Noble-metal-free hydroxyapatite activated by facile mechanochemical treatment towards highly-efficient catalytic oxidation of volatile organic compound

Controlling of volatile organic compound (VOC) emitted from industrial processes as most abundant and harmful air pollutant, has become one of the most important global environmental issues due to the rapid urbanization and industrialization. As an alternative and new type catalyst instead of conventional noble-metal nanoparticles widely utilized in oxidative decomposition of VOC, here we report the superior catalytic performance with 100% CO2/CO conversion on hydroxyapatite (HAp, Ca10(PO4)6(OH)2) with structurally well-controlled active surface tailored via facile one-step mechanochemical treatment in ambient air. With detailed characterizations of particle morphology, crystallinity and chemical structure with respects to surface defect/oxygen vacancy formation, acidity/basicity and VOC affinity on HAps activated through different mechanical stresses when altered ball size is utilized in planetary ball-milling assisted mechanochemical process, it was found that the predominant defect/oxygen vacancy generation in PO43− site and enhanced basic site population established by selective mechanochemical activation of c-plane, facilitates the favorable catalytic oxidation route towards highly-efficient CO2/CO conversion of VOC. Regards to the cost-effectiveness and non-toxic nature of HAp, incorporated with the sustainable mechanochemical surface structure tuning process, the results presented in this work opens new strategy in development of novel noble-metal-free catalyst for VOC elimination and environmental cleaning techniques.

COMPLEX COMPOUNDS BASED ON PINOSTROBIN OXIME

The article studied the structural features of solid dispersions of pinostrobin oxime with arabinogalactan, disodium salt of glycyrrhizic acid, polyvinylpyrrolidone and basic magnesium carbonate obtained by mechanochemical treatment. The obtained complexes of pinostrobin oxime with arabinogalactan, disodium salt of glycyrrhizic acid, polyvinylpyrrolidone, and basic magnesium carbonate have increased water solubility in comparison with the initial pinostrobin oxime. The thermal effects of pinostrobin oxime and its complex compounds have been studied by differential scanning calorimetry. At the same time, on the DSC-curve, the melting peak of solid dispersions of pinostrobin oxime with disodium salt of glycyrrhizated acid and pinostrobin oxime with arabinogalactan is not displayed, which is associated with the intermolecular interaction of the components of the complex, where the molecule of pinostrobin oxime forms a bond with a complexformation agent during mechanochemical treatment. The complex of pinostrobin oxime with magnesium carbonate is not formed, as evidenced by the thermal curve, where the melting of the sample begins at 182 °C, and complete destruction occurs at a temperature of 782 °C, which is similar to the melting peak of the initial pinostrobin oxime. The results of studying intermolecular bonds in complexes of pinostrobin oxime by the method of NMR-relaxation indicate that the times of spin-lattice and spin-spin relaxation are very sensitive to intermolecular interaction and to the diffusion mobility of molecules.

Mechanochemical Treatment of Historical Tungsten Tailings: Leaching While Grinding for Tungsten Extraction Using NaOH

Innovative tungsten (W) extraction techniques are continually being sought because of challenges of low leaching efficiencies, despite using advanced processing units such as autoclaves operating high temperatures and pressures. Compared to conventional leaching, mechanochemical treatment improves the efficiency of leaching. Therefore, in this study, an innovative mechanochemical treatment method, referred to as leaching while grinding (LWG), was employed as a reprocessing option to optimize W recovery from historical tungsten tailings. Experiments were run using the regular two-level factorial design to screen through the four factors of stirrer speed, liquid/solid ratio, temperature, and digestion time to assess their criticality and effects in the LWG process. The stirrer speed and the liquid/solid ratio were the most critical factors in the optimization of W recovery. The maximum W recovery (91.2%) was attained at the highest stirrer speed (410 rpm), low liquid/solid ratio (0.8), long digestion time (6 h), and low leaching temperature (60 °C). The attained low leaching temperature (60 °C) was due to the mechanical activation of scheelite resulting from the simultaneous grinding and leaching. For such low- grade W material, liquid/solid ratio optimizing is critical for maintaining the digestion mixture fluidity, and for environmental and economic sustainability regarding the sodium hydroxide (NaOH) consumption, which was low.

Mechanochemically Obtained Phytobiotics Suppress the Development of Pathogens

A study of the bactericidal action of a number of phytopreparations obtained as a result of mechanochemical treatment of mixtures of plant raw materials with solid sodium carbonate in relation to 10 species of opportunistic bacteria was carried out. The investigated phytopreparations have a selective effect on 1-3 types of microorganisms. The effect of the additive action of phytopreparations in mixtures, which can be used for the prevention and treatment of diseases of animals and humans with an established bacterial etiology, has been discovered