraded methylene blue dye in visible light, and 90% TiBALDH had the highest photocatalytic activity, i.e., it degraded 40% of the dye after 240 min.