Making the most of precious metal nanoparticles in the purification of industrial wastewater by catalytic wet air oxidation

The aim of catalytic wet air oxidation is to use air to remove organic contaminants from wastewater through their complete oxidation, without having to vaporise the water. To date, the widespread exploitation of this process has been held back by the low activity of available catalysts, which means that it has to be operated at above-atmospheric pressure in order to keep the water in the liquid phase at the elevated temperatures required to achieve complete oxidation. Here we present an overview of an ongoing study examining the key requirements of both the active phase and the support material in precious metal catalysts for wet air oxidation, using phenol as the model contaminant. The major outcome to date is that the results reveal a synergy between platinum and hydrophobic support materials, which is not apparent when the active phase is ruthenium

Multifunctional Role of Magnetic Nanoparticles in Efficient Microalgae Separation and Catalytic Hydrothermal Liquefaction

In this work, the efficiency of extracting algae from culture medium using magnetic nanoparticles (MNPs), converting the algal/particle slurry to biocrude using hydrothermal liquefaction (HTL), and successfully recycling the MNPs from the char phase was fully demonstrated for the first time. MNPs were synthesized by coprecipitation and used to extract algae from aqueous phase at a separation efficiency (SE) of 99%. The SE was optimized at pH 4. Liquefaction of algal/MNPs slurry gave a biocrude yield of 37.1% while algae only yielded 23.2%. The percentage areas in the GC-MS chromatogram corresponding to hydrocarbons (HCs) in Zn-ferrite catalyzed and uncatalyzed biocrude were 46.5% and 19.9%, respectively, while the percentage areas of heptadecane from Zn-ferrite catalyzed and uncatalyzed biocrude were 37.8% and 10%, respectively. Furthermore, the percentage area of heteroatom compounds in biocrude reduced substantially when liquefaction was done in the presence of Zn/Mg ferrites. The nanoparticles were recovered from biochar by sonication and recycled at a SE of 96.1%. Recycling of MNPs for magnetic separation of algae and catalytic HTL could lower the cost of microalgae harvesting and improve the yield and quality of biocrude. This could potentially reduce the cost of advanced biofuel processing from microalgae, making them more affordable in comparison to petroleum-derived fuels

Exploring the feasibility of continuous CWAO of bisphenol A at near-ambient temperature and pressure through use of hydrophobic Pt catalysts

Hydrophobic Pt CWAO-catalysts can achieve complete removal of bisphenol A from a flow of contaminated water in a trickle-bed reactor at an operating temperature of 120°C, total air pressure of 8 bar and a liquid-hourly space velocity of 26.6 h−1. Although increasing the throughput of contaminated water while lowering the operating temperature results in bisphenol A conversions below 100%, these more demanding conditions allow structurally similar catalyst formulations to be differentiated from one another. At 60°C and 8 bar total pressure of air, 2%Pt supported on a SiC-TiC composite material has the highest initial activity from a group of three hydrophobic catalysts with similar surface areas and Pt particle diameters, but it begins to deactivate progressively after 15 hours on stream. This catalyst contains some localised hydrophilicity arising from the presence of surface TiO2, which forms when the exposed TiC component of the support material oxidises during catalyst preparation. At 80 °C and ambient air pressure, the activity is lower but there are no signs of deactivation during 24 hours on stream. The results are consistent with metallic platinum providing the active sites for CWAO of bisphenol A, with oxygen being directly activated from the gas phase at elevated pressures, but with dissolved oxygen also contributing to the reaction particularly at ambient air pressure. Continuous and irreversible deactivation, which occurs at air pressures ≥4 bar, appears to be associated with high occupancy of the active sites by adsorbed oxygen, resulting in leaching of platinum into the aqueous phase

Synthesis, radiolabelling and in vitro imaging of multifunctional nanoceramics

Molecular imaging has become a powerful technique in preclinical and clinical research aiming towards the diagnosis of many diseases. In this work, we address the synthetic challenges in achieving lab‐scale, batch‐to‐batch reproducible copper‐64‐ and gallium‐68‐radiolabelled metal nanoparticles (MNPs) for cellular imaging purposes. Composite NPs incorporating magnetic iron oxide cores with luminescent quantum dots were simultaneously encapsulated within a thin silica shell, yielding water‐dispersible, biocompatible and luminescent NPs. Scalable surface modification protocols to attach the radioisotopes 64Cu (t1/2=12.7 h) and 68Ga (t1/2=68 min) in high yields are reported, and are compatible with the time frame of radiolabelling. Confocal and fluorescence lifetime imaging studies confirm the uptake of the encapsulated imaging agents and their cytoplasmic localisation in prostate cancer (PC‐3) cells. Cellular viability assays show that the biocompatibility of the system is improved when the fluorophores are encapsulated within a silica shell. The functional and biocompatible SiO2 matrix represents an ideal platform for the incorporation of 64Cu and 68Ga radioisotopes with high radiolabelling incorporation