Highly Efficient Photocatalytic Cr(VI) Reduction by Lead Molybdate Wrapped with D-A Conjugated Polymer under Visible Light

Well-designed composite photocatalysts are of increasing concern due to their enhanced catalytic performance compared to a single component. Here, a photocatalyst composed of PbMoO4 (PMO) and poly-benzothiadiazole (BBT, a D-A-conjugated polymer) was successfully synthesized by BBT polymerization on the surface of the PMO. The resultant BBT-PMO with a heterojunction structure represented an enhanced ability to reduce highly toxic heavy metal Cr(VI) from water under visible light irradiation. The 16.7% BBT-PMO(N, nanoscale) showed the best performance. The corresponding kobs over the 16.7% BBT-PMO(N) was 26-fold (or 53-fold) of that over the pure BBT (or pristine PMO(N)), and this activity was maintained after four cycles. The reasons for its good performance are discussed in detail based on the experimental results. Moreover, the synthesis of the BBT in situ of the PMO also altered the morphology of the BBT component, increasing the specific surface area of the BBT-PMO(N) and endowing it with the ability to adsorb Cr(VI). Additionally, the photocatalyst was also environmentally friendly as such a wrapped structure could sustain the high stability of the PMO without dissociation. This work provides a good strategy for efficient photocatalytic Cr(VI) reduction by designing an organic–inorganic hybrid system with high redox capacity.

DEVELOPMENT OF RATIONAL METHOD OF SYNTHESIS OF NANOCRYSTALLINE LEAD MOLYBDATE IN MELTS OF Na2MO2O7 - PbCO3 SYSTEM

The work presents material on interaction of dimolybdate of sodium and carbonate of lead, and also data on the development of a rational method for the synthesis of PbMoO4 in the melts, characterized by high productivity and yield of the target product of "h.с." brand in the nanocrystalline state. To achieve the work aims the thermodynamic assessment of the ability of the synthesis of molybdate of lead in melts of the system Na2Mo2O7 – PbCO3 was given. It is shown that the thermodynamic probability of formation of molybdate of lead in a number of Na2Mo2O7 – PbO(PbO2, PbCO3), is maximal for the process in the system of dimolybdate sodium – lead carbonate. The starting material for the synthesis of lead molybdate – dimolybdate sodium – was synthesized from recrystallized and dehydrated sodium molybdate and molybdenum oxide (VI). The melting temperature of synthesized dimolybdate sodium is 612 °C (614 °C – literature data). Synthesis of lead molybdate was done after careful grinding of the initial reagents and sifting through a sieve. The temperature of the synthesis process of 650 °C was maintained for 1.5 h until reaching the constant weight of mixture. Then mixture was sintered, cooled to room temperature and leached with hot (70-80 °C) distilled water. The precipitate of lead molybdate was filtered, washed on the filter to a negative reaction on molybdate ion. Synthesized molybdate of lead was dried, washed and calcined to constant weight. The yield of lead (II) molybdate was of 99.88% of the theoretical. Analysis of the obtained product was based on reaction between PbMoO4 with sodium carbonate with the formation of sodium molybdate, lead oxide (II) and carbon oxide (IV). Thus obtained sample was sintered, leached with hot distilled water and filtered. The residue was treated with acetic acid obtained from acetate of lead, the latter is determined in a form of lead molybdate (sodium molybdate deposition). To determine molybdenum from the filtrate from PbO, the inverse sedimentation method was used, in the form of BaMoO4, which is its weight form. The work also contains a material on the identification of the synthesized product by modern research methods.For citation:Shurdumov G.K., Cherkesov Z.A., Kandurova E.F. Development of rational method of synthesis of nanocrystalline lead molybdate in melts of Na2Mo2O7 – PbCO3 system. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 7. P. 78-84.