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 electrophotocatalytic synthesis of Glycine and Alanine from a simple gas mixture containing N2, CO2, CH4 and H2O under mild reaction conditions (95 °C and 6 bar) was recently developed using a catalyst formed by permanently polarized hydroxyapatite, which is achieved using a thermally stimulated polarization process, coated with two layers of aminotris(methylenephosphonic acid) (ATMP) separated by an intermediate layer of zirconyl chloride (ZC). This work reports the optimization of the ATMP- and ZC-coating content by examining the influence of their concentration of each component in each layer on the structural and electrochemical properties of the catalyst. After exhaustive analyses, such properties have been related with the efficiency of the catalysts prepared using different ATMP- and ZC-concentrations to yield Gly and Ala amino acids by fixing nitrogen from N2 and carbon from CO2 and CH4. Results show that, although the concentrations of ATMP and ZC in the first and the intermediate layers are important, the third layer plays a predominant role as is responsible of the apparition of supramolecular structures on the surface and the capacitive behavior of the coating

JTD Keywords: Carbon dioxide fixation, Electrocatalyst, Heterogeneous catalysis, Phosphonic acid, Photocatalyst, Polarized hydroxyapatite, Surface chemistry, Zirconyl chloride