Amorphous content on the photocatalytic performance of micrometer-sized tungsten trioxide particles

Bioactivity and Plant Growth Stimulation Studies using Mangifera indica L. Gum

The potential of plant gum as a bioactive agent and plant growth enhancer has not been exploited well and plant gums are suitable for such purposes as they are non-toxic and biodegradable. Therefore, the aim of this study was to verify the potential of Mangifera indica (MI) gum as a bioactive agent and plant growth enhancer. Plant gum was collected from the bark of MI and polysaccharides were extracted, purified and characterized with ultraviolet-visible (UV-Vis) spectroscopic, Fourier-transform infrared spectroscopy and gas chromatography (GC) analyses. Crude and purified polysaccharides were tested for their antibacterial and antioxidant activity. The crude gum was subjected to plant growth stimulation study like germination percentage, shoot length, root length and wet weight of chilli (Capsicum frutescens). The effect of MI gum on soil porosity and water holding capacity (WHC) was also tested. UV-Vis and GC analyses of gum polysaccharide showed the presence of several types of monosaccharides in MI gum. The plant gum did not show any antibacterial activity against Escherichia coli, Pseudomonas sp., Bacillus sp. and Staphylococcus aureus, but was found to exhibit low antioxidant activity. The gum was found to enhance the seed germination and seedling growth in-vitro and in-vivo.

A New Approach for Controlling Mesoporosity in Activated Carbon by the Consecutive Process of Air Oxidation, Thermal Destruction of Surface Functional Groups, and Carbon Activation (the OTA Method)

A new and simple method, based entirely on a physical approach, was proposed to produce activated carbon from longan fruit seed with controlled mesoporosity. This method, referred to as the OTA, consisted of three consecutive steps of (1) air oxidation of initial microporous activated carbon of about 30% char burn-off to introduce oxygen surface functional groups, (2) the thermal destruction of the functional groups by heating the oxidized carbon in a nitrogen atmosphere at a high temperature to increase the surface reactivity due to increased surface defects by bond disruption, and (3) the final reactivation of the resulting carbon in carbon dioxide. The formation of mesopores was achieved through the enlargement of the original micropores after heat treatment via the CO2 gasification, and at the same time new micropores were also produced, resulting in a larger increase in the percentage of mesopore volume and the total specific surface area, in comparison with the production of activated carbon by the conventional two-step activation method using the same activation time and temperature. For the activation temperatures of 850 and 900 °C and the activation time of up to 240 min, it was found that the porous properties of activated carbon increased with the increase in activation time and temperature for both preparation methods. A maximum volume of mesopores of 0.474 cm3/g, which accounts for 44.1% of the total pore volume, and a maximum BET surface area of 1773 m2/g was achieved using three cycles of the OTA method at the activation temperature of 850 °C and 60 min activation time for each preparation cycle. The two-step activation method yielded activated carbon with a maximum mesopore volume of 0.270 cm3/g (33.0% of total pore volume) and surface area of 1499 m2/g when the activation temperature of 900 °C and a comparable activation time of 240 min were employed. Production of activated carbon by the OTA method is superior to the two-step activation method for better and more precise control of mesopore development.

Cu/CuO Composite Track-Etched Membranes for Catalytic Decomposition of Nitrophenols and Removal of As(III)

One of the promising applications of nanomaterials is to use them as catalysts and sorbents to remove toxic pollutants such as nitroaromatic compounds and heavy metal ions for environmental protection. This work reports the synthesis of Cu/CuO-deposited composite track-etched membranes through low-temperature annealing and their application in catalysis and sorption. The synthesized Cu/CuO/poly(ethylene terephthalate) (PET) composites presented efficient catalytic activity with high conversion yield in the reduction of nitro aryl compounds to their corresponding amino derivatives. It has been found that increasing the time of annealing raises the ratio of the copper(II) oxide (CuO) tenorite phase in the structure, which leads to a significant increase in the catalytic activity of the composites. The samples presented maximum catalytic activity after 5 h of annealing, where the ratio of CuO phase and the degree of crystallinity were 64.3% and 62.7%, respectively. The catalytic activity of pristine and annealed composites was tested in the reduction of 4-nitroaniline and was shown to remain practically unchanged for five consecutive test cycles. Composites annealed at 140 °C were also tested for their capacity to absorb arsenic(III) ions in cross-flow mode. It was observed that the sorption capacity of composite membranes increased by 48.7% compared to the pristine sample and reached its maximum after 10 h of annealing, then gradually decreased by 24% with further annealing.

WO3/Buckypaper Membranes for Advanced Oxidation Processes

Photocatalytic materials, such as WO₃, TiO₂, and ZnO nanoparticles, are commonly linked onto porous polymer membranes for wastewater treatment, fouling mitigation and permeation enhancement. Buckypapers (BPs) are entanglements of carbon nanotubes, which have been recently proposed as innovative filtration systems thanks to their mechanical, electronic, and thermal properties. In this work, flexible membranes of single wall carbon nanotubes are prepared and characterized as efficient substrates to deposit by chemical vapor deposition thin layers of WO₃ and obtain, in such a way, WO₃/BP composite membranes for application in advanced oxidation processes. The photocatalytic efficiency of WO₃/BP composite membranes is tested against model pollutants in a small continuous flow reactor and compared with the performance of an equivalent homogeneous WO₃-based reactor.