AUTHOR=Guan Wei , Zhang Zhenghua , Tian Shichao , Du Jianwei 

TITLE=Ti4O7/g-C3N4 for Visible Light Photocatalytic Oxidation of Hypophosphite: Effect of Mass Ratio of Ti4O7/g-C3N4

JOURNAL=Frontiers in Chemistry

VOLUME=6

YEAR=2018

URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2018.00313

DOI=10.3389/fchem.2018.00313

ISSN=2296-2646

ABSTRACT=<p>Hypophosphite wastewater treatment is still a critical issue in metallurgical processes and the oxidation of hypophosphite to phosphate followed by the precipitation of phosphate is an important strategy for hypophosphite wastewater treatment. Herein, Ti<sub>4</sub>O<sub>7</sub>/g-C<sub>3</sub>N<sub>4</sub> photocatalysts with various mass ratios (Ti<sub>4</sub>O<sub>7</sub> (m): g-C<sub>3</sub>N<sub>4</sub> (m) = 0.5, 0.2, 0.1, and 0.05) were synthesized by a hydrolysis method and the effect of the mass ratio of Ti<sub>4</sub>O<sub>7</sub> (m): g-C<sub>3</sub>N<sub>4</sub> (m) on Ti<sub>4</sub>O<sub>7</sub>/g-C<sub>3</sub>N<sub>4</sub> visible light photocatalytic oxidation of hypophosphite was evaluated. The as-prepared Ti<sub>4</sub>O<sub>7</sub>/g-C<sub>3</sub>N<sub>4</sub> were characterized and confirmed by SEM, XPS, XRD and FTIR. Moreover, the specific surface area and the distribution of pore size of Ti<sub>4</sub>O<sub>7</sub>/g-C<sub>3</sub>N<sub>4</sub> was also analyzed. Our results showed that Ti<sub>4</sub>O<sub>7</sub>/g-C<sub>3</sub>N<sub>4</sub> exhibited remarkably improved photocatalytic performance on hypophosphite oxidation compared with g-C<sub>3</sub>N<sub>4</sub> and meanwhile 1:2-Ti<sub>4</sub>O<sub>7</sub>/g-C<sub>3</sub>N<sub>4</sub> with a mass ratio of 0.5 showed the best photocatalytic performance with the highest oxidation rate constant (17.7-fold and 91.0-fold higher than that of pure g-C<sub>3</sub>N<sub>4</sub> and Ti<sub>4</sub>O<sub>7</sub>, respectively). The enhanced performance of photocatalytic oxidation of hypophosphite was ascribed to the heterojunction structure of Ti<sub>4</sub>O<sub>7</sub>/g-C<sub>3</sub>N<sub>4</sub> with broader light absorption and significantly enhanced efficiency of the charge carrier (e<sup>−</sup>-h<sup>+</sup>) generation and separation. Additionally, the generated ·OH and ·<inline-formula><mml:math id="M1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mrow><mml:mtext>O</mml:mtext></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow><mml:mrow><mml:mo>-</mml:mo></mml:mrow></mml:msubsup></mml:math></inline-formula> radicals contributed to the hypophosphite oxidation during the photocatalytic system.</p>