Preparation and modification methods of defective titanium dioxide-based nanoparticles for photocatalytic wastewater treatment-a comprehensive review

Efficiency of TiO2 particle-coated filter using different binders in carbendazim degradation from Chinese chives

Dip-coating TiO2 (Degussa P25) onto the glass-fiber pre-filter using different binders (PEG1000, 2000, 4000, 6000, and Duramax B1000) for carbendazim degradation in Chinese chives was studied. To investigate the effects of binder types, TiO2 concentration was fixed at 1 % w/v, and amounts of binders were varied in a range of 0.3 to 1 wt% based on the TiO2 content. Then, effects of TiO2 and binder concentrations were further studied on the most effective binder type (PEG6000). It was revealed that 2 wt% of PEG6000 yielded the highest carbendazim degradation efficiency. The efficiency increased with the increased concentration of TiO2. At the best condition of coating, i.e., 1-1.5 % w/v of TiO2 and 2 wt% of PEG6000, more than 90% degradation efficiency was obtained although the initial carbendazim concentration in the chives was as high as 168.4 mg/kg.

Efficacy of Biogenic Zinc Oxide Nanoparticles in Treating Wastewater for Sustainable Wheat Cultivation

Water scarcity due to overuse and growing water pollution has led to the need for upgrading of conventional methods of wastewater treatment. The biological synthesis of zinc oxide nanoparticles (ZnO-NPs) and their photocatalytic capacity to degrade contaminants offer a promising and environment-friendly approach to municipal wastewater treatment. This technique is advantageous due to its cost-effectiveness, sustainability, and reduction in toxic residual substances. In this study, microbial-synthesized ZnO-NPs were used for the treatment of municipal wastewater. The objective of this study was to evaluate the potential of treated wastewater for wheat crop cultivation. Zinc oxide nanoparticles were synthesized from a pre-isolated bacterial strain, namely Shewanela sp., and characterized using UV-VIS, X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) analyses. The results showed that after the treatment of wastewater, the concentration of total dissolve solids (TDS), the chemical oxygen demand (COD), and sulfate and phosphate levels decreased by 76.5%, 57.1%, 81.1%, and 67.4%, respectively. However, the application of treated wastewater increased chlorophyll, carotenoids, and antioxidants by 45%, 40.8%, and 10.5 to 30.6%, respectively. Further, the application of treated wastewater also significantly decreased oxidative stress induced by hydrogen peroxide (H2O2) and malondialdehyde (MDA) by 8.1% and 30.1%, respectively. In conclusion, biosynthesized ZnO-NPs could be an important choice to treat municipal wastewater and to improve wheat productivity.

Impact of the Precursor on the Physicochemical Properties and Photoactivity of TiO2 Nanoparticles Produced in Supercritical CO2

The synthesis of TiO2 nanoparticles (NPs) in supercritical media has been reported over the last two decades. However, very few studies have compared the physicochemical characteristics and photoactivity of the TiO2 powders produced from different precursors, and even fewer have investigated the effect of using different ratios of hydrolytic agent/precursor (HA/P) on the properties of the semiconductor. To bridge this knowledge gap, this research focuses on the synthesis and characterization of TiO2 NPs obtained in a supercritical CO2 medium from four different TiO2 precursors, namely diisopropoxytitanium bis (acetylacetonate) (TDB), titanium (IV) isopropoxide (TIP), titanium (IV) butoxide (TBO), and titanium (IV) 2-ethylhexyloxide (TEO). Further, the effect of various HA/P ratios (10, 20, 30, and 40 mol/mol) when using ethanol as a hydrolytic agent has also been analyzed. Results obtained have shown that the physicochemical properties of the catalysts are not significantly affected by these variables, although some differences do exist between the synthesized materials and their catalytic performances. Specifically, photocatalysts obtained from TIP and TEO at the higher HA/P ratios (HA/P = 30 and HA/P = 40) led to higher CO2 photoconversions (6.3-7 µmol·g-1·h-1, Apparent Quantum Efficiency < 0.1%), about three times higher than those attained with commercial TiO2 P-25. These results have been imputed to the fact that these catalysts exhibit appropriate values of crystal size, surface area, light absorption, and charge transfer properties.

Novel silver-morphine-functionalized polypropylene (AgPP-mrp) nanocomposite for the degradation of dye removal by multivariate optimization approach

As a novel adsorbent, an opioid silver-morphine-functionalized polypropylene was synthesized through a one-pot reaction at room temperature and successfully used for the simple one-pot photocatalytic degradation catalyst of methyl orange removal from wastewater. UV spectral analysis reveals a special reference to the excitation of surface plasmon resonance as the main characteristic of the polymer-Ag nanocomposite in toluene solution peak at 420 nm in AgPP-mrp catalyst. The 1H NMR spectrum showed no sign of Ag NP peaks revealing small size distribution in the channels of morphine-functionalized polypropylene polymer. The morphology of silver nanoparticle-doped polymer through scanning electron microscopy (SEM-EDX) reveals PP-mrp with continuous matrix and Ag NPs (0.87 wt%). Furthermore, photocatalytic degradation of methyl orange was investigated on AgPP-mrp catalyst spectrophotometrically under solar irradiation in waste effluent, demonstrating high degradation efficiency. According to experimental findings, silver nanoparticles (AgPP-mrp) achieved high degradation capacities of 139 mg/g equivalent to 97.4% of photodegradation in a little period of time (35 min), as associated with previously stated materials and follow pseudo-second-order kinetic degradation tail of a high regression coefficient (R2 = 0.992). The suggested techniques offer a linear reaction for MO over the pH range of 1.5 to 5 and a degradation temperature of 25 to 60 °C. Central composite design and response surface methodology statistics recommend pH of the reaction medium and time as important variables for methyl orange degradation on AgPP-mrp photocatalytic. AgPP-mrp on the photocatalytic phenomenon based on heterojunction catalytic design producing electron holes (e-), as well as superoxides for the successful degradation of methyl orange.

Recent Advances in the Biocatalytic Mitigation of Emerging Pollutants: A Comprehensive Review

The issue of environmental pollution has been worsened by the emergence of new contaminants whose morphology is yet to be fully understood. Several techniques have been adopted to mitigate the pollution effects of these emerging contaminants, and bioremediation involving plants, microbes, or enzymes has stood out as a cost-effective and eco-friendly approach. Enzyme-mediated bioremediation is a very promising technology as it exhibits better pollutant degradation activity and generates less waste. However, this technology is subject to challenges like temperature, pH, and storage stability, in addition to recycling difficulty as it is arduous to isolate them from the reaction media. To address these challenges, the immobilization of enzymes has been successfully applied to ameliorate the activity, stability, and reusability of enzymes. Although this has significantly increased the uses of enzymes over a wide range of environmental conditions and facilitated the use of smaller bioreactors thereby saving cost, it still comes with additional costs for carriers and immobilization. Additionally, the existing immobilization methods have their individual limitations. This review provides state-of-the-art information to readers focusing on bioremediation using enzymes. Different parameters such as: the sustainability of biocatalysts, the ecotoxicological evaluation of transformation contaminants, and enzyme groups used were reviewed. The efficacy of free and immobilized enzymes, materials and methods for immobilization, bioreactors used, challenges to large-scale implementation, and future research needs were thoroughly discussed.