Publications

The accumulation of microplastics (& micro;Pls) in ecosystems has become a serious environmental concern. Despite increasing awareness, the development of efficient technologies for their removal and remediation remains a major challenge. Herein, we investigate the photocatalytic degradation of polypropylene (PP) & micro;Pls using nanocomposite catalysts composed of permanently polarized hydroxyapatite microparticles (pp-HAp) and rutile TiO2 nanoparticles (TiO2 NPs). pp-HAp, a macroporous bioceramic, is known for its ability to convert gases (CO2 or/and N2) into small value-added chemical products. While pp-HAp serves both as the substrate and thermocatalytic part of the composite, TiO2 NPs are incorporated as the photocatalytic component. A series of XTiO2/ pp-HAp photocatalyts, where X represents the weight percentage of TiO2 (X = 2.5, 5, 10 and 20), were prepared applying a thermal stimulated polarization treatment. The resulting materials show no formation of undesirable calcium titanate. After thorough chemical and physical characterization, the photocatalytic performance of the XTiO2/pp-HAp in the degradation of PP-& micro;Pls was evaluated. Under 1 sun irradiation, the process is selective toward ethanol, which indicates the cleavage of consecutive C-C bonds along the PP chains, with the highest yield obtained for 2.5TiO2/pp-HAp. When the irradiation intensity decreases (0.5 sun), ethanol and isopropanol are produced, suggesting a reduction in the efficiency of the C-C cleavage. In all cases, the nanocomposite catalysts exhibit significantly higher yields than TiO2 NPs or pp-HAp individually, which indicates cooperative electronic effects between both components. Regarding selectivity, in addition to the solar irradiation, the TiO2: pp-HAp ratio also determines which product is obtained. Within the framework of circular economy, our strategy yields added-value chemical products from PP waste using only sunlight and an environmentally friendly catalyst.

JTD Keywords: Anatase, Heterogeneous catalysis, Microplastics, Microplastics removal, Nanocomposites, Photocatalysts, Polypropylene photodegradation, Water treatment plants

The presence of organic pollutants in the environment is a global threat to human health and ecosystems due to their bioaccumulation and long-term persistence. Hereby a micromotor-in-sponge concept is presented that aims not only at pollutant removal, but towards an efficient in situ degradation by exploiting the synergy between the sponge hydrophobic nature and the rapid pollutant degradation promoted by the cobalt-ferrite (CFO) micromotors embedded at the sponge's core. Such a platform allows the use of extremely low fuel concentration (0.13% H2 O2 ), as well as its reusability and easy recovery. Moreover, the authors demonstrate an efficient multicycle pollutant degradation and treatment of large volumes (1 L in 15 min) by using multiple sponges. Such a fast degradation process is due to the CFO bubble-propulsion motion mechanism, which induces both an enhanced fluid mixing within the sponge and an outward flow that allows a rapid fluid exchange. Also, the magnetic control of the system is demonstrated, guiding the sponge position during the degradation process. The micromotor-in-sponge configuration can be extrapolated to other catalytic micromotors, establishing an alternative platform for an easier implementation and recovery of micromotors in real environmental applications.© 2022 Wiley-VCH GmbH.

JTD Keywords: effective removal, fabrication, microbots, microjets, organic pollutants, propelled micromotors, self-propelled micromotors, sponges, water treatment, Oil-water separation, Organic pollutants, Water treatment

Self-propelled micromotors have previously shown to enhance pollutant removal compared to non-motile nano-micro particles. However, these systems are expensive, difficult to scale-up and require surfactant for efficient work. Efficient and inexpensive micromotors are desirable for their practical applications in water treatment technologies. We describe cobalt-ferrite based micromotors (CFO micromotors) fabricated by a facile and scalable synthesis, that produce hydroxyl radicals via Fenton-like reaction and take advantage of oxygen gas generated during this reaction for self-propulsion. Once the reaction is complete, the CFO micromotors can be easily separated and collected due to their magnetic nature. The CFO micromotors are demonstrated for highly efficient advanced oxidative removal of tetracycline antibiotic from the water. Furthermore, the effects of different concentrations of micromotors and hydrogen peroxide on the antibiotic degradation were studied, as well as the generation of the highly reactive hydroxyl radicals responsible for the oxidation reaction.

JTD Keywords: Degradation, Fenton reaction, Microbots, Nanomotors, Self-propelled Micromotors, Water treatment

Self-powered micromachines are promising tools for future environmental remediation technology. Waste-water treatment and water reuse is an essential part of environmental sustainability. Herein, we present reusable Fe/Pt multi-functional active microcleaners that are capable of degrading organic pollutants (malachite green and 4-nitrophenol) by generated hydroxyl radicals via a Fenton-like reaction. Various different properties of microcleaners, such as the effect of their size, short-term storage, long-term storage, reusability, continuous swimming capability, surface composition, and mechanical properties, are studied. It is found that these microcleaners can continuously swim for more than 24 hours and can be stored more than 5 weeks during multiple cleaning cycles. The produced microcleaners can also be reused, which reduces the cost of the process. During the reuse cycles the outer iron surface of the Fe/Pt microcleaners generates the in-situ, heterogeneous Fenton catalyst and releases a low concentration of iron into the treated water, while the mechanical properties also appear to be improved due to both its surface composition and structural changes. The microcleaners are characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), nanoindentation, and finite-element modeling (FEM).

JTD Keywords: Catalysts, Heterogeneous catalysis, Microcleaners, Micromotors, Nanorobots, Wastewater treatment